Articoli di riviste: "Hexane Substitution"

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Silva, Gabriel Julio da, Julcelly Dayara de Oliveira Henriques e Patricia Fazzio Martins Martinez. "Sugarcane wax extraction using hexane and limonene mixtures". Revista Engenharia na Agricultura - REVENG 30 (21 febbraio 2022): 13–18. http://dx.doi.org/10.13083/reveng.v30i1.13241.

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Hexane is the most widely solvent used in the lipids extraction process, as the case of the sugarcane wax. However, the use of this solvent is highly harmful to the environment and to human health. Limonene is a monoterpene found in the citrus peel, with great potential for use as a green solvent. In this study, the partial and total substitution of hexane by limonene was performed in the process of the sugarcane peel wax extraction to evaluate the effect of this substitution on the physicochemical characteristics of the wax. The extracted samples were compared with a commercial wax sample (carnauba) using the Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Infrared by Fourier Transform (FTIR) analyses. Through this study, we can conclude that the waxes obtained from the use of the hexane and limonene mixture solvents presented similar physicochemical characteristics to those found in commercial waxes. Thus, the total and/or partial substitution of the hexane by solvents less harmful to health and the environment, such as limonene, can be an alternative in the wax extraction process.

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Cravotto, Christian, Anne-Sylvie Fabiano-Tixier, Ombéline Claux, Maryline Abert-Vian, Silvia Tabasso, Giancarlo Cravotto e Farid Chemat. "Towards Substitution of Hexane as Extraction Solvent of Food Products and Ingredients with No Regrets". Foods 11, n. 21 (28 ottobre 2022): 3412. http://dx.doi.org/10.3390/foods11213412.

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Hexane is a solvent used extensively in the food industry for the extraction of various products such as vegetable oils, fats, flavours, fragrances, colour additives or other bioactive ingredients. As it is classified as a “processing aid”, it does not have to be declared on the label under current legislation. Therefore, although traces of hexane may be found in final products, especially in processed products, its presence is not known to consumers. However, hexane, and in particular the n-hexane isomer, has been shown to be neurotoxic to humans and has even been listed as a cause of occupational diseases in several European countries since the 1970s. In order to support the European strategy for a toxic-free environment (and toxic-free food), it seemed important to collect scientific information on this substance by reviewing the available literature. This review contains valuable information on the nature and origin of the solvent hexane, its applications in the food industry, its toxicological evaluation and possible alternatives for the extraction of natural products. Numerous publications have investigated the toxicity of hexane, and several studies have demonstrated the presence of its toxic metabolite 2,5-hexanedione (2,5-HD) in the urine of the general, non-occupationally exposed population. Surprisingly, a tolerable daily intake (TDI) has apparently never been established by any food safety authority. Since hexane residues are undoubtedly found in various foods, it seems more than necessary to clearly assess the risks associated with this hidden exposure. A clear indication on food packaging and better information on the toxicity of hexane could encourage the industry to switch towards one of the numerous other alternative extraction methods already developed.

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Rapinel, Vincent, Aziadé Chemat, Cyrille Santerre, Justine Belay, Farnaz Hanaei, Nadine Vallet, Laurence Jacques e Anne-Sylvie Fabiano-Tixier. "2-Methyloxolane as a Bio-Based Solvent for Green Extraction of Aromas from Hops (Humulus lupulus L.)". Molecules 25, n. 7 (9 aprile 2020): 1727. http://dx.doi.org/10.3390/molecules25071727.

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The potential of using the bio-based solvent 2-methyloxolane, also known as 2-methyltetrahydrofuran or 2-MeTHF, as an alternative to petroleum solvents such as hexane, was investigated for the extraction of volatile compounds from hop cones (Humulus lupulus L.). Lab scale extractions were coupled with in silico prediction of solutes solubility to assess the technical potential of this bio-based solvent. The predictive approach was performed using the simulation software COSMO-RS (conductor like screening model for real solvants) and showed that the 2-methyloxolane is as good as or better than hexane to solubilize the majority of aromas from hop cones. The experimental results indicated that the highest aroma yield was obtained with 2-methyloxolane with 20.2% while n-hexane was only able to extract 17.9%. The characterization of aromas extracted by the two solvents showed a similar composition, where lupulone was the main component followed by humulone. No selectivity of the solvents was observed for any of the major analytes. Finally, a sensory analysis was performed on the extracts, showing that both concretes using 2-methyloxolane and hexane have similar olfactory profiles. The results indicate that 2-methyloxolane could be a promising bio-based extraction solvent for hexane substitution.

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Walton, John C. "Radical rearrangements of bicyclo[2.2.0]hexane: homolytic substitution of a cyclobutane ring". Journal of the Chemical Society, Chemical Communications, n. 16 (1987): 1252. http://dx.doi.org/10.1039/c39870001252.

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Keglevich, György, Attila Kovács, László Tőke, Kálmán Újszászy, Gyula Argay, Mátyás Czugler e Alajos Kálmán. "P-Substituted 3-phosphabicyclo [3.1.0] hexane 3-oxides from diastereoselective substitution at phosphorus". Heteroatom Chemistry 4, n. 4 (agosto 1993): 329–35. http://dx.doi.org/10.1002/hc.520040405.

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Gardecka, A. J., G. K. L. Goh, G. Sankar e I. P. Parkin. "On the nature of niobium substitution in niobium doped titania thin films by AACVD and its impact on electrical and optical properties". Journal of Materials Chemistry A 3, n. 34 (2015): 17755–62. http://dx.doi.org/10.1039/c5ta03772g.

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Hung, Nguyen Khanh, Nguyen Tuan Thanh, Nguyen Thi Thuy Luyen e Nguyen Huy Du. "Evaluating the enantioselective capability of a cellulose tris(3,5‐dimethylphenyl carbamate)‐based stationary phase towards 5,7,2'‐trihydroxyflavanone". Vietnam Journal of Chemistry 61, S2 (novembre 2023): 149–54. http://dx.doi.org/10.1002/vjch.202300193.

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AbstractIn this study, an evaluation of the enantioselective of a chiral flavanone with 2'‐OH substitution (5,7,2'‐trihydroxyflavanone) on ring C was studied by high performance liquid chromatography using the cellulose tris(3,5‐dimethylphenyl carbamate)‐based stationary phase with n‐hexane and iso‐propanol doped with 0.1% (v/v) trifluoroacetic acid as a mobile phase. Column temperature and mobile phase composition were investigated in the assessment of the chiral separation by considering the enantiomeric resolution factor (Rs). Also, the absolute configurations of single enantiomers were determined by measuring CD spectra based on the exciton‐coupling method. The results pointed out that the 2'‐hydroxy group was capable of advancing the enantioselective of flavanones on the cellulose tris(3,5‐dimethylphenyl carbamate)‐based stationary phase when the column temperature was higher than 30 oC and the mobile phase was of 10% iso‐propanol doped with 0.1% (v/v) TFA in n‐hexane. The absolute configuration determination showed that the enantiomer with the 2S configuration was the first eluted and, consequently, the elution order of the enantiomers of 5,7,2'‐trihydroxyflavanone at optimal conditions was in contrast to 5,7,4'‐trihydroxyflavanone and 5,7‐dihydroxyflavanone. The 2'‐OH substitution on the phenyl moiety appears to be capable of inducing or altering the strength of inter‐and intramolecular interactions when the chiral selectors are immobilized on the silica stationary phase.

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Shahin, Nabil, Nawaf Abu-Khalaf, Mazen Salman e Harun Parlar. "Testing the Possibility of Photochemical Synthesis of Chlorinated Phenols, Benzenes and Biphenyl: Pre-study Guide for Standards Synthesis". مجلة جامعة فلسطين التقنية للأبحاث 4, n. 2 (1 settembre 2016): 73–83. http://dx.doi.org/10.53671/pturj.v4i2.47.

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Since deuterium 2H (D) is an isotope of hydrogen 1H, the testing of the possibility of photochemical synthesis of marked chlorinated phenol, biphenyl and benzene using normal solvents was studied. The irradiation of full chlorinated compounds dissolved in normal solvents such as MeOH or n-hexane has led to a reaction substitution in which a chlorine atom was substituted by hydrogen atom forming less grade chlorinated chlorophenols, biphenyls and benzenes. The quantum yields of pentachlorophenol, decachlorobiphenyl and hexachlorobenzene under irradiation using polychromatic light were calculated and found to be 5.7 x 10-3, 1.6 x 10-2 and 1.2 x 10-2 Mol·Einstein-1, respectively. Depending on this study the production of marked chlorinated or non-chlorinated compounds using deuterated appropriate solvents such as MeOH d4 or n-hexane d14 is possible. However, more efforts should be made towards chromatographically separation of synthesized standards and byproducts in order to make the use of these marked compounds as standards in residue analysis feasible.

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Shahin, Nabil, Nawaf Abu-Khalaf, Mazen Salman e Harun Parlar. "Testing the Possibility of Photochemical Synthesis of Chlorinated Phenols, Benzenes and Biphenyl: Pre-study Guide for Standards Synthesis". مجلة جامعة فلسطين التقنية خضوري للأبحاث 4, n. 2 (1 settembre 2016): 73–83. http://dx.doi.org/10.53671/ptukrj.v4i2.47.

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Abstract (sommario):

Since deuterium 2H (D) is an isotope of hydrogen 1H, the testing of the possibility of photochemical synthesis of marked chlorinated phenol, biphenyl and benzene using normal solvents was studied. The irradiation of full chlorinated compounds dissolved in normal solvents such as MeOH or n-hexane has led to a reaction substitution in which a chlorine atom was substituted by hydrogen atom forming less grade chlorinated chlorophenols, biphenyls and benzenes. The quantum yields of pentachlorophenol, decachlorobiphenyl and hexachlorobenzene under irradiation using polychromatic light were calculated and found to be 5.7 x 10-3, 1.6 x 10-2 and 1.2 x 10-2 Mol·Einstein-1, respectively. Depending on this study the production of marked chlorinated or non-chlorinated compounds using deuterated appropriate solvents such as MeOH d4 or n-hexane d14 is possible. However, more efforts should be made towards chromatographically separation of synthesized standards and byproducts in order to make the use of these marked compounds as standards in residue analysis feasible.

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Fischer, Malte, Marc Schmidtmann e Rüdiger Beckhaus. "Crystal structure of the formal 20 electron zirconocene pentafulvene complex Cp2Zr(η5,η1-adamantylidenepentafulvene):toluene:n-hexane = 1:0.125:0.125". Acta Crystallographica Section E Crystallographic Communications 73, n. 12 (3 novembre 2017): 1823–26. http://dx.doi.org/10.1107/s2056989017015560.

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The crystal structure of a solvated zirconocene pentafulvene complex with a bulky adamantylidene substitution pattern, namely (η5,η1-adamantylidenepentafulvene)bis(η5-cyclopentadienyl)zirconium(IV)–toluene–n-hexane (8/1/1), [Zr(C15H18)(C5H5)2]·0.125C7H8·0.125C6H14, is reported. Reducing zirconocene dichloride with magnesium results in the formation of a low-valent zirconocene reagent that reacts readily with adamantylidenepentafulvene to give the aforementioned complex. Single crystal X-ray diffraction proves the dianion-like η5:η1binding mode of the fulvene ligand to the central ZrIVatom. The asymmetric unit contains four independent molecules of [η5:η1-adamantylidenepentafulvene]bis[(η5)-cyclopentadienyl]zirconium(IV), together with half a molecule of toluene disordered with half a molecule ofn-hexane (the solvent molecules have no direct influence on the complex). In each of the four complex molecules, the central ZrIVatom has a distorted tetrahedral coordination environment. The measured crystal consisted of two domains with a refined ratio of 0.77:0.23.

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Maha F. Abbass, Salah Al-Shukri e Ahmed A. Ahmed. "Selective mono substitution of cyclotri-phosphazene by 2-Hydroxyethylacrylate producing new acrylate cyclo-triphosphazene". GSC Advanced Research and Reviews 10, n. 3 (30 marzo 2022): 080–87. http://dx.doi.org/10.30574/gscarr.2022.10.3.0070.

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In this work, new acrylate cyclotriphosphazene moiety (PN-A) was successfully synthesized starting from cyclotriphosphazene (PN) compound. This compound reacted with 2-hydroxyethylacrylate utilizing 1:1 mole ratio to increase the priority of one substitution reaction and forming PN-A molecule. The crud product was purified by recrystallization using n-hexane and column chromatography using cyclohexane: ethyl acetate 60:40 mL ratio as eluent. The obtained pure target product was characterized using FTIR, 1H NMR, 13C NMR, and 31P NMR techniques. All spectra demonstrates the chemical structure of the product hence the showed all required peaks to identify it.

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Engering, Josef, Eva-Maria Peters e Martin Jansen. "Dimeres Di(N-lithium–tert–butylamino)bis(dimethylamino)silan - [Si(N(CH3)2)2(NLiC(CH3)3)2]2 – Darstellung und Kristallstruktur / Dimeric Di(N -lithio-tert-butylamino)bis(dimethylamino)silane - [Si(N(CH3)2)2(NLiC(CH3)3)2]2 – Synthesis und Crystal Structure". Zeitschrift für Naturforschung B 56, n. 1 (1 gennaio 2001): 90–94. http://dx.doi.org/10.1515/znb-2001-0115.

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Abstract [Si(N(CH3)2)2(NLiC(CH3)3)2]2 results from the reaction of silicon tetrachloride with excess terf-butylamine, followed by halogen substitution with LiN(CH3)2, and treatment with n-butyllithium in hexane. The title compound, found to be dimeric in the solid state, was characterised by single crystal X-ray diffraction (triclinic, Pi , a = 10.208(2), b = 12.140(2), c = 15.658(3) Å , a = 79.02(3), ß = 82.80(3), γ = 67.19(3)°, Z = 2, C24H60Li4N8Si2 ), and by solid state and solution NMR-spectroscopy and mass spectrometry.

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KEGLEVICH, G., A. KOVACS, L. TOEKE, K. UJSZASZY, G. ARGAY, M. CZUGLER e A. KALMAN. "ChemInform Abstract: P-Substituted 3-Phosphabicyclo(3.1.0)hexane 3-Oxides from Diastereoselective Substitution at Phosphorus." ChemInform 25, n. 2 (19 agosto 2010): no. http://dx.doi.org/10.1002/chin.199402219.

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Istyami, Astri Nur, Tatang Hernas Soerawidjaja, Tirto Prakoso e Tri Ari Penia Kresnowati. "Performance of Various Organic Solvents as Reaction Media in Plant Oil Lipolysis with Plant Lipase". Reaktor 18, n. 2 (24 agosto 2018): 71. http://dx.doi.org/10.14710/reaktor.18.2.71-75.

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Fatty acids are intermediate substances in synthesis of oleochemical products. Enzymatic technology of fatty acids production (also known as lipolysis) is now developing as potential substitution for the conventional production of fatty acid, i.e. thermal hydrolysis of triglyceride. It offers more economical process condition, low energy consumption, and minimal product degradation compared to the conventional process. This research aims to evaluate performance of various organic solvents as reaction media in lipolysis with plant latex lipase. Organic solvents observed were chloroform, n-hexane, diethyl ether, benzene, acetone, ethanol, methanol, n-heptane, and isooctane. Analysis of each organic solvent effect on lipolysis was described based on solvents properties. Conversion of lipolysis with organic solvents is 0,10-1,25 times fold compared to conversion of non-solvent lipolysis. We suggest that dielectric constant and viscosity are the two main organic solvent properties affecting lipase performance in lipolysis. Overall, n-hexane, n-heptane, and isooctane are recommended to be used as reaction media in lipolysis with plant lipase because their effects to degree of lipolysis are positive. Keywords: lipolysis; lipase; organic solvent; frangipani

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Landers, Gary M., e James A. Olson. "Absence of Isomerization of Retinyl Palmitate, Retinol, and Retinal in Chlorinated and Nonchlorinated Solvents Under Gold Light". Journal of AOAC INTERNATIONAL 69, n. 1 (1 gennaio 1986): 50–55. http://dx.doi.org/10.1093/jaoac/69.1.50.

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Abstract Purified solutions of all-trans retinyl palmitate, retinol, and retinaldehyde in chloroform, methylene chloride, or hexane were exposed to white light or gold fluorescent light or were kept in the dark, and the resulting isomer distributions were determined by LC (liquid chromatography). No significant isomerization of any of the retinoids occurred either in the dark or on exposure to gold light in any of the solvents tested. However, a large amount of the 9-cis isomer and only much smaller amounts of other cis isomers were produced when retinol or retinyl palmitate in chloroform or methylene chloride solution was exposed to white light. The isomerization pattern of retinyl palmitate in chloroform was not altered by the addition of free-radical scavengers, addition of an organic base, or substitution of deuterochloroform for chloroform as solvent. Use of other polar solvents such as tetrahydrofuran, acetone, or methanol produced isomer distributions similar to those obtained in chloroform solution. Retinol and retinyl palmitate in hexane solution, on exposure to white light, were isomerized much less extensively than in chloroform or methylene chloride and produced a significant amount of the 13-cis, as well as the 9-cis, isomer. Isomerization of retinaldehyde in chloroform or in methylene chloride solution under white light yielded 13-cis, 11-cis, 9-cis, and 7-cis isomers, in order of decreasing amount, whereas in hexane solution, only the 13-cis and 9-cis isomers were produced in significant quantity

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Wloch, J. "Influence of isomorphous substitution in MFI-type materials on the diffusion of n-hexane: Molecular dynamic studies". Applied Surface Science 253, n. 13 (aprile 2007): 5692–95. http://dx.doi.org/10.1016/j.apsusc.2006.12.047.

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Zapol’skii, Viktor A., Jan C. Namyslo, Armin de Meijere e Dieter E. Kaufmann. "Chemistry of polyhalogenated nitrobutadienes, 10: Synthesis of highly functionalized heterocycles with a rigid 6-amino-3-azabicyclo[3.1.0]hexane moiety". Beilstein Journal of Organic Chemistry 8 (23 aprile 2012): 621–28. http://dx.doi.org/10.3762/bjoc.8.69.

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The nitropolychlorobutadienes 3, 4 are valuable building blocks for various amination and successive heterocyclization products. Nucleophilic substitution reactions of the partially protected, bioactive amines 1, 2 with either vinyl, imidoyl or carbonyl chlorides result in the formation of the enamines 11, 12, 13, 16, 25, the amidine 6, and the amides 20, 21, respectively. In the following, cyclization to the highly functionalized pyrazoles 27, 28, pyrimidine 26 and pyridopyrimidine 24 succeeded. Deprotection of 21, 12 and 28 proved to be only partially feasible.

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Cibian, Mihaela, André Bessette, Andrew O'Connor, Janaina G. Ferreira e Garry S. Hanan. "Twofac-tricarbonylrhenium(I) azadipyrromethene (ADPM) complexes: ligand-substitution effect on crystal structure". Acta Crystallographica Section C Structural Chemistry 71, n. 2 (17 gennaio 2015): 122–27. http://dx.doi.org/10.1107/s2053229614027673.

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The crystal structures offac-(acetonitrile-κN)(2-{[3,5-bis(4-methoxyphenyl)-2H-pyrrol-2-ylidene-κN1]amino}-3,5-bis(4-<!?tlsb=0.2pt>methoxyphenyl)-1H-pyrrol-1-ido-κN1)tricarbonylrhenium(I)–hexane–acetonitrile (2/1/2), [Re(C36H30N3O4)(CH3CN)(CO)3]·0.5C6H14·CH3CN, (2), andfac-(2-{[3,5-bis(4-methoxyphenyl)-2H-pyrrol-2-ylidene-κN1]amino}-3,5-bis(4-methoxyphenyl)-1H-pyrrol-1-ido-κN1)tricarbonyl(dimethyl sulfoxide-κO)rhenium(I), [Re(C36H30N3O4)(C2H6OS)(CO)3], (3), at 150 K are reported. Both complexes display a distorted octahedral geometry, with afac-Re(CO)3arrangement and one azadipyrromethene (ADPM) chelating ligand in the equatorial position. One solvent molecule completes the coordination sphere of the ReIcentre in the remaining axial position. The ADPM ligand shows high flexibility upon coordination, while retaining its π-delocalized nature. Bond length and angle analyses indicate that the differences in the geometry around the ReIcentre in (2) and (3), and those found in three reportedfac-Re(CO)3–ADPM complexes, are dictated mainly by steric factors and crystal packing. Both structures display intramolecular C—H...N hydrogen bonding. Intermolecular interactions of the Csp2—H...π and Csp2—H...O(carbonyl) types link the discrete monomers into extended chains.

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Chiacchiera, Stella M., Joaqu�n O. Singh, Jorge D. Anunziata e Juana J. Silber. "Aromatic nucleophilic substitution reactions of 1,2-dinitrobenzene with aliphatic primary amines in n-hexane; catalysis by non-nucleophilic bases". Journal of the Chemical Society, Perkin Transactions 2, n. 8 (1987): 987. http://dx.doi.org/10.1039/p29870000987.

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Singh, Joaquín O., Jorge D. Anunziata e Juana J. Silber. "n–π Electron donor–acceptor complexes. II. Aliphatic amines with dinitrobenzenes". Canadian Journal of Chemistry 63, n. 4 (1 aprile 1985): 903–7. http://dx.doi.org/10.1139/v85-150.

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The interaction of several aliphatic amines as n-donors and dinitrobenzenes (DNB) as π-acceptors has been studied in n-hexane. The formation of electron donor – acceptor (EDA) complexes is proposed to explain the spectroscopic behaviour of the mixtures. The stability constants (Ks) for these complexes have been calculated by an iterative procedure. For a given acceptor, the donor strength of RNH2 > R2NH > R3N was found. This order is explained by considering the role that steric effect may play in the EDA complex formation. On the other hand, the fact that for a given donor Ks follows the order 1,2-DNB > 1,3-DNB > 1,4-DNB, and that 1,2-DNB reacts with primary amines, led to the proposal of orientational complexes. These EDA complexes may be considered intermediates in aromatic nucleophilic substitution reactions.

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Minka, S., e M. Bruneteau. "Isolement et caractérisation chimique des lipopolysaccharides de type R dans une souche hypovirulente de Yersinia pestis". Canadian Journal of Microbiology 44, n. 5 (1 maggio 1998): 477–81. http://dx.doi.org/10.1139/w98-029.

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The lipopolysaccharides LPS I and LPS II, isolated from the hypovirulent EV40 strain of Yersinia pestis, are composed only of type R lipopolysaccharides. This type consists of two forms, a and b, depending on their solubility pattern in a solvent mixture containing varying proportions of chloroform, methanol, hexane, and hydrochloric acid. LPS I consists of one subtype, RIb, while LPS II consists of two subtypes, RIIa and RIIb. Analysis by gel electrophoresis shows that the mass of these lipopolysaccharide forms are in the vicinity of 2000-3000 Da. The RIb and RIIb subtypes, which are found in the majority of lipopolysaccharide I and II fractions, are composed of ketoses and amines that are similar to those occurring in LPS I and LPS II. In contrast, the two subtypes RIIa and RIIb are different both in terms of the composition of lipid A and the extent of its substitution. Certain fractions of RIIa contain only lipid A and 3-deoxy-D-manno-octulosonic acid (KDO), while other fractions of RIIb possess a lipid A, which is not substituted by arabinose. The whole set of these R-type lipopolysaccharide forms are excellent models for the study of the role of the primary structure of the polysaccharide region, and for the effect of lipid A substitution on the biological activity of bacterial lipopolysaccharides.Key words: Yersinia pestis, hypovirulence, lipopolysaccharides, R type.[Journal translation]

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Engering, Josef, Eva-Maria Peters e Martin Jansen. "Synthesen und Kristallstrukturen von Bis(N-lithiumtrimethylsilylamino)- bis(dimethylamino)silan und 1,1-Dichloro-2,4-bis(trimethylsilylamino)- 3,3-bis(dimethylamino)siladiazatitanacyclobutan / Syntheses and Crystal Structures of Bis(N-lithio-trimethylsilylamino)bis(dimethylamino)- silane and 1,1-Dichloro-2,4-bis(trimethylsilylamino)-3,3-bis(dimethylamino)siladiazatitanacyclobutane". Zeitschrift für Naturforschung B 57, n. 9 (1 settembre 2002): 976–82. http://dx.doi.org/10.1515/znb-2002-0902.

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Bis(N-lithio-trimethylsilylamino)bis(dimethylamino)silane (1) is formed in the reaction of silicon tetrachloride with excess hexamethyldisilazane, followed by halogen substitution using two equivalents of LiN(CH3)2, and treatment with two equivalents of n-butyllithium in hexane. 1, found to be dimeric in the solid state, was characterised by single crystal X-ray diffraction (monoclinic, C2/c, a = 1925.2(4), b = 1501.7(2), c = 1389.7(3) pm, β= 101.98(2), Z = 4, C20H60Li4N8Si6), and by solid state and solution NMR spectroscopy and mass spectrometry. Further reaction with titanium tetrachloride (molar ratio 1:1) yields orange crystals of the dimer [TiClf(μ2-NSi(CH3)3)2Si(N(CH3)2)μ2-Cl]2 (2) characterised by single crystal X-ray diffraction (triclinic, P1, a = 942.1(4), b = 991.7(4), c = 1222.6(5) pm, α= 90.12(1), β= 94.42(2), γ= 107.64(1)°, Z = 1, C20H60Cl4N8Si6Ti2)

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Ollivier, Jean, Frédéric Lecornué e Florence Charnay-Pouget. "π-Allyl Palladium Complexes as Efficient and Powerful Alternative for Nucleophilic Substitution on Bicyclo[3.1.0]hexane Sulfonates: Regio-, Chemo- and Stereoselectivity". Synlett 2006, n. 9 (giugno 2006): 1407–9. http://dx.doi.org/10.1055/s-2006-939716.

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Leigh, William J., Andrey G. Moiseev, Eugenie Coulais, Farahnaz Lollmahomed e Mohammad S. Askari. "Substituent effects on silene reactivity — Reactive silenes from photolysis of phenylated tri- and tetrasilanes". Canadian Journal of Chemistry 86, n. 12 (1 dicembre 2008): 1105–17. http://dx.doi.org/10.1139/v08-165.

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Laser flash photolysis of 2-phenylheptamethyltrisilane (5d), 2,2-diphenylhexamethyltrisilane (5e), and phenyltris(trimethylsilyl)silane (5f) in hexane and acetonitrile solution affords strong, long-lived transient absorptions centered in the 440–470 nm range, which are assigned to the transient silenes formed via [1,3]-trimethylsilyl migration into the ortho-position of a phenyl ring on the basis of their UV–vis spectra and kinetic data for their reactions with methanol (MeOH), acetic acid (AcOH), acetone, 2,3-dimethyl-1,3-butadiene (DMB), carbon tetrachloride (CCl4), and oxygen. The silene derivatives are formed along with the corresponding silylenes (SiMePh, SiPh2, and Si(SiMe3)Ph, respectively) upon photolysis of these compounds in solution, and indeed, weak, short-lived transient absorptions assignable to the silylenes can also be detected in laser photolysis experiments with the three compounds in hexane, superimposed on the much more prominent absorptions due to the silenes. The silylene absorptions are quenched by MeOH and triethylsilane (Et3SiH) with absolute rate constants varying over the narrow ranges of (1.1–1.8) × 1010 (mol/L)–1 s–1 and (2.5–3.6) × 109 (mol/L)–1 s–1, respectively, in excellent agreement with previously reported values for SiPh2 and SiMe2 under the same conditions. The kinetic data obtained for the silenes are compared to previously reported data for the reactions of the same substrates with the related silenes (6a–6c) formed by photolysis of pentamethylphenyl-, 1,1,1,2-tetramethyl-2,2-diphenyl-, and 1,1,1-trimethyl-2,2,2-triphenyldisilane (5a–5c, respectively) under similar conditions. The comparison provides the first systematic, quantitative assessment of the stabilizing effects of trialkylsilyl substitution at the silenic silicon atom in silene derivatives.Key words: silene, silylene, trisilane, tetrasilane, kinetics.

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25

Budiarti, Mery, Anshary Maruzy, Nengah Ratri RK e Endang Brotojoyo. "Aktivitas Antimalaria Daun Gempol (Nauclea orientalis (L.) L) terhadap Plasmodium falciparum". Media Penelitian dan Pengembangan Kesehatan 30, n. 2 (30 settembre 2020): 135–46. http://dx.doi.org/10.22435/mpk.v30i2.3044.

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Abstract The use of gempol (Nauclea orientalis (L.) L) stem as a malaria medicine has been empirically and scientifically proven. This condition encourages exploitation which can lead to scarcity of raw materials. Substitution of plant parts as raw material for medicine is one of the innovations that can be done for the sustainability of the plant species. Leaves are one part of the plant that is often used as a raw material for medicine. The selection of leaves as the main ingredient has many advantages over other parts. Until now, research related to the antimalarial bioactive potential of N. orientalis (L.) L leaves has not been published. Therefore, this study aimed to explore the potential for leaf antimalarial activity as an alternative to substitution of stem parts. The leaf extract of N. orientalis (L.) L was prepared by maceration method with 96% ethanol then fractionation was carried out in stage using hexane, ethyl acetate and methanol as solvents. Antimalarial activity testing was carried out in vitro against Plasmodium falciparum 3D7 and Thin Layer Chromatography (TLC) for screening phytochemical compounds in each sample. The hexane solvent was known to produce the most optimum extract by with a yield of 20%. The antimalarial activity of the hexane (IC 50 1.93 μg/mL) and methanol (IC 3.91 μg/ mL) fractions were classified as ‘very active’ and had a tendency to be able to compete with chloroquine phosphate activity. The potential for antimalarial activity in both samples was influenced by the content of alkaloids, steroids, flavonoids and terpenoids which had been developed as active ingredients for malaria drugs. The results of this study indicate that the leaves of Nauclea orientalis (L.) L have the potential to be developed as an alternative to malaria medicine. Abstrak Pemanfaatan batang gempol (Nauclea orientalis (L.) L) sebagai obat malaria telah terbukti secara empiris dan ilmiah. Kondisi tersebut mendorong terjadinya eksploitasi hingga dapat berujung pada kelangkaan bahan baku. Substitusi bagian tumbuhan sebagai bahan baku obat merupakan salah satu inovasi yang dapat dilakukan untuk keberlanjutan hidup spesies tumbuhan tersebut. Daun merupakan salah satu bagian tumbuhan yang sering digunakan sebagai bahan baku obat. Pemilihan daun sebagai bahan utama memiliki banyak kelebihan dibandingkan bagian lainnya. Penelitian terkait potensi bioaktif antimalaria daun Nauclea orientalis (L.) L hingga saat ini belum dipublikasikan. Oleh karena itu, penelitian ini bertujuan untuk menggali potensi aktivitas antimalaria daun sebagai alternatif subtitusi bagian batang. Ekstrak daun Nauclea orientalis (L.) L disiapkan dengan metode maserasi dengan etanol 96%, kemudian dilakukan fraksinasi cair-cair bertingkat menggunakan pelarut heksana, etil asetat, dan metanol. Pengujian aktivitas antimalaria dilakukan secara in vitro terhadap Plasmodium falciparum 3D7 dan Kromatografi Lapis Tipis (KLT) untuk penapisan senyawa fitokimia pada masingmasing sampel. Pelarut heksana diketahui menghasilkan ekstrak paling optimum dengan rendemen 20%. Aktivitas antimalaria fraksi heksana (IC 50 1,93 µg/mL) dan metanol (IC 3,91 µg/mL) yang tergolong dalam kategori ‘sangat aktif, serta memiliki kecenderungan mampu bersaing dengan aktivitas klorokuin fosfat. Potensi aktivitas antimalaria pada kedua sampel tersebut dipengaruhi oleh kandungan senyawa alkaloid, steroid, flavonoid dan terpenoid yang telah banyak dikembangkan sebagai bahan aktif obat malaria. Hasil penelitian ini menunjukkan bahwa daun Nauclea orientalis (L.) L berpotensi untuk dikembangkan sebagai alternatif obat malaria.

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26

Ido, Atsushi, Atsushi Hashizume, Takashi Ohta, Takayuki Takahashi, Chiemi Miura e Takeshi Miura. "Replacement of Fish Meal by Defatted Yellow Mealworm (Tenebrio molitor) Larvae in Diet Improves Growth Performance and Disease Resistance in Red Seabream (Pargus major)". Animals 9, n. 3 (19 marzo 2019): 100. http://dx.doi.org/10.3390/ani9030100.

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Yellow mealworm (Tenebrio molitor) larvae are a potential alternative animal protein source for sustainable aquaculture. However, reports on the successful complete substitution of fish meal with yellow mealworm larvae in an aquaculture diet have been limited. In this study, we conducted a feeding trial with red seabream (Pagrus major) being fed diets with partial or complete replacement of fish meal with yellow mealworm larvae defatted with a hexane–ethanol solution. Feed intake in red seabream increased in accordance with yellow mealworm larvae inclusion, and diets including 65% defatted mealworm larvae (complete replacement of fish meal) showed significant growth promotion. The addition of the oil fraction from mealworm larvae to diets resulted in growth reduction, despite meeting the nutritional requirements of red seabream. Moreover, the survival rate of red seabreams fed diets with partial replacement of fish meal with mealworm larvae was significantly higher in a challenge test with pathogenic Edwardsiella tarda bacteria. The present study demonstrated that yellow mealworm larvae are not merely an alternative animal protein, but have potential as functional feed ingredients for aquaculture production.

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27

Marliyana, Surya Dewi, Sayekti Wahyuningsih e Nisa Nur Hayati. "Synthesis of Cardanol-Based Acetaldehyde Novolac Resin from Cashew Nut Shell Liquid (CNSL)". Jurnal Kimia Sains dan Aplikasi 25, n. 9 (24 novembre 2022): 316–21. http://dx.doi.org/10.14710/jksa.25.9.316-321.

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Abstract (sommario):

Polymers are currently in the limelight. Phenolic resin is one of the polymer products obtained from the polymerization process, either from natural or synthetic sources. One of the natural compounds that can be applied to polymers is cardanol. This study aimed to synthesize cardanol-based acetaldehyde novolac resin from Cashew Nut Shell Liquid (CNSL). Isolation of cardanol from CNSL was done by liquid-liquid extraction method with acetone and purified by gravity column chromatography in a mixture of n-hexane and ethyl acetate in a ratio of 9:1. HPLC analysis showed that cardanol compounds had aliphatic chains with different levels of saturation and the yield was 18.48%. The cardanol-acetaldehyde novolac resin was synthesized through a condensation polymerization reaction with a cardanol-acetaldehyde mole ratio (1:0.5), using HCl as a catalyst. FTIR and 1H-NMR analysis were employed to identify the novolac resin structure. The product was a brownish-orange solid with a yield of 12.80 mg (40%) and followed ortho-ortho substitution. Cardanol is one of the natural phenol sources that might be utilized to manufacture novolac resins.

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28

Krow, Grant R., Seth B. Herzon, Guoliang Lin, Feng Qiu e Philip E. Sonnet. "Complex-Induced Proximity Effects. Temperature-Dependent Regiochemical Diversity in Lithiation−Electrophilic Substitution Reactions ofN-BOC-2-Azabicyclo[2.1.1]hexane. 2,4- and 3,5-Methanoprolines". Organic Letters 4, n. 18 (settembre 2002): 3151–54. http://dx.doi.org/10.1021/ol026509b.

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29

Kim, Hak Sung, Michihiro Ohno, Bin Xu, Hea Ok Kim, Yongseok Choi, Xiao D. Ji, Savitri Maddileti, Victor E. Marquez, T. Kendall Harden e Kenneth A. Jacobson. "2-Substitution of Adenine Nucleotide Analogues Containing a Bicyclo[3.1.0]hexane Ring System Locked in a Northern Conformation: Enhanced Potency as P2Y1Receptor Antagonists". Journal of Medicinal Chemistry 46, n. 23 (novembre 2003): 4974–87. http://dx.doi.org/10.1021/jm030127+.

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30

KEGLEVICH, G., L. TOEKE, A. KOVACS, K. UJSZASZY, G. ARGAY, M. CZUGLER e A. KALMAN. "ChemInform Abstract: Ring Transformation of Phosphorus Containing Heterocycles. Part 12. P- Substituted 3-Phosphabicyclo(3.1.0)hexane 3-Oxides from Diastereoselective Substitution at Phosphorus." ChemInform 25, n. 52 (18 agosto 2010): no. http://dx.doi.org/10.1002/chin.199452204.

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31

Neugebauer, Peter, Uwe Klingebiel e Mathias Noltemeyer. "Silylfurane und Bis(silyl)butadiine -Synthese, Lithiumderivate, Kristallstrukturen/ Silylfurans and Bis(silyl)butadiynes - Synthesis, Lithium Derivatives, Crystal Structures". Zeitschrift für Naturforschung B 55, n. 10 (1 ottobre 2000): 913–23. http://dx.doi.org/10.1515/znb-2000-1005.

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Abstract (sommario):

AbstractFuran reacts with BuLi and halosilanes to give mono- (1, 5, 7), bis- (2, 6), tris- (3), and tetrakis(2-furanyl)silanes (4); (Fu-R; R = SiMe2Cl (1), SiisoPr2F (5), SitBu2F (7); Fu-R-Fu; R = SiMe2 (2), SiisoPr2 (6); Fu3SitBu (3), Fu4Si (4)), 2,5-Bis(silyl)furans (8, 9) are obtained in the reaction of dilithiated furan and fluorosilanes in a molar ratio 1:2 (R-Fu-R; R = SiisoPr2F (8), SitBu2F (9), 1,4-Bis(di-tert-butylfluorosilyl)butadiyne (10) is formed from furan four equivalents of BuLi, and two equivalents of F2SitBu2. 10 reacts with KOH to give tBu2(OH )Si-C =C -C =C-SitBu2OH (11). Substitution of the fluorine atoms of 5 and 7 by a NH2 group occurs with MNH2 (M = Li, Na). 12 and 13 are obtained. The reaction of 13 with BuLi and tBu2SiF2 leads to the formation of FuSitBu2NHSitBu2F (14) and tBu2Si(NH-SitBu2Fu)2 (15). The lithium derivative of 14 crystallizes as monomer from THF as FuSitBu2N(LiTHF2)SitBu2F and as a dimer containing a four-membered ring (16) from n-hexane (FuSitBu2NSitBu2LiF)2 (17). The crystal structures of 4, 10, 16,17 have been determined.

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32

Park, Hanna, Byeongho Kim, Kyoung-Chan Park, Yesun Kim, Taehee Kim, Min-Seok Kim, Sun-Eun Choi e Se-Yeong Park. "Biological Activities in Sapwood and Heartwood Extractives from Paulownia tomentosa". Forests 14, n. 11 (31 ottobre 2023): 2171. http://dx.doi.org/10.3390/f14112171.

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Abstract (sommario):

Paulownia tomentosa is a representative deciduous tree in South Korea. After 10 years of growth, its wood can be used to make various products through chemical modifications, such as impregnation with a polymer, substitution with chemicals, and physical compression. However, research on the biological resistance of the sapwood and heartwood parts of P. tomentosa xylem is lacking. To ensure the complete utilisation of Paulownia wood, this study aimed to collect baseline data on the necessity of xylem extraction before chemical modification to enhance wood porosity. First, we assessed the decay and termite resistance of sapwood and heartwood blocks. Furthermore, we evaluated the anti-microbial effect of sapwood and heartwood extracts after solvent fractionation. Quantitative and qualitative analyses of the active substances of the fractions with anti-microbial activity were also conducted. The hexane and chloroform solvent fractions of sapwood and heartwood extracts showed fungal resistance against Trametes versicolor and Fomiptosis palustis. Paulownin and sesamin were the main compounds showing anti-microbial activity, and their content in the extracts varied, depending on the wood part. These results provide valuable data for advancing research on porous wood materials and the utilisation of xylem-derived active compounds from Paulownia wood.

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33

Roacho, Robinson I., Alejandro Metta-Magaña, José L. Belmonte-Vázquez, Eduardo Peña-Cabrera e Keith H. Pannell. "Formation of 8-RS-BODIPYs via direct substitution of 8-MeS-BODIPY by RSH (R = Et, Pr, Bu, tBu, n-C12H25, C6H5, p-MeC6H4, p-MeOC6H4, and 2,6-Me2C6H3)". Canadian Journal of Chemistry 94, n. 3 (marzo 2016): 234–39. http://dx.doi.org/10.1139/cjc-2015-0303.

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Abstract (sommario):

Reactions between 8-RS-BODIPY (R = Me, 1) and alkyl and aryl thiols were readily accomplished in dichloromethane to provide a synthetic pathway to a range of new 8-organothio-BODIPYs in good yield. The new alkyl 8-RS-BODIPYs (R = Et, 2; Pr, 3; Bu, 4; tBu, 5; n-dodecyl, 6) exhibit absorption and emission properties essentially unchanged from those of 1 whereas the arylthio analogs (R = Ph, 7; 2,6-Me2C6H3, 8; p-MeC6H4, 9; p-MeOC6H4, 10) exhibit no fluorescence with the exception of 7, and then only in hexane. In common with other related 8-substituted BODIPYs, the new 8-alkylthio-BODIPY dyes show decreasing fluorescence intensity as solvent polarity increases. Compounds 2, 3, 7, and 8 were characterized via single-crystal X-ray analysis; the alkyl derivatives 2 and 3 exhibited planar BODIPY cores with co-planar organothio- substituents whereas the aryl derivatives exhibited both BODIPY core deformation and significant twisting about the S–C (8) bond removing co-planarity between the aryl group and the distorted BODIPY core. These deformations coincide with the significantly reduced emission properties.

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34

Della, EW, GM Elsey e G. Skouroumounis. "Rearrangement of Substituted Bicyclo[2.1.1]hex-2-yl Mesylates Under Solvolytic Conditions". Australian Journal of Chemistry 43, n. 7 (1990): 1231. http://dx.doi.org/10.1071/ch9901231.

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Abstract (sommario):

When heated in formic acid, methyl 2-mesyloxybicyclo[2.1.1]hexane-2-carboxylate (3) ionizes significantly faster than expected and yields the rearranged isomer (6) essentially quantitatively. The latter, on the other hand, solvolyses at a much reduced rate. These data are interpreted as evidence for the presence in the ester of a favourable mesomeric interaction which largely offsets an otherwise destabilizing inductive effect when the ester is attached to a carbocationic centre. The corresponding cyano mesylates (8) and (29) were found to behave in an analogous manner when exposed to the solvolytic conditions. Heating the related acid mesylate (25) in an aqueous medium leads to the 1,2 hydroxy acid (24), whereas its sodium salt (26) is considerably more reactive and gives the 2,2 hydroxy acid (11). These observations are rationalized on the basis of the greatly enhanced ability of the COO- group relative to a COOH to stabilize an adjacent positively charged centre. The methyl substituent is also found to exert a profound effect on the nature of the solvolysis products. In hot formic acid, for example, 1-methylbicyclo[2.1.1]hex-2-yl mesylate (31) produces the formate (32) in which the substitution pattern is retained. Under milder conditions, however, the ester (31) solvolyses with rearrangement to give the 2,2 formate (33).

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35

Dominguez, Carmen, Lourdes Prieto, Matthew J. Valli, Steven M. Massey, Mark Bures, Rebecca A. Wright, Bryan G. Johnson et al. "Methyl Substitution of 2-Aminobicyclo[3.1.0]hexane 2,6-Dicarboxylate (LY354740) Determines Functional Activity at Metabotropic Glutamate Receptors: Identification of a Subtype Selective mGlu2 Receptor Agonist". Journal of Medicinal Chemistry 48, n. 10 (maggio 2005): 3605–12. http://dx.doi.org/10.1021/jm040222y.

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36

Ginting, Mimpin. "Synthesis of 2-(4-Allyl-2-Methoxy Phenoxy)-N,N-Bis(2- Hydroxyethyl) Acetamide from the Transformation of Eugenol Isolated from Clove Oil". Journal of Chemical Natural Resources 1, n. 1 (28 febbraio 2019): 31–39. http://dx.doi.org/10.32734/jcnar.v1i1.832.

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Abstract (sommario):

Eugenol as the main component of clove oil has been isolated through NaOH salting procedure followed by H2SO4hydrolysis, n-hexane partitioning and purification with vacuum distillation. 71% (v/v) eugenol was produced with purity of 97.70% based on gas chromatography analysis. 2-(4-allyl-2-methoxy phenoxy)-N,N-bis(2-hydroxyethyl) acetamide compound has the potential as antibacterial or substances for medicine in pharmaceutical can be synthesized from eugenol isolated through alkoxylation, esterification and followed by amidase. Alkoxylation was done using Williamson method through NaOH transformation of hydroxyl functional group in eugenol to form sodium eugenolate then with α-monochloroacetate substitution in reflux condition, eugenyl acetate was produced. The acid produced was extracted with ether/Na2CO3, followed by recrystallization using hot water and produced 70.52% solid form. Eugenyl acetate esterification with methanol in benzene solvent with H2SO4 catalyst in reflux condition produced methyl eugenol acetate liquid with 81.36% of yield. Amidase of methyl eugenol acetate with diethanolamine and sodium methoxide catalyst with methanol solvent in reflux condition. After purification, 2-(4-allyl-2-methoxy phenoxy)-N,N-bis(2-hydroxyethyl) acetamide compound in solid form is produced with 72.99% yield. Eugenol isolated, eugenyl acetate and methyl eugenol acetate had their structures analyzed with FT-IR spectroscopy while 2-(4-allyl-2-methoxy phenoxy)-N,N-bis(2-hydroxyethyl) acetamide compound was analysed using FT-IR and H1-NMR.

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37

Kaur, Gunpreet, Vikas Gupta, R. G. Singhal e Parveen Bansal. "Isolation and Characterization of Stigmasterol from Fritillaria roylei". Biology, Medicine, & Natural Product Chemistry 9, n. 2 (16 novembre 2020): 77–80. http://dx.doi.org/10.14421/biomedich.2020.92.77-80.

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Abstract (sommario):

Fritillaria roylei (Kshirakakoli) is the threatened species of “Ashtwarga” group suffers lot of confusion for identification & authentification in Ayurvedic system of medicine. Due to lack of natural sources and insufficient availability of kshirakakoli, chances of adulteration and substitution increases which in turn leads to loss of faith of people in herbal drugs. Thus for identification and differentiation, quality standardization and quality assurance of kshirakakoli containing herbal formulations there is a need to isolate chemical marker compound using advanced analytical techniques. The methanol extract of root samples of plant was prepared and phytochemical screening was performed. Marker compound was isolated from the extract using column chromatography. Single compound having Rf value 0.31 was isolated with TLC by using mobile phase n-hexane: ethyl acetate: formic acid (8:2:0.1 v/v/v) and purified by re-crystallization with methanol. Isolated compound was further characterized by using melting point and spectral analysis. The methanol extract was dark brown in color and showed the presence of steroids, amino acids and flavonoids. The isolated compound was found to be white crystalline powder with melting point range of 167-169°C. Spectral analysis confirmed the presence of Stigmasterol. In present study stigmasterol was isolated for the first time and can be used as chemical marker for identification and differentiation of the plant from its substitutes.

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38

Vakhitova, L. M., N. A. Taran, V. I. Bessarabov, R. A. Vakhitov, G. F. Rayenko e A. F. Popov. "Rheologically improved microemulsion for deactivation of simulants of blister and nerve agents". Voprosy Khimii i Khimicheskoi Tekhnologii, n. 6 (dicembre 2023): 44–52. http://dx.doi.org/10.32434/0321-4095-2023-151-6-44-52.

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Abstract (sommario):

The efficiency of decontamination of blister and nerve agents was studied using the example of nucleophilic decomposition of paraoxone (O,O-diethyl-O-4-nitrophenyl phosphate) and oxidation of methylphenyl sulfide. Hydrogen peroxide solutions in an oil-in-water microemulsion containing synthetic nanoclay Laponite EP and polyvinylpyrrolidone polymer were studied as reactive decontamination systems. The base of the microemulsion consisted of an aqueous phase, a codetergent (isopropanol), oil (hexane), with a variation of detergent (cetylpyridinium chloride, sodium dodecyl sulfate, and Triton X-100). It was shown that the solubility of paraoxone and methylphenyl sulfide in the studied microemulsions increases by an average of 100 times or more compared to the solubility in water, and the substrate binding constants are 2–3 times higher than the binding constants in similar microemulsion media. It was found that the presence of nanoclay in the microemulsion provides a catalytic effect, i.e. an increase in the rate of decomposition of paraoxone and methylphenyl sulfide by at least 2 times. In addition, nanoclay thickens the microemulsion and, together with the polymer, increases the viscosity of the reaction medium. The determined kinetic parameters of decontamination and solubility of substrates allow us to conclude that the use of the investigated microemulsion system provides an acceleration of nucleophilic substitution and oxidation reactions by 150–350 times compared to the reaction rate in water.

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39

Arnold, Deirdre I., F. Albert Cotton, John H. Matonic e Carlos A. Murillo. "Substitution on a methyl group of an acetylacetonate ligand: synthesis and structural characterization of oxobis[6-(phenylamino)hexane-2,4-dionato-O,O′]vanadium(IV), VO(Phad)2". Chem. Commun., n. 18 (1996): 2113–14. http://dx.doi.org/10.1039/cc9960002113.

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40

Jean-Baptiste, KANGAH Niameke, KODJO Charles Guillaume, OUATTARA Zana Adama, KABLAN Ahmont Landry Claude, DIBI Konan Jacques, KOUAME Bosson Antoine e Ziao Nahosse. "Synthesis, Characterization and Biological Evaluation of New Series of Schiff Bases Derived from Hexamethylenediamine as Potential Antibacterial and Antifungal Agents". IRA-International Journal of Applied Sciences (ISSN 2455-4499) 7, n. 2 (27 maggio 2017): 69. http://dx.doi.org/10.21013/jas.v7.n2.p3.

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Abstract (sommario):

<div>We report herein synthesis, characterization and antimicrobial activity of four Shiff bases derived from hexamethylenediamine. Substitution of a nitro group on each aromatic ring in ortho, meta or para positions of N,N'-bis(phenylmethyl)hexane-1,6-diimineallowed to have a homogeneous series of positional isomers. These four symmetric diimine Schiff bases were characterized by conventional spectrometry methods (NMR, IR, MS), then tested against Gram-positive and Gram-negative bacterial strains. Among them, compounds 1b, 1c, 1d were found to be active against bacterial strain Staphylococcus aureus CIP with MIC value of 375μg/ ml, 187.5μg /ml and 375μg /ml respectively. Candida Albicans fungal strain showed resistance to all synthesized Schiff base compounds, butin the other hand, Candida glabrata has been sensitive to all compounds with MIC of 1500μg/ ml and one more time except 1a.</div>

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41

Ahmed, Tahseen, Ambreen Huma, Munnawar Rasheed, Mirza Tasawer Baig, Syed Shafqat Rizvi, Sadaf Gul e Sadaf Ibrahim. "Pharmacognostic Standardization and Phycochemical Evaluation of Green Seaweed Codium Flabellatum". Journal of Hunan University Natural Sciences 49, n. 6 (30 giugno 2022): 111–19. http://dx.doi.org/10.55463/issn.1674-2974.49.6.12.

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Abstract (sommario):

Codium flabellatum, a green seaweed belonging to the Codiaceae family, is renowned for its therapeutic effects, which may be attributed to the number of bioactive compounds it contains. Pharmacognostic standardization and phytochemical evaluation establish the identification of a specific plant and are valuable for authentication and the prevention of adulteration and substitution. In the current study, pharmacognostic studies were conducted through microscopic and macroscopic observations, and three different extracts (ethanol, ethyl acetate, and n-hexane) of Codium flabellatum were subjected to preliminary phytochemical tests for carbohydrates, lipids, tannins, flavonoids, gelatin, and proteins; a physiochemical test was also performed according to WHO guidelines. Macroscopic study showed that Codium flabellatum was green in color, with a thallus 25–30 cm in height and 1–3 cm in width, with a finger-like projection and a spherical air bladder. Microscopic evaluation revealed clavate utricles, 190–260 µm broad, cylindrical in shape, and 750–850 µm long when young, with one or two long hairs just below their tips. Gametangia were found laterally on the utricles, 300–400 µm in length and 100–175 µm in width. The different extracts revealed that all classes of compounds were present. Physiochemical tests showed that the highest extractive values were for chloroform and methanol at 96% and 80.95%, respectively. The moisture and ash content were 94.55% and 84.15%, respectively. This study of Codium flabellatum will contribute to authenticating its identity and will also help to evaluate its nutritional potential.

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42

Brodie, Nancy M. J., e Anthony J. Poë. "Systematic substitution kinetics of the clusters Ru3(CO)11L and Ru3(CO)10L2 (L = P-donor ligands): The unimolecular path". Canadian Journal of Chemistry 73, n. 7 (1 luglio 1995): 1187–95. http://dx.doi.org/10.1139/v95-146.

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The kinetics have been studied of the substitution reactions of Ru3(CO)11L and Ru3(CO)10L2 (L = PCy3 (Cy = C6H11), P-n-Bu3, P(p-MeOC6H4)3, P(p-ClC6H4)3, P(OPh)3 and etpb (P(OCH2)3CEt) with AsPh3 or various P-donor nucleophiles, L′, in hexane. The reactions proceed through both [L′]- independent (CO dissociative) and [L′]-dependent (associative) paths. The values of the rate constants, k1, for the dissociative path for Ru3(CO)11L can be combined with other published data and are found to fit well to the equation: log k1 = α + βLδL + γLθL (βL and γL are constants that define how sensitive the values of log k1 are to Bodner's electronic parameter, δL, and to Tolman's steric parameter, θL, respectively.) Values of (βL and γL are both positive, increasing electron donicity and increasing size of L both leading to increased rates. The steric effect is more important and accounts for ca. 60% of the decrease in the free energies of activation. The effects, on the fit and on the values of βL and γL, of using different electronic (Bartik's χ values) and steric (Brown's ER values) parameters are examined and found to be small, and the question of which goodness-of-fit parameters should be used is considered. The kinetic effects of the substituents are only a small (ca. 20%) perturbation on the average free energies of activation, and the steric effect shows that use is made of only a few percent of the available ligand–ligand repulsion energy in accelerating the reactions. The second-order reactions of M3(CO)11L with Mc3NO (M = Ru or Os) also fit an equation analogous to that given above and the values of βL and γL obtained for these assisted CO displacement reactions are compared with those for the unimolecular, unassisted, CO dissociation. Unassisted reactions of the Ru3(CO)10L2 clusters show values of βL and γL that are closely similar to those for Ru3(CO)11L, but published data for CO dissociative reactions of some Ru3(CO)9L3 clusters lead to much larger positive values of βL and a large inverse steric effect, i.e., rates actually decrease substantially with increasing substituent size after electronic effects are allowed for. This effect is accounted for in terms of the different natures of the Ru3(CO)8L3 intermediates. Keywords: metal carbonyls, ruthenium, clusters, kinetics, substituent effects.

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Bishimbayeva, G. K., A. M. Nalibayeva, S. A. Saidullayeva, A. K. Zhanabaeva, A. Bold e Y. N. Abdikalykov. "Synthesis and study of the extraction properties ofnew phosphorus-containing extractants of heavy metals". Proceedings of Universities. Applied Chemistry and Biotechnology 11, n. 3 (7 ottobre 2021): 340–48. http://dx.doi.org/10.21285/2227-2925-2021-11-3-340-348.

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Abstract: The metallurgical industry is one of the cornerstones of contemporary chemical science and industry and it is developing rapidly in many countries. The widespread introduction of metal extraction, concentration and separation as the most productive methods entails the need to search for and create new effective metal extractants. Among the compounds, suitable for use as extractants, the most widespread are organic phosphites and phosphates, which allow performing extraction processes with good selectivity and efficiency. The purposes of this article include finalizing the optimal synthesis conditions and developing larger batches of 4,5-dimethyl-2-(2,2,2-trifluoroethoxy)-1,3,2-dioxaphospholane and 5,5-dimethyl-2-(2,2,3,3,4,4,5,5- octafluoropentoxy)-1,3,2-dioxaphosphorinane, and study of the extraction properties of the obtained phosphorus- containing heterocyclic compounds in the separation of uranium from the commercial desorbate. The synthesis of new representatives of the indicated polyfluoroalkylated five- and six-membered heterocyclic phosphorus compounds was conducted using the interaction of 2-chloro-1,3,2-dioxaphospholane with trifluoroethanol and the substitution–cyclization reaction of polyfluoroalkylated dichlorophosphite with 2,2-dimethyl- 1,3-propanediol. Reactions easily proceed in triethylamine–hexane or pyridine–diethyl ether systems at temperatures ranging between minus ten to room temperature, with the output of target heterocycles of 53–57%. The studies of extraction properties of synthesized poly-fluorinealkylated dioxaphospholane and dioxaphosphorinane show that the use of these phosphorus-containing heterocyclic compounds as extractants allows extracting a technically valuable metal up to 12.4 and 15.2%, respectively. Nitric and sulfuric acid solutions of commercial desorbate of hydrometallurgical production in Kazakhstan were used as feedstock in the extraction process.

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Szczęsna, Weronika, Marta Tsirigotis-Maniecka, Łukasz Lamch, Lilianna Szyk-Warszyńska, Ewa Zboińska, Piotr Warszyński e Kazimiera A. Wilk. "Multilayered Curcumin-Loaded Hydrogel Microcarriers with Antimicrobial Function". Molecules 27, n. 4 (19 febbraio 2022): 1415. http://dx.doi.org/10.3390/molecules27041415.

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The design of multifunctional microcarriers has attracted significant attention because they combine various functions within a single system. In this study, we developed a set of multilayered hydrogel microcarriers, which were first loaded with chemotherapeutic curcumin (CUR), then, using the layer-by-layer (LbL) technique, coated through a polyelectrolyte shell consisting of chitosan (CHIT) or poly(allylamine hydrochloride) (PAH). As an outer layer with antimicrobial function, newly synthesised alkylene quaternary ammonium salt functionalised polyelectrolytes (A-QAS-PEs) were applied. For this purpose, poly(acrylic acid) (PAA) was decorated with different hydrophobic side chains (n-hexane and n-dodecane side entities) and different degrees of substitution (m) of quaternary ammonium groups (abbreviated as PAA-C(O)O-(CH2)n-N+(CH3)3(m); n = 6, 12; m = 8–14%). The grafting approach of PAA with the alkylene quaternary ammonium salt moiety was performed under mild reaction conditions using Steglich esterification followed by quaternisation. The structure of antimicrobial decorated PAA was confirmed by 1H NMR and FTIR, and the mean diameter of all multifunctional microparticles was characterised by SEM. The viscoelastic properties of the functional layers were studied using quartz crystal microbalance with a dissipation (QCM-D). The release of CUR from the microcarriers was described using a hybrid model, i.e., a combination of first-order kinetics and the Korsmeyer-Peppas model. The antimicrobial activity of functionalised PAA and multilayered CUR-loaded hydrogel microcarriers with quaternary ammonium function was assessed against Staphylococcus aureus and Serratia marcescens by the agar diffusion assay method. Only a limited inhibition zone of PAA was observed, but in the case of both antimicrobial decorated PAA and the corresponding multilayered nanocarriers, the inhibitory activity increase was achieved against both strains of bacteria.

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45

Wächtler, Erik, Robert Gericke, Theresa Block, Birgit Gerke, Rainer Pöttgen e Jörg Wagler. "Compounds of the types Pn(pyS)3 (Pn = P, As, Bi; pyS: pyridine-2-thiolate) and Sb(pyS) x Ph3–x (x = 3–1); molecular structures and electronic situations of the Pn atoms". Zeitschrift für Naturforschung B 76, n. 2 (15 gennaio 2021): 103–18. http://dx.doi.org/10.1515/znb-2020-0171.

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Abstract The compounds Pn(pyS)3 (Pn = P, As, Sb, Bi) were synthesized from the respective chloride (Pn = P, As, Sb) or nitrate (Bi), pyridine-2-thiol (pySH) and triethylamine (NEt3) as a supporting base in THF (P, Sb), CHCl3 (As) or methanol (Bi). Sb(pyS)3 was also obtained from the reaction of SbCl3 with LipyS (prepared in situ) in methanol. The compounds Sb(pyS)2Ph and Sb(pyS)Ph2 were prepared in a one-pot reaction starting from SbCl3 and SbPh3 (1:1 ratio). Upon Cl/pyS substitution, the resulting reaction mixture allows for a facile separation of the products in hot hexane. P(pyS)3 and As(pyS)3 crystallize isostructurally to the reported structure of Sb(pyS)3 with κ-S-bound pyS ligands. These crystal structures feature close Pn···Pn contacts which are most pronounced for the arsenic derivative. Bi(pyS)3 adopts a different molecular structure in the solid state, which features two chelating (κ 2-S,N-pyS) ligands and a κ-S-bound ligand. The presence of N→Bi interactions between the nitrogen atom of the κ-S-pyS ligand and the Bi atom of another molecule renders this structure a polymer chain along the crystallographic b axis with Bi⋅⋅⋅Bi van-der-Waals contacts. The structures of this set of Pn(pyS)3 compounds were also studied in solution using 1H NMR spectroscopy, revealing equivalent pyS ligands in discrete Pn(pyS)3 molecules. The molecular structure of Sb(pyS)Ph2 was optimized by quantum chemical methods, and a comparison with the structures reported for the other Sb/pyS/Ph combinations reveals Sb(pyS)2Ph to feature the strongest Sb···N interactions with the κ-S-pyS ligand. The results of 1H NMR spectroscopic investigations of the compounds Sb(pyS) x Ph3–x (x = 3–0) suggest the Ph protons in ortho position to be incorporated into intramolecular C–H···S contacts for x = 2 and 1. Natural localized molecular orbital (NLMO) calculations were employed in order to gain insights into the electronic situations of the Pn atoms and Pn–R bonds (R = S, C), especially for the effects caused by formal substitution of Pn in the compounds Pn(pyS)3 and the ligand patterns in the compounds Sb(pyS) x Ph3–x (x = 3–0). For the latter series of compounds, the electronic situation of the Sb atom was further studied by 121Sb Mössbauer spectroscopy, providing a correlation between the calculated electron density at Sb [ρ(0)] and the experimentally observed isomer shift δ. The missing link between group 15 and group 13 metal compounds of the type M(pyS)3, compound Al(pyS)3, was synthesized in this work. In the solid state (confirmed crystallographically), the mer isomer of this tris-chelate complex with distorted octahedral Al coordination sphere was found. This coordination mode was confirmed for the solution state (CDCl3) by 1H and 13C NMR spectroscopy at T = −40 °C.

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Nakayama, Katsuyuki, Yuichi Kondo e Koji Ishihara. "A kinetic study of the reactions of dimethyl sulfide bridged tetramethylplatinum(II) and octamethylplatinum(IV) complexes with dimethyl sulfide and bidentate ligands". Canadian Journal of Chemistry 76, n. 1 (1 gennaio 1998): 62–70. http://dx.doi.org/10.1139/v97-203.

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Kinetics for the reactions of [1] [PtIV2Me8 (μ - SMe2 )2] + 2 Me 2S kf<-->kd 2[PtIVMe4 (SMe2 ) 2] [2] [PtII2Me4 (μ - SMe2 )2] + 2 Me 2S kf--> 2[PtIIMe2(SMe2 ) 2 ] and [3] [PtIV2Me8 (μ - SMe2 ) 2 ] + 2NN --> 2 [PtIVMe4 (NN)]+2Me2S where NN = bipy or 4,4'-Me2-bipy, have been studied at various temperatures and pressures. Reaction [3] was shown to consist of the rapid conversion of the dimer to a monomer and the much slower subsequent substitution of the dimethyl sulfide with bidentate ligand NN: [PtIV2Me8 (μ - SMe2 )2] + 2 Me 2S <--> 2 [PtIVMe4 (SMe2 ) 2 ] and [PtIVMe4(SMe2)2] + NN --> [PtIVMe4(NN)] + 2 Me2S The rate constants and activation parameters for the reactions are as follows: kf = 3.16 ± 0.06 M-1 s-1 (25°C), Δ H doubledaggerf= 51.8 ± 1.7 kJ mol-1, Δ S doubledaggerf= -61.0 ± 5.8 J mol-1 K-1, kd = 1.18 ± 0.22 M-1 s-1 (25°C), Δ H doubledaggerd= 65 ± 22 kJ mol-1, Δ S doubledaggerd= -26 ± 73 J mol-1 K-1 for reaction [1] in n-hexane; kf = 6.68 ± 0.06 M-1 s-1 (25°C), Δ H doubledaggerf= 58.0 ± 3.1 kJ mol-1, Δ S doubledaggerf= -34.5 ± 10.5 J mol-1 K-1, Δ V doubledaggerf= -10.7 ± 1.3 cm3 mol-1 for reaction [2] in dichloromethane; k2 = (7.09 ± 1.89) x 10-4 M-1 s-1, Δ H doubledagger2= 95 ± 21 kJ mol-1, and Δ S doubledagger2= 18 ± 70 J mol-1 K-1, Δ V doubledagger2= 9 ± 9 cm3 mol-1 for reaction [3] with bipy, and k1 = (1.10 ± 0.10) x 10-2 s-1, k3/k-1 = (4.33 ± 0.30) x 10-2, and k2 = (6.09 ± 1.35) x 10-4 M-1 s-1 for reaction [3] with 4,4'-Me2-bipy. It was shown that reactions [1] and [2] proceed nucleophilically without any intermediates, and reaction [3] proceeds through a mainly k2 path for NN = bipy and through both k1 and k2 paths for NN = 4,4'-Me2-bipy, without appreciable participation of the direct reaction between the dimer and NN as shown by the following reaction scheme.Key words: octamethylplatinum(IV) dimer, tetramethylplatinum(II) dimer, reaction mechanism, high-pressure kinetics.

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Sundaramurthy, V., I. Eswaramoorthi e N. Lingappan. "The catalytic effect of boron substitution in MCM-41-type molecular sieves". Canadian Journal of Chemistry 82, n. 5 (1 maggio 2004): 631–40. http://dx.doi.org/10.1139/v04-017.

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A series of B-MCM-41 samples has been synthesized with a wide range of boron content (SiO2:B2O3 ratio from 20 to 200), using ethyl silicate ester-40 (ES-40) as the silica source and characterized by XRD, BET, FT-IR, 11B-MAS NMR, SEM, pyridine adsorption, TPDA, and chemical analysis. The interplanar d100 spacing varies from 40 to 45 Å, depending on the Si:B ratio. On calcination, a significant amount of four-coordinated boron is converted into less stable three-coordinated boron, and some boron is removed from the framework. The degree of deboronation increases with an increase of boron content of the sample. The B substitution in the MCM-41 framework results in only weak and mild acid sites. The isomerization of 1-hexene is found to be influenced by the boron content in the framework. The isomerization leads to both a hydrogen shift and skeletal rearrangement. The selectivity ratios of cis-2-hexene to trans-2-hexene and 2-hexene to 3-hexene were found to decrease with an increase of temperature and a decrease of the SiO2:B2O3 ratio of the catalysts. Skeletal isomerization starts at 250 °C, forming secondary products, and increases with an increase of temperature and an increase of boron content of the catalysts. Key words: ES-40, B-MCM-41, deboronation, catalyst characterization, XRD, BET, FT-IR, 11B-MAS NMR, SEM, 1-hexene isomerization, 2-hexene.

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48

Wang, Qian, e Yuichi Kobayashi. "Allylic Substitution on Cyclopentene and -hexene Rings with Alkynylcopper Reagents". Organic Letters 13, n. 23 (2 dicembre 2011): 6252–55. http://dx.doi.org/10.1021/ol202711k.

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49

Maslivetc, Vladimir, Colby Barrett, Nicolai A. Aksenov, Marina Rubina e Michael Rubin. "Intramolecular nucleophilic addition of carbanions generated from N-benzylamides to cyclopropenes". Organic & Biomolecular Chemistry 16, n. 2 (2018): 285–94. http://dx.doi.org/10.1039/c7ob02068f.

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An unusual reaction is described, involving a formal intramolecular nucleophilic substitution of bromocyclopropanes with nitrogen ylides generated in situ from N-benzyl carboxamides. This reaction involves cyclopropene intermediates and allows for the facile preparation of 3-azabicyclo[3.1.0]hexan-2-ones.

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Duczmal, Wojciech, Bogdan Marciniec e Elżbieta Śliwinska. "Substitution of phosphine in the complex [RhCl(cyclooctadiene)(phosphine)] by 1-hexene". Transition Metal Chemistry 14, n. 2 (aprile 1989): 105–9. http://dx.doi.org/10.1007/bf01040601.

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