Статті в журналах: "Amide resonance"

1

Albatany, Mohammed, Susan Meakin, and Robert Bartha. "Brain pH Measurement Using AACID CEST MRI Incorporating the 2 ppm Amine Resonance." Tomography 8, no. 2 (March 9, 2022): 730–39. http://dx.doi.org/10.3390/tomography8020060.

Повний текст джерела

Анотація:

Many pathological conditions lead to altered intracellular pH (pHi) disrupting normal cellular functions. The chemical exchange saturation transfer (CEST) method, known as Amine and Amide Concentration Independent Detection (AACID), can produce image contrast that is predominantly dependent on tissue intracellular pHi. The AACID value is linearly related to the ratio of the 3.5 ppm amide CEST effect and the 2.75 ppm amine CEST effect in the physiological range. However, the amine CEST effect at 2 ppm is often more clearly defined in vivo, and may provide greater sensitivity to pH changes. The purpose of the current study was to compare AACID measurement precision utilizing the 2.0 and 2.75 ppm amine CEST effects. We hypothesized that the 2.0 ppm amine CEST resonance would produce measurements with greater sensitivity to pH changes. In the current study, we compare the range of the AACID values obtained in 24 mice with brain tumors and in normal tissue using the 2 ppm and 2.75 ppm amine resonances. All CEST data were acquired on a 9.4T MRI scanner. The AACID measurement range increased by 39% when using the 2 ppm amine resonance compared to the 2.75 ppm resonance, with decreased measurement variability across the brain. These data indicate that in vivo pH measurements made using AACID CEST can be enhanced by incorporating the 2 ppm amine resonance. This approach should be considered for pH measurements made over short intervals when no changes are expected in the concentration of metabolites that contribute to the 2 ppm amine resonance.

Стилі APA, Harvard, Vancouver, ISO та ін.

2

Piontek, Aleksandra, Elwira Bisz, Błażej Dziuk, Roman Szostak, and Michal Szostak. "Structures and energetic properties of 4-halobenzamides." Acta Crystallographica Section C Structural Chemistry 74, no. 11 (October 23, 2018): 1395–402. http://dx.doi.org/10.1107/s2053229618013463.

Повний текст джерела

Анотація:

The amide bond represents one of the most fundamental functional groups in chemistry. The properties of amides are defined by amidic resonance (nN→π*C=O conjugation), which enforces planarity of the six atoms comprising the amide bond. Despite the importance of 4-halo-substituted benzamides in organic synthesis, molecular interactions and medicinal chemistry, the effect of 4-halo-substitution on the properties of the amide bond in N,N-disubstituted benzamides has not been studied. Herein, we report the crystal structures and energetic properties of a full series of 4-halobenzamides. The structures of four 4-halobenzamides (halo = iodo, bromo, chloro and fluoro) in the N-morpholinyl series have been determined, namely 4-[(4-halophenyl)carbonyl]morpholine, C11H12 XNO2, for halo = iodo (X = I), bromo (X = Br), chloro (X = Cl) and fluoro (X = F). Computations have been used to determine the effect of halogen substitution on the structures and resonance energies. 4-Iodo-N-morpholinylbenzamide crystallized with a significant distortion of the amide bond (τ + χN = 33°). The present study supports the correlation between the Ar—C(O) axis twist angle and the twist angle of the amide N—C(O) bond. Comparison of resonance energies in synthetically valuable N-morpholinyl and N-piperidinyl amides demonstrates that the O atom of the morpholinyl ring has a negligible effect on amidic resonance in the series.

Стилі APA, Harvard, Vancouver, ISO та ін.

3

Glover, Stephen A., Adam A. Rosser та Robert M. Spence. "Studies of the Structure, Amidicity, and Reactivity of N-Chlorohydroxamic Esters and N-Chloro-β,β-dialkylhydrazides: Anomeric Amides with Low Resonance Energies". Australian Journal of Chemistry 67, № 9 (2014): 1344. http://dx.doi.org/10.1071/ch14270.

Повний текст джерела

Анотація:

Density functional calculations have been carried out to determine the properties of the title anomeric amides. At the B3LYP/6-31G(d) level, N-chloro-N-methoxyacetamide 8a is computed to be strongly pyramidal at nitrogen with a long amide bond that is untwisted. N-Chloro-N-dimethylaminoacetamide 9a is completely planar, but its amide bond is still much longer than that in N,N-dimethylacetamide 4. This is a steric, rather than a resonance, effect. COSNAR and a trans-amidation method calculate low resonance energies for both model amides, which is attributed to the combined electronegativity of the heteroatoms at the amide nitrogen and the strong anomeric effect when there is a chlorine substituent on nitrogen. When M06 and ωB97X-D dispersion-corrected density functional methods are used with the expanded 6-311++G(d,p) basis set, the resonance energies of 8a (–34 kJ mol–1) and 9a (–49 kJ mol–1) are in line with the gross electronegativity of the substituent atoms. Unlike other anomeric amides, 8a and 9a are not predicted to undergo HERON reactivity.

Стилі APA, Harvard, Vancouver, ISO та ін.

4

Glover, Stephen, and Adam Rosser. "Heteroatom Substitution at Amide Nitrogen—Resonance Reduction and HERON Reactions of Anomeric Amides." Molecules 23, no. 11 (October 31, 2018): 2834. http://dx.doi.org/10.3390/molecules23112834.

Повний текст джерела

Анотація:

This review describes how resonance in amides is greatly affected upon substitution at nitrogen by two electronegative atoms. Nitrogen becomes strongly pyramidal and resonance stabilisation, evaluated computationally, can be reduced to as little as 50% that of N,N-dimethylacetamide. However, this occurs without significant twisting about the amide bond, which is borne out both experimentally and theoretically. In certain configurations, reduced resonance and pronounced anomeric effects between heteroatom substituents are instrumental in driving the HERON (Heteroatom Rearrangement On Nitrogen) reaction, in which the more electronegative atom migrates from nitrogen to the carbonyl carbon in concert with heterolysis of the amide bond, to generate acyl derivatives and heteroatom-substituted nitrenes. In other cases the anomeric effect facilitates SN1 and SN2 reactivity at the amide nitrogen.

Стилі APA, Harvard, Vancouver, ISO та ін.

5

Zeimaran, Ehsan, Sobhan Bahraeian, Taravat Ghanbari, Sara Pourshahrestani, and Hussin Mohd Nor. "Synthesis and Characterization of Supramolecular Elastomers from Polyacids Composed of Vegetable Oils." Advanced Materials Research 747 (August 2013): 505–8. http://dx.doi.org/10.4028/www.scientific.net/amr.747.505.

Повний текст джерела

Анотація:

Supramolecular elastomers were synthesized using vegetable oil materials namely palm acid oil (PAO) and sunflower oil (SFO). The oils were first epoxidized using formic acid and hydrogen peroxide. The epoxidized oils and adipic acid were then reacted to make polyacids, mainly triacid. Finally, diethylenetriamine (DETA) was added to polyacid to yield fatty amide and a polycondensation with urea performed to achieve the desired elastomers. The synthesized materials were characterized by using Fourier Transform Infrared (FTIR), Nuclear Magnetic Resonance (NMR) and Thermogravimetric Analyzer (TGA) in order to determine structure, type of bonding and thermal stability. The spectrums revealed that the synthesized fatty amides are contained amide groups that correctly formed from reaction of amine groups of DETA and acid functionality of polyacids. Moreover, the resulted structures showed the formation of multiple hydrogen-bonding in the elastomers. TGA thermograms clearly indicated good thermal stability of the elastomers to 500 °C.

Стилі APA, Harvard, Vancouver, ISO та ін.

6

Nagae, Haruki, Takahiro Hirai, Daiki Kato, Shusei Soma, Shin-ya Akebi, and Kazushi Mashima. "Dinuclear manganese alkoxide complexes as catalysts for C–N bond cleavage of simple tertiary N,N-dialkylamides to give esters." Chemical Science 10, no. 10 (2019): 2860–68. http://dx.doi.org/10.1039/c8sc05819a.

Повний текст джерела

Анотація:

Amide bonds are stable due to the resonance between the nitrogen lone pair and the carbonyl moiety, and therefore the chemical transformation of amides, especially tertiary amides, involving C–N bond fission is considered one of the most difficult organic reactions, unavoidably requiring harsh reaction conditions and strong acids or bases.

Стилі APA, Harvard, Vancouver, ISO та ін.

7

McVicar, Nevin, Alex X. Li, Daniela F. Gonçalves, Miranda Bellyou, Susan O. Meakin, Marco AM Prado, and Robert Bartha. "Quantitative Tissue Ph Measurement during Cerebral Ischemia Using Amine and Amide Concentration-Independent Detection (AACID) with MRI." Journal of Cerebral Blood Flow & Metabolism 34, no. 4 (February 5, 2014): 690–98. http://dx.doi.org/10.1038/jcbfm.2014.12.

Повний текст джерела

Анотація:

Tissue pH is an indicator of altered cellular metabolism in diseases including stroke and cancer. Ischemic tissue often becomes acidic due to increased anaerobic respiration leading to irreversible cellular damage. Chemical exchange saturation transfer (CEST) effects can be used to generate pH-weighted magnetic resonance imaging (MRI) contrast, which has been used to delineate the ischemic penumbra after ischemic stroke. In the current study, a novel MRI ratiometric technique is presented to measure absolute pH using the ratio of CEST-mediated contrast from amine and amide protons: amine/amide concentration-independent detection (AACID). Effects of CEST were observed at 2.75 parts per million (p.p.m.) for amine protons and at 3.50 p.p.m. for amide protons downfield (i.e., higher frequency) from bulk water. Using numerical simulations and in vitro MRI experiments, we showed that pH measured using AACID was independent of tissue relaxation time constants, macromolecular magnetization transfer effects, protein concentration, and temperature within the physiologic range. After in vivo pH calibration using phosphorus (31P) magnetic resonance spectroscopy (31P-MRS), local acidosis is detected in mouse brain after focal permanent middle cerebral artery occlusion. In summary, our results suggest that AACID represents a noninvasive method to directly measure the spatial distribution of absolute pH in vivo using CEST MRI.

Стилі APA, Harvard, Vancouver, ISO та ін.

8

Katagiri, Gen, James D. Leonard, and Terry L. Gustafson. "Ultraviolet Resonance Raman Study of Nylon-6." Applied Spectroscopy 49, no. 6 (June 1995): 773–79. http://dx.doi.org/10.1366/0003702953964507.

Повний текст джерела

Анотація:

Ultraviolet resonance Raman spectra of nylon-6 have been investigated with the use of a quasi-continuous UV excitation source based on cw mode-locked Nd:YAG and Nd:YLF lasers. The selective enhancement of the amide vibrational modes is discussed in relation to the reported results for simple amide compounds and polypeptides in aqueous solution. The ultraviolet excitation can extract the amide III mode at 1280 cm−1 for the first time, from significantly overlapped CH2 vibrational modes. The UV-enhanced mode is observed at 1380 cm−1 and is attributed to the controversial amide S mode. We also demonstrate the utility of the present quasi-continuous laser system as an excellent UV source for ultraviolet resonance Raman studies of solid materials.

Стилі APA, Harvard, Vancouver, ISO та ін.

9

Bernhardt, Paul V., and Curt Wentrup. "Structures of 4-Iminopyrido[1,2-a]pyrimidines, Pyrido[1,2-a]pyrimidin-4-ones, Pyridopyrimidinium Olates, and Thiazolo[3,2-a]pyrimidine Analogues." Australian Journal of Chemistry 65, no. 4 (2012): 371. http://dx.doi.org/10.1071/ch12040.

Повний текст джерела

Анотація:

The Structure-Correlation Principle of Bürgi and Dunitz is invoked in an analysis of the structures of 2-chloro-8-methyl-4-(2-(4-picolinyl)imino-4H-pyrido[1,2-a]pyrimidine 8, 7-chloro-5-(2-thiazolyl)imino-5H-thiazolo[3,2-a]pyrimidine 9, 2-methylamino-4H-pyrido[1,2-a]pyrimidin-4-one 10, 7-methylthio-5H-thiazolo[3,2-a]pyrimidin-5-one 11, 2,3-dihydro-7-methylthio-5H-thiazolo[3,2-a]pyrimidin-5-one 12, and 1-methyl-2-[(o-tert-butylphenyl)imino]-1,2-dihydropyrido[1,2-a]pyrimidin-1-ium-4-olate 13, which have been determined by X-ray crystallography. The most notable structural peculiarities are the long ‘amidine’ and ‘amide’ C–N bonds (1.40–1.50 Å) and the tilting of the ‘amidine’ C=N and ‘amide’ C=O groups towards a ring nitrogen atom (NCX = 114–118°). Also the ‘amidine’ C=N (1.28 Å) and ‘amide’ C=O bonds (1.22–1.24 Å) are long, i.e. in the normal range for resonance-stabilized amidines and amides in spite of the lack of such resonance in these compounds. These features mimic the transition states for ring opening to ketenes. The long amidine and amide C–N bonds and acute NCX angles are in accord with the observed thermal ring opening to ketenimines and ketenes, respectively.

Стилі APA, Harvard, Vancouver, ISO та ін.

10

Glover, Stephen A., and Adam A. Rosser. "The role of substituents in the HERON reaction of anomeric amides." Canadian Journal of Chemistry 94, no. 12 (December 2016): 1169–80. http://dx.doi.org/10.1139/cjc-2016-0300.

Повний текст джерела

Анотація:

Anomeric amides, RCON(X)(Y), have two electronegative atoms at the amide nitrogen, a configuration that results in greatly reduced amide resonance and strongly pyramidal nitrogen atoms. This, combined with facilitation of anomeric interactions, can result in the HERON reaction, an intramolecular migration of the more electronegative atom, X, from nitrogen to the carbonyl with production of a Y-stabilised nitrene. We have modelled, at the B3LYP/6-31G(d) level, a variety of anomeric amides that undergo the HERON reaction to determine factors that underpin the process. The overriding driving force is anomeric destabilisation of the bond to the migrating group. Rotated transition states show loss of residual resonance and this is a component of the overall activation energies. However, the reduced resonance in these systems plays only a minor role. We have determined the resonance energies (RE) and HERON activation barriers (EA) of five anomeric systems. REs for the amides have been calculated isodesmically using our calibrated trans amidation method and COSNAR calculations. Reduction of their overall EAs by the corresponding RE gives rearrangement energies (Erearr.), a measure of relative impact on rearrangement of substituents on nitrogen. In CH3CON(OMe)(Y) systems producing (CH3CO2Me + NY), a loosely bound electron pair on the donor atom, Y, in nY–σ*NOMe anomeric interactions drives the reaction. Erearr. increases in the sequence Y = N(nitrene) < O−(oxide) ≪ NMe2 < SMe ≪ OMe. For the same systems, RE increases in the order Y = N < O− ≪ OMe ≪ NMe2 ∼ SMe. Other effects such as molecular conformation, nature of the migrating group, X, and acyl substituents at the carbonyl carbon are discussed.

Стилі APA, Harvard, Vancouver, ISO та ін.

11

Bain, Alex D., P. Hazendonk, and P. Couture. "Article." Canadian Journal of Chemistry 77, no. 8 (August 1, 1999): 1340–48. http://dx.doi.org/10.1139/v99-143.

Повний текст джерела

Анотація:

Recent theoretical work on amide systems has brought into question the application of the concept of resonance. In particular, the role of the oxygen atom was questioned, since the calculations showed little change in its properties when the amide bond was rotated. This paper investigates, both experimentally and computationally, the effect of a substituent on the carbonyl carbon on the amide barrier, in order to test this view. The barriers to the amide rotation in seven spiro-fused oxazolidines were measured by NMR, to within 1 kJ mol-1. A subset of three of them was modelled to the 6-31G** level. For all three substituents the computed and measured barriers corresponded to within 7 kJ mol-1. The electron densities were analyzed using the Atoms in Molecules (AIM) theory. The AIM analysis revealed that the oxazolidines behaved similarly to formamide. The substituent effect was described in terms of the atomic populations and energies of the amide C, O, and N. A substituent on the carbonyl carbon caused electron redistributions between N and C, changing their basin attractive energies. Neither the population nor the energy of oxygen changed significantly. When interactions outside the basin of interest were considered, the energy of C was seen to be more sensitive to changing the substituent than the energy of N. However, the atomic parameters from the AIM analysis did not fully reflect the substituent effects observed. For these molecules, the barrier includes contributions from several sources - there is no single, dominant contribution.Key words: amides, barrier, substituent, nuclear magnetic resonance spectroscopy, chemical exchange, atoms in molecules, slow exchange, NMR lineshape analysis.

Стилі APA, Harvard, Vancouver, ISO та ін.

12

Talaikis, Martynas, Simona Strazdaitė, Mantas Žiaunys та Gediminas Niaura. "Far-Off Resonance: Multiwavelength Raman Spectroscopy Probing Amide Bands of Amyloid-β-(37–42) Peptide". Molecules 25, № 15 (4 серпня 2020): 3556. http://dx.doi.org/10.3390/molecules25153556.

Повний текст джерела

Анотація:

Several neurodegenerative diseases, like Alzheimer’s and Parkinson’s are linked with protein aggregation into amyloid fibrils. Conformational changes of native protein into the β-sheet structure are associated with a significant change in the vibrational spectrum. This is especially true for amide bands which are inherently sensitive to the secondary structure of a protein. Raman amide bands are greatly intensified under resonance conditions, in the UV spectral range, allowing for the selective probing of the peptide backbone. In this work, we examine parallel β-sheet forming GGVVIA, the C-terminus segment of amyloid-β peptide, using UV–Vis, FTIR, and multiwavelength Raman spectroscopy. We find that amide bands are enhanced far from the expected UV range, i.e., at 442 nm. A reasonable two-fold relative intensity increase is observed for amide II mode (normalized according to the δCH2/δCH3 vibration) while comparing 442 and 633 nm excitations; an increase in relative intensity of other amide bands was also visible. The observed relative intensification of amide II, amide S, and amide III modes in the Raman spectrum recorded at 442 nm comparing with longer wavelength (633/785/830 nm) excited spectra allows unambiguous identification of amide bands in the complex Raman spectra of peptides and proteins containing the β-sheet structure.

Стилі APA, Harvard, Vancouver, ISO та ін.

13

Li, Guangchen, Siyue Ma, and Michal Szostak. "Amide Bond Activation: The Power of Resonance." Trends in Chemistry 2, no. 10 (October 2020): 914–28. http://dx.doi.org/10.1016/j.trechm.2020.08.001.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

14

Konuma, Tsuyoshi, Aritaka Nagadoi, Jun-ichi Kurita, and Takahisa Ikegami. "Analysis of Artifacts Caused by Pulse Imperfections in CPMG Pulse Trains in NMR Relaxation Dispersion Experiments." Magnetochemistry 4, no. 3 (July 30, 2018): 33. http://dx.doi.org/10.3390/magnetochemistry4030033.

Повний текст джерела

Анотація:

Nuclear magnetic resonance relaxation dispersion (rd) experiments provide kinetics and thermodynamics information of molecules undergoing conformational exchange. Rd experiments often use a Carr-Purcell-Meiboom-Gill (CPMG) pulse train equally separated by a spin-state selective inversion element (U-element). Even with measurement parameters carefully set, however, parts of 1H–15N correlations sometimes exhibit large artifacts that may hamper the subsequent analyses. We analyzed such artifacts with a combination of NMR measurements and simulation. We found that particularly the lowest CPMG frequency (νcpmg) can also introduce large artifacts into amide 1H–15N and aromatic 1H–13C correlations whose 15N/13C resonances are very close to the carrier frequencies. The simulation showed that the off-resonance effects and miscalibration of the CPMG π pulses generate artifact maxima at resonance offsets of even and odd multiples of νcpmg, respectively. We demonstrate that a method once introduced into the rd experiments for molecules having residual dipolar coupling significantly reduces artifacts. In the method the 15N/13C π pulse phase in the U-element is chosen between x and y. We show that the correctly adjusted sequence is tolerant to miscalibration of the CPMG π pulse power as large as ±10% for most amide 15N and aromatic 13C resonances of proteins.

Стилі APA, Harvard, Vancouver, ISO та ін.

15

Baskaran, Kumaran, Colin W. Wilburn, Jonathan R. Wedell, Leonardus M. I. Koharudin, Eldon L. Ulrich, Adam D. Schuyler, Hamid R. Eghbalnia, Angela M. Gronenborn, and Jeffrey C. Hoch. "Anomalous amide proton chemical shifts as signatures of hydrogen bonding to aromatic sidechains." Magnetic Resonance 2, no. 2 (October 25, 2021): 765–75. http://dx.doi.org/10.5194/mr-2-765-2021.

Повний текст джерела

Анотація:

Abstract. Hydrogen bonding between an amide group and the p-π cloud of an aromatic ring was first identified in a protein in the 1980s. Subsequent surveys of high-resolution X-ray crystal structures found multiple instances, but their preponderance was determined to be infrequent. Hydrogen atoms participating in a hydrogen bond to the p-π cloud of an aromatic ring are expected to experience an upfield chemical shift arising from a shielding ring current shift. We surveyed the Biological Magnetic Resonance Data Bank for amide hydrogens exhibiting unusual shifts as well as corroborating nuclear Overhauser effects between the amide protons and ring protons. We found evidence that Trp residues are more likely to be involved in p-π hydrogen bonds than other aromatic amino acids, whereas His residues are more likely to be involved in in-plane hydrogen bonds, with a ring nitrogen acting as the hydrogen acceptor. The p-π hydrogen bonds may be more abundant than previously believed. The inclusion in NMR structure refinement protocols of shift effects in amide protons from aromatic sidechains, or explicit hydrogen bond restraints between amides and aromatic rings, could improve the local accuracy of sidechain orientations in solution NMR protein structures, but their impact on global accuracy is likely be limited.

Стилі APA, Harvard, Vancouver, ISO та ін.

16

Zahardis, J., S. Geddes, and G. A. Petrucci. "The ozonolysis of primary aliphatic amines in single and multicomponent fine particles." Atmospheric Chemistry and Physics Discussions 7, no. 5 (October 15, 2007): 14603–38. http://dx.doi.org/10.5194/acpd-7-14603-2007.

Повний текст джерела

Анотація:

Abstract. The oxidative processing by ozone of the particulate amines octadecylamine (ODA) and hexadecylamine (HDA) is reported. Ozonolysis of these amines resulted in strong NO2− and NO3− ion signals that increased with ozone exposure as monitored by photoelectron resonance capture ionization aerosol mass spectrometry. These products suggest a mechanism of progressive oxidation of the particulate amines to nitro alkanes. Additionally, a strong ion signal at 125 m/z is assigned to the ion NO3−(HNO3). For ozonized mixed particles containing ODA or HDA + oleic acid (OL), with pO3≥3×10−7 atm, imine, secondary amide, and tertiary amide products were measured. These products most likely arise from reactions of amines with aldehydes (for imines) and stabilized Criegee intermediates (SCI) or secondary ozonides (for amides) from the fatty acid. The routes to amides via SCI and/or secondary ozonides was shown to be more important than comparable amide forming reactions between amines and organic acids, using azelaic acid as a test compound. Finally, direct evidence is provided for the formation of a surface barrier in the ODA + OL reaction system that resulted in the retention of OL at high ozone exposures (up to 10−3 atm for 17 s). This effect was not observed in HDA + OL or single component OL particles, suggesting that it may be a species-specific surfactant effect from an in situ generated amide or imine. Implications to tropospheric chemistry, including particle bound amines as sources of oxidized gas phase nitrogen species (e.g. NO2, NO3), formation of nitrogen enriched HULIS via ozonolysis of amines and source apportionment are discussed.

Стилі APA, Harvard, Vancouver, ISO та ін.

17

Zahardis, J., S. Geddes, and G. A. Petrucci. "The ozonolysis of primary aliphatic amines in fine particles." Atmospheric Chemistry and Physics 8, no. 5 (February 29, 2008): 1181–94. http://dx.doi.org/10.5194/acp-8-1181-2008.

Повний текст джерела

Анотація:

Abstract. The oxidative processing by ozone of the particulate amines octadecylamine (ODA) and hexadecylamine (HDA) is reported. Ozonolysis of these amines resulted in strong NO2– and NO3– ion signals that increased with ozone exposure as monitored by photoelectron resonance capture ionization aerosol mass spectrometry. These products suggest a mechanism of progressive oxidation of the particulate amines to nitroalkanes. Additionally, a strong ion signal at 125 m/z is assigned to the ion NO3– (HNO3). For ozonized mixed particles containing ODA or HDA + oleic acid (OL), with pO3≥3×10–7 atm, imine, secondary amide, and tertiary amide products were measured. These products most likely arise from reactions of amines with aldehydes (for imines) and stabilized Criegee intermediates (SCI) or secondary ozonides (for amides) from the fatty acid. The routes to amides via SCI and/or secondary ozonides were shown to be more important than comparable amide forming reactions between amines and organic acids, using azelaic acid as a test compound. Finally, direct evidence is provided for the formation of a surface barrier in the ODA + OL reaction system that resulted in the retention of OL at high ozone exposures (up to 10−3 atm for 17 s). This effect was not observed in HDA + OL or single component OL particles, suggesting that it may be a species-specific surfactant effect from an in situ generated amide or imine. Implications to tropospheric chemistry, including particle bound amines as sources of oxidized gas phase nitrogen species (e.g.~NO2, NO3), formation of nitrogen enriched HULIS via ozonolysis of amines and source apportionment are discussed.

Стилі APA, Harvard, Vancouver, ISO та ін.

18

Nanubolu, Jagadeesh Babu, Balasubramanian Sridhar, and Krishnan Ravikumar. "Resonance-assisted amide protonation in dutasteride hydrochloride salt." CrystEngComm 14, no. 7 (2012): 2571. http://dx.doi.org/10.1039/c2ce06421a.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

19

Xu, Mizhi, Krista K. Bullard, Aja M. Nicely, and Will R. Gutekunst. "Resonance promoted ring-opening metathesis polymerization of twisted amides." Chemical Science 10, no. 42 (2019): 9729–34. http://dx.doi.org/10.1039/c9sc03602d.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

20

Salehi-Mobarakeh, Hamid, Ali Yadegari, Javad Didehvar, and Fahimeh Khakzad-Esfahlan. "Polyamide grafting onto ethylene-vinyl alcohol copolymer." Journal of Polymer Engineering 33, no. 9 (December 1, 2013): 843–50. http://dx.doi.org/10.1515/polyeng-2013-0104.

Повний текст джерела

Анотація:

Abstract Ethylene-vinyl alcohol copolymers (EVOH), with appropriate barriers and processability, can be chemically modified through vinyl alcohol units. Amides and polyamides based on condensation reactions of adipoyl chloride and hexamethylenediamine were grafted onto EVOH. Grafting was characterized by contact angle measurement, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), nuclear magnetic resonance spectroscopy (NMR) and scanning electron microscopy (SEM). Amide peaks at 3302 cm-1 corresponding to –NH bond stretching and the absorption of HN-CH2 at 7.8 ppm, were observed from ATR-FTIR and NMR, respectively, as a result of grafting. SEM showed the formation of amide structures as bundles, agglomerates and needle-like particles. Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) showed considerable changes in onset of melt temperature, crystallinity and various transitions in grafted EVOH, showing an effective alteration in the physical properties compared with the virgin resin. Nylon grafted EVOH can be considered as a potential compatibilizer in polyethylene (PE)/polyamide blends via increasing interactions at the interface.

Стилі APA, Harvard, Vancouver, ISO та ін.

21

Glover, Stephen A. "Comment on “Penicillin’s catalytic mechanism revealed by inelastic neutrons and quantum chemical theory” by Z. Mucsi, G. A. Chass, P. Ábrányi-Balogh, B. Jójárt, D.-C. Fang, A. J. Ramirez-Cuesta, B. Viskolczc and I. G. Csizmadia, Phys. Chem. Chem. Phys., 2013, 15, 20447." Physical Chemistry Chemical Physics 21, no. 32 (2019): 18012–25. http://dx.doi.org/10.1039/c8cp02413h.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

22

Laidig, Keith E., and Lynn M. Cameron. "Barrier to Rotation in Thioformamide: Implications for Amide Resonance." Journal of the American Chemical Society 118, no. 7 (January 1996): 1737–42. http://dx.doi.org/10.1021/ja952678y.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

23

Glover, Stephen A., and Meredith Adams. "Reaction of N-Acyloxy-N-alkoxyamides with Biological Thiol Groups." Australian Journal of Chemistry 64, no. 4 (2011): 443. http://dx.doi.org/10.1071/ch10470.

Повний текст джерела

Анотація:

Mutagenic N-acyloxy-N-alkoxyamides 1 react with thiols by an SN2 process at nitrogen with displacement of carboxylate. They react with glutathione 4 in [D6]DMSO/D2O and methyl and ethyl esters of cysteine hydrochloride, 11 and 12, in [D4]methanol but the intermediate N-alkoxy-N-(alkylthio)amides undergo a rapid substitution reaction at sulfur by a second thiol molecule to give hydroxamic esters and disulfides. Arrhenius activation energies and entropies of activation obtained for a series of different N-benzyloxy-N-(4-substitutedbenzoyloxy)benzamides 13–17 were similar to those found for the SN2 reaction of the same series with N-methylaniline. Entropies of activation were strongly negative in keeping with polar separation and attendant solvation in the transition state, and in keeping with this, bimolecular reaction rate constants at 298 K correlated with Hammett σ constants with a positive ρ-value of 1.1. The structure of model N-methoxy-N-(methylthio)acetamide has been computed at the B3LYP/6–31G(d) level and exhibits properties atypical of other anomeric amides with more electronegative atoms at nitrogen. Relative to N,N-bisoxyl substitution, the combination of a sulfur and an oxygen atom at the amide nitrogen results in a relatively small reduction in amide resonance.

Стилі APA, Harvard, Vancouver, ISO та ін.

24

Liu, Yongmei, Marcel Achtenhagen, Ruzhang Liu, and Michal Szostak. "Transamidation of N-acyl-glutarimides with amines." Organic & Biomolecular Chemistry 16, no. 8 (2018): 1322–29. http://dx.doi.org/10.1039/c7ob02874a.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

25

Clarkson, G. J., and C. A. Adah. "Alkylation of Galactosyl, Mannosyl and Lactosyl Barbiturate." NIGERIAN ANNALS OF PURE AND APPLIED SCIENCES 6 (December 28, 2015): 91–98. http://dx.doi.org/10.46912/napas.13.

Повний текст джерела

Анотація:

The reactions of galactosyl, mannosyl and lactosyl barbiturates with 4-benzyloxybenzyl chloride and á- halo amide with galactose barbiturate were investigated. The products (benzyloxybenzyl-galactosyl barbiturate, benzyloxybenzyl-mannosyl barbiturate, benzyloxybenzyl-lactosyl barbiturate and galactose amide) were characterised by high field nuclear magnetic resonance spectroscopy, mass spectrometry, carbon, hydrogen and nitrogen combustion analyses and further characterised as per- acetate. The alkylation or the barbituric salts proceeds well with the electrophiles and are routes to novel C-glycosyl lectin binders.

Стилі APA, Harvard, Vancouver, ISO та ін.

26

Glover, Stephen A. "Development of the HERON Reaction: A Historical Account." Australian Journal of Chemistry 70, no. 4 (2017): 344. http://dx.doi.org/10.1071/ch16683.

Повний текст джерела

Анотація:

This account describes the discovery and development of the HERON reaction, a reaction with special connection to the Heron Island Conferences on Reactive Intermediates and Unusual Molecules. This modern ‘named’ reaction describes an unusual rearrangement of bisheteroatom-substituted amides RCON(X)(Y) whereby the more electron deficient group, X, migrates from nitrogen to the carbonyl carbon giving an acyl derivative, RC(O)X, and Y-stabilised nitrenes. In it, the origins, mechanistic elucidation, and theoretical validation are described in more or less chronological order. Along that time line we introduce the concepts of ‘anomeric amides’, ‘amidicity’ in anomeric amides, and their role in the HERON reaction. All known versions of the reaction that have since been discovered are outlined and a basic understanding of the relative roles of reduced resonance and the anomeric driving force, both functions of the heteroatom substituents at the amide nitrogen, are quantified.

Стилі APA, Harvard, Vancouver, ISO та ін.

27

Slaich, P. K., W. U. Primrose, D. H. Robinson, C. W. Wharton, A. J. White, K. Drabble, and G. C. Roberts. "The binding of amide substrate analogues to phospholipase A2. Studies by 13C-nuclear-magnetic-resonance and infrared spectroscopy." Biochemical Journal 288, no. 1 (November 15, 1992): 167–73. http://dx.doi.org/10.1042/bj2880167.

Повний текст джерела

Анотація:

(R)-(2-dodecanamidoisohexyl)phosphocholine (DAHPC), labelled with 13C at the amide carbonyl group, has been synthesized and its binding to bovine pancreatic phospholipase A2 (PLA2) studied by n.m.r. and i.r. spectroscopy. Two-dimensional 1H-n.m.r. spectra show that, in the presence of Ca2+, DAHPC binds to the active site of the enzyme in a similar manner to other phospholipid amide substrate analogues. The environment of the labelled carbonyl group has been investigated by a combination of 13C n.m.r. and difference-Fourier-transform i.r. spectroscopy. The carbonyl resonance shifts 3 p.p.m. downfield on the binding of DAHPC to PLA2. The carbonyl absorption frequency decreases by 14-18 cm-1, accompanied by a marked sharpening of the absorption band. These results indicate that the carbonyl bond undergoes significant polarization in the enzyme-ligand complex, facilitated by the enzyme-bound Ca2+ ion. This suggests that ground-state strain is likely to promote catalysis in the case of substrate binding. Simple calculations, based on the i.r. data, indicate that the carbonyl bond is weakened by 5-9 kJ.mol-1. This is the first report of observation of the amide vibration of a bound ligand against the strong background of protein amide vibrations.

Стилі APA, Harvard, Vancouver, ISO та ін.

28

Hu, Feng, Roger Lalancette, and Michal Szostak. "Structural Characterization of N-Alkylated Twisted Amides: Consequences for Amide Bond Resonance and N−C Cleavage." Angewandte Chemie International Edition 55, no. 16 (March 8, 2016): 5062–66. http://dx.doi.org/10.1002/anie.201600919.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

29

Hu, Feng, Roger Lalancette, and Michal Szostak. "Structural Characterization of N-Alkylated Twisted Amides: Consequences for Amide Bond Resonance and N−C Cleavage." Angewandte Chemie 128, no. 16 (March 8, 2016): 5146–50. http://dx.doi.org/10.1002/ange.201600919.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

30

Kaur, Damanjit, Punita Sharma, and Prasad V. Bharatam. "Amide resonance in thio- and seleno- carbamates: A theoretical study." Journal of Molecular Structure: THEOCHEM 757, no. 1-3 (December 2005): 149–53. http://dx.doi.org/10.1016/j.theochem.2005.09.019.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

31

deLearie, Lynn, Wayne H. Lin, Dennis A. Moore, and David H. White. "5508388 Process for manufacturing DTPA-bis amide magnetic resonance imaging." Magnetic Resonance Imaging 14, no. 9 (January 1996): XI. http://dx.doi.org/10.1016/s0730-725x(97)87365-1.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

32

Park, Yeon Sil, Juwan Park, and Kyungsoo Paek. "A chromogenic molecular capsule attributable to dipolar amide resonance structure." Chemical Communications 51, no. 27 (2015): 6006–9. http://dx.doi.org/10.1039/c4cc10412a.

Повний текст джерела

Анотація:

A new chromogenic, self-assembled molecular capsule G@2₂is developed by introducing four (N,N-dimethyl-4-aminophenyl) azobenzyl moieties on the upper rim of a resorcin[4]arene-based amidoimino-cavitand. The tuning of conjugation between amido and (N,N-dimethyl-4-aminophenyl)azobenzyl groups by acid–base titration allows naked-eye observation of molecular capsule formation.

Стилі APA, Harvard, Vancouver, ISO та ін.

33

Mujika, Jon I., Jon M. Matxain, Leif A. Eriksson, and Xabier Lopez. "Resonance Structures of the Amide Bond: The Advantages of Planarity." Chemistry - A European Journal 12, no. 27 (September 18, 2006): 7215–24. http://dx.doi.org/10.1002/chem.200600052.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

34

Reibnegger, Gilbert, Brian J. Denny, and Helmut Wachter. "Ab Initio Quantum Chemical Calculations on the Stability of Different Tautomers of 6- and 7-Phenacetyl Pterin." Pteridines 4, no. 1 (February 1993): 23–26. http://dx.doi.org/10.1515/pteridines.1993.4.1.23.

Повний текст джерела

Анотація:

Summary In order to investigate the stabilities of different tautomeric forms of pteridine derivatives with a phenacetyl side chain in the 6- or 7-position, we have performed ab initio quantum chemical geometry optimizations of both the keto form and the vinylogous amide form of 6- and 7-phenacetyl pterin. The results are in accordance with experimental expectations: the keto form is slightly more stable for the 6-substituted derivative (1 .8 kcal per mol). while the vinylogous amide form is substantially more stable for the 7-substituted compound (8 .7 kcal per mol). The vinylogous amide forms are planar molecules, and this geometry enables the interaction between the hydrogen atom at N-5 (or N-8) and the carbonyl function of the side chain. Inspection of the calculated electron densities (population analysis) underlines the suggestion that the vinylogous amide form of 7-phenacetyl pterin is stabilized by a shift of electron density from the nitrogen bonded to C-2 to the carbonyl oxygen atom of the side chain (resonance stabilization via an additional highly conjugated vinylogous amide structure).

Стилі APA, Harvard, Vancouver, ISO та ін.

35

Siddiki, S. M. A. Hakim, Md Nurnobi Rashed, Abeda Sultana Touchy, Md A. R. Jamil, Yuan Jing, Takashi Toyao, Zen Maeno, and Ken-ichi Shimizu. "Hydrolysis of amides to carboxylic acids catalyzed by Nb2O5." Catalysis Science & Technology 11, no. 5 (2021): 1949–60. http://dx.doi.org/10.1039/d0cy02230f.

Повний текст джерела

Анотація:

An efficient heterogeneous Nb₂O₅ catalytic system has been developed for industrially important and challenging amide hydrolysis reaction to carboxylic acid through cleavage of resonance stabilized amidic C–N bond.

Стилі APA, Harvard, Vancouver, ISO та ін.

36

Hammond, Michael S., R. Scott Houliston, and Elizabeth M. Meiering. "Two-dimensional 1H and 15N NMR titration studies of hisactophilin." Biochemistry and Cell Biology 76, no. 2-3 (May 1, 1998): 294–301. http://dx.doi.org/10.1139/o98-032.

Повний текст джерела

Анотація:

We have used two-dimensional 1H-15N heteronuclear single quantum correlation spectroscopy to measure the pH dependence of backbone amide group chemical shifts in the actin binding protein hisactophilin over the pH range 5.7-11.1. Most of the resonances can be analyzed using a simple equation involving a single apparent ionization constant, pKapp. The majority of resonances in the protein titrate with pKapp values of 5.6-7.4. The results can be rationalized in terms of titration of many histidine residues in hisactophilin. The titration data provide direct experimental support for the proposed models of the atomic basis of actin and membrane binding by hisactophilin.Key words: hisactophilin, histidine, ionization constants, nuclear magnetic resonance, NMR.

Стилі APA, Harvard, Vancouver, ISO та ін.

37

Li, Jian, Shuang Yue Li, Shu Jun Li, Jing Wang, and Dan Liu. "Synthesis of a Rosin Amide and Its Inhibition of Wood Decay Fungi." Advanced Materials Research 113-116 (June 2010): 2232–36. http://dx.doi.org/10.4028/www.scientific.net/amr.113-116.2232.

Повний текст джерела

Анотація:

Rosin was used as raw material to prepare a rosin amide derivative. First, rosin was modified by acrylic acid with the weight ratio of 4.5:1. Then the modified rosin was reacted with diethyltriamine and the rosin amide derivative was produced under the following conditions: modified rosin and diethyltriamine mole ratio of 1:3.5, dimethylbenzene as water carrying agent, reaction temperature of 160-180 °C, and reaction time of 8h. The chemical structure of the product as a rosin amide derivative was identified by Fourier transform infrared spectroscopy, electrospray ionization-mass spectrometry, and 1H nuclear magnetic resonance analysis. The anti-fungal activity of the derivative was determined in vitro with wood decay fungi such as Aspergillus niger, Paecilomyces variotii, Trametes versicolor and Gloeophyllum trabeum. The anti-fungal experiment results signified that the derivative is active vs. these fungi, but less effective with Aspergillus niger. Since it is produced easily from rosin, which is renewable and not expensive, this rosin amide could be a potential wood preservative.

Стилі APA, Harvard, Vancouver, ISO та ін.

38

Sosa-González, Wadi Elim, Ramón del Jesús Palí-Casanova, Yamile Pérez-Padilla, María Isabel Loría-Bastarrachea, José Luis Santiago-García, and Manuel de Jesús Aguilar-Vega. "Sulfonated aromatic copoly(ether–amide) membranes II." High Performance Polymers 30, no. 4 (March 30, 2017): 437–45. http://dx.doi.org/10.1177/0954008317699863.

Повний текст джерела

Анотація:

Several aromatic sulfonated copoly(ether–amide)s, based on the aromatic diamines 4,4′-(hexafluoroisopropylidene)bis(p-phenyleneoxy)-dianiline (HFD) and 2,4-diaminobenzensulfonic acid (DABS) and 4,4′-oxybis(benzoic acid) (OBA), were synthesized through a polycondensation reaction. The sulfonation degree was controlled by introducing different concentrations of 2,4-DABS from 40 mol% up to 80 mol%. Proton nuclear magnetic resonance validated the expected concentrations of sulfonic acid groups in the sulfonated aromatic copoly(ether–amide)s. Thermal decomposition of sulfonic groups was found to initiate at 280°C, while main chain decomposition initiates at 410°C. Proton conductivity between 30°C and 75°C was 19.0 and 45.0 mS/cm, respectively, for the copolymer with the highest concentration of sulfonic groups (–SO3H). Comparison with structurally similar sulfonated copolyamides and copoly(ether–amide)s indicates that these new sulfonated copoly(ether–amide)s based on 4,4′-OBA show improved mechanical properties, but a decrease in ion exchange capacity and proton conductivity.

Стилі APA, Harvard, Vancouver, ISO та ін.

39

Wu, Wengang, Jun Yi, Huipeng Xu, Shuangjun Li, and Rongxin Yuan. "An Efficient, One-Pot Transamidation of 8-Aminoquinoline Amides Activated by Tertiary-Butyloxycarbonyl." Molecules 24, no. 7 (March 29, 2019): 1234. http://dx.doi.org/10.3390/molecules24071234.

Повний текст джерела

Анотація:

The efficient, one-pot access to the transamidation of 8-aminoquinoline (8-AQ), notorious for its harsh removal conditions, has been widely employed as an auxiliary in C–H functionalization reactions due to its strong directing ability. In this study, the facile and mild Boc protection of the corresponding 8-AQ amide was critical to activate the amide C(acyl)–N bond by twisting its geometry to lower the amidic resonance energy. Both aryl and alkyl amines proceeded transamidation in one-pot, user-friendly conditions with excellent yields.

Стилі APA, Harvard, Vancouver, ISO та ін.

40

Al-Khalaf, Abdullah A. "Synthesis and Characterization of some New 3,3'-(1,4-Phenylene) Bis (1-(4-Aminophenyl) Prop-2-en-1-one) Amide Derivatives." BASRA JOURNAL OF SCIENCE 40, no. 2 (September 1, 2022): 437–64. http://dx.doi.org/10.29072/basjs.20220214.

Повний текст джерела

Анотація:

A new amide derivative series [A1-A8] was prepared in good yield by direct reflux condensation of bis-chalcone [3,3'-(1,4-phenylene) bis (1-(4-aminophenyl) prop-2-en-1-one)] with different carboxylic acids and acrylamide in the presence of a suitable solvent and amount of sodium hydroxide (NaOH). The structures of the synthesized amide were characterized by various spectral techniques, including FTIR (Fourier-Transform Infrared Spectroscopy), 1H-NMR (Proton Nuclear. Magnetic Resonance Spectroscopy), and mass spectroscopy, and the resultant spectra confirmed the expected structure of the prepared bis-chalcone derivative.

Стилі APA, Harvard, Vancouver, ISO та ін.

41

Stroke Conference, Malaysian. "MSC 2021 Virtual E-Abstract." Journal Of Cardiovascular, Neurovascular & Stroke 3, no. 3 (September 30, 2021): 43–44. http://dx.doi.org/10.32896/cvns.v3n3.43-44.

Повний текст джерела

Анотація:

1. A Cluster-Randomised Controlled Trial Evaluating The Effectiveness Of Stroke Riskometer In Improving Stroke Risk Probability In Adults: A Preliminary Analysis.2. Ph-Weighted Amide Proton Transfer Magnetic Resonance Imaging (APT MRI) Better Delineates The Acidotic Ischemic Penumbra.

Стилі APA, Harvard, Vancouver, ISO та ін.

42

Ji, Yan, XiaoLiang Yang, and Ying Qian. "Poly-amidoamine structure characterization: amide resonance structure of imidic acid (HO–CN) and tertiary ammonium." RSC Adv. 4, no. 90 (2014): 49535–40. http://dx.doi.org/10.1039/c4ra09081k.

Повний текст джерела

Анотація:

The dendrimer PAMAM has an amide resonance structure,i.e.imidic acid (HO–CN), and a tertiary ammonium structure, which can be characterized using¹⁵N/¹H/2D NH/¹³C NMR, IR and MS.

Стилі APA, Harvard, Vancouver, ISO та ін.

43

Kim, Sungsoo, Jungyu Kim, Jieun Kim, Daeun Won, Suk-Kyu Chang, Wansik Cha, Keunhong Jeong, Sangdoo Ahn, and Kyungwon Kwak. "Electronic Effect on the Molecular Motion of Aromatic Amides: Combined Studies Using VT-NMR and Quantum Calculations." Molecules 23, no. 9 (September 8, 2018): 2294. http://dx.doi.org/10.3390/molecules23092294.

Повний текст джерела

Анотація:

Rotational barrier energy studies to date have focused on the amide bond of aromatic compounds from a kinetic perspective using quantum calculations and nuclear magnetic resonance (NMR). These studies provide valuable information, not only regarding the basic conformational properties of amide bonds but also the molecular gear system, which has recently gained interest. Thus, we investigate the precise motion of the amide bonds of two aromatic compounds using an experimental rotational barrier energy estimation by NMR experiments and a theoretical evaluation of the density functional theory calculation. The theoretical potential energy surface scan method combined with the quadratic synchronous transit 3 method and consideration of additional functional group rotation with optimization and frequency calculations support the results of the variable temperature 1H NMR, with deviations of less than 1 kcal/mol. This detailed experimental and theoretical research strongly supports molecular gear motion in the aromatic amide system, and the difference in kinetic energy indicates that the electronic effect from the aromatic structure has a key role in conformational movements at different temperatures. Our study provides an enhanced basis for future amide structural dynamics research.

Стилі APA, Harvard, Vancouver, ISO та ін.

44

Zong, Xiaopeng, Ping Wang, Seong-Gi Kim, and Tao Jin. "Sensitivity and Source of Amine-Proton Exchange and Amide-Proton Transfer Magnetic Resonance Imaging in Cerebral Ischemia." Magnetic Resonance in Medicine 71, no. 1 (February 11, 2013): 118–32. http://dx.doi.org/10.1002/mrm.24639.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

45

Grzesiek, Stephan, and Ad Bax. "Correlating backbone amide and side chain resonances in larger proteins by multiple relayed triple resonance NMR." Journal of the American Chemical Society 114, no. 16 (July 1992): 6291–93. http://dx.doi.org/10.1021/ja00042a003.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

46

Alam, Manawwer, Mukhtar Ahmed, Mohammad Altaf, and Fohad Mabood Husain. "Rapeseed oil-based hippurate amide nanocomposite coating material for anticorrosive and antibacterial applications." Open Chemistry 20, no. 1 (January 1, 2022): 725–35. http://dx.doi.org/10.1515/chem-2022-0193.

Повний текст джерела

Анотація:

Abstract Industrial crops and products have proved to be an excellent alternative to petro-based chemicals. Vegetable oils are rich in functional groups that can be transformed into monomers and polymers with applications such as biodiesel, lubricants, inks, coatings, and paints. This study describes the synthesis of rapeseed oil (RO)-based esteramide for the first time. The reaction was carried out by amidation of RO, producing diol fatty amide (N,N-bis(2-hydroxyethyl) RO fatty amide), followed by its esterification reaction with hippuric acid, resulting in RO-based hippurate amide (ROHA). Fourier-transform infrared spectroscopy and nuclear magnetic resonance confirmed the introduction of amide and ester moieties in ROHA. ROHA was further reinforced with silver nanoparticles (SNPs) to develop corrosion-protective nanocomposite coatings. ROHA/SNP coatings were scratch-resistant, impact-resistant, and flexible and showed good corrosion resistance performance toward 3.5 w/w% NaCl medium, with adequate corrosion protection efficiency, and antimicrobial behavior against Staphylococcus aureus, Chromobacterium violaceum, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. ROHA/SNP coatings can be safely used up to 250°C.

Стилі APA, Harvard, Vancouver, ISO та ін.

47

Berg, David J., and Roland AL Gendron. "Synthesis, solid state structure, and solution behaviour of the lighter lanthanide bis(trimethylsilyl)amido chlorides, [Ln{N(SiMe3)2}2(THF)(µ-Cl)]2 (Ln = Ce, Nd)." Canadian Journal of Chemistry 78, no. 4 (April 1, 2000): 454–58. http://dx.doi.org/10.1139/v00-036.

Повний текст джерела

Анотація:

The synthesis of [Ln{N(SiMe3)2}2(THF)(µ-Cl)]2 (Ln = Ce, 1; Nd, 2) by reaction of sodium bis(trimethylsilyl)amide (2 equiv.) with LnCl3 is reported. The same complexes were also isolated from the ligand redistribution reactions of Ln[N(SiMe3)2]3 and LnCl3 (2:1 ratio) in THF at 80°C. The crystal structure of 2, determined by X-ray diffraction, revealed a centrosymmetric dimer with bridging chlorides and pentacoordinate metal centres. 1H NMR studies show that the solid state structure is not maintained in solution. NMR evidence for the presence of Ln[N(SiMe3)2]3 and two other bis(trimethylsilyl)amide containing species, presumably Ln[N(SiMe3)2]Cl2(THF)x and Ln[N(SiMe3)2]2Cl(THF)y, is presented.Key words: lanthanide, amide, neodymium, cerium, crystal structure, X-ray, nuclear magnetic resonance, redistribution.

Стилі APA, Harvard, Vancouver, ISO та ін.

48

Kemnitz, Carl R., and Mark J. Loewen. "“Amide Resonance” Correlates with a Breadth of C−N Rotation Barriers." Journal of the American Chemical Society 129, no. 9 (March 2007): 2521–28. http://dx.doi.org/10.1021/ja0663024.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

49

Asher, Sanford A., Zhenhuan Chi та Pusheng Li. "Resonance Raman examination of the two lowest amide ππ* excited states". Journal of Raman Spectroscopy 29, № 10-11 (жовтень 1998): 927–31. http://dx.doi.org/10.1002/(sici)1097-4555(199810/11)29:10/11<927::aid-jrs334>3.0.co;2-r.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

50

Mielczarek-Puta, Magdalena, Marta Struga, and Piotr Roszkowski. "Synthesis and anticancer effects of conjugates of doxorubicin and unsaturated fatty acids (LNA and DHA)." Medicinal Chemistry Research 28, no. 12 (September 25, 2019): 2153–64. http://dx.doi.org/10.1007/s00044-019-02443-0.

Повний текст джерела

Анотація:

Abstract Doxorubicin (DOX) is a leading cytostatic drug with many adverse effects in use. We are still looking for methods that will allow us to preserve the therapeutic effect against the tumor cells and reduce the toxicity to the normal cells. In our work, we obtained amide derivatives of DOX by reaction of the amino group with α-linolenic (LNA) and docosahexaenoic (DHA) acids (2, 3), as well as double-substituted derivatives via amide and ester linkages (4, 5). The structures of the compounds were confirmed by Proton Nuclear Magnetic Resonance (1H NMR), Carbon-13 Nuclear Magnetic Resonance (13C NMR), and High Resolution Mass Spectrometry (HRMS) analyses. For all compounds 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay was used to determine the cytotoxic effect on human cancer cell lines (SW480, SW620, and PC3) and Chinese hamster lung fibroblasts (V79) that were used as a control. The cytotoxic activity was established by calculation of the inhibitory concentration IC50. In addition, a cytotoxic capacity against tumor cells for tested compounds was expressed as a selectivity factor (selectivity index, SI). Lactate dehydrogenase (LDH) assay was performed for all compounds to assess the level of cell damage. To explain the basic mechanism of cell death induction the Annexin V-FITC/IP flow cytometry analysis was investigated. We found that all studied conjugates exhibit lower cytotoxicity but higher selectivity than DOX. Among the all derivatives, the conjugates formed by the amide and ester linkages (4, 5) were found to be more promising compared with conjugates (2, 3) formed only by the amide linkage. They show high cytotoxicity toward the tumor cell lines and moderate cytotoxicity towards the normal cell line.

Стилі APA, Harvard, Vancouver, ISO та ін.

Статті в журналах з теми "Amide resonance"

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями