Journal articles: 'Bond exchange reaction'

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Zhao, Dongbing, Wen-Tao Zhao, and Fang Gao. "Recent Progress in σ-Bond Cross-Exchange Reactions to Access Diverse Silacycles." Synlett 29, no. 20 (August 30, 2018): 2595–600. http://dx.doi.org/10.1055/s-0037-1610266.

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The σ-bond cross-exchange reaction, which involves cleavage and subsequent exchange between different nonpolar σ-bonds, constitutes an attractive protocol for rapid access to organic skeletons with 100% atom economy. Herein, we give a brief summary of recent achievements in this approach for the synthesis of diverse silacycles, highlighting our recent advances in the first intermolecular σ-bond exchange between C–C bonds of cyclopropenones and C–Si bonds of (benzo)silacyclobutanes.1 Introduction2 σ-Bond Exchange-Reaction of Benzocyclobutanones to Silacycles3 σ-Bond Exchange-Reaction of Ethyl Cyclopropylideneacetates to Silacycles4 σ-Bond Exchange-Reaction of Cyclopropenones to Silacycles5 Conclusion

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Arisawa, Mieko, Tomoki Yamada, Saori Tanii, Yuta Kawada, Hisako Hashimoto, and Masahiko Yamaguchi. "Rhodium-catalyzed P–P bond exchange reaction of diphosphine disulfides." Chemical Communications 52, no. 93 (2016): 13580–83. http://dx.doi.org/10.1039/c6cc07302f.

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A rhodium-catalyzed exchange reaction of diphosphine disulfides, a diphosphine oxide, and a diphosphine is developed. Various symmetric diphosphine disulfides containing alkyl and phenyl groups are exchanged.

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Yang, Xichuan, Mikael Kritikos, Björn Åkermark, and Licheng Sun. "Axial ligand exchange reaction on ruthenium phthalocyanines." Journal of Porphyrins and Phthalocyanines 09, no. 04 (April 2005): 248–55. http://dx.doi.org/10.1142/s1088424605000319.

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Bis(4-methylpyridine)phthalocyaninato ruthenium(II) has been synthesized. It was proved by single-crystal X-ray diffraction that the central Ru(II) atom is bonded to six N atoms in an elongated octahedral configuration, and the axial ligands have a significantly longer Ru - N bond distance, 2.101(4) Å, than the independent pyrrol Ru - N bond, 1.99 Å. Therefore, the axial ligands can be exchanged by other ligands. The ligand exchange reactions with diethyl pyridyl-4-phosphonate and diethyl pyridylmethyl-4-phosphonate were studied in high boiling-point solvents at elevated temperatures, ca 160 °C. Mono-ligand as well as double-ligand replaced complexes were obtained. The complexes have been isolated by column chromatography. These complexes have potential applications, such as in dye sensitized solar cells.

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Sutrisno, Sutrisno, and Rahayu Ningtiyas. "DERERMINANTS OF ISLAMIC BOND MARKET REACTION Empirical Study of Islamic Bond in Indonesia." Jurnal Apresiasi Ekonomi 9, no. 2 (May 31, 2021): 152–58. http://dx.doi.org/10.31846/jae.v9i2.379.

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The main objective of this study is to examine several factors that cause islamic bonds market reaction as measured by cumulative abnormal return. The factors that are believed to be the determinants of islamic bond market reaction are the value of islamic bonds issuance, islamic bond rating, age of islamic bonds and size of the islamic bond issuing company. The population in this study are companies that issue Islamic bonds and are listed on the Indonesia Stock Exchange with a four-year observation period (2015-2018). The sample selection in this study uses purposive sampling based on certain criteria. In sample selection 36 Islamic bonds were obtained as samples. This study uses secondary data where the data is obtained from the annual report and the website of the issuing company. To test the hypothesis, using a multiple regression analysis tool with a significance level of 0.05. The results showed that the value of Islamic bonds issuance and rating of Islamic bonds issuance had a positive effect on market reaction. While the age of islamic bonds and the firm size have no effect on the reaction of the islamic bond market

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Ryabov, Alexander D. "The Exchange of Cyclometalated Ligands." Molecules 26, no. 1 (January 3, 2021): 210. http://dx.doi.org/10.3390/molecules26010210.

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Reactions of cyclometalated compounds are numerous. This account is focused on one of such reactions, the exchange of cyclometalated ligands, a reaction between a cyclometalated compound and an incoming ligand that replaces a previously cyclometalated ligand to form a new metalacycle: + H-C*~Z ⇄ + H-C~Y. Originally discovered for PdII complexes with Y/Z = N, P, S, the exchange appeared to be a mechanistically challenging, simple, and convenient routine for the synthesis of cyclopalladated complexes. Over four decades it was expanded to cyclometalated derivatives of platinum, ruthenium, manganese, rhodium, and iridium. The exchange, which is also questionably referred to as transcyclometalation, offers attractive synthetic possibilities and assists in disclosing key mechanistic pathways associated with the C–H bond activation by transition metal complexes and C–M bond cleavage. Both synthetic and mechanistic aspects of the exchange are reviewed and discussed.

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LI, PING, XIAOYAN XIE, YUXIANG BU, WEIHUA WANG, NANA WANG, JUNYOU SHI, and ZHAOXIA MOU. "THEORETICAL STUDIES ON THE COUPLING INTERACTIONS AND SELF-EXCHANGE REACTION MECHANISMS IN THE COMPLEXES OF NO WITH ONH AND NOH." Journal of Theoretical and Computational Chemistry 07, no. 03 (June 2008): 435–46. http://dx.doi.org/10.1142/s0219633608003848.

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The coupling interactions and self-exchange reaction mechanisms between NO and ONH (NOH) have been systematically investigated at the B3LYP/6-311++G** level of theory. All the equilibrium complexes are characterized by the intermolecular H-bonds and co-planar geometries. The cisoid NOH/ON species is the most stable one among all the complexes considered due to the formation of an N – N bond. Moreover, all the cisoid complexes are found to be more stable than the corresponding transoid ones. The origin of the blueshifts occurring in the selected complexes has been explored, employing the natural bond orbital (NBO) calculations. Additionally, the proton transfer mechanisms for the self-exchange reactions have been proposed, i.e. they can proceed via the three-center proton-coupled electron transfer or five-center cyclic proton-coupled electron transfer mechanism.

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DENG, XIN, LIN GE, and XUAN WU. "SPILLOVER EFFECT OF THE FEDERAL RESERVE’S FORWARD GUIDANCE ON CHINA’S FINANCIAL MARKETS: FROM MECHANISM ANALYSIS TO EMPIRICAL TEST." Singapore Economic Review 67, no. 02 (October 7, 2021): 603–34. http://dx.doi.org/10.1142/s0217590821500612.

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This study analyzed the channels responsible for the spillover effect of the US Federal Reserve’s (Fed’s) forward guidance on China’s financial markets with an event study and EGARCH model with data collected over the past decade. The Fed’s forward guidance affects China’s foreign exchange, bond, stock and money markets. In the three trading days before and after the event, China’s foreign exchange market had an instantaneous reaction, the bond and stock market had lagged reactions, and the money market reaction lasted for the full event window. The Fed’s forward guidance on China’s financial market differs based on the Fed’s monetary policy, guidance type and whether the guidance content is adjusted or not.

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8

Harcourt, Richard D., and Rickie Ng. "Valence bond representation for the hydrogen atom exchange reaction." Journal of Physical Chemistry 97, no. 47 (November 1993): 12210–14. http://dx.doi.org/10.1021/j100149a019.

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9

Casey, W. H. "A view of reactions at mineral surfaces from the aqueous phase." Mineralogical Magazine 65, no. 3 (June 2001): 323–37. http://dx.doi.org/10.1180/002646101300119439.

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AbstractThe processes by which a metal–oxygen bond dissociates in aqueous complexes are discussed and the reactions related to more complicated pathways of mineral dissolution. The dissolution of oxide minerals, and in fact many other classes of surface reactions, can be viewed as a ligand-exchange reaction because the bridging oxygens that link the metal to the mineral are progressively replaced by non-bridging functional groups. These ligand-exchange reactions are accelerated by protonations, hydroxylations and ligand substitutions that modify the lability of surface oxygens, but always at specific sites. Molecular information is important because reactions at some sites retard rates while reaction at other sites enhance them. Virtually all of the important variables that affect these reaction rates are local.

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Lutfiyah, Lailatul, and Mu’minatus Sholichah. "Pengaruh Nilai Sukuk Dan Risiko Sukuk Terhadap Reaksi Pasar Modal." Journal of Culture Accounting and Auditing 1, no. 1 (July 14, 2022): 107. http://dx.doi.org/10.30587/jcaa.v1i1.4233.

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This study aims to analyze the effect of Sharia Bond Issuance Value (sukuk), Shariah Bond Risk (sukuk) on Capital Market Reaction. This study uses a sample of companies that issue sukuk listed on the Indonesia Stock Exchange for the period 2017 – 2020. This research is a quantitative type that uses secondary data types with data collection methods carried out by accessing reports conducted by the Indonesia Stock Exchange Website, Yahoo Finance and Investing.com. The data analysis technique used in this research is multiple linear regression analysis. The test results show that only the sukuk value variable has a positive and significant effect on capital market reactions. Meanwhile, the risk of sukuk is stated to have a negative and insignificant effect on the reaction of the capital market.

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11

Folga, E., and T. Ziegler. "A theoretical study on the activation of hydrogen–hydrogen and hydrogen–alkyl bonds by electron-poor early transition metals." Canadian Journal of Chemistry 70, no. 2 (February 1, 1992): 333–42. http://dx.doi.org/10.1139/v92-047.

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A theoretical study has been carried out on four σ-bond metathesis reactions mediated by the electron-poor lutetium metal centre. The four processes include hydrogen exchange, X2Lu-H + D2 → X2Lu-D + HD (1), and hydrogenolysis X2Lu-CH3 + H2 → Cl2Lu-H + CH4 (2), in which a H—H bond is activated, as well as methane exchange, X2Lu-CH3 + CH4 → X2Lu-CH3 + CH4 (3), and methylation, Cl2Lu-H + CH4 → X2Lu-CH3 + H2 (4), in which a C—H bond is activated. The [Formula: see text] fragment employed in a number of experimental studies was modelled by Cl2Lu and all calculations were based on approximate Density Functional Theory (DFT). The study combined methods from quantum mechanics and statistical mechanics to obtain enthalpies and entropies of activation as well as transition state structures. All four processes were found to have an ordered four-centre transition state with negative entropies of activation given by ΔS≠ = −109(1), −124(2), −131 (3), and −134(4)&nbspJ mol−1 K−1 at T = 298.15 K. The Gibb's free energies of activation, ΔG≠(= ΔH≠ − TΔS≠) were calculated as ΔG≠ = 81.6 (1), 126.0 (2), 136.7 (3), and 130.6 (4) kJ mol−1 at T = 298.15 K. The calculated trends in ΔG≠ are consistent with the observed order of reactivity for σ-bond metathesis reactions between R—H and M—R′ bonds: R = R′ = H >> R = H, R′ = CH3 > R = R′ = CH3. The decrease in the reaction rate is related to the different abilities of the 1s hydrogen orbital and the [Formula: see text] methyl orbital to stabilize the four-centre transition state. Thus, the spherical 1s hydrogen orbital is better able to overlap fully with orbitals on adjacent centres than the directional [Formula: see text] orbital. As a consequence, the electronic barrier is seen to increase from the hydrogen exchange reaction towards the hydrogenolysis and methane exchange processes as one or two hydrogens, respectively, are replaced by methyl groups in the four-centre transition state. Keywords: Density Functional Theory, C—H activation, metathesis, hydrogenolysis, H—H activation.

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12

Pulatov, Khayrulla, Rano Nazirova, Umida Sharipova, Alisher Yuldashev, Aziza Usmonova, Shakhriyor Sattorov, and Yorkinjon Ergashev. "Research new type of cation-exchange resin for waste water treatment." E3S Web of Conferences 497 (2024): 02035. http://dx.doi.org/10.1051/e3sconf/202449702035.

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This article presents the studies obtaining and research new polycondensation type phosphoric cation-exchange resin. The conditions for the phosphorylation of this polymer were selected from the experiments accumulated in relation to the phosphorylation reactions of low- and high-molecular compounds. The resulting polymer had an exchange capacity for a 0.1 N NaOH solution – 5,5-5,6 mEq/g and contained 16,5% phosphorus. Based on the studies carried out, the optimal conditions for the synthesis of the styrene-furfural polymer are assumed to be: the reaction temperature is 90°C, the concentration of the ZnCl2 catalyst is 0.07 mol per mole of furfural, and the molar ratio of styrene to furfural is 1:1. There was studied an interaction of the cation exchanger in Na- and H-forms with solutions of salts of copper sulfate, nickel, cobalt, sodium chloride, calcium and uranyl nitrate. In order to elucidate the mechanism of sorption of the cations of these metals, were taken the IR-spectra of the cation exchanger in the H- and Na- form, saturated with copper ions. The less dissociated phosphoric acid groups, the stronger hydrogen bond forms phosphoryl oxygen with OH-groups. Therefore, it can be expected that as the cation exchanger is saturated with sodium, the maximum of the band corresponding to the phosphorus-oxygen bond vibrations will slightly shift to longer wavelengths as a result of the destruction of the weaker hydrogen bond.

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13

Janzen, Alexander F., and Meehae Jang. "Isomerization, fluorine exchange, and stereoselective synthesis of cis- and trans-F2TePh3Cl: application of the coordination model of reaction mechanisms." Canadian Journal of Chemistry 67, no. 1 (January 1, 1989): 71–75. http://dx.doi.org/10.1139/v89-012.

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The stereoselective synthesis of cis- and trans-F2TePh3Cl (phenyl substituents adopt a mer arrangement) via 5-coordinate cations Ph3TeFCl+ and [Formula: see text] is described. trans-F2TcPh3Cl isomerizes to the thermodynamically more stable cis isomer, and cis -F2TePh3Cl has non-equivalent fluorines which undergo stereoselective fluorine exchange, as confirmed by 19F and l25Te nmr spectroscopy. These results are consistent with an intermolecular mechanism of isomerization and fluorine exchange involving Te—F bond cleavage.The coordination model of reaction mechanisms provides a unified description of stereochemical rearrangements, ligand exchange processes, and chemical reactions in these, and related, octahedral and trigonal bipyramidal compounds. Keywords: synthesis of cis- and trans-F2TcPh3Cl, isomerization of octahedral Te compounds, fluorine exchange in cis-F2TePh3Cl, synthesis of Ph3TeF, coordination model of reaction mechanisms.

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14

Giebler, Michael, Clemens Sperling, Simon Kaiser, Ivica Duretek, and Sandra Schlögl. "Epoxy-Anhydride Vitrimers from Aminoglycidyl Resins with High Glass Transition Temperature and Efficient Stress Relaxation." Polymers 12, no. 5 (May 17, 2020): 1148. http://dx.doi.org/10.3390/polym12051148.

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Epoxy-anhydride vitrimers are covalent adaptable networks, which undergo associative bond exchange reactions at elevated temperature. Their service temperature is influenced by the glass transition temperature (Tg) as well as the topology freezing transition temperature (Tv), at which the covalent bond exchange reactions become significantly fast. The present work highlights the design of high-Tg epoxy-anhydride vitrimers that comprise an efficient stress relaxation at elevated temperature. Networks are prepared by thermally curing aminoglycidyl monomers with glutaric anhydride in different stoichiometric ratios. The tertiary amine groups present in the structure of the aminoglycidyl derivatives not only accelerate the curing reaction but also catalyse the transesterification reaction above Tv, as shown in stress relaxation measurements. The topology rearrangements render the networks recyclable, which is demonstrated by reprocessing a grinded powder of the cured materials in a hot press. The epoxy-anhydride vitrimers are characterised by a high Tg (up to 140 °C) and an adequate storage modulus at 25 °C (~2.5 GPa), which makes them interesting candidates for structural applications operating at high service temperature.

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15

Uhlig, Wolfram. "Zur gezielten Synthese funktionell substituierter Oligosilane aus Silyltriflaten und Aminosilyllithiumverbindungen / Tailor-Made Synthesis of Functional Substituted Oligosilanes from Silyl Triflates and (Aminosilyl)Lithium Compounds." Zeitschrift für Naturforschung B 58, no. 1 (January 1, 2003): 183–90. http://dx.doi.org/10.1515/znb-2003-0128.

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Abstract Diethylamino substituted silyllithium compounds have been prepared in situ from the corresponding phenylchlorosilanes and lithium. These reagents undergo coupling reactions with triflate derivatives of silanes and oligosilanes. Exchange processes analogous to metal halogen exchange and Si-Si bond cleavage, which are side reactions with chlorosilanes, were not observed. Based on the coupling reaction and the amino-to-triflate transformation, functionalized tri-, tetra-, penta- und hexasilanes have been synthesized. α,ω-Triflate substituted oligosilanes containing π-systems have also been obtained. These compounds are useful building blocks for new organosilicon polymers. The formation of the silicon polymers at low temperatures, in short reaction times, and with high yields is reported. The 29Si NMR spectra indicate a regular, alternating arrangement of the building blocks in the polymer backbone.

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Tao, Sheng, Enhui Ji, Lei Shi, Ning Liu, Liang Xu, and Bin Dai. "Copper-Catalyzed C–N Bond Exchange of N-Heterocyclic Substituents around Pyridine and Pyrimidine Cores." Synthesis 49, no. 23 (August 28, 2017): 5120–30. http://dx.doi.org/10.1055/s-0036-1590893.

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A copper-catalyzed transfer N-heteroarylation strategy using a C–N bond exchange reaction is described. This reaction accommodates a wide range of pyridine and pyrimidine rings bearing halogen atoms, which have wide utility for subsequent transformations. This method provides a direct and operationally simple approach for modifying complex molecules by the exchange of N-heterocyclic substituents.

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17

Yu, Sheng-Sheng, Ramanarayanan Krishnamurthy, Facundo M. Fernández, Nicholas V. Hud, F. Joseph Schork, and Martha A. Grover. "Kinetics of prebiotic depsipeptide formation from the ester–amide exchange reaction." Physical Chemistry Chemical Physics 18, no. 41 (2016): 28441–50. http://dx.doi.org/10.1039/c6cp05527c.

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18

Mais, Rimi Gusliana, Dea Maharani, and Agus Prasetyo. "Issuance Value, Issuance Rating and Life of Sharia Bond on Sharia Capital Market Reaction." JFBA: Journal of Financial and Behavioural Accounting 1, no. 1 (April 5, 2021): 83–92. http://dx.doi.org/10.33830/jfba.v1i1.2241.2021.

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This study aims to examine whether the value of islamic bonds issuance, rating of islamic bonds issuance, and age of islamic bonds issuance to the capital market reaction. The value of islamic bonds issuance is proxied by sukuk equity ratio, rating of islamic bonds issuance, and age of islamic bonds are used as independent variables. The capital market reaction is proxied by abnormal return as the dependent variable on Companies Issuing Bonds on the Indonesia Stock Exchange. This study uses a descriptive quantitative approach, which is measured using a multiple regression analysis method with Eviews 10. The population of this study is Companies Issuing Bonds on the Indonesia Stock Exchange (IDX) from 2017 to 2019. With a total sample size of 16 companies with the amount of islamic bonds as much as 135. The results of this study prove that (1) The value of islamic bonds issuance has an effect on the capital market reaction, (2) The rating of islamic bonds issuance has an effect on the capital market reaction, and (3) The age of islamic bonds has no effect on the capital market reaction on Companies Issuing Bonds on the Indonesia Stock Exchange 2017-2019.

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19

Walewska, Małgorzata, Judith Baumgartner, and Christoph Marschner. "1,2- and 1,1-Migratory Insertion Reactions of Silylated Germylene Adducts." Molecules 25, no. 3 (February 6, 2020): 686. http://dx.doi.org/10.3390/molecules25030686.

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The reactions of the PMe3 adduct of the silylated germylene [(Me3Si)3Si]2Ge: with GeCl2·dioxane were found to yield 1,1-migratory insertion products of GeCl2 into one or two Ge–Si bonds. In a related reaction, a germylene was inserted with tris(trimethylsilyl)silyl and vinyl substituents into a Ge–Cl bond of GeCl2. This was followed by intramolecular trimethylsilyl chloride elimination to another cyclic germylene PMe3 adduct. The reaction of the GeCl2 mono-insertion product (Me3Si)3SiGe:GeCl2Si(SiMe3)3 with Me3SiC≡CH gave a mixture of alkyne mono- and diinsertion products. While the reaction of a divinylgermylene with GeCl2·dioxane only results in the exchange of the dioxane of GeCl2 against the divinylgermylene as base, the reaction of [(Me3Si)3Si]2Ge: with one GeCl2·dioxane and three phenylacetylenes gives a trivinylated germane with a chlorogermylene attached to one of the vinyl units.

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20

Byrne, Aaron, Eduardo Bringa, Mario Del Pópolo, Jorge Kohanoff, Vanesa Galassi, and Niall English. "Mechanisms of Iodide–Triiodide Exchange Reactions in Ionic Liquids: A Reactive Molecular-Dynamics Exploration." International Journal of Molecular Sciences 20, no. 5 (March 5, 2019): 1123. http://dx.doi.org/10.3390/ijms20051123.

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Efficient charge transport has been observed in iodine-doped, iodide-based room-temperature ionic liquids, yielding high ionic conductivity. To elucidate preferred mechanistic pathways for the iodide ( I − )-to-triiodide ( I 3 − ) exchange reactions, we have performed 10 ns reactive molecular-dynamics calculations in the liquid state for 1-butyl-3-methylimidazolium iodide ([BMIM][I]) at 450 to 750 K. Energy-barrier distributions for the iodine-swapping process were determined as a function of temperature, employing a charge-reassignment scheme drawn in part from electronic-structure calculations. Bond-exchange events were observed with rate-determining energy barriers ranging from ~0.19 to 0.23 ± 0.06 eV at 750 and 450 K, respectively, with an approximately Arrhenius temperature dependence for iodine self-diffusivity and reaction kinetics, although diffusion dominates/limits the bond-exchange events. This charge transfer is not dissimilar in energetics to those in solid-state superionic conductors.

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Sugiura, Takumi, Takurou Kanada, Daisuke Mori, Hiroyuki Sakai, Aya Shibata, Yoshiaki Kitamura, and Masato Ikeda. "Chemical stimulus-responsive supramolecular hydrogel formation and shrinkage of a hydrazone-containing short peptide derivative." Soft Matter 16, no. 4 (2020): 899–906. http://dx.doi.org/10.1039/c9sm01969c.

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22

Arisawa, Mieko, and Masahiko Yamaguchi. "Rhodium-Catalyzed Synthesis of Organosulfur Compounds using Sulfur." Synlett 30, no. 14 (July 2, 2019): 1621–31. http://dx.doi.org/10.1055/s-0037-1611867.

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Sulfur is one of the few elements that occurs uncombined in nature. Sulfur atoms are found in natural amino acids and vitamins. In the chemical industry, organosulfur compounds are used for fabricating rubber, fibers, and dyes, pharmaceuticals, and pesticides. Although sulfur, which is cheap and easy to handle, is a useful source of sulfur atom in functional organosulfur compounds, it is rarely used in organic synthesis. Activation of sulfur by high temperature, light irradiation, treatment with nucleophiles and electrophiles, and redox conditions often results in the formation of various active sulfur species, which complicate reactions. The development of a method that mildly activates sulfur is therefore desired. The use of transition-metal catalysts is a new method of activating sulfur under mild conditions, and, in this article, we describe the rhodium-catalyzed synthesis of various organosulfur compounds by the insertion of sulfur atoms into single bonds and by the addition of sulfur to unsaturated bond in various organic compounds.1 Introduction2 Sulfur Activation without using Transition Metal3 Transition-Metal-Catalyzed Activation of Sulfur4 Rhodium-Catalyzed Reactions using Sulfur4.1 Rhodium-Catalyzed Sulfur Atom Exchange Reactions using Sulfur4.2 Synthesis of Diaryl Sulfides using Rhodium-Catalyzed Exchange Reaction of Aryl Fluorides and Sulfur/Organopolysulfides4.3 Rhodium-Catalyzed Synthesis of Isothiocyanate using Sulfur4.4 Rhodium-Catalyzed Sulfur Addition Reaction to Alkenes for Thiiranes Synthesis4.5 Rhodium-Catalyzed Sulfur Addition Reaction to Alkynes for 1,4-Dithiins Synthesis5 Conclusion

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Tachikawa, Hiroto. "SN2 and SN2′ reaction dynamics of cyclopropenyl chloride with halide ion A direct ab initio molecular dynamics (MD) study." Canadian Journal of Chemistry 83, no. 9 (September 1, 2005): 1597–605. http://dx.doi.org/10.1139/v05-176.

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Direct ab initio molecular dynamics (MD) calculations have been carried out for the reaction of cyclopropenyl chloride with halide ion (F) (F + (CH)3Cl → F(CH)3 + Cl) in gas phase. Both SN2 and SN2′ channels were found as product channels. These channels are strongly dependent on the collision angle of F to the target (CH)3Cl molecule. The collision at one of the carbon atoms of the C=C double bond leads to the SN2′ reaction channel; whereas the collision at the methylene carbon atom leads to the SN2 reaction channel. The reactions proceed via a direct mechanism without long-lived complexes. The reaction mechanism is discussed on the basis of the theoretical results.Key words: SN2 reaction, direct ab initio molecular dynamics, halogen exchange, reaction mechanism.

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Ye, Chenqing, Yichun Xie, Liping Zheng, Yuxiang Lin, Weixiang Guo, and Xueqiang Qi. "The anode oxidation reaction in fuel cell: A DFT study." E3S Web of Conferences 267 (2021): 02054. http://dx.doi.org/10.1051/e3sconf/202126702054.

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Although fuel cell (FC) has been regarded as promising “green” power generator, the Pt-based catalysts in the FC hampered their further development for its high cost and scarcity. Direct methanol fuel cell (DMFC) as another kind of proton exchange membrane fuel cell (PEMFC) has been manifested that Pd also performs a certain activity for methanol oxidation reaction (MOR). To better know the mechanism of MOR, we present a DFT study on the first step reaction of MOR on the Pd(111). The results show that methanol prefers to physically adsorb on the Pd(111) through oxygen atom, while the dehydrogenated hydrogen atoms can adsorb either on face-cantered cubic (FCC) or hexagonal close packed (HCP) sites. The intermediate products will form a much stronger interaction with the Pd(111) since they contain more unsaturated bonds. The energy barrier of O-H bond scission is most favourable, while the C-O bond is unfavourable in the first step of MOR.

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Meyer, Matthias, Johannes Kadel, and Heinz Oberhammer. "Triazaphosphinine – Reaktionen, Zwitterionen, P–B-Austausch/ Triazaphosphinines – Reactions, Zwitter Ions, P – B-Exchange." Zeitschrift für Naturforschung B 43, no. 8 (August 1, 1988): 1010–16. http://dx.doi.org/10.1515/znb-1988-0816.

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Abstract2,2-Dichloro-triazaphosphinine (2) reacts with SbF3 in the molar ratio 3:1 to give the mixed halogenated triazaphosphinine (3). New addition compounds 5 and 6 can be formed in the reaction of the zwitter ion 4 and amines or in the reaction of 2.2-difluoro-triazaphosphinine (1) with KCN. Phosphorus-boron-exchange is observed in the reactions of 4 or 2 with BF3 · OEt2. The new C-B -N-heterocycles 8 and 9 are obtained. The gas-phase structure of 1 has been determined by electron diffraction. The scattering intensities are compatible with a planar ring conformation with C2v symmetry and with equivalent NC bond lengths (PN = 1.579(10) Å, NC = 1.299(7) Å, NPN = 109.2(7)°, PNC - 118.1(9)°, CNC - 119.6(7)° and NCN = 127.5(12)°).

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Gast, Rainer, Thomas Kaukorat, Ion Neda, and Reinhard Schmutzler. "Das 2-Halogen-5,6-benzo-1,3,2-dioxaphosphorinan-4-on-Ringsystem / The 2-Halogeno-5,6-benzo-1,3,2-dioxaphosphorinan-4-one Ring System." Zeitschrift für Naturforschung B 48, no. 7 (July 1, 1993): 867–74. http://dx.doi.org/10.1515/znb-1993-0703.

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The reaction of salicylic acid with phosphorus trichloride furnished the previously known 2-chloro-5,6-benzo-1,3,2-dioxaphosphorinan-4-one heterocycle 1 which was unambiguously characterized, for the first time, by NMR spectroscopy and mass spectrometry. The fluorine and bromine analogues of 1, 2 and 3 were synthesized from 1, using exchange reactions. The iodo derivative, 4, owing to its instability, could be identified only in the reaction mixture by 1H and 31P NMR spectroscopy. The amine derivatives 5-8 were obtained from 1 using standard exchange reactions, either with silylated amines or with secondary amines in the presence of base. There was no evidence by 1H NMR spectroscopy for intramolecular Me2N→P coordination in 6. The 31P NMR investigation of 7 revealed the presence of two rotational isomers, presumably as a result of steric hindrance at the P–N bond by the methyl substituent of the piperidine group. The reaction of 6 with methyl iodide led to methylation at the nitrogen atom of the Me2N group, producing the ammonium iodide, 9. The reactions of 5,6 and 8 with norbornadiene tetracarbonyl molybdenum failed to furnish isolable products.

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27

Barth, Andreas, and Natalya Bezlyepkina. "P–O Bond Destabilization Accelerates Phosphoenzyme Hydrolysis of Sarcoplasmic Reticulum Ca2+-ATPase." Journal of Biological Chemistry 279, no. 50 (September 27, 2004): 51888–96. http://dx.doi.org/10.1074/jbc.m410867200.

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The phosphate group of the ADP-insensitive phosphoenzyme (E2-P) of sarcoplasmic reticulum Ca2+-ATPase (SERCA1a) was studied with infrared spectroscopy to understand the high hydrolysis rate of E2-P. By monitoring an autocatalyzed isotope exchange reaction, three stretching vibrations of the transiently bound phosphate group were selectively observed against a background of 50,000 protein vibrations. They were found at 1194, 1137, and 1115 cm–1. This information was evaluated using the bond valence model and empirical correlations. Compared with the model compound acetyl phosphate, structure and charge distribution of the E2-P aspartyl phosphate resemble somewhat the transition state in a dissociative phosphate transfer reaction; the aspartyl phosphate of E2-P has 0.02 Å shorter terminal P–O bonds and a 0.09 Å longer bridging P–O bond that is ∼20% weaker, the angle between the terminal P–O bonds is wider, and –0.2 formal charges are shifted from the phosphate group to the aspartyl moiety. The weaker bridging P–O bond of E2-P accounts for a 1011–1015-fold hydrolysis rate enhancement, implying that P–O bond destabilization facilitates phosphoenzyme hydrolysis. P–O bond destabilization is caused by a shift of noncovalent interactions from the phosphate oxygens to the aspartyl oxygens. We suggest that the relative positioning of Mg2+and Lys684between phosphate and aspartyl oxygens controls the hydrolysis rate of the ATPase phosphoenzymes and related phosphoproteins.

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28

Wu, Jian-Bo, Shu-Jia Li, Hong Liu, Hu-Jun Qian, and Zhong-Yuan Lu. "Dynamics and reaction kinetics of coarse-grained bulk vitrimers: a molecular dynamics study." Physical Chemistry Chemical Physics 21, no. 24 (2019): 13258–67. http://dx.doi.org/10.1039/c9cp01766f.

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We used the hybrid molecular dynamics–Monte Carlo (MD–MC) algorithm to establish a molecular dynamics model that can accurately reflect bond exchange reactions, and reveal the intrinsic mechanism of the dynamic behavior of the vitrimer system.

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29

Bao, Junwei Lucas, Xin Zhang, and Donald G. Truhlar. "Barrierless association of CF2and dissociation of C2F4by variational transition-state theory and system-specific quantum Rice–Ramsperger–Kassel theory." Proceedings of the National Academy of Sciences 113, no. 48 (November 10, 2016): 13606–11. http://dx.doi.org/10.1073/pnas.1616208113.

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Bond dissociation is a fundamental chemical reaction, and the first principles modeling of the kinetics of dissociation reactions with a monotonically increasing potential energy along the dissociation coordinate presents a challenge not only for modern electronic structure methods but also for kinetics theory. In this work, we use multifaceted variable-reaction-coordinate variational transition-state theory (VRC-VTST) to compute the high-pressure limit dissociation rate constant of tetrafluoroethylene (C2F4), in which the potential energies are computed by direct dynamics with the M08-HX exchange correlation functional. To treat the pressure dependence of the unimolecular rate constants, we use the recently developed system-specific quantum Rice–Ramsperger–Kassel theory. The calculations are carried out by direct dynamics using an exchange correlation functional validated against calculations that go beyond coupled-cluster theory with single, double, and triple excitations. Our computed dissociation rate constants agree well with the recent experimental measurements.

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30

El Hamidi, Sana, Malika Khnifira, El Mokhtar Lemdek, Redouan Hammal, Noureddine Barka, M’hamed Sadiq, Ahmed Benharref, Ahmed Chekroun, Hssaine Zgou, and Mohamed Abdennouri. "Understanding the Mechanism and Selectivities of the Reaction of Meta-Chloroperbenzoic Acid and Dibromocarbene with β-Himachalene: A DFT Study." Heteroatom Chemistry 2020 (September 18, 2020): 1–8. http://dx.doi.org/10.1155/2020/8885991.

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This study was performed to understand the site selectivity in the reaction between β-himachalene and meta-chloroperbenzoic acid (m-CPBA) in the first step followed by the addition of dibromocarbene (CBr2) to the main monoepoxidation product Pα formed in the first reaction. Calculations were performed using the Becke three-parameter hybrid exchange functional and the Lee–Yang–Parr correlation functional (B3LYP) with the 6-311 + G (d, p) basis set. Transition states were located by QST2, and their highlighting was validated by the existence of only one imaginary frequency in the Hessian matrix. The action of m-CPBA on β-himachalene was analyzed on the two double bonds of β-himachalene whose theoretical calculations show that the attack affects the most substituted double bond on α side containing hydrogen of ring junction. The obtained Pα product thereafter treated with dibromocarbene leads via an exothermic reaction to the six-membered ring double bond position of α-monoepoxide. The major products Pαα are kinetically and thermodynamically favored with a high stereoselectivity in perfect correlation with the experimental observations.

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31

Chen, Baolong, Xin Hu, and Xiaoqing Zhu. "Essential Rule Derived from Thermodynamics and Kinetics Studies of Benzopyran Compounds." Molecules 28, no. 24 (December 11, 2023): 8039. http://dx.doi.org/10.3390/molecules28248039.

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Compounds with benzopyran as the core structure play an important role in the total synthesis of antioxidants, drugs, and natural products. Herein, the thermodynamic data of benzopyran compounds and their intermediates were measured and calculated by combining thermodynamics with kinetics. The mechanism of reactions between four benzopyran compounds and organic hydride acceptors was proven to be a one-step hydride transfer. The thermodynamic properties of these compounds and their corresponding intermediates were elucidated. The rationality and accuracy of the electrochemical measurement method were proved. Furthermore, the essential rule of unique structures being present between the C–H bond and para-substituent constants on the benzene ring, as shown in previous studies, was investigated. A simultaneous correlation between thermodynamics and kinetics was found for the hydride transfer reaction, in which the reaction site is connected with the substituent through the benzene ring, a double bond, or a N atom. The likely reason for the correlation between thermodynamic and kinetic is that the benzene ring, double bond, or N atom have the role of transferring the electronic effect. This finding can be applied to the calculation of the activation energy of hydride self-exchange reactions, the prediction of kinetic isotope effects, and explorations of selective reduction processes of hydride transfer in such organic hydride compounds.

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32

Lee, Changmin, Eunhee Nam, Woosuk Lee, and Heeyeop Chae. "Hydrosilylation of Reactive Quantum Dots and Siloxanes for Stable Quantum Dot Films." Polymers 11, no. 5 (May 18, 2019): 905. http://dx.doi.org/10.3390/polym11050905.

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The reactive acrylate-terminated CdZnSeS/ZnS quantum dots (QDs) were designed and prepared by the effective synthetic route to bond with a siloxane matrix via hydrosilylation. The conventional QD with oleic acid ligands does not have any reactivity, so the QDs were functionalized to assign reactivity for the QDs by the ligand modification of two step reactions. The oleic acid of the QDs was exchanged for hydroxyl-terminated ligands as an intermediate product by one-pot reaction. The hydroxyl-terminated QDs and acrylate-containing isocyanates were combined by nucleophilic addition reaction with forming urethane bonds and terminal acrylate groups. No degradation in quantum yield was observed after ligand exchange, nor following the nucleophilic addition reaction. The modification reactions of ligands were quantitatively controlled and their molecular structures were precisely confirmed by FT-IR and 1H-NMR. The QDs with acrylate ligands were then reacted with hydride-terminated polydimethylsiloxane (H-PDMS) to form a QD-siloxane matrix by thermal curing via hydro-silylation for the first time. The covalent bonding between the QDs and the siloxane matrix led to improvements in the stability against oxygen and moisture. Stability at 85 °C and 85% relative humidity (RH) were both improved by 22% for the QD-connected siloxane QD films compared with the corresponding values for conventional QD-embedded poly(methylmethacrylate) (PMMA) films. The photo-stability of the QD film after 26 h under a blue light-emitting diode (LED) was also improved by 45% in comparison with those of conventional QD-embedded PMMA films.

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33

Undheim, Kjell. "Bond Formation at C8 in the Nucleoside and Nucleotide Purine Scaffold: An Informative Selection." Molecules 29, no. 8 (April 17, 2024): 1815. http://dx.doi.org/10.3390/molecules29081815.

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This paper presents methods for the introduction and exchange of substituents in a nucleobase and its nucleosides and nucleotides with emphasis on the C8-position in the purine skeleton. The nucleobase is open for electrophilic and nucleophilic chemistry. The nucleophilic chemistry consists mainly of displacement reactions when the C8-substituent is a good leaving group such as a halogen atom. The heteroatom in amines, sulfides, or oxides is a good nucleophile. Halides are good reaction partners. Metal-promoted cross-coupling reactions are important for carbylations. Direct oxidative metalation reactions using sterically hindered metal amides offer chemo- and regio-selectivity besides functional tolerance and simplicity. The carbon site is highly nucleophilic after metalation and adds electrophiles resulting in chemical bond formation. Conditions for metal-assisted reactions are described for nucleobases and their glycosides.

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34

Frand, Alison R., and Chris A. Kaiser. "Two Pairs of Conserved Cysteines Are Required for the Oxidative Activity of Ero1p in Protein Disulfide Bond Formation in the Endoplasmic Reticulum." Molecular Biology of the Cell 11, no. 9 (September 2000): 2833–43. http://dx.doi.org/10.1091/mbc.11.9.2833.

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In the major pathway for protein disulfide-bond formation in the endoplasmic reticulum (ER), oxidizing equivalents flow from the conserved ER-membrane protein Ero1p to secretory proteins via protein disulfide isomerase (PDI). Herein, a mutational analysis of the yeast ERO1 gene identifies two pairs of conserved cysteines likely to form redox-active disulfide bonds in Ero1p. Cys100, Cys105, Cys352, and Cys355 of Ero1p are important for oxidative protein folding and for cell viability, whereas Cys90, Cys208, and Cys349 are dispensable for these functions. Substitution of Cys100 with alanine impedes the capture of Ero1p-Pdi1p mixed-disulfide complexes from yeast, and also blocks oxidation of Pdi1p in vivo. Cys352 and Cys355 are required to maintain the fully oxidized redox state of Ero1p, and also play an auxiliary role in thiol–disulfide exchange with Pdi1p. These results suggest a model for the function of Ero1p wherein Cys100 and Cys105 form a redox-active disulfide bond that engages directly in thiol–disulfide exchange with ER oxidoreductases. The Cys352–Cys355 disulfide could then serve to reoxidize the Cys100–Cys105 cysteine pair, possibly through an intramolecular thiol–disulfide exchange reaction.

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35

Ye, Runyou, Maoshuai Zhu, Xufei Yan, Yang Long, Ying Xia, and Xiangge Zhou. "Pd(II)-Catalyzed C═C Bond Cleavage by a Formal Group-Exchange Reaction." ACS Catalysis 11, no. 14 (July 1, 2021): 8678–83. http://dx.doi.org/10.1021/acscatal.1c01850.

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36

Neves, Rui P. P., Pedro Alexandrino Fernandes, and Maria João Ramos. "Mechanistic insights on the reduction of glutathione disulfide by protein disulfide isomerase." Proceedings of the National Academy of Sciences 114, no. 24 (May 30, 2017): E4724—E4733. http://dx.doi.org/10.1073/pnas.1618985114.

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We explore the enzymatic mechanism of the reduction of glutathione disulfide (GSSG) by the reduced a domain of human protein disulfide isomerase (hPDI) with atomistic resolution. We use classical molecular dynamics and hybrid quantum mechanics/molecular mechanics calculations at the mPW1N/6–311+G(2d,2p):FF99SB//mPW1N/6–31G(d):FF99SB level. The reaction proceeds in two stages: (i) a thiol-disulfide exchange through nucleophilic attack of the Cys53-thiolate to the GSSG-disulfide followed by the deprotonation of Cys56-thiol by Glu47-carboxylate and (ii) a second thiol-disulfide exchange between the Cys56-thiolate and the mixed disulfide intermediate formed in the first step. The Gibbs activation energy for the first stage was 18.7 kcal·mol−1, and for the second stage, it was 7.2 kcal·mol−1, in excellent agreement with the experimental barrier (17.6 kcal·mol−1). Our results also suggest that the catalysis by protein disulfide isomerase (PDI) and thiol-disulfide exchange is mostly enthalpy-driven (entropy changes below 2 kcal·mol−1 at all stages of the reaction). Hydrogen bonds formed between the backbone of His55 and Cys56 and the Cys56-thiol result in an increase in the Gibbs energy barrier of the first thiol-disulfide exchange. The solvent plays a key role in stabilizing the leaving glutathione thiolate formed. This role is not exclusively electrostatic, because an explicit inclusion of several water molecules at the density-functional theory level is a requisite to form the mixed disulfide intermediate. In the intramolecular oxidation of PDI, a transition state is only observed if hydrogen bond donors are nearby the mixed disulfide intermediate, which emphasizes that the thermochemistry of thiol-disulfide exchange in PDI is influenced by the presence of hydrogen bond donors.

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37

Swaddle, T. W. "Inorganic solution chemistry at elevated pressures." Canadian Journal of Physics 73, no. 5-6 (May 1, 1995): 258–66. http://dx.doi.org/10.1139/p95-037.

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Recent interest in pressure effects on inorganic systems in solution has been centred upon the use of volumes of activation ΔV‡ as criteria of reaction mechanism. Work in our laboratory has sought to determine whether ΔV‡ is indeed a useful parameter in this respect, i.e., whether it is substantially independent of pressure and reaction conditions and whether it can be quantitatively predicted for suitably "simple" reactions. For solvent exchange on metal ions (the simplest conceivable substitution process), a semi-empirical model predicts ΔV‡ for limiting dissociative (bond breaking) and associative (bond making) mechanisms in water, but experimental values lie between these extremes, vindicating the Langford–Gray "interchange" model in which associative and dissociative processes are viewed as being concerted. For adiabatic electron transfer reactions of the outer-sphere type (the simplest conceivable oxidation–reduction process) in water, an adaptation of Marcus theory accounts for the essentially pressure-independent ΔV‡ satisfactorily, and failures of such predictions can be ascribed to complications such as nonadiabaticity or the incursion of inner-sphere (ligand-bridged) reaction pathways. The theory is less successful in nonaqueous solvents. Experimental methods used for these and related studies include high pressure adaptations of nuclear magnetic resonance, UV–visible spectrophotometry, stopped-flow techniques, cyclic voltammetry, and sampling under pressure.

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38

Renodon-Corniere, Axelle, Tsutomu Mikawa, Naoyuki Kuwabara, Kentaro Ito, Dmitri Levitsky, Hiroshi Iwasaki, and Masayuki Takahashi. "Human Rad51 Protein Requires Higher Concentrations of Calcium Ions for D-Loop Formation than for Oligonucleotide Strand Exchange." International Journal of Molecular Sciences 25, no. 7 (March 24, 2024): 3633. http://dx.doi.org/10.3390/ijms25073633.

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Human Rad51 protein (HsRad51)-promoted DNA strand exchange, a crucial step in homologous recombination, is regulated by proteins and calcium ions. Both the activator protein Swi5/Sfr1 and Ca2+ ions stimulate different reaction steps and induce perpendicular DNA base alignment in the presynaptic complex. To investigate the role of base orientation in the strand exchange reaction, we examined the Ca2+ concentration dependence of strand exchange activities and structural changes in the presynaptic complex. Our results show that optimal D-loop formation (strand exchange with closed circular DNA) required Ca2+ concentrations greater than 5 mM, whereas 1 mM Ca2+ was sufficient for strand exchange between two oligonucleotides. Structural changes indicated by increased fluorescence intensity of poly(dεA) (a poly(dA) analog) reached a plateau at 1 mM Ca2+. Ca2+ > 2 mM was required for saturation of linear dichroism signal intensity at 260 nm, associated with rigid perpendicular DNA base orientation, suggesting a correlation with the stimulation of D-loop formation. Therefore, Ca2+ exerts two different effects. Thermal stability measurements suggest that HsRad51 binds two Ca2+ ions with KD values of 0.2 and 2.5 mM, implying that one step is stimulated by one Ca2+ bond and the other by two Ca2+ bonds. Our results indicate parallels between the Mg2+ activation of RecA and the Ca2+ activation of HsRad51.

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39

List, Benjamin, Hui Zhou, and Pinglu Zhang. "The Silicon–Hydrogen Exchange Reaction: Catalytic Kinetic Resolution of 2-Substituted Cyclic Ketones." Synlett 32, no. 19 (October 15, 2021): 1953–56. http://dx.doi.org/10.1055/a-1670-5829.

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AbstractWe have recently reported the strong and confined, chiral acid-catalyzed asymmetric ‘silicon−hydrogen exchange reaction’. One aspect of this transformation is that it enables access to enantiopure enol silanes in a tautomerizing σ-bond metathesis, via deprotosilylation of ketones with allyl silanes as the silicon source. However, until today, this reaction has not been applied to racemic, 2-substituted, cyclic ketones. We show here that these important substrates readily undergo a highly enantioselective kinetic resolution furnishing the corresponding kinetically preferred enol silanes. Mechanistic studies suggest the fascinating possibility of advancing the process to a dynamic kinetic resolution.

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40

Soon, Julian Wong, Koji Oohora, and Takashi Hayashi. "A disulphide bond-mediated hetero-dimer of a hemoprotein and a fluorescent protein exhibiting efficient energy transfer." RSC Advances 12, no. 44 (2022): 28519–24. http://dx.doi.org/10.1039/d2ra05249k.

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Hetero-dimerization of a hemoprotein and green fluorescent protein via a thiol–disulphide exchange reaction is achieved. The heterodimer has suitable cross-linking points and displays efficient energy transfer.

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41

Zhou, Zhongqun, Yanning Zeng, Caili Yu, Haibo Chen, and Faai Zhang. "Mechanically robust, intrinsically self-healing crosslinked polymer enabled by dynamic urea bond exchange reaction." Smart Materials and Structures 29, no. 11 (October 8, 2020): 115041. http://dx.doi.org/10.1088/1361-665x/abb574.

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42

Wark, Teresa A., and Douglas W. Stephan. "Rhodium induced titanium–sulfur bond cleavage: crystal and molecular structure of ((COD)Rh(μ-SMe))2." Canadian Journal of Chemistry 68, no. 4 (April 1, 1990): 565–69. http://dx.doi.org/10.1139/v90-086.

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Reactions of Ti(III) and Ti(IV) thiolates with Rh complexes have been investigated. In the reaction of Cp2Ti(SMe)2 and [(COD)2Rh]BF4 or [(COD)Rh(sol)2]PF6, thiolate abstraction yields ((COD)Rh(μ-SMe))2, 1. Reaction of (Cp2Ti(μ-SMe))2 with ((COD)Rh(μ-Cl))2 results in ligand exchange affording (Cp2Ti(μ-Cl))2 and 1. The complex 1 crystallizes in the monoclinic space group P21/n, with a = 8.551(2) Å, b = 10.058(3) Å, c = 22.187(4) Å, β = 92.54(1)°, Z = 4, and V = 1906(1) Å3. The structural data show a relatively short approach between the Rh centres (2.948 Å) and between the bridging sulfur atoms (2.888 Å). The implications of these structural features in terms of metal–metal and sulphur–sulfur bonding are discussed. In addition, the implications of these results with respect to the formation of thiolato-bridged, early–late heterobimetallics is considered. Keywords: thiolate abstraction, rhodium thiolate bridged dimer.

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43

Wrackmeyer, Bernd, Christoph Bihlmayer, Khadija Shahid, and Wolfgang Milius. "Reaction of 9-Borabicyclo[3.3.1]nonane with Alkyn-1-yltin Compounds. Molecular Structure of the 9-Propyn-1-yl-9-borabicyclo[3.3.1]nonane Pyridine Adduct." Zeitschrift für Naturforschung B 64, no. 4 (April 1, 2009): 399–402. http://dx.doi.org/10.1515/znb-2009-0407.

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Trimethyl- and triethyl(propyn-1-yl)tin react with 9-borabicyclo[3.3.1.]nonane (9-BBN) mainly by exchange of the propynyl group against hydrogen, accompanied by numerous side reaction. This is in contrast to the findings for other alkynyltin compounds bearing a second bulky substituent at the C≡C bond. The exchange product, 9-propyn-1-yl-9-borabicyclo[3.3.1]nonane, was isolated as its crystalline pyridine adduct and fully characterised by NMR spectroscopy in solution and X-ray structural analysis in the solid state.

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44

Jones, William, Brett Swartz, and William Brennessel. "Lewis Acid Assisted C–CN Cleavage of Benzonitrile Using [(dippe)NiH]2." Synlett 29, no. 06 (July 20, 2017): 747–53. http://dx.doi.org/10.1055/s-0036-1590801.

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Reactions of [(dippe)NiH]2 with benzonitrile and varying concentrations of Lewis acids (primarily BPh3 and BF3) have shown a dramatic variation of reaction rate compared to the same reaction without Lewis acids. When less than one equivalent of Lewis acid is used, the reaction rate is as much as 100 times greater than without Lewis acid. Boron exchange was observed with less than one equivalent of Lewis acid allowing the formation of a Ni(0)–η2-aryl complex (observed by low-temperature NMR and calculations) to which the Lewis acid is postulated to re-coordinate as the rate-limiting step allowing the formation of a stable Ni(II) product. When one equivalent or greater of Lewis acid is used, the reaction shows dramatic inhibition even compared to the reaction without Lewis acid. Lewis acid dissociation can be considered as the rate-limiting step under these conditions. The overall work detailed herein has shown the importance of Lewis acids in the activation of benzonitriles due to the strengthening of the C–N bond allowing for increased stabilization of the products.

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45

Tiritiris, Ioannis, and Willi Kantlehner. "Crystal structure ofN,N,N′,N′,N′′,N′′-hexamethylguanidinium cyanate 1.5-hydrate." Acta Crystallographica Section E Crystallographic Communications 71, no. 12 (December 1, 2015): o1076—o1077. http://dx.doi.org/10.1107/s2056989015024317.

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The title hydrated salt, C7H18N3+·OCN−.1.5H2O, was synthesized starting fromN,N,N′,N′,N′′,N′′-hexamethylguanidinium chloride by a twofold anion-exchange reaction. The asymmetric unit contains two cations, two cyanate anions and three water molecules. One cation shows orientational disorder and two sets of N-atom positions were found related by a 60° rotation, with an occupancy ratio of 0.852 (6):0.148 (6). The C—N bond lengths in both guanidinium ions range from 1.329 (2) to 1.358 (10) Å, indicating double-bond character, pointing towards charge delocalization within the NCN planes. Strong O—H...N hydrogen bonds between the crystal water molecules and the cyanate ions and strong O—H...O hydrogen bonds between the water molecules are present, resulting in a two-dimensional hydrogen bonded network running parallel to the (001) plane. The hexamethylguanidinium ions are packed in between the layers built up by water molecules and cyanate ions.

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46

Matsumoto, Mitsuru, Shigenobu Funahashi, and Hideo D. Takagi. "Electrochemical Electron Transfer Reactions of M(ttcn)23+/2+ (M = Co, Pd, Pt, Au; ttcn = 1,4,7-trithiacyclononane): the Relation of Reaction Volumes and Electron Transfer Rate Constants." Zeitschrift für Naturforschung B 54, no. 9 (September 1, 1999): 1138–46. http://dx.doi.org/10.1515/znb-1999-0909.

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The reaction volumes (ΔV0M), corresponding to the volume change for the half-cell reactions for a series of M(ttcn)23+/2+ couples were measured by using cyclic voltammetry at elevated pressures. The ΔV0Mvaluesreflect the changes in the bond length between M and ligands accompanying the changes in the oxidation state of M from 3+ to 2+. The values of the estimated ΔV0M are in the order of Co < Au < Pd < Pt. The reaction volume is larger for the slower ET reactions, indicating that the reaction volumes reflect the inner-sphere contribution to the activation free energies. The heterogeneous electron exchange rate constants for the M(ttcn)23+/2+ couples, kel, were measured by AC voltammetry, and by cyclic voltammetry. The latter method on the basis of the Kochi-Nicholson’s method was carried out to examine the reliability of this rather simple method by setting the scan rate very fast to make the redox system irreversible. The results obtained by these two methods are in fair agreement with each other, especially when a glassy carbon working electrode was used for the measurements. The relation between the activation free energies for the heterogeneous electron exchange rate constants, ΔG*el, and those for the homogeneous reactions, ΔG*ex, is linear, which indicates that the homogeneous electron transfer reactions of a series of M(ttcn)23+/2+ is also governed by the intrinsic structural change. However, the slope of log kel vs. log kex plot is far smaller than 0.5 as predicted by the Marcus theory.

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47

Cao, Dapeng, Qifang Li, Manxi Zhou, Lei Zhu, Zhimin Sun, and Zhenqing Yang. "Tri-Petal Lilac-Like Perylene: Asymmetrical Substituted Platform for Regioselective Ether-Exchange Reaction." Synlett 28, no. 16 (July 6, 2017): 2121–25. http://dx.doi.org/10.1055/s-0036-1590808.

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An asymmetrical tri-petal lilac-like platform based on perylene bisimide (PBI) was designed and synthesized to further perform the ether-exchange reaction, while common tetraphenoxy PBI analogue cannot do it. We found that the tri-petal lilac-like platform strategy not only avoids the regioisomers of difunctionalized PBI, but also is a precise and facile way to achieve regioselective introduction of alkyloxy, alkylthio and C=C double bond ended substituents onto the 1-position of perylene bay without the use and removal of the protecting groups. Due to the tunable photoelectrical properties and functional groups at bay position, these n-type PBI derivatives are promising materials for photovoltaic and supramolecular application.

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48

Pokorny, Diana, Lothar Brecker, Mateja Pogorevc, Walter Steiner, Herfried Griengl, Thomas Kappe, and Douglas W. Ribbons. "Proton-Nuclear Magnetic Resonance Analyses of the Substrate Specificity of a β-Ketolase from Pseudomonas putida, Acetopyruvate Hydrolase." Journal of Bacteriology 181, no. 16 (August 15, 1999): 5051–59. http://dx.doi.org/10.1128/jb.181.16.5051-5059.1999.

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ABSTRACT A revised purification of acetopyruvate hydrolase from orcinol-grown Pseudomonas putida ORC is described. This carbon-carbon bond hydrolase, which is the last inducible enzyme of the orcinol catabolic pathway, is monomeric with a molecular size of ∼38 kDa; it hydrolyzes acetopyruvate to equimolar quantities of acetate and pyruvate. We have previously described the aqueous-solution structures of acetopyruvate at pH 7.5 and several synthesized analogues by1H-nuclear magnetic resonance (NMR)-Fourier transform (FT) experiments. Three 1H signals (2.2 to 2.4 ppm) of the methyl group are assigned unambiguously to the carboxylate anions of 2,4-diketo, 2-enol-4-keto, and 2-hydrate-4-keto forms (40:50:10). A1H-NMR assay for acetopyruvate hydrolase was used to study the kinetics and stoichiometries of reactions within a single reaction mixture (0.7 ml) by monitoring the three methyl-group signals of acetopyruvate and of the products acetate and pyruvate. Examination of 4-tert-butyl-2,4-diketobutanoate hydrolysis by the same method allowed the conclusion that it is the carboxylate 2-enol form(s) or carbanion(s) that is the actual substrate(s) of hydrolysis. Substrate analogues of 2,4-diketobutanoate with 4-phenyl or 4-benzyl groups are very poor substrates for the enzyme, whereas the 4-cyclohexyl analogue is readily hydrolyzed. In aqueous solution, the arene analogues do not form a stable 2-enol structure but exist principally as a delocalized π-electron system in conjugation with the aromatic ring. The effects of several divalent metal ions on solution structures were studied, and a tentative conclusion that the enol forms are coordinated to Mg2+ bound to the enzyme was made. 1H–2H exchange reactions showed the complete, fast equilibration of 2H into the C-3 of acetopyruvate chemically; this accounts for the appearance of2H in the product pyruvate. The C-3 of the product pyruvate was similarly labelled, but this exchange was only enzyme catalyzed; the methyl group of acetate did not undergo an exchange reaction. The unexpected preference for bulky 4-alkyl-group analogues is discussed in an evolutionary context for carbon-carbon bond hydrolases. Routine one-dimensional 1H-NMR in normal1H2O is a new method for rapid, noninvasive assays of enzymic activities to obtain the kinetics and stoichiometries of reactions in single reaction mixtures. Assessments of the solution structures of both substrates and products are also shown.

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49

Harcourt, Richard D., Karin Schaefer, and Michelle L. Coote. "Some Comments on Valence Bond Representations for the Radical Exchange Reaction X•+ R:Y → X:R + Y•." Journal of Physical Chemistry A 111, no. 50 (December 2007): 13278–82. http://dx.doi.org/10.1021/jp076864p.

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50

Kondo, Michio, Kouji Okamoto, Ichiro Nishi, Makoto Yamamoto, Masood Jelokhani-Niaraki, and Hiroaki Kodama. "Hydrogen-Bond Detection in Peptides by1H-Nuclear Magnetic Resonance through a Hydrogen–Chlorine Exchange Reaction." Bulletin of the Chemical Society of Japan 67, no. 4 (April 1994): 1064–68. http://dx.doi.org/10.1246/bcsj.67.1064.

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Journal articles on the topic 'Bond exchange reaction'

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