Analysis of the electron density redistribution in the course of nucleophilic addition reactions of H− and F− to acetylene and methylacetylene molecules according toab initio calculations |
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Authors: | N M Klimenko K V Bozhenko V M Geskin O N Temkin |
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Institution: | (1) M. V. Lomonosov State Academy of Fine Chemical Technology, 86 prosp. Vernadskogo, 117571 Moscow, Russian Federation;(2) N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 4 ul. Kosygina, 117977 Moscow, Russian Federation |
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Abstract: | Energy characteristics and peculiarities of variation of structural parameters along the minimum energy pathways (MEP) calculated earlier of six reactions of nucleophilic addition of H– and F– to acetylene and methylacetylene have been analyzed. The electronic mechanism of the reactions, the character of the electron density redistribution, and its relation with the changes in structural parameters have been discussed. It has been found for all six reactions that the structural reorganization of an alkyne + Nu system is completed before the barriers. However, the increase in the alkyne multiple bond length and changes in electronic characteristics for the reactions with F– (endothermic reactions) take place before the barrier (late transition state) and for the reaction with H– (exothermic reactions), after the barrier (early transition state).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2373–2377, December, 1995. |
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Keywords: | nucleophile alkyne ab initio calculations electron density Markovnikov rule chemical shifts structure minimum energy pathways orbital and charge control |
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