Dasfefaf Essay

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Thematic Division: Theoretical and Computational Chemistry. __________________________________________________________ Subdivision: Quantum Chemistry. Registration Code of Publication: q3v1 Full Paper Received 28 September, 1998 Thematic course: Quantum-Chemical Study of the Reactions of Elimination, Addition and Substitution. Part I. AB INITIO STUDY OF E2 AND SN2 REACTIONS OF F- WITH CHLOROCYCLOALKANES. © Svetlana A. Appolonova,1 Lyudmila V. Ermolaeva,1 Vitaly V. Plemenkov,2*+ and Alexander I. Konovalov1 A.E. Arbuzov Institute of Organic and Physical Chemistry of Kazan Scientific Centre of Russian Academy of Sciences. Arbuzov St., 8. Kazan 420088. Russia. Fax: +7 (8432) 752-253; E-mail: jess@glass.ksu.ras.ru 2 Department of Organic Chemistry. Kazan State Medical University. Butlerova St., 49. Kazan 420012. Russia. Tel.: +7 (8432) 389-744; Fax: +7 (8432) 360-393 ____________________________________________ *Leader of the thematic course; +Corresponding author Keywords: E2 elimination, SN2 substitution, chlorocycloalkanes, transition state, ion-dipole complexes. 1 Abstract With the use of ab initio quantum-chemical calculations (6-31(+)G*//HF/6-31(+)G* level) E2 and SN2 reactions have been investigated for the interactions of fluoride anion with chlorocyclopropane and chlorocyclobutane. The transition states of E2(anti), E2(syn) and SN2 processes were localized. It has been found, that for chlorocyclopropane the barrier of syn-elimination is only 3.5 kcal⋅mol-1 higher than the barrier of anti-elimination, whereas the difference for chlorocyclobutane is 8.09 kcal⋅mol-1. These values are much less, than in the case of chlorocyclopentane (ЕE2(anti)-E2(syn)= 13.8 kcal⋅mol-1) and chlorocyclohexane (18.7 kcal⋅mol-1). Thus, the diminution of the size of the cycle causes a considerable reduction of energy difference between E2(anti)and E2(syn)-transition

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