An Ab Initio Study of SN2 Reactivity at C6 in Hexopyranose Derivatives. II. Role of Populations, Barriers, and Reaction Path Curvature

Abstract

This paper continues our investigation into a simple dipole-dipole interaction model proposed to explain the dramatically reduced SN2. reactivity at the primary C6 position of galacto-configured pyranose systems relative to their gluco isomers. We present ab initio calculations (B3LYP/6-31+G(d,p)) on six model structures that show that this effect is not a major influence. Reactant rotameric equilibria as well as free-energy reaction barriers and reaction path curvature were evaluated. Results point to a number of other factors that could account for the observed reactivity differences. Our results cast doubt on the general relevance of transition structure dipole-dipole repulsions to SN2 reactivity.

Department(s)

Chemistry

Keywords and Phrases

Dipole-dipole interactions; Galacto-configurations; Hexopyranose derivatives; Tetrahydropyran model structures, Carbohydrates; Chemical reactions; Electrostatics; Free energy; Mathematical models; Negative ions; Stereochemistry, Derivatives, carbohydrate; carbon, article; chemical structure; chemistry; computer simulation; thermodynamics, Carbohydrates; Carbon; Computer Simulation; Models, Molecular; Molecular Structure; Thermodynamics

International Standard Serial Number (ISSN)

1089-5639

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2005, American Chemical Society (ACS), All rights reserved.

Publication Date

01 Jan 2005

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