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Steric Effects on Reaction Rates. Part IX. Force-Field Parameters for Bridgehead and Rigid Tertiary Carbenium Ions

By Paul Muller and Jiri Mareda

Abstract

Molecular-mechanics calculations for strain of carbenium ions are tested using Bentley's unified reactivity scale for bridgehead solvolysis as reference. Excellent correlations are obtained for solvolytic bridgehead reactivity with the calculated steric-energy difference (?Est) between substrate (R--H or R--OH) and cation (R+). After adjustment of appropriate force-field parameters, the approach is successfully extended to the rigid, but planar cations derived from structures 15-20; however, the general set of parameters cannot be applied to highly strained systems such as the cation formed from 17. With all of the 18 sets of parameters tested, the 2-endo-norbornyl derivative 16, is adequately correlated, while the exo isomer 15 exhibits enhanced reactivity by a factor of ca. 102 to 103

Topics: info:eu-repo/classification/ddc/540
Publisher: 'Wiley'
Year: 1987
DOI identifier: 10.1002/hlca.19870700414
OAI identifier: oai:unige.ch:unige:6219
Provided by: Archive ouverte UNIGE
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