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MO study of the possibility of a concerted mechanism in the pinacol rearrangement
Author(s) -
Nakamura Kensuke,
Osamura Yoshihiro
Publication year - 1990
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610031107
Subject(s) - chemistry , carbocation , transition state , concerted reaction , protonation , computational chemistry , hydride , reaction mechanism , rearrangement reaction , pinacol , mechanism (biology) , ab initio , photochemistry , ion , catalysis , organic chemistry , philosophy , hydrogen , epistemology
The ab initio SCF‐MO method was employed to examine the possibility of a reaction pathway without a carbocation intermediate in the pinacol rearrangement. The molecular geometries of the transition states were obtained for the 1,2‐hydride shift together with H 2 O elimination, starting from the various methyl‐substituted protonated 1,2‐diols. It was found that the activation energies depend strongly on the substitutents. A comparison of the relative energies between β‐hydroxycarbonium ions and the transition states of the concerted mechanism suggests that the stepwise mechanism is less favourable than the concerted path in each case.