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Steric Effects on Reaction Rates. IV. Evaluation of the Ketone Model for the Solvolysis Transition State of Secondary p ‐Toluenesulfonates
Author(s) -
Müller Paul,
Blanc Jacky,
Pcrlberger JeanClaude
Publication year - 1982
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19820650514
Subject(s) - solvolysis , chemistry , steric effects , 2 norbornyl cation , ketone , transition state , reactivity (psychology) , acetic acid , substrate (aquarium) , medicinal chemistry , ion , leaving group , computational chemistry , photochemistry , stereochemistry , organic chemistry , catalysis , medicine , oceanography , alternative medicine , pathology , hydrolysis , geology
Abstract The rates of solvolysis of secondary p ‐toluenesulfonates in acetic acid or 97% trifluoroethanol are interpreted in terms of strain changes between substrate and the corresponding ketone. Such strain changes are obtained from force‐field calculations (Δ E st ) and from equilibration of alcohols and ketones (Δ G ox ). This simple model reproduces the behaviour of substrates reacting by k c‐pathways to afford unstrained carbenium ions. Anchimeric assistance and leaving group hindrance in the transition state are recognized in clear‐cut cases by deviations from the expected reactivity. However, the model breaks down when highly strained carbenium ions of the cyclobutyl or 7‐norbornyl type are involved.