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Updated: Mar 12, 2026

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI
Published on: November 22, 2016
Formation and Mechanism for Reactions of Ring-Substituted Phenonium Ions in Aqueous Solution
Yutaka Tsuji1, John P Richard2
1Department of Biochemistry and Applied Chemistry, Kurume National College of Technology, Komorinomachi, Kurume 830-8555, Japan.
Abstract:
The results of studies on the structure and reactivity of spiro[5.2]oct-5,7-diene-4yl carbocation [phenonium ion] have had a significant impact on the course of discussion about the distinction between classical and nonclassical carbocations. This minireview will present a brief overview of the structure, bonding and reactivity of ring substituted phenonium ions (X-4+), with an emphasis on work completed since 2004. The discussion will focus on the development of new experimental protocol for determination of the selectivity for addition of nucleophilic anions to X-4+ in aqueous solution. The existing relationships between carbocation lifetime and nucleophilic selectivity, and the known lifetime of ca 140 sec for spiro[2.5]oct-4,7-diene-6-one provide rough estimates of the lifetimes for 4-Me-X-4+ and 4-MeO-X-4+ in aqueous solution. Evidence is presented that nucleophile addition to X-4+ proceeds through an "exploded" transition state, with relatively weak bonding the nucleophile and leaving group, and the development of significant positive charge at the reacting primary cyclopropyl carbon.
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