Designing fast radical clocks.
Date
1996
Authors
Nevill, Sandra Marjorie.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
Rate constants of radical reactions may be determined directly, using fast spectroscopic techniques such as laser flash photolysis, pulse radiolysis or esr, or indirectly, using product yield ratios. For indirect measurement, two competing reactions are required, one with a known rate constant called the radical clock. Radical clocks also may be used to investigate whether a reaction mechanism involves radical intermediates.
The photolysis of naphthylmethyl esters in nucleophilic solvents gives products derived from both ions and radicals. Initial studies on the photosolvolysis of benzylic esters suggested that the ions were formed by heterolytic cleavage from the excited state, and the radicals by homolytic cleavage. In contrast, DeCosta and Pincock suggested that only homolysis occurs, and then ions are produced by electron transfer in the initially-formed radical pair. The radicals that lead to products are produced by decarboxylation of the acyloxy radical. The rate constants determined from product yields for the electron transfer and decarboxylation steps fall in the range $10\sp9$ to $\rm 10\sp \ s\sp{-1}.$
In this thesis, this mechanism was further investigated by synthesis of five naphthylmethyl esters, 1. The rate constants for these radical clocks may be determined by product-yield ratios and the known rate constant of either the electron transfer or decarboxylation reactions.* ftn*Please refer to the dissertation for diagrams.
Thesis (Ph.D.)--Dalhousie University (Canada), 1996.
The photolysis of naphthylmethyl esters in nucleophilic solvents gives products derived from both ions and radicals. Initial studies on the photosolvolysis of benzylic esters suggested that the ions were formed by heterolytic cleavage from the excited state, and the radicals by homolytic cleavage. In contrast, DeCosta and Pincock suggested that only homolysis occurs, and then ions are produced by electron transfer in the initially-formed radical pair. The radicals that lead to products are produced by decarboxylation of the acyloxy radical. The rate constants determined from product yields for the electron transfer and decarboxylation steps fall in the range $10\sp9$ to $\rm 10\sp \ s\sp{-1}.$
In this thesis, this mechanism was further investigated by synthesis of five naphthylmethyl esters, 1. The rate constants for these radical clocks may be determined by product-yield ratios and the known rate constant of either the electron transfer or decarboxylation reactions.* ftn*Please refer to the dissertation for diagrams.
Thesis (Ph.D.)--Dalhousie University (Canada), 1996.
Keywords
Chemistry, Organic.