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The kinetics, stereochemistry, and deuterium isotope effects in the α-pinene pyrolysis. Evidence for incursion of multiple conformations of a diradical by Joseph J Gajewski; Ilya Kuchuk; Christopher Hawkins; Robert Stine is a Chemistry article available to read on EtoBox.

What is The kinetics, stereochemistry, and deuterium isotope effects in the α-pinene pyrolysis. Evidence for incursion of multiple conformations of a diradical about?

Pyrolysis of optically active a-pinene gave 95% racemic limonene (dipentene), alloocimine, racemic a-pinene, a-pyronene. Activation parameters are reported. Pyrolysis of (S ) syn-6-trideuteriomethyl a-pinene at 256.78C for 2400 s gave dipentene with twice as much deuterium as hydrogen transfer with k H /k D 1⁄41.49 and alloocimine with a Z and E trideuteriomethyl ratio of ca. 5 with k H /k D 1⁄40.89. The isotope effect on loss of starting material was 1.16. Separation of the enantiomers of a-pinene from 3600 s pyrolyses at 256.78C followed by NMR analysis revealed that the ratio of the R-syn to R-anti to S-anti isomers is 4.6:3.7:1 at roughly two half-lives. Kinetic analysis reveals that the previously proposed mechanism for all conversions involving slow interconversion of two diradicals with C s symmetry is not consistent with the distribution of the a-pinene isomers, particularly the formation of more suprafacial-retention product (R-anti ) than bondrotated isomer (S-anti ). Inclusion of another C s species (ignoring the deuteriums) that would be intermediate between the originally proposed C s species, appears more consistent with the observations.

Who reads The kinetics, stereochemistry, and deuterium isotope effects in the α-pinene pyrolysis. Evidence for incursion of multiple conformations of a diradical?

Author

Joseph J Gajewski; Ilya Kuchuk; Christopher Hawkins; Robert Stine

Publisher

Elsevier Science; Elsevier ; Elsevier Ltd.; Elsevier BV (ISSN 0040-4020)

Published

2002

Language

EN

Field

Chemistry (Physical Sciences)