A redetermination of the heats of formation of chloro- and dichlorocarbene and the deprotonation of methyl cation, a spin forbidden process?

Zhixin Tian, Steven R. Kass

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

The reactions of CH3+, CH2Cl+ and CHCl2+ with standard reference bases were examined in a dual cell Fourier transform mass spectrometer. Deprotonation of methyl cation occurs rapidly via a spin forbidden process to afford triplet methylene even when the reaction is nearly thermoneutral. Bracketing results enable us to assign PA(CHCl) = 209.7 ± 2.2 kcal mol-1 and PA(CCl2) = 205.2 ± 1.9 kcal mol-1, the latter value of which is considerably larger than previous determinations. The resulting heats of formation, however, are in good accord with other measurements and lead to recommended values of Δ Hf °(CHCl) = 74.6 ± 2.4 kcal mol-1 and Δ Hf °(CCl2) = 53.0 ± 2.6 kcal mol-1. These values correspond to a 2-3 kcal mol-1 lowering of these quantities and are within 1-2 kcal mol-1 of high level G3 and W1 predictions based upon the atomization energies and a series of four isodesmic reactions.

Original languageEnglish (US)
Pages (from-to)288-294
Number of pages7
JournalInternational Journal of Mass Spectrometry
Volume267
Issue number1-3 SPEC. ISS.
DOIs
StatePublished - Nov 1 2007

Bibliographical note

Funding Information:
Support from the National Science Foundation, the donors of the Petroleum Research Foundation, as administered by the American Chemical Society and the Minnesota Supercomputer Institute are gratefully acknowledged.

Copyright:
Copyright 2007 Elsevier B.V., All rights reserved.

Keywords

  • Chlorocarbene
  • Dichlorocarbene
  • FTMS
  • Methyl cation
  • Spin-forbidden reaction

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