Activation Parameters for the Additions of Arylhalocarbenes to Alkenes

Robert A. Moss, Witold Ławrynowicz, Nicholas J. Turro, Ian R. Gould, Yuan Cha

Research output: Contribution to journalArticle

66 Scopus citations

Abstract

By use of nanosecond laser flash photolytic methods, absolute rate constants have been obtained for the additions of p-(trifluoromethyl)phenylbromocarbene (CF3C6H4CBr), phenylbromocarbene (PhCBr), phenylchlorocarbene (PhCCl), phenylfluorocarbene (PhCF), and p-methoxyphenylfluorocarbene (CH3OC6H4CF) to tetramethylethylene (TME) and 1-hexene. The rate constants ranged from 1.7 × 109 (CF3C6H4CBr/TME) to 5.0 × 104 L/(M•s) (CH3OC6H4CF/1-hexene); classical structure/reactivity relations were obeyed. Determination of the rate constants at temperatures between 315 and 200 K gave Ea, log A, ΔH*, ΔS*, and ΔG* for the 10 reactions. All of the reactions were dominated by ΔS*. ΔG* ranged from 5.0 to 11 kcal/mol for the fastest and slowest reactions. Negative values of Ea were observed for some of the faster reactions at higher temperatures. These results are analyzed in terms of single-step addition reactions where ΔG* is dominated by ΔS* and, alternatively, in terms of a two-step mechanism proceeding through a carbene-alkene complex.

Original languageEnglish (US)
Pages (from-to)7028-7032
Number of pages5
JournalJournal of the American Chemical Society
Volume108
Issue number22
DOIs
StatePublished - Jan 1 1986
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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