Variable-temperature rate coefficients of proton-transfer equilibrium reaction C2H4 + H3O+ ↔ C 2H5+ + H2O measured with a coaxial molecular beam radio frequency ring electrode ion trap

Mark A. Smith, Bing Yuan, Andrei M Sanov

Research output: Contribution to journalArticle


The rate coefficients for the forward and reverse proton-transfer reactions C2H4 + H3O+ ↔ C 2H5+ + H2O are studied with respect to independent varied neutral molecule and ion temperatures. The measurements are performed using a coaxial molecular beam radio frequency ring electrode ion trap at trap temperatures down to 23 K and beam temperatures up to 450 K. The temperature-dependent rate coefficients suggest that in this temperature window, the reaction proceeds through a statistically equilibrated complex. In order to explain the observed rate coefficients, a new type of reaction temperature was defined in these studies that considered collisional and internal (rotational and vibrational) degrees of freedom of both H3O+ and C2H4. The enthalpy and entropy of the equilibrium reaction deduced from a Van't Hoff plot are δH = (5.1 ± 0.5) kJ̇mol-1 and δS = (-15.0 ± 0.9) J̇mol -1̇K-1, respectively.

Original languageEnglish (US)
Pages (from-to)11596-11600
Number of pages5
JournalJournal of Physical Chemistry A
Issue number47
Publication statusPublished - Nov 29 2012


ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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