Facile Formation of Acetic Sulfuric Anhydride: Microwave Spectrum, Internal Rotation, and Theoretical Calculations

Anna K. Huff, Rebecca B. Mackenzie, C. J. Smith, Kenneth R. Leopold

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16 Scopus citations


Acetic sulfuric anhydride, CH3COOSO2OH, was produced by the reaction of SO3 and CH3COOH in a supersonic jet. Four isotopologues were observed by microwave spectroscopy. Spectra of both A and E internal rotor states were observed and analyzed, yielding a value of 241.093(30) cm-1 for the methyl group internal rotation barrier of the parent species. Similar values were obtained for the other isotopologues studied. M06-2X/6-311++G(3df,3pd) calculations indicate that the formation of the anhydride proceeds via a π2 + π2 + σ2 cycloaddition reaction within the CH3COOH-SO3 complex. The equilibrium orientation of the methyl group relative to the O-C-C plane is different in the anhydride and in the CH3COOH-SO3 complex, indicating that the -CH3 internal rotation accompanies the cycloaddition reaction. The energies of key points on the potential energy surface were calculated using CCSD(T)/complete basis set with double and triple extrapolation [CBS/(D-T)], and the transformation from the CH3COOH-SO3 complex to CH3COOSO2OH is shown to be nearly barrierless regardless of the orientation of the methyl group. This study provides the second experimental observation of the reaction between a carboxylic acid and SO3 to form a carboxylic sulfuric anhydride in the gas phase. Possible connections to atmospheric aerosol formation are discussed.

Original languageEnglish (US)
Pages (from-to)5659-5664
Number of pages6
JournalJournal of Physical Chemistry A
Issue number30
StatePublished - Aug 3 2017

Bibliographical note

Funding Information:
This work was supported by the National Science Foundation Grant Nos. CHE-1266320 and CHE-1563324, and the Minnesota Supercomputer Institute. We thank Dr. W. Isley for valuable discussions about the computational aspects of this work.

Publisher Copyright:
© 2017 American Chemical Society.

Copyright 2017 Elsevier B.V., All rights reserved.


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