Hydrogen bonding in the sulfuric acid-methanol-water system: A matrix isolation and computational study

Mark Rozenberg, Aharon Loewenschuss, Claus J. Nielsen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Frozen core MP2 and DFT computations were carried out on possible configurations of 1:1 H2SO4·CH3OH and 1:1:1 H2SO4·CH3OH·H2O complexes. Minimum energy structures, stabilization energies, H-bond lengths and vibrational frequencies were calculated. The latter complex can exist in either sequential "linear" configurations involving four H-bonds or "cyclic" structures involving three H-bonds only. However, there is little difference in the energy of stabilization between these two possible forms, indicating a "cooperative effect" between the H-bonds in the latter. This effect is also evidenced by the calculated H-bond lengths. In the cyclic complex, the hydroxyl of either CH3OH or H2O may be the proton donor to the H-bond between them. Argon matrix isolation FTIR spectra of layers with various concentration ratios were recorded. In the hydroxyl stretch wavenumber regions several weak new bands were observed. Their position was found to fit best the cyclic structures. The observed red shifts exceed the corresponding calculated values. Together with the considerable observed bandwidths they are further manifestations of the cooperative effect between the H-bonds. The lower skeletal mode wavenumber regions show a number of sharper bands compatible with those previously reported for dimethyl sulfate and hydrogen methyl sulfate, indicating their formation in the vapor mixing region or at the solid matrix layer interface.

Original languageEnglish
Pages (from-to)2271-2280
Number of pages10
JournalJournal of Physical Chemistry A
Volume119
Issue number11
DOIs
StatePublished - 19 Mar 2015

Bibliographical note

Publisher Copyright:
© 2014 American Chemical Society.

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