A vibrational sum frequency spectroscopy study of the liquid-gas interface of acetic acid-water mixtures: 2: orientation analysis
2005 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 1, 329-341 p.Article in journal (Refereed) Published
Vibrational sum frequency spectroscopy has been used to investigate the surface of aqueous acetic acid solutions. By studying the methyl and carbonyl vibrations with different polarization combinations, an orientation analysis of the acetic acid molecules has been performed in the concentration range 0-100%. The surface tension of acetic acid solutions was also measured in order to obtain the surface concentration. The orientation of the interfacial acetic acid molecules was found to remain essentially constant in an upright position with the methyl group directed toward the gas phase in the whole concentration range. The tilt angle (theta(CH3)) of the symmetry axis of the methyl group with respect to the surface normal was found to be lower than 15degrees when considering a delta distribution of angles or as narrow as 0 +/- 11degrees when assuming a Gaussian distribution. Further investigations showed that the C=O bond tilt (theta(C=O)) of the acetic acid hydrated monomer was constant and close to 55degrees in the concentration range where it was detected. Finally, the orientation information is discussed in terms of different species of acetic acid, where the formation of a surface layer of acetic acid cyclic dimers is proposed at high acid concentrations.
Place, publisher, year, edition, pages
2005. Vol. 109, no 1, 329-341 p.
MOLECULAR MECHANICS METHOD; CH3COOH CH3COOD CD3COOH; CH STRETCHING MODES; SPECTRES INFRAROUGES; GENERATION SPECTRUM; INTERNAL-ROTATION; CARBOXYLIC-ACIDS; BINARY-MIXTURES; RAMAN-SPECTRUM; SFG SPECTRUM
IdentifiersURN: urn:nbn:se:kth:diva-7700DOI: 10.1021/jp047337yISI: 000226213200049ScopusID: 2-s2.0-12344308339OAI: oai:DiVA.org:kth-7700DiVA: diva2:12804
QC 201008252005-10-202005-10-202010-10-29Bibliographically approved