Infrared spectroscopy of the acetyl cation and its protonated ketene isomer

[C2,H3,O](+) ions are generated with a pulsed discharge in a supersonic expansion containing methyl acetate or acetone. These ions are mass selected and their infrared spectra are recorded via laser photodissociation and the method of argon tagging. Computational chemistry is employed to investigate...

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Bibliographic Details
Published in:The Journal of chemical physics 2014-07, Vol.141 (2), p.024306-024306
Main Authors: Mosley, J D, Young, J W, Duncan, M A
Format: Article
Language:English
Subjects:
ABSORPTION SPECTROSCOPY
ACETONE
ARGON
Astrochemistry
CALCULATION METHODS
CATIONS
Computational chemistry
DISSOCIATION
INFRARED SPECTRA
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
Interstellar
Ions
ISOMERS
KETENES
METHYL ACETATE
Organic chemistry
Photodissociation
PHOTOLYSIS
PRECURSOR
Precursors
PULSES
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Summary:[C2,H3,O](+) ions are generated with a pulsed discharge in a supersonic expansion containing methyl acetate or acetone. These ions are mass selected and their infrared spectra are recorded via laser photodissociation and the method of argon tagging. Computational chemistry is employed to investigate structural isomers and their spectra. The acetyl cation (CH3CO(+)) is the global minimum and protonated ketene (CH2COH(+)) is the next lowest energy isomer (+176.2 kJ/mol). When methyl acetate is employed as the precursor, the infrared spectrum reveals that only the acetyl cation is formed. Partially resolved rotational structure reveals rotation about the C3 axis. When acetone is used as the precursor, acetyl is still the most abundant cation, but there is also a minor component of protonated ketene. Computations reveal a significant barrier to interconversion between the two isomers (+221 kJ/mol), indicating that protonated ketene must be obtained via kinetic trapping. Both isomers may be present in interstellar environments, and their implications for astrochemistry are discussed.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.4887074