Gas-phase properties and reactivity of the acetate radical anion. Determination of the C-H bond strengths in acetic acid and acetate ion

Journal Article · Wed Dec 28 04:00:00 EST 1994 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00105a032· OSTI ID:6868319

Wenthold, P G; Squires, R R ^[1]

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1. Purdue Univ., West Lafayette, IN (United States)

The acetate radical anion, CH[sub 2]CO[sub 2] [sup [center dot]-], has been generated in the gas phase at room temperature and its thermochemical properties and reactivity have been examined with use of a flowing afterglow-triple quadrupole instrument. This ion is formed in high yield from the reaction between F[sub 2] and the enolate ions of either acetic acid or trimethylsilyl acetate. Collision-induced dissociation (CID) of CH[sub 2]CO[sub 2][sup [center dot]-] occurs by loss of CO[sub 2] forming CH[sub 2][sup [center dot]-] with a measured threshold energy of 60.9 [+-] 2.7 kcal/mol. The (oxygen) proton affinity of CH[sub 2]CO[sub 2][sup [center dot]-] ([Delta]H[sub acid[sub -]] [[sub [center dot]]CH[sub 2]CO[sub 2]-H]) has been determined to be 347.0 [+-] 1.1 kcal/mol from measurements of the relative yields of the carboxylate ion fragments resulting from CID of proton-bound dimer ions formed by termolecular association of CH[sub 2]CO[sub 2][sup [center dot]-] with carboxylic acids with known gas-phase acidities (i.e., by the Cooks kinetic method). This result indicates that removal of a hydrogen atom from the [alpha]-carbon of acetic acid ([Delta]H[sub acid](CH[sub 3]CO[sub 2]H) = 348.6 [+-] 2.9 kcal/mol) increases the acidity by 1.6 kcal/mol. These data are used to derive the 298 K heat of formation for acetate radical anion and the C-H bond dissociation energies. 38 refs., 5 figs., 2 tabs.

• OSTI ID: 6868319
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 116:26; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
661300 -- Other Aspects of Physical Science-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACETATES
ACETIC ACID
ANIONS
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL BONDS
CHEMICAL REACTIONS
COMPILED DATA
DATA
DECOMPOSITION
ELEMENTS
FLUORINE
HALOGENS
INFORMATION
IONS
MASS SPECTROSCOPY
MONOCARBOXYLIC ACIDS
NITRIC OXIDE
NITROGEN COMPOUNDS
NITROGEN DIOXIDE
NITROGEN OXIDES
NONMETALS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RADICALS
SPECTROSCOPY
SULFUR COMPOUNDS
SULFUR DIOXIDE
SULFUR OXIDES
THERMODYNAMICS