Mechanisms of photodissociative ionization of HCOOH: The heat of formation of COOH sup +

Journal Article · Fri Dec 01 04:00:00 EST 1989 · Journal of Chemical Physics; (USA)

DOI:https://doi.org/10.1063/1.457346· OSTI ID:5296000

Ruscic, B; Schwarz, M; Berkowitz, J ^[1]

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1. Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439 (US)

The dissociative ionization of HCOOH to form COOH{sup +} +H+{ital e} has been reinvestigated. Experiments with DCOOH and HCOOD demonstrate that rearrangement competes with direct bond cleavage in this dissociation, even near threshold. Extrapolation of the photoion yield curve of COOH{sup +} to the background level is ambiguous. A photoelectron--photoion coincidence experiment was thereupon performed, to obtain a breakdown diagram. From the 0 K cross over energy of 12.30{plus minus}0.02 eV, we infer {Delta}{ital H}{sub {ital f}{sup 0}{sub 0}} (COOH{sup +})=143.2{plus minus}0.5 kcal/mol, and proton affinity (PA) (CO{sub 2})=129.2{plus minus}0.5 kcal/mol. Some possible mechanisms for the rearrangement process are explored, but the calculated barriers are too high to explain the observation.

• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5296000
• Journal Information: Journal of Chemical Physics; (USA), Journal Name: Journal of Chemical Physics; (USA) Vol. 91:11; ISSN JCPSA; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400500 -- Photochemistry
AFFINITY
BARYONS
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DECOMPOSITION
DISSOCIATION
ELEMENTARY PARTICLES
ENTHALPY
FERMIONS
FORMATES
FORMATION HEAT
FORMIC ACID
HADRONS
IONIZATION
MONOCARBOXYLIC ACIDS
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOIONIZATION
PHOTOLYSIS
PHYSICAL PROPERTIES
PROTONS
RADICALS
REACTION HEAT
THERMODYNAMIC PROPERTIES