Unimolecular dissociation of energy-selected methyl formate ion

Journal Article · Thu Oct 15 04:00:00 EDT 1987 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.452870· OSTI ID:6144646

Nishimura, T; Zha, Q; Meisels, G G

Fragmentation mechanisms of the methyl formate and methyl formate-d/sub 1/ ions have been investigated using threshold photoelectron--photoion coincidence (TPEPICO) mass spectrometry. The breakdown diagrams and ion kinetic energies of fragment ions were measured at internal energies of the molecular ion from 0 to 7 eV, and fragmentation pathways were elucidated. The formation of HCO/sup +/ showed a large kinetic isotope effect. The formation of CH/sub 3/O/sup +/ from methyl formate-d/sub 1/ is accompanied by a large kinetic energy release, about twice that calculated using quasiequilibrium theory (QET). Its relative abundance in the breakdown curve also appears to be inconsistent with statistical theory. Direct dissociation from an isolated state of the molecular ion was one possible explanation. Slow dissociations were observed for the formation of methanol ions resulting from a migration of the formyl hydrogen while QET predicts no metastable dissociation for this process. Two-component reaction rates for methanol ion formation suggest participation of more than one state or isomer. The heat of formation of HCOO was found to be -40 +- 6 kcal/mol, indicating that it is less stable than COOH (..delta..H/sub f/ = -58+4 kcal/mol).

• Research Organization: Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0312
• OSTI ID: 6144646
• Journal Information: J. Chem. Phys.; (United States), Journal Name: J. Chem. Phys.; (United States) Vol. 87:8; ISSN JCPSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CARBOXYLIC ACID ESTERS
CARBOXYLIC ACID SALTS
CHARGED PARTICLES
CHEMICAL REACTION KINETICS
DISSOCIATION
ESTERS
FORMATES
IONS
ISOTOPE EFFECTS
KINETICS
MASS SPECTROSCOPY
MOLECULAR IONS
ORGANIC COMPOUNDS
REACTION KINETICS
SPECTROSCOPY