A study of the metastable dissociations of formate esters: A McLafferty rearrangement to a distonic radical cation
- Univ. of Nebraska, Lincoln (USA)
The metastable dissociations of formate ester radical cations were studied by using both threshold photoelectron photoion coincidence and tandem mass spectrometry. Kinetic energy releases for the unimolecular fragmentations were obtained from both mass analyzed ion kinetic energy (MIKE) and time-of-flight spectra. An important dissociation property of propyl formate radical cation is that the appearance energies of the three major fragment ions (C{sub 3}H{sub 6}{sup {sm bullet}+}, HC(OH){sub 2}{sup +}, and m/z 60 ({sup {sm bullet}}CH{sub 2}OCHOH{sup +} and C{sub 3}H{sub 7}OH{sup {sm bullet}+})) are the same as the ionization energy of the propyl formate molecule, resulting in the absence of a molecular ion in the braekdown graph. The three major fragment ions are all formed via rearrangement processes (stepwise McLafferty rearrangement) involving a common distonic intermediate. The rearrangements are exothermic and occur without an activation energy, a conclusion in agreement with that of Benoit, Harrison, and Lossing for the formation of HC(OH){sub 2}{sup +}. The heat of formation of the distonic intermediate formed by an {beta} hydrogen atom transfer was determined to be <579 kJ mol{sup {minus}1}. The rearrangement also pertains to butyl formate and may be a characteristic of the unimolecular dissociations of larger alkyl formate ester radical cations at low internal energies.
- DOE Contract Number:
- AC02-76ER02567
- OSTI ID:
- 6712592
- Journal Information:
- Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 94:4; ISSN 0022-3654; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ACYL RADICALS
CALCULATION METHODS
CARBOXYLIC ACID SALTS
DATA
DATA ANALYSIS
DISSOCIATION
ELECTRON SPECTROSCOPY
ENERGY
ESTERS
EXPERIMENTAL DATA
FORMATES
FORMYL RADICALS
INFORMATION
KINETIC ENERGY
MASS SPECTROSCOPY
MEASURING INSTRUMENTS
MEASURING METHODS
NUMERICAL DATA
ORGANIC COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
RADICALS
SPECTROSCOPY