Photoelectron spectroscopy of 1-propyl, 1-butyl, isobutyl, neopentyl, and 2-butyl radicals: free radical precursors to high-energy carbonium ion isomers. [Studied at elevated temperature to increase extent of radical decomposition]

Journal Article · Wed Jul 11 04:00:00 EDT 1984 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00326a006· OSTI ID:6417014

Schultz, J C; Houle, F A; Beauchamp, J L

The first photoelectron bands of 1-propyl, 1-butyl, isobutyl, neopentyl, and 2-butyl radicals have been obtained. Adiabatic and vertical ionization potentials, respectively, are 8.15 +/- 0.02 and 8.43 +/- 0.02 eV for 1-propyl radical, 8.02 (+0.04 - 0.1) and 8.50 +/- 0.04 ev for 1-butyl radical, 7.93 (+0.03-0.1) and 8.31 +/- 0.03 eV for isobutyl radical, 7.88 +/- 0.05 and 8.25 +/- 0.03 eV for neopentyl radical, and 7.25 +/- 0.02 and 7.59 +/- 0.03 eV for 2-butyl radical. From recently determined or estimated heats of formation of the radicals, heats of formation of the corresponding carbonium ions are calculated to be 210.5 +/- 1.1 kcal/mol for 1-propyl cation, 201.9 +/- 3 kcal/mol for 1-butyl cation, 197.9 +/- 3 kcal/mol for isobutyl cation, 188.8 +/- 2.3 kcal/mol for neopentyl cation, and 181.0 +/- 1.1 kcal/mol for 2-butyl cation. The energetics of ion solvation processes are assessed from a comparison of the gas-phase results to solution data where these ions are generated as nascent products of ionization processes or are proposed as reaction intermediates in isomerization reactions. With the exception of the 1-propyl radical spectrum, the spectra exhibit no resolved vibrational structure. The possible origins of a weakly resolved 540 +/- 160 cm/sup -1/ vibrational progression observed on the 1-propyl radical band are discussed. An analysis of these spectra, along with those of ethyl and 2-propyl radicals, reveals treads in ionization potentials that may be interpreted in terms of inductive and hyperconjugative effects of methyl substituents ..beta.. to primary or secondary cation centers. 96 references, 7 figures, 2 tables.

• Research Organization: California Inst. of Tech., Pasadena
• OSTI ID: 6417014
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 106:14; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
ALKYL RADICALS
BUTYL RADICALS
CHEMICAL REACTIONS
CORRELATIONS
DATA
DATA ANALYSIS
ELECTRON SPECTROSCOPY
ELECTRONIC STRUCTURE
ENTHALPY
EXPERIMENTAL DATA
FORMATION HEAT
INFORMATION
IONIZATION POTENTIAL
ISOBUTYL RADICALS
ISOMERIZATION
MOLECULAR STRUCTURE
NUMERICAL DATA
PHOTOELECTRON SPECTROSCOPY
PHYSICAL PROPERTIES
PROPYL RADICALS
PYROLYSIS PRODUCTS
RADICALS
REACTION HEAT
SPECTROSCOPY
STRUCTURAL CHEMICAL ANALYSIS
THERMODYNAMIC PROPERTIES