ESR study of the photochemistry of benzoic acid derivatives

Journal Article · Tue Dec 15 23:00:00 EST 1992 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00052a048· OSTI ID:6566586

Jeevarajan, A S; Fessenden, R W ^[1]

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1. Univ. of Notre Dame, IN (United States)

Electron spin resonance (ESR) has been used to study radical intermediates in the photochemistry of a number of aromatic carboxylic acids, esters, anhydrides, amides, imides, and nitriles. Continuous photolysis was used to produce the radicals in either aqueous or alcoholic media. The triplet states of the compounds undergo two reactions in the presence of a hydrogen donor such as 2-propanol. A hydrogen atom is transferred to certain carbon atoms of the aromatic ring forming cyclohexadienyl radicals. In most cases, addition occurs at or opposite the carboxyl (or cyano) group. The pattern of addition is attributed to the higher spin density in the triplet at those positions. This pattern also correlates with the positions of higher hyperfine splitting in the corresponding anion radicals. In a parallel reaction, a hydrogen atom is also transferred to an oxygen of the carboxyl group (for acids, anhydrides, and esters) to form the one-electron-reduction product. The cyclohexadienyl radicals are not formed by protonation on a carbon of an anion radical. The ESR spectra of most of the cyclohexadienyl radicals are highly polarized to the extent that the low-field lines appear in emission. This effect is believed to be normal chemically induced dynamic spin polarization (CIDEP) as a result of cross reactions with the other radicals present. 46 refs., 7 figs., 10 tabs.

• OSTI ID: 6566586
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 114:26; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
AMIDES
ANHYDRIDES
BENZOIC ACID
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
ELECTRON SPIN RESONANCE
EMISSION
ESTERS
IMIDES
MAGNETIC RESONANCE
MONOCARBOXYLIC ACIDS
NITRILES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
PHOTOLYSIS
POLARIZATION
RADICALS
REACTION INTERMEDIATES
REDUCTION
RESONANCE