Molecular Rearrangements. XXVIII. Thermolysis and Photolysis of Some Hydroxamic Acid Derivatives

Abstract

Thermolysis and photolysis of benzohydroxamic acid and some of its derivatives have been investigated. Thermolysis of benzohydroxamic acid (BHA) either by heating in air or in a sealed tube gives NH3, H2O, CO, benzil, aniline, o- and p-aminophenols, phenoxazine, benzanilide, and benzoic acid. Whereas, thermolysis of N-(benzyloxy)benzamide (BBA) affords toluene, benzaldehyde, bibenzyl, stilbene, phenanthrene, acridine, and o- and p-aminodiphenylmethane in addition to the previous products. Analogous products were also obtained on pyrolysis of phenylacetohydroxamic acid. Photolysis of BHA and BBA in acetonitrile gives similar results to those of pyrolysis. A free-radical mechanism involving homolysis at different sites was postulated to account for the formation of such products.

Thermal fragmentation and rearrangement of N-arylbenzamidoxime and O-phenylsulfonyloxime derivatives

“…Moreover, the homolysis of the C-N bond (route b), via the tautomeric form of I as reported by Tiemann [28], gives anilino and benziminoxyl radical pairs. The anilino radical may abstract hydrogen to give aniline, whereas the benziminoxyl radical undergoes fragmentation to form benzonitrile and the hydroxyl radical [29] (Scheme 3).…”

UV Laser-Induced Photodecomposition of Matrix-Isolated Salicylhydroxamic Acid: Identification of New Isocyanate Complexes

“…The generation of salicylaldehyde as well as salicylamide may be a result of the o -hydroxybenzoyl radical hydrogenation. Amides or anilides are the primary products of the thermolysis of hydroxamic acids [ 11 , 19 , 46 ], so their formation during photodegradation should also be considered. Identification of CO monomer bands at 2138 and 2136 cm −1 may be the effect of the total disintegration of different molecules trapped in matrices.…”

Characterization of Tepoxalin and Its Related Compounds by High-Performance Liquid Chromatography/Mass Spectrometry

“…Hydroxamic acids may also undergo thermal and photochemical reactions that involve homolytic cleavage of the NsO or OdCsN bonds of the hydroxamic acid moiety. 17,18 Products such as 7, 8, 12, and 13, therefore, may have been a result of these radical reactions. The pyrazole acid (4), primarily the result of a hydrolysis reaction, may also arise from radical reactions.…”