Benzohydroxamate anion

The reaction between the benzohydroxamate anion (109) and bis(2,4-dinitrophenyl)phosphate (110) has been examined kinetically, and the products were characterized by mass and NMR spectroscopies. The phosphate (110) underwent nucleophilic attack of (109) on phosphorus, giving 2,4-dinitrophenolate and an unstable intermediate (111) that underwent the Lossen rearrangement to alford phenylisocyanate, aniline, diphenylurea, and O-phenylcarbamyl benzohydroxamate and (ii) attack on the aromatic carbon, giving an intermediate (112) that was detected but slowly decomposed to aniline and 2,4-dinitrophenol (Scheme 25)." The benzohydroxamate anion represented a unique type of reactive nucleophile since it behaved as a one-cut self destructive molecular scissor, which lost its... 

Three papers from Ghosh s group deal with the hydrolysis of benzohydroxamic acids in acidic and alkaline conditions. A pre-equihbrium protonation followed by a slow A-2 type nucleophilic attack by water is seen as the mechanism of the acid-catalysed hydrolysis of j -chlorophenylbenzohydroxamic acid (107 R = / -ClCgEU) by mineral acids (HCl, HCIO4) in 20% aqueous dioxane. An A-2 mechanism was also supported for the reaction of (107 R = Me) imder comparable conditions. The alkaline hydrolysis imder micellar conditions of (107 R = Ph) and a series of para-substituted derivatives has been investigated in the presence of cationic and anionic micelles in 5% dioxane-water medium at 55 °C. Cationic surfactants exerted a catalytic effect and anionic surfactants were inhibitory. The rate-surfactant profiles were analysed in terms of the pseudophase and Piszkiewicz models. The detection of N2O in the products of the oxidation of hydroxamic acids suggests the intermediacy of nitroxyl, HNO, in the process. Scheme 9 may represent the pathway followed. 

The effect of cetyltrimethylammonium bromide on the rate constants of hydrolysis of ethyl glycinate hydrochloride has been reported. " Cationic and non-ionic micelles inhibited and anionic micelles accelerated the acid hydrolysis of A-p-tolyl-benzohydroxamic acid (189). The rates of acid hydrolysis of acetohydroxamic acid, MeCONHOH, benzohydroxamic acid, PhCONHOH, and A-phenylbenzohydroxamic acid, PhCON(OH)Ph, were increased by perfiuorooctanoic acid and by sodium 1-dodecanesulfonate and sodium dodecyl sulfate (SDS). " The effects of micelles of SDS upon the rates of reaction of ionized phenyl salicylate with Bu"NH2, piperidine and pyrroiidine have been reported. 

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