title: Borate complexes of benzohydroxamic acid and some of its derivatives.
abstract: Ultraviolet spectrophotometric measurements in dilute aqueous solution give pK(a) values of 8.78, 8.27, 8.96 and 8.68, respectively, for benzohydroxamic, N-phenylbenzohydroxamic, p-methoxybenzohydroxamic and N-methyl-p-methoxybenzohydroxamic acids. The acids carrying no substituent on nitrogen form 1:1 complexes with boric acid according to the general equation RCONHOH + H(3)BO(3) --> (1:1 complex)(-) + H(+). Equilibrium constants (log K) were found to be -5.70 for benzohydroxamic acid and -5.8 for p-methoxybenzohydroxamic acid. The complexes behave as very weak monoprotic acids and decompose at high pH to yield borate ions and the corresponding hydroxamate ions. The N-substituted hydroxamic acids showed no reaction with boric acid under the same conditions.
authors.affiliation: Wichita State University, Wichita, Kansas, U.S.A.
authors.forename: A R
authors.initials: AR
authors.lastname: Fields
authors.forename: B M
authors.initials: BM
authors.lastname: Daye
authors.forename: R
authors.initials: R
authors.lastname: Christian