R. Banerjee, Anamika Bhattacharya, P. Das
1988
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0
Influential Citations
4
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Journal
Journal of The Chemical Society-dalton Transactions
Abstract
N 1 -Phenylbiguanide RHN–C(X)NH–C(NH)NH2(R = Ph, X = NH) reacts quantitatively in aqueous sulphuric acid media with CrVI and CeIV to produce 1,4-benzoquinone, carbamimidoylurea (R = H, X = O), and ammonium ion. N1-(4-Methoxyphenyl)biguanide (R = 4-MeOC6H4, X = NH) reacts similarly except that, instead of a quinone, more extensively oxidized products are produced. Phenylbiguanide (pbg) itself, in acid solution, undergoes slow hydrolysis, and anilinium ion is one of the products. The hydrolyzed solution reacts rapidly with CrVI and CeIV. None of the other six biguanides investigated and three other structurally related compounds reacts with CrVI under the experimental conditions. The kinetics of the reactions is in accord with the rate law (I). A typical –d[CrVI]//dt=–4//3d[pbg]//dt=k[pbg](i) value of k is (0.25 ± 0.03)× 10–5 s–1 at 20 °C, [H+]= 1.0 mol dm–3, and I= 2.0 mol dm–3, and when determined from experiments with an excess of CrVI(first-order kinetics observed) agrees closely with that determined in the presence of an excess of pbg (zero-order kinetics) and also that determined for reactions with CeIV. These results have been interpreted in terms of a mechanism involving the acid-promoted hydrolysis of phenylbiguanide [and (4-methoxyphenyl)biguanide], the oxidant functioning as an analytical assay of the anilinium product.