S. Pyun, Y. Lee, T.-R. Kim
2005
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Influential Citations
4
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Journal
Kinetics and Catalysis
Abstract
Hydrolysis reactions of N-aryliminotriphenylphosphoranes (I) at varying pH have been investigated kinetically. The reactions produced aniline derivatives and triphenylphosphine oxide as the products. The reactions are first-order, and the Hammett ρ values are −0.29 and −0.63 at pH 3.0 and 8.0, respectively. The reaction rate increased linearly with acetate ion concentration at [AcO−] < 0.05 M and approached a limiting value at higher base concentration. The plot of logkt versus pH shows that there are two different regions in the rate profile; one part in which logkt increases with hydronium ion concentration and the other where kt is a constant regardless of pH. On the basis of these results, a plausible hydrolysis mechanism is proposed. At pH < 8.0, the reaction proceeds by protonation of the iminophosphorane nitrogen atom, followed by the addition of a water molecule. At pH > 8.0, the proton transfer from water to α-nitrogen of the iminophosphorane becomes the rate limiting step.