抄録
The hydrolysis of monodecyl phosphate (C12MAP) Na and K salts at various degrees of neutralization (DN) in 5.0 wt% aqueous solution was studied by analysis of dodecyl alcohol formed by hydrolysis of C12 MAP. The hydrolysis rate followed a first-order kinetics and the rate constants (kobs) showed Λ-shape dependence on DN (Fig.-2) and the maximum kobs were found at DN=1.08. The extrapolated kobs at DN=0.18 was zero. Under highly alkaline conditions (at DN=4.0) hydrolysis did not occur. In the pH-DN profile in aqueous solution, there were three equivalent points at DN=0.5, 1.0 and 2.0, indicating MAP to have three dissociation equilibria (Scheme-3, pK1=2.45, pK2=5.60, pK3=7.80) including bimolecular aggregates (A0, A1). The Arrhenius activation energy was Ea-29.7 kcal/mol and did not depend on DN. This value is essentially the same as that for monomethyl phosphate (Ea=30.6 kcal/mol).
A possible hydrolysis mechanism is proposed and discussed based on the obtained results.
