[Effects of temperature and pH on hydrolysis of monoacetoacetin in an aqueous phase].
The kinetics of hydrolysis of monoacetoacetin (MAA; 1,2-dihydroxy-3-acetoacetyloxypropane) in 300 mM phosphate buffer was studied by means of high performance liquid chromatography. MAA was hydrolyzed to glycerin (Glyc) and acetoacetate (AA), the latter of which furthermore decomposed to acetone (Acet) and CO2 at high temperature. The rate constant, k1, for the reaction of MAA-->AA+Glyc increased with increases in temperature and pH. On the other hand, another one, k2, for the reaction of AA-->Acet+CO2 increased with an increase in temperature but showed a minimum around pH 7.5 when pH was changed at a given temperature. The activation energy for k1 was almost constant in the range of studied pHs (5-8) but the pre-exponential factor, k1,0, increased with an increase in pH. It was concluded that the decomposition reaction of MAA is consecutive in a sequence of MAA-->AA-->Acet. Calculated concentrations of MAA, AA, and Acet through the obtained k1 and k2 together with a given initial concentration of MAA (= 40 mM) were compared with those experimentally observed on the time course of the hydrolysis. They were in good agreement with each other.
Shimabayashi
S
S
Faculty of Pharmaceutical Sciences, University of Tokushima, Japan.
Harada
C
C
D000090:Acetoacetates; D005989:Glycerides; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D012996:Solutions; D014867:Water
D000090:Acetoacetates; D005989:Glycerides; D012996:Solutions; D014867:Water; C020417:monoacetoacetin