Decomposition and Stabilization of Drugs. XII. Structure and Stability of Aminoalkylesters. (4)

In order to examine the structure and stability relationship of tertiary amine of aminoalkylesters, derivatives of [(C6H5)(m-CH3O-C6H4) CHCOOCH2CH2R3] were synthesized, changing R3 to N (CH3)2 (I), N (C2H5)2 (II), N (n-C3H7)2 (III), N (iso-C3H7)2 (IV), N (n-C4H9)2 (V), [chemical formula] (VI) and [chemical formula] (VII). By the use of a protonated amine ester as a reaction species, catalytic constants of hydrogen ion (kH) and hydroxyl ion (kOH) were determined. The substituents in tertiary amine ester were less effective, either for kH or kOH than in secondary amine ester. Although the reactivity of diethylamino esters decreased in the order of secondary amine>tertiary amine≈quaternary ammonium salt for kH, or secondary amine>tertiary amine>>quaternary ammonium salt for kOH, the ratios of (kH)sec/(kH)ter and (kOH)sec/(kOH)ter (sec and ter denoting secondary and tertiary, respectively) decreased when the ester reactivity decreased.