プロカインおよびテトラカインの分解の反応速度的研究

抄録

Tetracaine and procaine undergo decomposition in an aqueous solution respectively into p-butylaminobenzoic acid and p-aminobenzoic acid. The compounds are more stable in acid range than in alkalinity and the extent of their decomposition cannot be measured correctly from the lowering of ultraviolet absorption alone. It was found that extraction of a sample at around the isoelectric point of p-butylamino-or p-aminobenzoic acid was the most effective in extracting these products and this was utilized for their determination (Charts 1-4).
On the other hand, reaction velocity was examined with tetracaine by varying the pH from 0.29 to 11.08 and it was found that, at a definite pH, the reaction is a first-order reaction and the relationship between log k_TC and pH was an acid-base catalyzed reaction, as shown in Fig. 3. This k_TC was dissolved into each elementary reaction and equation (7) was obtained. Similar experiment was carried out with procaine at pH 2.5-6.0 and the relationship between log k_PC and pH was found to be an acid-base catalyzed reaction, as shown in Fig. 5, giving equation (8).