p-Nitrostyrylphenylsulfone 基質에 對한 L-Cysteine의 反應 = On the Reaction of L-Cysteine to p-Nitrostyryphenylsulfone Substrate

다국어 초록 (Multilingual Abstract)

The kinetics and mechanism of nucleophilic addition of L-Cysteine to P-nitrostyrlphenyl-sulfone substrate over wide pH range was presented and analyzed in detail. The rate constants were determined by ultra-violet spectrophotometry in 50% methanol water mixed solvent at 25℃ and the following rate equation which can be applied over wide pH range was obtained. i.e
kt = ko + kp [OH^(-)]
=(1.92×10^(-3)+3.71×10^(3)[OH^(-)]/8.94×10^(-2)+1.03×10^(5)[OH^(-)]) +4.56×10^(2)OH^(-)]
From the rate equation, the following mechanism were proposed; above pH 10. 50,
the reaction proceed by the attack of L-Cy-S^(-) on the activated carbon-carbon double bind of substrate. Below pH 8.50, the reaction proceed by addition of L-Cysteine to p-nitrostyrl phenylsulfone substrate. And in the range of pH 8.50-10.50, these two reaction occur competitively.