Nucleophilic Substitutions at a Carbonyl Carbon Atom (). Solvolysis of Methylchloroformate and Its Thioanalogues in CH3CN-H2O and CH3COCH3-H2O Mixtures

Journal of the Korean Chemical Society

Kyeong Shin Koh¹  Ikchoon Lee¹  Sangmoo La¹ 

DOI  :  

学科分类：化学（综合）

来源: Korean Chemical Society

【 摘 要 】

Solvolysis rate constants for methylchloroformate, CH3O(CO)Cl, methylthiono-chloroformate, CH3O(CS)Cl, and methylthiolchloroformate, CH3S(CO)Cl, have been determined conductometrically in acetone-water and acetonitrile-water mixtures, and activation parameters, ¥ÄH¡Á and ¥ÄS¡Á, have been derived. Results show that in water-rich regions the order of rate increases as CH3O(CO)Cl < CH3O(CS)Cl < CH3S(CO)Cl while in dipolar aprotic solvent-rich region this order reverses. The plots of log k vs. solvent parameters, Y, (D - 1) / (2D + 1) and log(H2O) show that the order of rate increase in water-rich region is the results of increase in SN1 character. It is concluded that CH3S(CO)Cl solvolyzes via SN1 mechanism whereas CH3O(CO)Cl reacts via SN2 and CH3O(CS)Cl via intermediate mechanism in water-rich region.

【 授权许可】

Unknown