Correlation of the Rates of Solvolysis of Phenyl Chlorodithioformate

摘要

Solvolytic rate constants at 25 ∩ are reported for solvolysis of chlorodithioformate (1) in binary mixtures of water with acetone, ethanol, methanol, methanol-d, 50%methanol-d/50%D₂O, and 2,2,2-trifluroethanol (TFE), and also in TFE-ethanol mixtures. The Grunwald-Winstein plot shows that the three aqueous mixtures exhibit dispersions into separate line. The correlation is improved only slightly by additional parameters N_T for solvent nucleophilicity and/or I for aromatic ring parameter. Rate ratios in solvents of the same Y_Cl value, having different nucleophilicity provide measures of the minimum extent of nucleophilic solvent assistance, and the value of 3.35 for [k_40EW/k_97TFE]_Y (EW = ethanol-water), is consistent with an essentially S_N1 reaction mechanism. This study has shown that the magnitude of l, m and h values associated with a change of solvent composition is able to predict the S_N1 reaction mechanism. log(k/ko) = mY + lN + hI