Nucleophilic Participation in the Solvolyses of (Arylthio)methyl Chlorides and Derivatives: Application of Simple and Extended Forms of the Grunwald-Winstein Equations

Abstract

The specific rates of solvolysis of chloromethyl phenyl sulfide [(phenylthio)methyl chloride] and its p-chloro-derivative have been determined at 0.0 °C in a wide range of hydroxylic solvents, including several containing a fluroalcohol. Treatment in terms of a two-term Grunwald-Winstein equation, incorporating terms based on solvent ionizing power (YCl) and solvent nucleophilicity (NT) suggest a mechanism similar to that for the solvolyses of tert-butyl chloride, involving in the rate-determining step a nucleophilic solvation of the incipient carbocation in an ionization process. A previous suggestion, that a third-term governed by the aromatic ring parameter (I) is required, is shown both for the new and for the previously studied related substrates to be an artifact, resulting from an appreciable degree of multicollinearity between I values and a linear combination of NT and YCl values.

A comprehensive N+ scale of nucleophilicity in an equation including a Swain‐Scott response/selectivity parameter

“…For solvolyses of MeOTs using Eqn , the same effect as a decrease in s is illustrated by the low l value of 0.7 in Eqn , and the increase in the mY term is illustrated by Eqn . The above results further illustrate the general observation that compensation effects complicate the interpetation of multi‐parameter equations . Importantly, both N OTs and N T scales usually lead to almost the same l values…”

Extent of Nucleophilic Participation in the Solvolyses of an Aryl Chloromethyl Ether, α,p-Dichloroanisole

“…12 This observation suggests that the transition-state structures are very similar for both aryl and alkyl chloromethyl ether solvolyses. The m values are only a little lower than those for the corresponding sulfides, with values of 0.67 for both chloromethyl phenyl sulfide and its p-chloro derivative 11 and 0.71 for chloromethyl methyl sulfide 12 having been reported. Comparisons of the l values with those for the above mentioned α-chlorosulfides are more complex because of a fairly large variation between the sulfides with an aryl group (0.27 and 0.22) and with the methyl group (0.55).…”

“…14 The present results, coupled with earlier data 11 for chloromethyl ethyl ether (2) allow the comparison of an alkyl chloromethyl ether with an aryl chloromethyl ether under more typical solvolytic conditions. The values reported in Table 2 for solvolyses in four solvents at 15.0, 35.0, and 45.0 °C, coupled with the value at 25.0 °C from Table 1, allow an estimate to be made of the specific rates at -10.0 °C, the temperature of the earlier study 11 of the solvolyses of 2. The values obtained are given, in parentheses, in Table 2.…”

“…Our earlier reports 11,12 included brief reviews of previously carried out mechanistic studies and, accordingly, only those directly relating to (aryloxy)methyl chlorides are given further mention here. It was claimed that aryl α-chloroethyl ethers undergo unimolecular solvolyses in water and alcohols 13 and it was shown that, in 98% dioxane -2% water (~1.1 M in water) at 25.0 °C, the solvolysis of chloromethyl phenyl ether is about three orders of magnitude slower than that of chloromethyl methyl ether.…”

LFER Studies Evaluating Solvent Effects on an α-Chloro- and two β,β,β-Trichloro-Ethyl Chloroformate Esters

“…In equation 2, h represents the sensitivity of solvolyses to changes in the aromatic ring parameter I [44–46]. $$\text{log}false(k/k_{o}false)=lN+mY+hI+c$$ …”