Abstract
Specific rates of solvolysis in hydroxylic solvents available for the solvolysis of 2-thiophenesulfonyl chloride and phenylmethanesulfonyl chloride are supplemented by determining the values in fluoroalcohol-containing solvents. The data sets are then correlated using the extended Grunwald-Winstein equation. For both substrates, it is found that a single correlation controls the influence of solvent over the full range of solvent composition. The sensitivities to solvent nucleophilicity and solvent ionizing power are compared to values available for other substrates. Three of these previous studies are upgraded by the incorporation of additional specific rate values from the recent literature. With a methyl, isopropyl, benzyl, aromatic or heteroaromatic group as the R group of RSO2Cl, a concerted SN2 mechanism is proposed for the solvolysis.
Highlights
The mechanism of solvolysis of sulfonyl halides has been the subject of several reports and reviews
NT and YCl using the extended Grunwald-Winstein equation for all 34 available solvents at 25.0 oC, lead to l and m values which are slightly higher than those obtained for solvolysis of 4 and for two earlier correlations of para-substituted benzenesulfonyl chlorides (Table 3)
The solvolyses of phenylmethanesulfonyl chloride (2) are of interest in that hydrolysis under basic conditions has previously shown to exhibit a dominant pathway involving elimination-addition rather than the direct substitution observed under neutral conditions [27]
Summary
The mechanism of solvolysis of sulfonyl halides has been the subject of several reports and reviews. In the presence of an αhydrogen, substitution products can be formed by an initial elimination reaction to give the sulfene followed by addition of solvent to the highly reactive intermediate This pathway is especially favored after the addition of a tertiary amine but, with electron-withdrawing substituents on the αcarbon (trifluoromethyl [4]; chlorine [5], etc.), it can be observed under solvolytic conditions [1, 2, 6]. The specific rates of solvolysis of 1 have been determined previously in several pure and binary solvents [13] but this study did not include any fluoroalcohol-containing solvents Such solvents are highly recommended for treatments involving equation 1, because the interrelationship of NT and YCl is very different to that observed with variation of the composition of binary mixtures of water with conventional alcohols. As with solvolysis of 1, literature values [15] are supplemented, so as to give a better mix of solvents for the application of equation 1
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