Kinetics of the hydrolysis of thiochloroformate esters in pure water

Abstract

The effects of structural changes on the rates of hydrolysis of a series of thiochloroformate esters in water have been investigated. The reactivity is enhanced by increased electron donation by the hydrocarbon group. These results, the activation parameters for the hydrolysis of methyl thiochloroformate and the solvent deuterium isotope effect, are shown to be consistent with the operation of the SN1 mechanism.Canadian Journal of Chemistry, 48, 522 (1970) Introduction It is well known that alkyl chloroformates (1; X = 0) undergo solvolytic reactions much more slowly than other acid chlorides (1, 2) and also seem to find the S,1 mechanism unfavorable. Two factors are responsible for these characteristics.( i ) The initial states are stabilized by conjugation (2; X = 0) and the effect is enhanced by structural changes that increase electron donation by the alkyl group. This is shown by the rate sequence

Influence of Sulfur for Oxygen Substitution in the Solvolytic Reactions of Chloroformate Esters and Related Compounds

“…Indeed, the observation by Queen and co-workers of 2-propanethiol as the major product from the hydrolysis in pure water of isopropyl chlorothioformate [40] requires the retention of the isopropyl-sulfur bond throughout the pathway for this solvolysis. This could be a consequence of sulfur being better able to support a positive charge in the resonance-stabilized carboxylium than oxygen (Scheme 4).…”

Use of Empirical Correlations to Determine Solvent Effects in the Solvolysis of S-Methyl Chlorothioformate

“…On analyzing the rate data for a series of alkyl chloro-, thio-, thiono-, and dithio-formate esters, Queen et al proposed [44,45] that the thio- containing substrates hydrolyze by a unimolecular process, whereas their chloroformate counterparts tend to favor a bimolecular mechanism. Lee et al .…”

Kinetics and Mechanism for the Hydrolysis of Chlorothionoformate and Chlorodithioformate Esters in Water and Aqueous Acetone

“…This effect is enhanced by structural changes that increase electron donation by the hydrocarbon group (R) (3,4) and is diminished in compounds where the hetero-atom (X) has only a limited tendency to use its unshared electrons for n-bond formation. Thus, chloroformates are much less reactive than their thio analogues (3). …”