Sulphonic anhydrides, hydrolysis

In mixed anhydrides in which thiophosphoryl phosphorus is bonded to another heteroatom other than phosphorus, attack by a nucleophile may be diverted away from the phosphorus should the second reactive centre be more electrophilic. So, in the case of phos-phinothioic sulphonic anhydrides, although hydrolysis or acid-catalysed methanolysis of 101 (X = H) proceeds with inversion at phosphorus, attack by HO occurs at sulphur with retention of configuration of phosphorus whilst the hydrolysis of the much more reactive 101 (X = F) in aqueous dioxane proceeds with preponderant inversion of phosphorus... 

We will now assume all of the species in reaction 55 are in their condensed phases and again fail to distinguish heats of vaporization and sublimation. For the sulphonyl sulphenate 46, we again use equation 47 where the ncessary value of b was derived as the sum of those for sulphones, ethers and sulphides, resulting in a predicted AHf(g, 46) value of —83 kcal mol-1. Relatedly, the value of b for sulphenic acids was taken as the sum of those for alcohols and sulphides, and thus AHf(g, 85)= —26 kcal mol-1. The left-hand side of reaction 39 is [ — 117 + ( — 26)] — [ — 83 +( — 68)] = 8 kcal mol-1 more stable than the right, where we remember that the value for PhS02—O—S—Ph is an upper bound. The results for the gaseous and condensed phases are thus seen as consonant. It is safe to say that benzenesulphonyl benzenesulfenate is best not viewed as an anhydride since its hydrolysis is endothermic. 

Preparation.—An important addition to methods for the reduction of sulphonyl compounds to sulphenyl analogues, i.e. the direct reduction of sulphonic acids to thiols using trifluoroacetic anhydride and Bu iN+has been reported. A mixture of thiol and the corresponding trifluorothiolacetate is obtained this, on hydrolysis. 

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