ORGN 326

We have recently reported analysis of (Me₂N)₂POCl and XC₆H₄SO₂Cl specific rates of solvolysis. Both gave similar results, with l and m values suggesting a direct displacement (S_N2) reaction at the phosphorus or sulfur. A study almost 50 years ago (Hall, H. K., Jr. J. Am. Chem. Soc. 1956, 78, 1450) of the Me₂NSO₂Cl solvolyses concluded that a rate-determining ionization (S_N1 reaction) was involved. This was not found in our earlier analyses of either a sulfur or phosphorus site of attack in solvolysis and a study of the N,N-dimethylsulfamyl chloride shows that, indeed, the l value of 1.17 and m value of 0.70 are very similar to values reported earlier for other substrates of this general type, suggesting an S_N2 pathway. In these analyses, l represents the sensitivity of the specific rates of solvolysis to changes in N_T value and m the sensitivity to changes in Y_X value.

Selectivity ratios have been found to be quite constant (about 2.5, favoring alcohol attack) in aqueous methanol, and at about 0.14 in 90%-50% TFE. The value rises slightly as water is added to ethanol and a range of 1.4 to 2.4 is observed. Similar, but slightly higher, values have been observed for solvolyses of arenesulfonyl chlorides.