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The isomer distributions for the mono-, di-, and tri-sulphonation of 1 -methylnaphthalene in respectively 90.1,98.4, and 11 0% sulphuric acid a t 25 "C have been determined. The degree of sulphonation at the 2-position is smaller for sulphonation in 98.4 than 90.1% H2S04. The results are discussed in terms of sulphonation by H,SO4+, H2S20,, and H2S4O13 as sulphonating entities and compared with those of the polymethylbenzenes. The mechanistic conclusion that the sulphonation with H3S04+ has a ' later ' transition state than that with H, S, O, is in agreement with the results of simple Huckel MO calculations. The deviating behaviour for the 2-substitution of 1 -methylnaphthalene is ascribed to enhanced steric control, because of the shorter C ( l )-C(2) bond distance in 1 -methylnaphthalene as compared with toluene. The isomer distribution for the mono-, and di-sulphonates resulting from 1 -methylnaphthalene with SO, in nitromethane is also reported.

The kinetic isotope effect of hydrogen in the sulphonation of [I ,3,5-2H3] benzene in trichlorofluoromethane has been determined askH/kD = 1.23 f 0.08 at -35"; with nitromethane as solvent kH/kD = 1.34 f 0.08 at 20'. The kinetic isotope effect for the accompanying sulphonylation in trichlorofluoromethane w a s found to be kH/kD = 1-1 f 0.1 at -35".These results are discussed in terms of the recently established mechanism for aromatic sulphonation with sulphur trioxide in aprotic solvents. It has been determined, by competitive experiments, that the sulphonation rate ratio of toluene to benzene and the degree of para-substitution in toluene are greater with nitromethane than with trichlorofluoromethane as solvent. The apparent greater selectivity in the case of the former solvent is explained in terms of complex formation between sulphur trioxide and nitromethane.

The photolysis of azoethane a t X 3660 A has been reinvestigated. The quantum yield of nitrogen formation was found to be dependent on the azoethane pressure and the temperature, indicating collisional deactivation of excited azoethane molecules.'I'he results conhrm the mechanism proposed by Ausloos and Stcacie (1). For the activatiorl energy of the addition reaction C?HS+C.'H~X~CYH;, a value of 6 . 0 f 0.3 kcal./nlole has been obtained, assunling a ~legligible acti\.ation energy for the combillation reaction of two ethyl radicals. INTRODUCTIOX