The rates of solvolysis of ¿-butyl chloride have been measured at 24.80 and 30.00°in aqueous methanol solutions, at 5.12, 24.80 and 30.00°in aqueous dioxane solutions and at 24.80 and 30.00°in aqueous acetone solutions. The rates of solvolysis of ¿-butyl bromide have been measured at 5.12, 24.80 and 30.00°, in aqueous acetone solutions. Both conductance and titration methods were used for following the reactions.The solvolysis of tertiary halides has been the subject of many investigations since the original paper by Hughes2 twenty years ago. The mechanisms proposed for the solvolysis range from (a) the simple primary ionization to carbonium ions followed by various rapid bimolecular reactions to produce the products, to (b) several simultaneous primary bimolecular or higher order reactions to produce the products. One of the factors contributing to this lack of agreement must be the lack of a sufficiently extensive set of precise data. This article is the first in a series designed partially to remedy this situation. Experimental Preparation of Materials.-¿-Butyl chloride, either the Eastman Kodak Co. product or that prepared in this Laboratory by the usual method3 was distilled twice in a meter long column; the fraction boiling between 51.4 and 51.6°w as used for the experiments. Weighed samples, permitted to solvolyze completely in approximately 50 volume per cent, aqueous methanol and then titrated with standard base, were always found to be more than 99% pure on the basis of the amount of acid produced. Rate measurements made with different preparations of ¿-butyl chloride agreed as well as duplicate measurements made with the same preparation.¿-Butyl bromide was prepared by the method described by Cooper and Hughes.38 Commercial methyl alcohol was distilled once in a meter long column; the fraction boiling between 64.7 and 64.9°was used. A Fischer reagent titration showed the water content to be 0.05 mole/L or 0.2%. The density found with a Westphal balance was 0.7916 at 20°.Commercial acetone was purified by the method of Conant and Kirner.3b The water content of different preparations varied somewhat; a single batch having 0.83% water was used for the runs followed by conductance.Dioxane was purified by Fieser's method.30 The material distilling at 101°was retained. It had a density of 1.0338 at 20°and m.p. of 11.1 to 11.3°. The water content by a Fischer Reagent titration was 0.78%. The aqueous solvents were prepared by weight. Thermostat temperatures, maintained to ±0.02°, were read from NBS calibrated thermometers. Rate Measurements by the Conductance Method.-Conductances as such were not used since resistance, the measured quantity, can be converted directly to the concentration of acid, i.e., HC1, a reaction product of the solvolysis of ¿-butyl chloride, or HBr, a product of the soivolysis of tbutyl bromide. A Jones-Josephs precision conductance bridge was used for the resistance measurements. Readings, taken periodically on a large known resistance, were found never to vary more than 0.5 ohm.
Methods of analyzing for isobutene, methyl /-butyl ether and /-butyl alcohol in aqueous methanol solutions are described. These methods are then used to determine the fractions of these substances that are produced in the solvolysis of /-butyl chloride in aqueous methanol solutions at several compositions and temperatures.The products of solvolysis of ¿-butyl chloride in aqueous methanol solutions are methyl ¿-butyl ether, ¿-butyl alcohol and isobutene. The purpose of the work presented here has been to determine (1) This work was supported in part by the Office of Naval Research. United States Navy.(2) This is the second in a series of papers dealing with the solvolysis of /-butyl compounds in aqueous organic solvents; see Cropper, Spieth
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