The temperature at which the sulfur is kept affects the yields: at 300°the reaction was slow (5% conversion per passage) while at 400°the ultimate yield was 41% and an inconveniently large amount of sulfur distilled over. Dilution of the isopfene with carbon bisulfide (1:1) increased the yield Of crude 3-uléthylthiophene at 350°to 51%.Thiophene.-Crude 50% butadiene6 yielded 6% of thiophene when bubbled through molten sulfur at temperatures ranging from 320 to 420°, The same yield was obtained when pure liquid butadiene (from the tetrabromide) was dropped into the apparatus from a chilled separatory funnel. The thiophene boiled at 82-84°, had a density ¿is 1.05, gave a blue indophenin reaction, and with mercuric chloride yielded 2-chloro-mercurithiophene which did not depress the meltirrg point of authentic material. Carbon bisulfide was again noted as a by-product.2,3-Dimethylthiophene.-A distillate fraction boiling at 45-160°was obtained from the pyrolysis products of a mixture of crepe rubber and zinc oxide. This fraction had previously been shown to contain about 4% of 3methyl l,3-pefttadíene, mixed with mono-olefins and hydromatic compounds. One hundred grams of this ma-(6) We are indebted to Dr. B. T. Brooks for a generous supply of this material.
I. Introduction. Nolting and Kolinl record the preparation of an aminosulfonic acid of p-xylene to which they ascribe the formula : 1,4 6 2 CsHz (CH3) z"zS0s.H This acid was prepared by reducing with ammonium sulfide, or with tin and hydrochloric acid, the solution resulting from the treatment of p-xylenesulfonic acid with red, fuming nitric acid. The nitro-acid was not isolated, nor were any of its derivatives prepared. Guy G. Frary2 describes a nitrosulfonic acid of p-xylene which he prepared by nitrating p-xylenesulfonic acid with nitric acid (sp. gr. 1.60) in the cold. The potassium, sodium, calcium, barium, strontium, magnesium, copper, and zinc salts were prepared and of these the potassium, barkm, copper, and zinc salts were analyzed. Most of these were prepared from the crude acid solution and were purified with difficulty.
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