Ethylene glycol, dehydrogenation product

Treatment of the disulfide (90) with iodine in dioxane under various conditions gives low yields of 5,6-dimethoxy-2,3-dihydrobenzo[6]-thiophene.346 At high temperatures in ethylene glycol a mixture of this compound and the dehydrogenated product, 5,6-dim ethoxy-benzo[6]thiophene, is obtained. These observations demonstrate the importance of the double bond in the side chain of the mercapto-acrylic acids (88) in promoting their cyclization. 

For separation of the olefins, reliance was placed largely on efficient fractional distillation under pressure, using techniques now familiar to the petroleum industry the unusual feature was the low temperature required for concentration of ethylene. The main olefin reactions developed were hydration with sulfuric acid to give the alcohol, which was then dehydrogenated to the corresponding aldehyde or ketone, and conversion to the olefin oxide by reaction with hypochlorous acid. The ready commercial availability of the olefin oxides led to a continuous stream of new products, such as glycols, glycol ethers, and alkanolamines. 

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