Aluminium bromide, adduct

The unsymmetrical acetylene (43) yields cw-(CF3)iN-CH CH-CFs with hydrogen-Raney nickel at 20 C, undergoes slow hydration in the presence of aqueous sulphuric acid and mercuric sulphate at 53 °C to give the propion-amide (CFa)jN CO-CH2 CF3, combines with methanol in the presence of sodium methoxide to yield a 96 4 mixture of (CF3)aN-C(OMe) CH CF3 and (CFj)jN CH C(OMe)-CF3, and when subjected to photochemical hydrobromination gives the 1 1 adduct (CFs)jN-CH CBr-CF3 almost quantitatively. Slow electrophilic hydrobromination of the acetylene can be achieved in the presence of aluminium bromide at 20 °C, the main product being the same as that obtained in the photochemical reaction (H trans to Br in each case) this unexpected direction of addition is suggested to result... 

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