Problem 7

A, C₂H₄, reacts with hydrogen bromide in the gas phase to give B, C₂H₅Br. This reacts with aqueous sodium hydroxide solution to give C, C₂H₆O, which can be oxidised by acidified potassium dichromate solution to give successively D, C₂H₄O, and E, C₂H₄O₂. D reacts with both 2,4-dinitrophenylhydrazine and ammoniacal silver nitrate.

With magnesium in dry ether B gives F, C₂H₅MgBr; this reagent will react with D to give G, C₄H₁₀O. Oxidation of this compound with acidified potassium dichromate solution gives H, C₄H₈O. This will also react with F, giving I, C₆H₁₄O. I is not oxidised by acidified potassium dichromate solution.

If A is reacted with bromine in the presence of sodium chloride, two compounds are obtained; J, C₂H₄Br₂, and K, C₂H₄BrCl. No C₂H₄Cl₂ is formed.

(a) Identify each of the compounds A – K, and explain all the observations as fully as you can.

(b) Why is no C₂H₄Cl₂ formed in the reaction given in the last paragraph?

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