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?

Answer 7    Organic problems contents   Home page