Give one good chemical test to distinguish between the following pairs of compounds:

(i) Methanal and ethanal.    
ii) Urea and benzoic acid

42.

 An aliphatic hydrocarbon Aon treatment with sulphuric acid in the presence of HgSO₄ yields a liquid B with molecular formula C₂H₄0. B on oxidation with acidified potassium dichromate yields C which gives effervescence with sodium bicarbonate. C when treated with SOCl₂gives D. When D reacts with ethanol it gives a sweet smelling liquid E. E is also formed when C reacts with ethanol in the presence of conc. H₂S0₄.

(i) Identify A, B, C, D and E.

(ii) Draw the structure of the isomer of compound B.

(iii) Write the balanced equation for the conversion of A to B.

(i)The compound C₆H_l2 shows optical isomerism. Draw the structural formula of the compound and name it.

(ii) Name any three types of isomerisms that the compound with molecular formula C₄H₇Cl can give rise to. Also, represent the structures of the compounds relevant to these isomers.