Ethyne reacts with dil. H_2SO_4 in presence of mercury salts to give acetaldehyde but with dil. HCl under similar conditions, it gives vinyl chloride . Explain why ?

Ethyne reacts with dil. H_2SO_4 in presence of mercury salts to give a

1.	Ethyne reacts with dil. H_2SO_4 in presence of mercury salts to give acetaldehyde but with dil. HCl under similar conditions, it gives vinyl chloride . Explain why ?
Answer» Solution :FIRST of all, MERCURY ions form a complex (I) with aetylene . Since `H_2O` is more nucleophilic than `SO_4^(2-)` ion, it attacks the complex (I) to form first vinyl ALCOHOL which then tautomerises to give ACETALDEHYDE In case of dil. HCl, since , `Cl^-` ion is more nucleophilic than `H_2O` it reacts with complex (I) to form vinyl chloride.