(a) Discuss briefly the following reactions : (i) Gattermann Koch reaction (ii) Rosenmund reaction. (b) Trichloro acetic acid is stronger acid than dichloro acetic acid. Explain.

(a) Discuss briefly the following reactions : (i) Gattermann Koch rea

1.	(a) Discuss briefly the following reactions : (i) Gattermann Koch reaction (ii) Rosenmund reaction. (b) Trichloro acetic acid is stronger acid than dichloro acetic acid. Explain.
Answer» Solution :(a) (i) Gattermann Koch reaction. BENZENE on passing through a mixture of carbon monoxide and hydrochloric acid gas in the presence of anhydrous `AICI_(3)` and traces of cuprous chloride is converted to benzaldehyde by this reaction. It is modified form of Friedel-Crafts reaction in which -CHO GROUP is introduced in the benzene ring. (II) Rosenmund.s reaction. Acid chloride on reacting hydrogen in the presence of palladium suspended over barium SULPHATE and poisoned with sulphur or quinoline gets converted to an aldehyde by this reaction. `CH_(3)COCl+H_(2) overset(Pd. BaSO_(4))to underset("Ethanol")(CH_(3)CHO)+HCl` (b) Due to the presence of more number of electron withdrawing groups in trichloroacetic than dichloroacetic acid, the-Inductive effect causes the electron withdrawal more strongly towards oxygen of O-H bond and promotes the release of `H^(+)` ions more effectively. Thus trichloroacetic is more acidic than dichloro acetic acid.