(a) Illustrate the following name reactions:
(i) Cannizzaro's reaction.
(ii) Clemmensen reduction
(b) How would you obtain the following:
(i) But-2-enal from ethanal.
(ii) Butanoic acid from butanol.
(iii) Benzoic acid from ethylbenzene.

Explanation

(a) (i) Cannizzoaro's reactions: Aldehydes which do not contain any `alpha`- hydrogebn such as formaldehyde HCHO and benzaldehyde `C_(6)H_(5)CHO` undergo self oxidation and reduction reaction on treatment with concentrated alkalie . A mixture of an alcohol and a salt of a carboxyic acids is formed .
`underset("Methanal")(HCHO) + (HCHO) overset(NaOH)to underset("Methnaol")(CH_(3)OH)+underset("Sod. fomrate")(HCOONa)`
`underset("Benaldehyde")(C_(6)H_(5)CHO+C_(6)H_(5)CHO)overset(NaOH)tounderset("Benzyl alcohal")(C_(6)H_(5)CH_(2)OH)+underset("Sod. benzoate")(C_(6)H_(5)COO Na)`
(b) (ii) `CH_(3)CH_(2)CH_(2)CH_(2)OHunderset(K_(2)Cr_(2)O_(7))overset("acidified")to CH_(3)CH_(2)CH_(2)COOH`
(iii)