Question

Write the reactions involved in the following reactions:
(i) Clemmensen reduction
(ii) Cannizzaro reaction

Answer 1

(i) Clemmensen reduction: Reduction of an aldehyde or ketone to give alkanes. For eg:
`underset("Acetaldehyde")(CH_(3) CHO + 4[H]) overset(Zn-Hg, HCl)rarr underset("Ethane")(CH_(3) CH_(3) + H_(2)O)`
`underset("Propanone")(CH_(3)COCH_(3)) + 4[H] overset(Zn-Hg, HCl)rarr underset("Propane")(CH_(3)CH_(2)CH_(3)) + H_(2)O`
(ii) Cannizzaro reaction: Aldehydes which do not contain `alpha-` hydrogen, when treated with conc. NaOH undergo self oxidation -reduction
`underset("Formaldehyde")(2H - overset(O)overset(||)(C) - H) + underset((50%))(NaOH) rarr underset("Methylalcohol")(CH_(3) - OH) + H - underset("Sod. formate")(overset(O)overset(||)(C) - ONa)`