(A) Hoffmann degradation reaction: Hoffmann developed a method for the preparation of primary amines by treating an amide with bromine in an aqueous or ethanolic solution of sodium hydroxide.
O∥R−C−NH2+Br2+4NaOH→R−NH2+Na2CO3+2NaBr+2H2O
(B) Clemmensen reduction reaction: The Clemmensen reduction is a reaction that is used to reduce aldehydes or ketones to alkanes using hydrochloric acid and zinc amalgam.
(C) Cannizzaro reaction: Aldehydes which do not have an α-hydrogen atom, undergo self-oxidation and reduction (disproportionation) reaction on heating with concentrated alkali.
(D) Reimer-Tiemann reaction: On treating phenol with chloroform in the presence of sodium hydroxide, a –CHO group is introduced at ortho position of benzene ring. This reaction is known as Reimer-Tiemann reaction.
So, the correct matching is given in the following table:
| Reactions | Reagent used |
| (A) Hoffmann degradation | Br2/NaOH |
| (B) Clemmensen reduction | Zn−Hg/HCl |
| (C) Cannizzaro reaction | conc.KOH/ KOH/Δ |
| (D) Reimer-Tiemann reaction | CHCl3,NaOH/H3O+ |