Question

The appropriate reagent for the following transformation is

• A. $Zn\left(Hg\right),HCl$
• B. $N{H}_{2}N{H}_2,O{H}^{-}$
• C. $H_2/Ni$
• D. $NaB{H}_4$

Answer 1

The correct option is B $N{H}_{2}N{H}_2,O{H}^{-}$

$Zn\left(Hg\right),HCl$ can not be used when acid sensitive group such as $O{H}^{-}$ is present in the molecule, but $N{H}_{2}N{H}_2,O{H}^{-}$ can be used. It is called Wolff-Kishner reduction. Wolff Kishner reduction mechanism begins with the formation of a hydrazone anion which then releases the nitrogen atom to form a carbanion. This carbanion then reacts with the water in the system to give a hydrocarbon. Typically, diethylene glycol is used as a solvent for this method.
Hence, (b) is correct.