Which of the following reducing agents cannot be used to convert Ar `NO_(2)` to `ArNH_(2)` ? .

Options

A. Sn in dil HCI
B. `SnCI_(2)` in HCI
C. `H_(2)//Pd-C`
D. `LiAIH_(4)`

Answer

D

Explanation

The most widely used method for preparing aromtic amines involves nitration of the ring and subsequent reduction of the nitro group to an amino group
`Ar-H-underset(H_(2)SO_(4))overset(HNO_(3))rarrAr - NO_(2) overset([H])rarrArNH_(2)`
Reduction of the nitro group can be carried out in a number of ways The frequently used methods employ catalyic hydrogenation using `Pd//C` catalyst in ethano1 or treatment of the nitro compound with acid and relatively inexpensive metals like Fe , Sn or Zn or a metal salt such as `SNCI_(2)`
`C_(6)H_(5)NO_(2)underset(Ethano1)overset(H_(2)//pd-C)rarrC_(6)H_(5)NH_(2)`
`C_(6)H_(5)NO_(2)underset(HCI)overset(Sn)rarrunderset(Anili n e hydrochlo ridei de)(C_(6)H_(5)NH_(2)HCI)overset(OHbar)rarrC_6H_(5)+underset(sal ts)(Sn^(2+)`
`C_(6)H_(5)NO_(2)underset(HCI)overset(Fe)rarrunderset(Anili n e hydrochlo ridei de)(C_(6)H_(5)NH_(2)HCI)overset(OHbar)rarrC_
6H_(5)+underset(sal ts)(Fe^(2+)`
However`LiAIH_(4)`does not reduce `phNO_(2)` to `phNH_(2)` but to azobenzen
`C_(6)H_(5)NO_(2)underset(ether)overset(LiAIH_(4))rarr C_(6)H_(5)--underset(Azobenzen e)(N=N-C_(6)H_(5))` .