The total number of reagents from those given below, that can convert nitrobenzene into aniline is ______ (integer answer)

(I) Sn-HCl            (II) Sn-NH₄OH          (III) Fe-HCl                 (IV) Zn-HCl             (V) H₂-Pd                (VI) H₂ –Raney nickel

We want to convert nitrobenzene (C₆H₅NO₂) → aniline (C₆H₅NH₂).

This is a reduction reaction, where the –NO₂ (nitro group) is reduced to a –NH₂ (amino group).

So, we are looking for reagents that can reduce a nitro group to an amine.
I) Sn + HCl (Tin + Hydrochloric acid)

YES – This is a classic reducing agent used in labs to reduce nitro compounds to amines. It forms SnCl₂ in situ, which acts as the reducing species.

Reaction: C₆H₅NO₂ + 6[H] → C₆H₅NH₂ + 2H₂O

II) Sn + NH₄OH (Tin + Ammonium hydroxide)

NO – Tin without acidic conditions (like HCl) is not effective for reducing nitrobenzene. NH₄OH provides basic medium, which doesn't work well here. Reduction requires an acidic environment.

III) Fe + HCl (Iron + Hydrochloric acid)

YES – This is another commonly used reagent to reduce nitrobenzene to aniline. Fe is cheaper and works similarly to Sn.

IV) Zn + HCl (Zinc + Hydrochloric acid)

YES – Zinc in acidic medium is also a good reducing agent for nitro groups. Zn gets oxidized and reduces the nitro group to amine.

V) H₂ + Pd (Hydrogen gas + Palladium catalyst)

YES – This is a catalytic hydrogenation method. Nitrobenzene is reduced to aniline using hydrogen gas in the presence of a metal catalyst like Pd.

VI) Raney Nickel

NO (but tricky) – Raney Ni can be used in catalytic hydrogenation, but only in presence of H₂ gas. On its own, it's just a catalyst, not a reducing agent.

In the absence of H₂, Raney Ni won’t work. Since no hydrogen gas is mentioned here, this is not effective as written.

Final Count:

Reagents that can reduce nitrobenzene to aniline:

Total = 4

Correct Answer: 4
To reduce a nitro group to an amine, you need a strong reducing environment, usually acidic metal reductions or catalytic hydrogenation with H₂.