[arani.b]

Recently I encountered a problem which reads,

Ph-NO₂ + LiAlH₄   PhN=NPh (azobenzene)  but,

Ph-NO₂ + NaBH₄/Pd-C   Ph-NH₂ (aniline)

Explain.

Now I know that nitrobenzene on reduction in acidic media gives aniline and on reduction in alkaline media gives azobenzene. But I can't understand how is it applicable in the above case. Please help.

[nox]

I presume that H₂ generated from decomposition of NaBH₄ is the actual reductant in the second example.