Nitrobenzene is reduced to aniline by what reagents?

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Reducing a nitro group to an amine needs a strong source of electrons and protons to push the NO2 group all the way to NH2. Tin metal in hydrochloric acid provides that combination: tin donates electrons and the acid supplies protons, allowing the nitro group on nitrobenzene to be reduced step by step to aniline. This setup is a classic, reliable method that is widely used and taught for converting nitrobenzenes to anilines.

Iron in hydrochloric acid can accomplish the same transformation, but tin in acid is the standard example emphasized in many texts and exams. Catalytic hydrogenation could also reduce nitrobenzene to aniline under hydrogenation conditions, but it requires hydrogen gas and a catalyst, making it less of a straightforward reagent choice. Sodium borohydride, on the other hand, is too mild to reduce a nitro group directly to an amine.