Summary of aromatic nitro reduction methods tested
- Stannous chloride in ethanol (tin(II) chloride) — 15 g SnCl₂·2H₂O in 25 mL absolute ethanol; ortho-nitrotoluene as substrate; refluxed until reduction appears complete; workup requires neutralization and steam distillation due to tin chloride acidity; ethanol preferred (methanol slower); verdict: effective but requires long reflux and 5–6× molar excess; no shortcuts in workup.
- Iron(II) sulfate in ammoniacal solution — FeSO₄·7H₂O in warm water with 25% NH₃ and ortho-nitrotoluene; heated to ~50°C with additional NH₃; afterworkup, reduction not successful; persistent nitro aroma; poor separation; verdict: no.
- Sodium diphenate method (Zn/diphenate in alkali) — prepare sodium diphenate in situ from sodium bisulfite and zinc; nitro-toluene in methanol–water with co-solvent; alkaline workup with sodium carbonate; reflux ~30 minutes; nitro aroma disappears, amine odor appears; pale yellow solid forms; filtrate extractable under alkaline conditions; result indicates rapid, mild, effective reduction; verdict: winner among tested methods.
Overall takeaway: tin reduction works with long reflux and excess; iron sulfate approach is ineffective under tested conditions; sodium diphenate method shows fast, mild, practical reduction with good potential for sensitive substrates.
