Write the formula to measure % atom economy according to green chemistry.(ii) Convert : (a) Benzene into benzaldehyde (b) Cyclohexene into adipic acid

Answer:

(i)

(ii)(a) Benzene → benzaldehyde (Gattermann–Koch formylation): benzene is treated with carbon monoxide and hydrogen chloride in the presence of anhydrous AlCl₃ and CuCl:

C₆H₆ + CO —(HCl, anhyd. AlCl₃/CuCl)→ C₆H₅CHO (benzaldehyde)

(b) Cyclohexene → adipic acid: cyclohexene is oxidised, breaking the C=C bond and converting both ends into –COOH. The green method uses 30% hydrogen peroxide with a sodium tungstate catalyst (and a phase transfer catalyst); the classical method uses hot acidified KMnO₄ (or K₂Cr₂O₇/H₂SO₄):

C₆H₁₀ (cyclohexene) + 4H₂O₂ —(Na₂WO₄, heat)→ HOOC–(CH₂)₄–COOH (adipic acid, hexanedioic acid) + 4H₂O

The green route gives water as the only by-product.