C6H5CHO forms precipitate with 2,4-DNP solution due to the presence of carbonyl group. With Tollens reagent, it gives silver mirror test.
C6H5CHO+2Ag(NH3)2OH → C6H5COONH4 + 2Ag + H2O+3NH3 With ammoniacal AgNO3, propyne gives white precipitate as follows: CH3C≡CH
Ammonical
→
AgNO3
CH3−C≡C−Ag+ White ppt. Similarly, CN− and I− form precipitate with AgNO3 AgNO3+CN− → AgCN↓ AgNO3+I− → AgI↓ Carbonyl compounds (C6H5CHO) and CN− react to form cynohydrins.