Malachite green is prepared by the condensation of benzaldehyde and dimethylaniline to give leuco malachite green (LMG): Second, this colorless leuco compound, a relative of triphenylmethane, is oxidized to the cation that is MG: C6H5CH(C6H4N(CH3)2)2 + HCl + 1⁄2 O2 → [C6H5C(C6H4N(CH3)2)2]Cl + H2O.
