Лако-красочные материалы — производство

As discussed in Section 7.4.2.5, the reduction of tetrazolium salts to formazans often results in further reduction products. As seen in Scheme 24, reduction of formazans with ammonium sulfide leads to the hydrazidine 161. The reduction can proceed further eliminating an arylamine, yielding an amidrazone, e. g., 162.364 By contrast, alcoholic hydrogen sulfide attacks

G = Galactose

Ph

Zn/Ac20

Ph

sugar formazans e. g., 212, to form the thiogalactonic acid phenylhydrazone (213) (Eq. 26).365 Zinc and dilute acids reduce symmetric and unsymmetric formazans to a mixture of a hydrazine and acyl hydrazides.318,323,348,366,367 Zinc and acetic anhydride lead cleanly to a diacetylhydrazidine, e. g., 214 (Eq. 27)10; by contrast, zinc dust in dilute acids leads to degradative reduction with no identifiable products.8