[N+:1]([C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][C:5]=1[O:10][CH2:11][CH:12]([CH3:14])[CH3:13])([O-])=O.[OH-:15].[Na+]>[Fe].[Zn].O.[O-2].[Zn+2].O>[CH2:11]([O:10][C:5]1[CH:6]=[C:7]([C:7]2[CH:8]=[CH:9][C:4]([NH2:1])=[C:5]([O:15][CH2:11][CH:12]([CH3:14])[CH3:13])[CH:6]=2)[CH:8]=[CH:9][C:4]=1[NH2:1])[CH:12]([CH3:14])[CH3:13]An iron apparatus equipped with horseshoe stirrer and heating and cooling means is charged with 293 g of o-nitro-isobutoxybenzene, 395 g of solvent naphtha and 220 g of zinc dust. The reaction mixture is heated with stirring to 80° C., and first 24 g of 50% strength sodium hydroxide solution and then 21 g of water are added with temporary cooling. To complete the reduction, stirring is continued at 80° C. with the addition of further zinc dust a little at a time (in total 53 g) until a spot test with the reaction solution shows a colorless runoff. By further addition of water the zinc oxide hydrate is then grained. The zinc oxide hydrate is then separated by filtration from the organic phase containing the 2,2'-diisobutoxyhydrazobenzene and as byproduct 1-isobutoxy-2-aminobenzene. After extraction of the byproduct with dilute hydrochloric acid the organic phase is added dropwise at 15°-20° C. to hydrochloric acid and stirring is continued at 25° C. until the rearrangement reaction has ended (test: hydrazo compound no longer detectable). The crude product is purified by filtration, dissolving in hot water and clarification of the solution with Carboraffin. Precipitation with concentrated hydrochloric acid gives 106 g of 3,3'-diisobutoxybenzidine dichlorohydrate having a diazotization value of 96%, melting point 270° C.
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