C(NC1C=CC=CC=1)=O.[K].C(NC1C=CC=CC=1)=O.[NH2:20][C:21]1[CH:26]=[CH:25][CH:24]=[CH:23][CH:22]=1.C([O-])=O.[K+].[N+:31]([C:34]1[CH:39]=[CH:38][C:37](Cl)=[CH:36][CH:35]=1)([O-:33])=[O:32].[C]=O>C1(C)C(C)=CC=CC=1>[CH:24]1[CH:25]=[CH:26][C:21]([NH:20][C:37]2[CH:38]=[CH:39][C:34]([N+:31]([O-:33])=[O:32])=[CH:35][CH:36]=2)=[CH:22][CH:23]=1To the aforedescribed slurry of 103.0 parts by weight of potassium formanilide 30.2 parts by weight of formanilide, 2.1 parts by weight of aniline and 0.3 parts by weight potassium formate in 272.0 parts by weight of xylene is added 78.5 parts by weight of p-nitrochlorobenzene at 75°±5° C. The solution is heated to reflux under a 5-plate column with a take-off allowing sampling of the overhead between the reactor and column. The pot temperature is 145°±5° C. at reflux. The reaction begins at a batch temperature of 120°±10° C., as indicated by the evolution of carbon monoxide accompanied by a color change of the batch from yellow to deep red. As soon as heatup is complete and the reflux is established, forward flow of the overhead is begun at a rate sufficient to remove 200 parts by weight of xylene. When this is accomplished, the batch temperature is 162°±3° C. and p-nitrochlorobenzene conversion is over 90%. The endpoint of the reaction is indicated when the para-nitrochlorobenzene content is less than about 0.01%. If necessary, a hold period at the upper batch temperature is used to reach the endpoint. The time required is about 3±0.5 hours. After completion of the reaction, the reaction mass is transferred to a washing vessel and washed twice with 270 parts by weight of hot water. The washed oil layer contains 100.0 parts by weight (about 94% yield) of 4-nitrodiphenylamine, no p-nitrochlorobenzene, 10.4 parts by weight of by-products, 16.3 parts by weight of aniline, 25.3 parts by weight of formanilide and 72.0 parts by weight of xylene. From 225.0 parts by weight of the washed oil, there is recovered approximately 90 wt. % of the 4-nitrodiphenylamine by crystallization, the difference being eventually recovered after xylene, aniline and formanilide have been separated and recycled to the system.
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