catalyst since said hydrogenation is preferably carried out with toluene as the reaction medium when in the above reaction the acid catalyst is used in amounts above 1 0 molar percent no adverse results are observed in the reaction but removal of the excess or its neutralization may prove cumbersome or costly without providing a substantial increase in reaction speed the reaction between maleic anhydride and 2 methyl 1 naphthylamine in the presence of the specified acid catalyst is almost instantaneous but to insure that said reaction proceeds to mnm and not only to the monoester of maleic acid heating of the reaction mixture for at least one hour is preferred as specified this heating is done at a temperature whereby the formed water evaporates to assure substantial completion of the reaction the heating step is carried out in such a fashion that the evaporating water is elminated from the reaction mixture completion of the reaction can easily be checked by analyzing successive portions of the distillate for absence of substantial amounts of water alternately if all the materials used in the reaction are free of water or the amount of water therein is known the reaction may be continued until the calculated reaction formed water has distilled in a.