ON A DIHYDRO-QUINOXALINE 



129 



necessary to assume that, on condensation of the diamine with mesi- 

 tyloxide, a hydrogen atom from the carbon atom of the oxide carrying 

 the double bond passes to the carbon atom holding the methyl group. 

 It would seem more likely that this hydrogen atom would pass to the 

 isopropylene group. The fact that a normal quinoxaline is undoubtedly 

 formed on oxidation of the base would seem to support this view. 



The reaction taking place between orthophenylene-diamine and 

 mesityloxide would then be represented by the equation, 



c CH 3 



,CH, + H.O 



EXPERIMENTAL PART 



PREPARATION OF THE BASE 



Dry hydrochloric acid gas was passed for two hours into a cold con- 

 centrated solution of orthophenylene-diamine in dry acetone. A wine- 

 colored solid separated out in a hard compact mass. The container 

 was broken and the mass pressed out on a porous plate. This hydro- 

 chloric acid salt was then dissolved in a small amount of water, filtered, 

 and treated with a slight excess of concentrated potassium hydroxide. 

 The impure base, thus precipitated as a sand- colored solid, was filtered 

 off by suction, and pressed out on a porous plate. Bone black took 

 the impurities from a hot benzene solution of the base, from which it 

 crystallized in large, straw-colored monoclinic prisms. M. P. 124 . 

 The yield is almost quantitative. 



Similarly the hydrochloric acid salt was prepared by passing the 

 dry acid gas through a warm solution in molecular proportions of the 

 diamine and mesityloxide. 



Experiment showed that the base could also be formed by heating 

 a mixture of the diamine and oxide with phosphorus pentoxide on the 

 oil bath at 160 . The yield here, however, is not good. 



