TOWARDS A COLORIMETRIC SPOT-TEST FOR THE DETECTION OF METHYLAMINE .1.REACTION OF ALIPHATIC-AMINES WITH NITROSUBSTITUTED BENZENE AND TOLUENE COMPOUNDS TO FORM MEISENHEIMER COMPLEXES

The reactions of a series of nitro-substituted benzene and toluene com pounds with methylamine, diethylamine and triethylamine were studied i n dimethylsulfoxide (DMSO), with the ultimate aim of producing a dipst ick spot test for methylamine, These reagents form Meisenheimer comple xes that are coloured for the primary and secondary amines, 2,4-Dinitr otoluene and 1,3-dinitrobenzene showed the greatest promise, although the reaction times with 1,3-dinitrobenzene were excessively long, taki ng about 1 h to develop fully their colour, The reactions of methylami ne and diethylamine in DMSO solution with 2,4-dinitrotoluene were almo st immediate, yielding pale yellow-to-green colour changes, Both produ cts produce a lambda(max.) at 650 nm and in DMSO at this wavelength th e molar absorption coefficient of the methylamine-2,4-dinitrotoluene c omplex was 395 +/- 5 mol(-1) cm(2) and that of the diethylamine-2,4-di nitrotoluene complex was 40 +/- 2 mol(-1) cm(2), Triethylamine showed virtually no response, giving only a pale yellow-green coloration with 2,4-dinitrotoluene on a spot-plate test with the pure amine, (It is p ossible that the colour may have been due to an impurity).