THERMOCHEMICAL AND CRYSTALLOGRAPHIC STUDIES OF SOME BETA-KETOIMINE DERIVATIVES

The standard (p-degrees = 0.1 M Pa) molar enthalpies of formation at 298.15 K in the gaseous state of some beta-ketoimines, RCOCH=C(CH3)NHR1, were determined from their enthalpies of combustion and of sublimation, DELTA(f)H(m)degrees(g)/kJ mol-1: R=CH3, {R1 = C6H5, -66.0 +/- 4.2; R1 = p-C6H4NO2, -98.9 +/- 5.0}: R = C6H5, {R1 = H, -48.7 +/- 3.5; R1 = CH3, -53.7 +/- 4.7; R1 = C6H5, 69.1 +/- 4.2). From these results it is shown that the increase in delocalization energy from R = CH3 to R = C6H5 matches the corresponding increase between acetylacetone and benzoylacetone. Crystal structures are reported for R = CH3, R1 = p-C6H4NO2, and R = C6H5 {R1 = H, R1 = CH3}, and show that those beta-ketoimines with R = C6H5 have a more delocalized structure in the -COCH=C(CH3)NH-moiety than those with R = CH3 in accord with the thermochemical results.