Thermochemical and crystallographic studies of some β-ketoimine derivatives
Abstract
The standard (p°= 0.1 MPa) molar enthalpies of formation at 298.15 K in the gaseous state of some β-ketoimines, RCOCHC(CH3)NHR1, were determined from their enthalpies of combustion and of sublimation, ΔfH°m(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 β-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.