The plausible aromaticity of 1,8-naphthalimides: The enthalpy of formation of N-methyl-1,8-naphthalimide

In order to understand the aromaticity of 1,8-naphthalimides, the enthalpies of combustion and sublimation of N-methyl-1,8-naphthalimide were determined. The numerical values are −6095.8 ± 3.5 and 109.7 ± 0.8 kJ · mol−1. The enthalpies of formation of condensed and gas phase N-methyl-1,8-naphthalimide are accordingly −306.1 ± 3.9 and −196.4 ± 4.0 kJ · mol−1. It is deduced that naphthalimides enjoy some 40 kJ · mol−1 of aromatic stabilization over that of the maleimides, shown to be nominally destabilized and modestly antiaromatic in our recently published thermochemical study