Enthalpies of combustion of three benzylidene t-butylamine N-oxide derivatives and of 4-nitrobenzylidene t-butylamine: the dissociation enthalpies of the (NO) bonds

Abstract

The standard ( p o=0.1 MPa) molar enthalpies of combustion at 298.15 K were measured by static-bomb calorimetry and the standard molar enthalpies of sublimation at 298.15 K were measured by microcalorimetry for three benzylidene t-butylamine N-oxide derivatives and for 4-nitrobenzylidine t-butylamine: −Δ c H m o(cr)/(kJ·mol −1) Δ cr g H m o/(kJ·mol −1) 4-NO 2C 6H 4CHNC(CH 3) 3 6287.7 ± 1.0 91.1 ± 3.1 4-NO 2C 6H 4CHN(O)C(CH 3) 3 6224.0 ± 1.2 116.5 ± 3.1 4-(CH 3) 2CHC 6H 4CHN(O)C(CH 3) 3 8357.7 ± 1.8 101.8 ± 4.1 C 6H 5CHN(O)C(CH 3) 3 6416.4 ± 1.1 86.8 ± 0.9 From the standard molar enthalpies of formation of the gaseous compounds, the molar dissociation enthalpies of the (NO) bonds were derived, and these were found to be constant within experimental error to give a weighted mean value: D(NO)/(kJ·mol −1) = (285.9 ± 3.6).