Thermochemical study of some chloro and bromo alkyl substituted phthalimides: Structural–energetic correlations

Abstract

The standard ( p ∘ = 0.1 MPa) massic energies of combustion, Δ c u ∘, for crystalline N-chloromethylphthalimide, N-(2-chloroethyl)phthalimide, N-(2-bromoethyl)phthalimide, and N-(3-bromopropyl)phthalimide were determined, at the temperature 298.15 K, using a rotating-bomb combustion calorimeter. The standard molar enthalpies of sublimation, Δ cr g H m ∘ , at T = 298.15 K were determined for all compounds by Calvet microcalorimetry and for N-chloromethylphthalimide also derived from the variation with the temperature of its vapour pressures measured by the Knudsen effusion technique. The results obtained were as follows: −Δ c u ∘(cr)/(kJ · g −1) Δ cr g H m ∘ / ( kJ · mol - 1 ) N-Chloromethylphthalimide 20720.1 ± 4.5 103.6 ± 0.9 N-(2-Chloroethyl)phthalimide 22479.3 ± 6.8 98.4 ± 1.9 N-(2-Bromoethyl)phthalimide 18501.6 ± 2.8 108.7 ± 1.0 N-(3-Bromopropyl)phthalimide 19965.8 ± 5.4 116.0 ± 1.0 These values were used to derive the standard molar enthalpies of formation of the compounds in their crystalline and gaseous phases, respectively. The derived standard molar enthalpies of formation, in the gaseous state, are analyzed in terms of enthalpic increments and interpreted in terms of molecular structure.