Structure - property relationship for the fluorinealcanes

The enthalpy of formation (Δ_fH⁰) of molecules CH₃-(CH₂)_n-CH₂F, where 3≤n≤5, CH₃-(CH₂)_n-CHF₂ (3≤n≤4), CH₂F-(CH₂)₃-CH₂F, CHF₂-(CH₂)₃-CHF₂, CF₃-(CH₂)₃-CHF₂, CF₃-(CH₂)₃-CF₃, CHF₂-(CH₂)₃-CH₂F, CF₃-(CH₂)₃-CH₂F, fluorinated isobutane C₄H_mF_k, where 0≤m≤9, k = 10-m, and neopentane C₅H_mF_k, where 0≤m≤11, k = 12-m has been calculated by the G4 method. Within the ΔH_f⁰ for molecules of fluoroethanes, fluorobutanes, and fluoropropanes this values has been formed learning sample, which totally includes 180 values. The calculation scheme for the enthalpy of formation of fluorine-containing molecules M have been proposed: ΔH_f⁰_add(M) = åΔH_f⁰(R) + a∙ΔH_f⁰(F-F)_1,2 + b∙ΔH_f⁰(F-F)_1,3 + c∙ΔH_f⁰(F-F)_1,4, where ΔH_f⁰(R) is contribution of group R into the enthalpy of formation (R = СH₃, CH_2, CH, С, CH₂F, CHF₂, CF₃, CHF, CF₂, CF), ΔH_f⁰(F-F)_1,2, ΔH_f⁰(F-F)_1,3, ΔH_f⁰(F-F)_1,4 are contributions of interaction of two fluorine atoms, which bounded with the carbon atoms from one, two and three С-С bounds, respectively, a, b, c are numbers of fluorine-fluorine interactions from one, two and three С-С bounds, respectively. All the group contributions have been computed. The comparison have been shown that new scheme is more effective than the simple group-additive methods.

structure - property relationship, thermodynamic properties, additive model, electron structure, enthalpy of formation, quantum theory of atoms in molecules, electron density, fluorine alkanes, Neopentane, isobutane