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The enthalpy of formation (ΔfH0) 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 C4HmFk, where 0≤m≤9, k = 10-m, and neopentane C5HmFk, where 0≤m≤11, k = 12-m has been calculated by the G4 method. Within the ΔHf0 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: ΔHf0add(M) = ΔHf0(R) + a∙ΔHf0(F-F)1,2 + b∙ΔHf0(F-F)1,3 + c∙ΔHf0(F-F)1,4, where ΔHf0(R) is contribution of group R into the enthalpy of formation (R = СH3, CH2, CH, С, CH2F, CHF2, CF3, CHF, CF2, CF), ΔHf0(F-F)1,2, ΔHf0(F-F)1,3, ΔHf0(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.

Within the «quantum theory of atoms in molecules» the charge q and volume V of topological atoms A and atomic groups R of fluorinated molecules of ethanes C2HmFk, where 0 ≤ m, k ≤ 6 and m+k = 6 and propanes C3HmFk, where 0 ≤ m, k ≤ 8, m+k = 8, has been calculated by Aimall software package. Optimization of the geometry and finding of the electron density distribution (ρ(r)) has been carried out by the GAUSSIAN 03 program with the B3LYP 6-311++G (3df,3pd) 6d 10f level of theory. Influence of fluorine atoms on near atomic groups has been studied. The absence of the transferable functional groups has been showed. A conclusion has been made about unsuitability of the evaluation of properties by additive methods, which do not consider differences in electron structures for this class of compounds. The enthalpy of formation ΔfH0 of 38 molecules of fluorethanes and fluorpropanes has been computed by the G4 method. The comparison with the experimental values has shown good coherence. Results of this work is planned to be used in designing additive models for prediction of thermodynamic and thermochemical properties of organic fluorinated compounds.

The investigation of the electronic structure of the 6,6 difluorine undecane (6,6 — F2C11H22 ) and structural isomers of k,k - difluorine octane molecules ( k,k — F2C8H16 , 1 ≤ k ≤ 8 where k is a position of the fluorine atoms in alkyl chain) has been carried out. Within the «quantum theory of atoms in molecules» the transferable or «standard» electron parameters of topological atoms and atomic groups (charge, energy and volume) have been determined. The inductive effect spread from the fluorine and the fluorine-containing fragments (CHF2 and CF2 ) on local environment was explored. The influence of CHF2 applies to four CH2 groups along the hydrocarbon chain, the influence of CF2 applies to two CH2 groups in both sides along the hydrocarbon chain. Data on changes in electronic parameters depending on the distance from the fluorine atom were obtained. Series of electronegativity of the functional groups has been made up. According to it CF2 group is a stronger acceptor of electron density, than CHF2 .

Fifteen conformers of the CHF2 – (CH2)6 – CH3 molecule were found. Within a «quantum theory of atoms in molecules», their equilibrium geometry, total energies and the electron structure were studied. Analysis and comparison of electron parameters revealed in some structures a steric effect from CHF2.

Within a «quantum theory of atoms in molecules» (QTAIM) the equilibrium geometry and the electron structure of fluoro-substituted molecules (CH3)2−CH−CH(3-n)Fn and (CH3)3−C−CH(3-n)Fn, where 1 ≤ n ≤ 3, were studied. Intramolecular interactions also discussed.

14 potential functions V(φ) of the internal rotations around the C — C bonds in molecules of 1,1,1-trifluorine alkanes CF3 — (CH2)n — CH3, where 1 ≤ n ≤ 4, were obtained and approximated by Fourier series. The local minima of V(φ) and transition states (TS) have been studied for all examined compounds. A comparison of the rotation characteristics of studied molecules those of same in n-alkanes and 1-monofluorine alkanes was performed. The transferability of rotation parameters around C — C bonds has been showed.

Eight potential functions of the internal rotations around the C-C bonds in molecules 1,n- difluorine alkanes F-(CH2)n-F, where 3 ≤ n ≤ 6, were obtained and approximated by Fourier series. The local minima and transition states (TS) have been studied for all the examined compounds. A comparison of the rotation characteristics of studied molecules with same in 1-monofluorine alkanes was performed. The transferability of rotation parameters around C-C bonds has been showed.