Thermochemistry of Heteroatomic Compounds : Calculation of the heat of Combustion and the heat of Formation of some Bioorganic Molecules with Different Hydrophenanthrene Rows

On the basis of the known experimental heats of combustions of the seventeen alkanes in condensed state, the general equation has been deduced, in which i and f are correlation coefficients, N and g are a numbers of valence electrons and lone electron pairs of heteroatoms in molecule. The presented dependence has been used for the calculation of the heats of combustion of thirteen organic molecules with biochemical properties: holestan, cholesterol, methyl-cholesterol, ergosterol, vitamin-D  comb H i f N g      2, estradiol, androstenone, testosterone, androstanedione, morphine, morphinanone, codeine and pentasozine. It is noted that good convergence was obtained within the limits of errors of thermochemical experiments known in the literature and calculations of the heats of combustion for some of them were conducted. With the application of Hess law and the heats of vaporization   vap H    1 , which has been calculated with the use of a topological solvation index of the first order s x , the heats of formation   f H   for condensed and gaseous phases were calculated for the listed bioorganic molecules.


Introduction
In living organisms the organic molecules named as steroids are synthesized many.Extremely low reactivity of steroids complicates their metabolism, which can be compared to full oxidation (burning) in a live organism.In such cases, researchers use the theoretical calculation of the heat (enthalpy) of combustion for the biochemical substances.
The electronic conception of the interdependence of valence and the heat of combustion of organic compounds has been formulated in review of Kharasch and Sher [2] (Equation 1) The number -109.0 has been deduced from the combustion enthalpy of n-octane.It has dimension kJ•mol -1 electron -1 and characterizes the shift energy of the one electron.Such power is nearly equal to the sum of the heats of C-H and C-C breaking bonds in molecule at the combustion.The parameters a and b are a numbers of all carbon and hydrogen atoms and c is a number of the moving electrons from carbon to the more electronegative atoms in molecule.The sum of the heat corrections   i hc has been introduced by authors of the above mentioned work for the identical types of bonds, spatial structures or groups in researching compounds.

Results and Discusion
In the complex organic and biochemical compounds with various heteroatoms, it is difficult to define a degree the group electronegativity and correspondingly a number of moving to them or inside of them, accordingly to Kharasch and Sher conception, electrons.In our opinion the majority of missing structural and energetic correc- V. V. OVCHINNIKOV tions can be in a complex considered within the limits of one-factorial regression analysis [3].This consists in construction of a various correlations between the experimentally known values of the heats of combustion  comb H  of organic or heteroatomic compounds and a general number of the bond-forming electrons N in its Equation (2), in which Proceeding from the listed above and also scheme of the process combustion of saturated, unsaturated and aromatic hydrocarbons (Equation 3) in which p, q, r, s are stoichiometric coefficients (values of ∆ f H о for CO 2 = -393.5 and H 2 O = -285.8kJ•mol -1 are taken from monography [4]), we have calculated dependence (4), which included itself the heat of combustion of saturated of alkanes (Table 1, compounds 1-17) of a various normal-and cyclic structure and a number valence electrons in its (g = 0)    r 0.999, s o 32.9, n 17.From the deduced Equation ( 4) it is possible to see, pletely corresponds to the suggested earlier by Kharasch and Sher, that testifies to qualitative and their quantita-tive conformity.Besides, using last dependence, we calculated the combustion enthalpy of cis-decalin (18) and compared it with known in the literature.It is equal -6320.4± 31.6 and within the error, estimated by us in ± 0.5 %, coincides with experimental -6287.7 ± 0.9 kJ•mol -1 [4].The specified circumstances gives the possibility to apply the last equation for calculations of the heat of combustions for the variously substituted alkanes: cholestane, (19), cholesterol (20), O-methyl-cholesterol (21), ergosterol (22), vitamin D 2 , received by the isomerization of ergosterol [5], (23), estradiole (24), androstenone (25), testosterone (26), androstanedione (27), having the important biochemical properties.It is necessary to note also a good correspondence (within the limits of ± 2%) of the thermochemical parameters calculated by us with the known in the literature ( In structure of other well-known bioorganic molecules [5], such as morphine (28), morphinanone (29), codeine (30) and pentasozine (31) the aromatic rings are included.Nevertheless, accordingly to Kharasch-Sher-conception there is a mention about the application of the Equation (1) to the saturated and aromatic compounds.For this reason expediently to calculate the combustion enthalpy of these substances with the use dependence (4) of for saturated hydrocarbons.16524.0 [12] ± 3.9 16590.0 [13] ± 67.0 13.254 157.2 ± 7.9 114.6 [14]  (sub) 620.5 ± 3.1 674.9 [12]  607.0 [13]   463.11080.0 [13] ± 30.0 9.949 126.6 ± 6.3 544.1 ± 2.7 390.0 [13]   417.10930.0 [13] ± 46.0 9.949 99.4 ± 5.0 598.5 ± 2.7 544.0 [13]   449.With a view of the correct of the Equation (4) application, it has been lead the calculation of the combustion enthalpy of tetraline (32) (-5620.2± 28.1 kJ•mol -1 ) and then it compared to the literary value H comb (-5621.54± 0.88 kJ•mol -1 ) [6].Except for listed above it is necessary to note, that with a view of the efficiency of the calculation of the combustion enthalpy by us, as soon as by Kharasch and Sher, the corrections on the presence in bioorganic molecules primary and secondary НО-groups, С = С-bond, a five-membered cycle with oxygen -54.4,-27.2, -54.4 and 27.2 kJ•mol -1 correspondingly were introduced.
The formation enthalpies ( f H о cond ) of all bioorganic molecules (19-31) in the condensed state have been calculated according to the resulted above equations (3,4) and Hess law (Equation 6) Good correspondence between the calculated and the experimental literary data [4,13] for the combustion of some biochemical molecules (Table 2) is observed.

Conclusions
Thus, as it has been shown during this work the simple linear Equation (4), worked up for the correlations be-tween the heats of combustion of saturated alkanes of the different spatial structure and the general number of the valence electrons, excluding of the lone electron pare of heteroatoms in its, could be useful applicable to the calculation of the same thermochemical parameters of the bioorganic molecules of hydrophenanthrene rows.
The calculated the heats of formation in a gaseous phase are necessary for an estimation of the bond energies in biochemical substances.

Table 2 ,
column 5, 8)are very different each to other in the essential values, but they are rather near to calculated by us values (

of some types of biochemical molecules. P 101 kPa; T 298.15; all compounds are in condensed state.
has been successfully used by us earlier