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Thermochemistry of Heteroatomic Compounds:Calculation of the Heat

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Thermochemistry of Heteroatomic Compounds:Calculation of the Heat Open Journal of Physical Chemistry, 2011, 1, 1-5 doi:10.4236/ojpc.2011.11001 Published Online May 2011 (http://www.SciRP.org/journal/ojpc) Thermochemistry of Heteroatomic Compounds: Calculation of the heat of Combustion and the heat of Formation of some Bioorganic Molecules with Different Hydrophenanthrene Rows Vitaly V. Ovchinnikov Tupolev Kazan State Technical University, St- K. Marks 10, 420111 Kazan, Russian Federation E-mail: [email protected] Received March 23rd, 2011; revised April 10th, 2011; accepted May 10th, 2011. Abstract On the basis of the known experimental heats of combustions of the seventeen alkanes in condensed state, the general equation comb HifNg 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 pre- sented 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-D2, estradiol, an- drostenone, 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 , which has been calculated with the use of a topological 1 s solvation index of the first order x , the heats of formation f H for condensed and gaseous phases were calculated for the listed bioorganic molecules. Keywords: Alkanes, Biochemical Molecules, the Heat of Combustion, Heat of Formation, Heat of Vaporiza- tion, Topological Solvation Index 1. Introduction electron. Such power is nearly equal to the sum of the heats of C-H and C-C breaking bonds in molecule at the In living organisms the organic molecules named as ster- combustion. The parameters a and b are a numbers of all oids are synthesized many. Extremely low reactivity of carbon and hydrogen atoms and c is a number of the steroids complicates their metabolism, which can be moving electrons from carbon to the more electronega- compared to full oxidation (burning) in a live organism. tive atoms in molecule. The sum of the heat corrections In such cases, researchers use the theoretical calculation hci has been introduced by authors of the above men- of the heat (enthalpy) of combustion for the biochemical tioned work for the identical di types of bonds, spa- substances. tial structures or groups in researching compounds. The electronic conception of the interdependence of valence and the heat of combustion of organic com- 2. Results and Discusion pounds has been formulated in review of Kharasch and Sher [2] (Equation 1) In the complex organic and biochemical compounds with H 109.0 4abc hcd* (1) various heteroatoms, it is difficult to define a degree the comb * i i group electronegativity and correspondingly a number of The number -109.0 has been deduced from the com- moving to them or inside of them, accordingly to bustion enthalpy of n-octane. It has dimension kJ·mol–1 Kharasch and Sher conception, electrons. In our opinion electron–1 and characterizes the shift energy of the one the majority of missing structural and energetic correc- Copyright © 2011 SciRes. OJPC 2 V. V. OVCHINNIKOV tions can be in a complex considered within the limits of tive conformity. Besides, using last dependence, we one-factorial regression analysis [3]. This consists in calculated the combustion enthalpy of cis-decalin (18) construction of a various correlations between the ex- and compared it with known in the literature. It is equal perimentally known values of the heats of combustion –6320.4 ± 31.6 and within the error, estimated by us in comb H of organic or heteroatomic compounds and a ± 0.5 %, coincides with experimental –6287.7 ± 0.9 general number of the bond-forming electrons N in its kJ·mol–1 [4]. The specified circumstances gives the pos- Equation (2), in which sibility to apply the last equation for calculations of the heat of combustions for the variously substituted al- H ifNg (2) comb kanes: cholestane, (19), cholesterol (20), O-methyl- cho- i and f are the correlation coefficients, describing struc- lesterol (21), ergosterol (22), vitamin D2, received by turally-energetic contributions in the enthalpy of com- the isomerization of ergosterol [5], (23), estradiole (24), bustion and sensitivity of the last to a general number androstenone (25), testosterone (26), androstanedione of electrons N, from which subtracted a number (g) of (27), having the important biochemical properties. It is lone electron pairs of heteroatoms in the different necessary to note also a good correspondence (within functional groups. So, for IV group of Periodic Table the limits of ± 2%) of the thermochemical parameters (C, Si and below) g is equal 0, for V group (N, P and calculated by us with the known in the literature (Table below) g is equal 1, for VI group (O, S and below) g is 2, Equation (5)) equal 2. Proceeding from the listed above and also scheme of H / kJ mol1 476.4 308.2 comb exp (5) the process combustion of saturated, unsaturated and 96.6 216.7 * H / kJ mol1 aromatic hydrocarbons (Equation 3) comb calc pCH q O r CO gas s HO liq H r 0.999, so 158.7, n 6 (20-22, 25-27). n2n2 2 2 2 comb Moreover, necessary to note, that the experimental re- (3) sults for cholesterol (20), androstenone (25), testosterone in which p, q, r, s are stoichiometric coefficients (values (26) and androstanedione (27) (Table 2, column 5, 8) are о –1 of ∆fH for CO2 = –393.5 and H2O = –285.8 kJ·mol very different each to other in the essential values, but are taken from monography [4]), we have calculated de- they are rather near to calculated by us values (Table 2, pendence (4), which included itself the heat of combus- column 4). tion of saturated of alkanes (Table 1, compounds 1-17) In structure of other well-known bioorganic molecules of a various normal-and cyclic structure and a number [5], such as morphine (28), morphinanone (29), codeine valence electrons in its (g = 0) (30) and pentasozine (31) the aromatic rings are included. H /kJ mol1 comb (4) Nevertheless, accordingly to Kharasch-Sher-conception 25.63 27.37 108.54 0.49 * N there is a mention about the application of the Equation (1) to the saturated and aromatic compounds. For this r 0.999, so 32.9, n 17. From the deduced Equation (4) it is possible to see, reason expediently to calculate the combustion enthalpy pletely corresponds to the suggested earlier by Kharasch of these substances with the use dependence (4) of for and Sher, that testifies to qualitative and their quantita- saturated hydrocarbons. Table 1. The number of valence electrons (N) and the heats of combustion (kJ·mol–1 of the different structural n-and cyclo- lkanes [4]. P 101kPa; T 298.15; all compounds are in condensed state. No Compound, formula N -ΔcombH No Compound, formula N -ΔcombH 1 Methylcyclopentane (С6Н12) 36 3938.6 10 2-Methylheptane, (С8Н18) 50 5456.5 2 Cyclohexane, (С6Н12) 36 3920.0 11 2,5- Dimethylhexane, (С8Н18) 50 5460.2 3 n-Hexane, (С6Н14) 38 4163.3 12 3,4- Dimethylhexane, (С8Н18) 50 5468.7 4 Cycloheptane, (С7 Н14) 42 4597.0 13 Ethylhexane, (С8 Н18) 50 5470.2 5 Methylcyclohexane, (С7Н14) 42 4565.3 14 n-Decane, (С10Н22) 62 6778.6 6 1,1-Diethylcyclohexane, (С8Н16) 48 5216.0 15 n-Dodecane, (С12Н26) 74 8090.6 7 trans-1,3- Dimethyl-cyclohexane, (С 8Н16) 48 5219.0 16 trans-syn-trans-Pentahydroanthracene,(С14Н24) 80 8608.5 8 trans-1,4- Dimethyl-cyclohexane, (С 8Н16) 48 5212.3 17 n-Hexadecane, (С16Н34) 98 10700.1 9 n-Octane, (С8Н18) 50 5471.8 Copyright © 2011 SciRes. OJPC V. V. OVCHINNIKOV 3 Table 2. The structural ( 1 xs ) and thermochemical parameters (kJ·mol–1) of some types of biochemical molecules. P 101 kPa; T 298.15; all compounds are in condensed state. No Compound, formula о (N-g) electrons -combH 1 s - f H x H Eq.2 Eq.4 Experiment vap Condens Gas 1 2 3 4 5 6 7 8 9 Me Me 156 16958.1 12.860 126.4 526.6 400.2 Me 2 ± 84.8 ± 6.3 ± 2.6 ± 2.0 Me 19 C27H48 Me Me 152 16578.3 16524.0[12] 13.254 157.2 620.5 463.3 Me 2 Me ± 82.9 ± 3.9 ± 7.9 ± 3.1 ± 2.3 20 [13] [14] [12] 16590.0 114.6 674.9 [13] HO ± 67.0 (sub) 607.0 C27H46O Me Me [4] 158 17226.4 13.503 132.3 675.8 543.5 Me 17202.4 2 ± 5.0 ± 6.6 ± 3.4 ± 2.7 Me ± 86.0 21 O Me C28H48O Me Me 154 16877.0 16516.7[4] 13.664 161.0 429.5 268.5 Me 2 ± 84.4 ± 5.7 ± 8.0 ± 2.1 ± 1.3 Me Me 22 O H C28H44O Me Me Me 2 154 16985.8 13.719 161.5 320.8 159.2 Me ± 84.9 ± 8.1 ± 1.6 ± 0.8 23 OH C28H44O OH Me 92 10093.0 9.593 177.7 420.1 242.4 ±50.4 ±8.9 ±2.1 ±1.2 24 HO C18H24O2 OH Me 100 10934.2 11080.0[13] 9.949 126.6 544.1 417.5 ± 54.7 ± 30.0 ± 6.3 ± 2.7 ± 2.1 Me 26 [13] 390.0 O C19H28O2 Copyright © 2011 SciRes.
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