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
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 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-D

comb HifNg

2, 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

1
, which has been calculated with the use of a topological
solvation index of the first order
s
x
, the heats of formation


fH 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
In living organisms the organic molecules named as ster-
oids 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 com-
pounds has been formulated in review of Kharasch and
Sher [2] (Equation 1)
 
*
109.0 4*
combi i
H
abchc d (1)
The number -109.0 has been deduced from the com-
bustion 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 electronega-
tive atoms in molecule. The sum of the heat corrections


i
hc has been introduced by authors of the above men-
tioned work for the identical types of bonds, spa-
tial structures or groups in researching compounds.

i
d
2. 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-

2

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 ex-
perimentally 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

comb

H
ifNg (2)
i and f are the correlation coefficients, describing struc-
turally-energetic contributions in the enthalpy of com-
bustion and sensitivity of the last to a general number
of electrons N, from which subtracted a number (g) of
lone electron pairs of heteroatoms in the different
functional groups. So, for IV group of Periodic Table
(C, Si and below) g is equal 0, for V group (N, P and
below) g is equal 1, for VI group (O, S and below) g is
equal 2.
Proceeding from the listed above and also scheme of
the process combustion of saturated, unsaturated and
aromatic hydrocarbons (Equation 3)

 
n2n2 22comb 2
CHO COHOpqrgas sliqH

(3)
in which p, q, r, s are stoichiometric coefficients (values
of ∆fHо for CO2 = –393.5 and H2O = –285.8 kJ·mol–1
are taken from monography [4]), we have calculated de-
pendence (4), which included itself the heat of combus-
tion 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)

1
comb /kJ mol
25.6327.37108.540.49 *
H
N


 

(4)
r 0.999, so 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 pos-
sibility to apply the last equation for calculations of the
heat of combustions for the variously substituted al-
kanes: cholestane, (19), cholesterol (20), O-methyl- cho-
lesterol (21), ergosterol (22), vitamin D2, 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 (Table
2, Equation (5))


1
comb exp
1
comb
/ kJmol476.4308.2
96.6216.7*/ kJmol
calc
H
H



 (5)
r 0.999, so 158.7, n 6 (20-22, 25-27).
Moreover, necessary to note, that the experimental re-
sults for cholesterol (20), androstenone (25), testosterone
(26) and androstanedione (27) (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 (Table 2,
column 4).
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.
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 -ΔcombHNoCompound, 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, (С7Н14 ) 42 4597.0 13 Ethylhexane, (С8Н18 ) 50 5470.2
5 Methylcyclohexane, (С7Н14 ) 42 4565.3 14 n-Decane, (С10 Н22) 62 6778.6
6 1,1-Diethylcyclohexane, (С8Н16 ) 48 5216.0 15 n-Dodecane, (С12 Н26 ) 74 8090.6
7 trans-1,3- Dimethyl-cyclohexane, (С8Н16 ) 48 5219.0 16 trans-syn-trans-Pentahydroanthracene,(С14 Н24 ) 80 8608.5
8 trans-1,4- Dimethyl-cyclohexane, (С8Н16 ) 48 5212.3 17 n-Hexadecane, (С16Н34 ) 98 10700.1
9 n-Octane, (С8Н18 ) 50 5471.8

V. V. OVCHINNIKOV
3
Table 2. The structural (1
s
x
) and thermochemical parameters (kJ·mol–1) of some types of biochemical molecules. P 101 kPa;
T 298.15; all compounds are in condensed state.
(N-g) electrons-combH - f Hо
No Compound, formula
Eq.2 Eq.4 Experiment
1xs vapH Condens Gas
1 2 3 4 5 6 7 8 9
19
Me
Me
Me
Me
2
C27 H48
156 16958.1
± 84.8
12.860 126.4
± 6.3
526.6
± 2.6
400.2
± 2.0
20
Me
Me
Me
Me 2
C27 H46O
152 16578.3
± 82.9
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]
463.3
± 2.3
21
Me
Me
Me
Me
Me
2
C28 H48O
158
17202.4
± 86.0
17226.4[4]
± 5.0
13.503 132.3
± 6.6
675.8
± 3.4
543.5
± 2.7
22
Me
Me
Me
Me
Me 2
H
C28 H44O
154 16877.0
± 84.4
16516.7[4]
± 5.7
13.664 161.0
± 8.0
429.5
± 2.1
268.5
± 1.3
23
Me
Me
Me
Me
2
C28 H44O
154
16985.8
± 84.9
13.719
161.5
± 8.1
320.8
± 1.6
159.2
± 0.8
24
HO
Me
OH
C18 H24O2
92 10093.0
±50.4
9.593 177.7
±8.9
420.1
±2.1
242.4
±1.2
26
O
Me
OH
Me
C19 H28O2
100 10934.2
± 54.7
11080.0[13]
± 30.0
9.949 126.6
± 6.3
544.1
± 2.7
390.0[13]
417.5
± 2.1

V. V. OVCHINNIKOV
4
27
Me
Me
O
O
C19 H28O2
100 10879.8
± 54.4
10930.0[13]
± 46.0
9.949 99.4
± 5.0
598.5
± 2.7
544.0[13]
449.1
± 2.5
28
Me
C17 H19NO3
82 9034.8
± 45.1
9.892 180.5
± 9.0
370.2
± 1.8
189.8
± 0.9
29 O
N-Me
O
HO
C17 H19NO3
82 8980.4
± 44.9
9.504 149.7
± 7.5
424.6
± 2.1
274.9
± 1.4
30
Me
Me
C18 H21NO3
88 9631.7
± 48.1
10.330 130.1
± 6.5
452.7
± 2.3
322.6
± 1.6
31
Me
Me
Me
C20 H29NO
108 11856.9
± 59.3
10.414 158.1
± 7.9
157.8
± 8.0
0.300
± 0.1
With a view of the correct of the Equation (4) applica-
tion, 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 Hcomb (–5621.54
± 0.88 kJ·mol–1) [6]. Except for listed above it is neces-
sary 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 (fHо
cond) of all bioorganic
molecules (19-31) in the condensed state have been cal-
culated according to the resulted above equations (3,4)
and Hess law (Equation 6)

comb f condf cond
p
rod reag
HH H 


(6)
Good correspondence between the calculated and the
experimental literary data [4,13] for the combustion of
some biochemical molecules (Table 2) is observed.
The heat of vaporization

vap

H
 for compounds (19
-31) are calculated on the Equation (7), in which the
topological solvation index of the first order is included.
Such way of the ΔvapН estimation for neutral trivalent
compounds of P, As, Sb and Bi [1,3,8,9], phosphorus
acids [10] and 2-methoxy-2-oxo-1,3,2-dioxaphoapholane
[11] has been successfully used by us earlier
1
7.29 9.26
s
vap
H
x (7).
Such circumstance gives a possibility for the calculation
the formation enthalpies of researching biocompounds in
gaseous phase


fgas
H as a sum of the same values in
condensed state


f cond
H and their heat of vaporiza-
tion


vap
H
.
3. Conclusions
Thus, as it has been shown during this work the simple
linear Equation (4), worked up for the correlations be-

V. V. OVCHINNIKOV
5
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 cal-
culation 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 ener-
gies in biochemical substances.
4. References
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doi:10.1007/s11172-009-0105-4
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[5] M. Goodman and F. Morehouse, “Organic Molecules in
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