THE STANDARD ENTHALPY AND ENTROPY OF
FORMATION OF GASEOUS AND LIQUID
POLYCHLORINATED BIPHENYLS, POLYCHLORINATED
DIBENZO-n-DIOXINS AND DIBENZOFURANS
T.V. Kulikova, A.V. Mayorova, K.Yu. Shunyaev
Institute of Metallurgy, Ural Branch RAS
Yekaterinburg, Russia
E-mail: kuliko@gmail.com
Abstract
The study deals with analysis and systematization of the known
and calculation of the unknown thermodynamic characteristics (the
standard enthalpy of formation, the standard entropy of formation) of
widespread hazardous isomers of gaseous and liquid compounds of
polychlorinated biphenyls (PCBs), polychlorinated dibenzo-n-dioxins
(PCDDs), and polychlorinated dibenzofurans (PCDFs). The
comparison of results obtained in different studies reveals a
considerable discrepancy between values reported by highly
respected investigators. In this connection, «independent» results of
the thermodynamic characteristics have been calculated.
Introduction
Unique technological and physicochemical properties of
polychlorinated biphenyls (PCBs), a huge volume of their
production, considerable volatility and solubility, and extreme
chemical inertness have led to the world-wide spread of PCBcontaining equipment and materials, resulting in the universal
contamination with these substances. The most common method used
in Russia for destruction of PCBs is their incineration with the
formation of polychlorinated dibenzo-n-dioxins (PCDDs) and
dibenzofurans (PCDFs), which are among the most hazardous
chemical substances known to the mankind.
As often happens, the hazard of PCBs has long been
underestimated. With respect to their severe toxicological effect,
PCBs are identical to substances that are referred to the high class of
hazard. Since these substances are especially toxic, they have been
assigned low toxicological standards, which necessitate special
78
requirements on the organization of processes assuming formation of
these substances (the so-called dioxinogenic processes) so that
industrial emissions meet the norms. Instrumental investigations of
these substances are very expensive and, in this connection, interest
is attracted to calculation methods for simulation of processes by the
data on their thermochemical properties.
A quality thermodynamic simulation requires the knowledge of
thermodynamic and thermochemical properties of all reliably
certified compounds of the system under study in the gaseous or
condensed state. Therefore the present study deals with the analysis
and systematization of the known and calculation of the unknown
thermochemical properties (the standard enthalpy and entropy of
formation) of most toxic and hazardous isomers of gaseous PCBs,
PCDDs and PCDFs, and liquid PCBs.
Calculation of thermochemical properties
It is known that there are 209 individual PCB congeners, 420
polychlorinated
dibenzo-n-dioxins
and
polychlorinated
dibenzofurans, which differ by the number and positions of chlorine
atoms in a molecule. The most widespread PCB compounds
containing up1 to 10 chlorine atoms were chosen for the study. In
deciding on isomers, preference was given to ortho-unsubstituted
PCBs because they are most toxic and their effect is similar to the
effect of PCDDs and PCDFs. Congeners, which do not have chlorine
atoms in ortho-positions of molecules (ortho-unsubstituted PCBs),
can acquire the planar configuration, which is more favorable in
energy terms. Such congeners are isostereoisomeric to PCDDs and
PCDFs and present the greatest hazard. As to the PCDD and PCDF
isomers, of special hazard to humans and the environment are tri-,
tetra-, penta-, and hexa-substituted dioxins and furans containing
halogen atoms in lateral positions 2, 3, 7, and 8.
In this study we analyzed the known and calculated the
unknown thermodynamic properties of 17 most widespread and
hazardous isomers of PCBs, PCDDs and PCDFs in the gaseous state
and 11 compounds of liquid PCBs.
79
Gaseous PCBs, PCDDs and PCDFs
The literature survey showed that studies dealing with
estimation of the thermochemical properties of gaseous PCB, PCDD
and PCDF compounds are few. Most of them are based on
calculations or are semi-empirical. For example, Saito and Fuwa [1]
calculated thermodynamic functions of all PCBs and some PCDDs
and PCDFs on the basis of semi-empirical calculations in terms of
the PM3 model. O.V. Dorofeeva et al. [2-4] used statistical methods.
Table 1 presents the literature data on standard enthalpies and
entropies of formation of gaseous and liquid PCBs, PCDDs and
PCDFs. The comparison of results obtained in different studies
reveals a considerable discrepancy between values reported by highly
respected investigators who did very arduous work. In particular,
values of the formation enthalpy [1] are 8-70% larger and the entropy
is 11-15% smaller than the corresponding values in [2-4]; the
discrepancy grows with the number of chlorine atoms in a molecule.
So, we thought it reasonable and topical to attempt an independent
result.
Benson's method [5] was used to calculate thermodynamic
characteristics (the standard enthalpy of formation ΔН°298, the
standard entropy of formation ΔS°298) of the gaseous PCBs, PCDDs
and PCDFs. We shall dwell briefly on this method
Benson's method is the group additivity method involving
analysis of the molecule structure. Atomic or molecular groups are
separated and the nearest neighbors of the atom or the group are
considered. Table 2 gives the number of groups necessary for
determination of group increments in structural formulas of PCBs,
PCDFs and PCDDs. Values of the thermodynamic characteristics of
group increments were determined from available reference and
literature data [5, 6]. Information about the energy contribution of
each group (see Table 3) and the number of groups was used to
calculate thermochemical properties of the PCBs, PCDDs and
PCDFs.
80
Table 1. Standard enthalpies (∆Нo298, kJ/mole) and entropies (∆So298,
J/mole K) of formation of gaseous and liquid PCBs, PCDDs and
PCDFs
Gaseous state
Compounds
1
Liquid state
So298
the
∆Нo298
So298
∆Нo298
O.V. Dorofeeva et
Saito, Fuwa [1],
[7, 8, 12, [7,8,10, the given given
al.
the given work
16,17] 14, 16, 17] work and work
[2-4]
[8,14]
and
[14]
2
3
4
5
6
390.8
[3]
181.9
[8]
181.4
[16]
7
8
9
392.7
[16]
117.1
116.2[8]
117.10
[14]
257.40
257.4
[14]
C12H10
(biphenyl)
198.6
[1]
179.7
345.4
[1]
410.4
C12H9Cl
(3-monochlorbiphenyl)
170.5
[1]
150.0
385.1
[1]
441.3
156.1
[2]
432.3
[2]
154.8
[8]
150.88
[16]
421.4
[16]
76.29
284.0
C12H8Cl2 142.2
(4,4’-dichlor- [1]
biphenyl) 120.2
399.2
[1]
472.1
126.0
[2]
451.8
[2]
127.6
[8]
120.04
[16]
449.2
[16]
35.84
310.6
478.0
[16]
-4.52
337.2
C12H7Cl3
(3,4,4’trichlorbiphenyl)
C12H6Cl4
(3,3’,4,4’tetrachlorbiphenyl)
C12H5Cl5
(3,3’,4,4’,5pentachlorbiphenyl
182.0
[3]
119.4
[1]
90.5
424.0
[1]
503.0
104.1
[2]
492.3
[2]
96.9
[1]
60.8
444.4
[1]
533.8
89.9
[2]
521.6
[2]
74.8
[1]
31.0
462.0
[1]
564.7
56.9
[2]
550.2
[2]
C12H4Cl6
52.9
(3,3’,4,4’,5,
[1]
5’-hexachlor1.3
biphenyl)
461.5
[1]
595.6
31.4
[2]
567.5
[2]
C12H3Cl7
(2,3,3’,4,4’5, 40.0
5’-hepta[1]
chlor-28.4
biphenyl)
484.2
[1]
626.4
15.2
[2]
100.4
[8]
89.2
[16]
73.2
[8]
58.36
[16]
46.0
[8]
27.52
[16]
506.8
[16]
-44.88
363.8
535.6
[16]
-85.24
390.4
19.0
[8]
-3.32
[16]
564.4
[16]
-125.58
417.0
-8.4
[8]
-4.16
[16]
607.7
[2]
81
593.2
[16]
-165.96
443.6
1
2
C12H2Cl8
(2,2’,3,3’,4, 24.1
4’,5,5’[1]
octachlor- -58.1
biphenyl)
C12HCl9
(2,2’,3,3’4 8.73
4’,5,5’6[1]
nanochlor- -87.8
biphenyl)
C12Cl10
(2,2’,3,3’,4, -6.7
4’,5,5’6,6’[1]
decachlor- -117.6
biphenyl)
C12H8O2
(dibenzo-ndioxin)
-40.2
[1]
-44.8
3
4
5
6
7
8
9
488.6
[1]
657.3
-9.0[2]
634.2
[2]
-35.6
[16]
-65.0
[8]
504.8
[1]
688.1
-15.3
[2]
660.7
[2]
-62.8
[16]
-95.8
[8]
650.8
[8]
-246.68
496.8
503.4
[1]
719.0
-24.7
[2]
675.7
[2]
-90.1
[16]
-126.7
[8]
679.6
[8]
-286.04
523.4
396.5
[4]
-59.2
[12]
-59.2
[7]
-55.0
[17]
395.1
[7]
388.0
[17]
-
-
478.1
[4]
-134.5
[7]
-158
[17]
513.6
[7]
478.4
[17]
478.1
[10]
478.4
[9]
-
-
-116.2
[7]
-196
[17]
553.1
[10]
501.0
[17]
-
-
376.4
[1]
-59.2
[4]
622.0
[8]
-206.32
470.2
C12H4Cl4O2
(2,3,7,8,- -137.2
tetrachlor[1]
dibenzo-n- -159.2
dioxin)
455.3
[1]
С12H3Cl5O2
(1,2,3,7,8- -153.2
pentachlor- [1]
dibenzo-n- -190.0
dioxin)
493.1
[1]
-190.0
[4]
540.35
[4]
-169.1
[1]
-216.4
484.1
[1]
-219.6
[4]
569.12
[4]
-122.4
[7]
575.59
[7]
523.6
[17]
-
-
-184.8
[1]
-247.2
500.5
[1]
-246.0
[4]
597.89
[4]
-119.6
[7]
610.31
[7]
546.2
[17]
-
-
106.1
[1]
51.8
378.7
[1]
55.3
[4]
375.9
[4]
55.2
[17]
374.4
[17]
-
-
20.3
[1]
-62.5
450.5
[1]
-50.0 [4]
-
-
С12H2Cl6O2
(1,2,3,4,7,8hexachlordibenzo-ndioxin)
С12HCl7O2
(1,2,3,4,6,7,
8-heptachlordibenzo-ndioxin)
C12H8O
(dibenzofuran)
C12H4Cl4O
(1,2,3,4tetrachlordibenzofuran)
-164.0
[4]
490.98
[4]
-52.8
[17]
82
464.8
[14]
1
2
С12H3Cl5O
(1,2,3,7,8- -12.3
pentachlor- [1]
dibenzo-93.4
furan)
С12H2Cl6O
(1,2,3,4,7,8-28.3
hexachlor[1]
dibenzo-124.2
furan)
С12HCl7O
(1,2,3,4,6,7,8 -44.1
heptachlor[1]
dibenzo-155.0
furan)
3
459.2
[1]
4
5
6
7
-75.9
[4]
519.75
[4]
-74.8
[17]
487.4
[14]
8
9
-
-
471.3[1]
-105.1
[4]
548.52
[4]
-104.3
[17]
510.0
[14]
-
-
483.3
[1]
-131.5
[4]
577.29
[4]
-131.3
[17]
532.6
[14]
-
-
Table 2. Number of groups for determination of group increments in
structural formulas of PCBs, PCDFs and PVDDs
Compound
Св*-H
PCBs
PCDFs
PCDDs
10 - n
8-n
8-n
Number of groups
Св-Cl
Св-O
Св-Св
n
n
n
2
4
2
2
-
Number of
chlorine atoms
in a molecule (n)
1 – 10
1–8
1–8
Св* is the carbon atom in an aromatic ring.
Values presented in Table 1 show the thermodynamic
characteristics of PCBs, PCDDs and PCDFs calculated in this study
and by other investigators.
It is seen, for example, ( Table 1) that the formation enthalpy
o
( H 298 ) of biphenyl (C12H10) equals (kJ/mole) 198.6 [1], 182.0 [3],
o
181.9 [7], and 181.4 [8], while the formation entropy ( S 298 ) of
2,3,7,8-tetrachlordibenzo-n-dioxin (C12H4Cl4O2) is (J/(mole K))
455.3 [1], 478.1 [4], 478.4 [9], and 478.1 [10].
83
Table 3. Values of the thermodynamic characteristics determined by
the method of group increments[5,8].
Group
Св*-H
Св-Св
Св-Cl
(Св)2-O
orto corr
Cl-Cl
meta corr
Cl-Cl
(gas)
o
H 298 ,
kJ/mole
13,81[8]
13,82[5]
21,66[8]
20,77[13]
-17,03[8]
-15,91[5]
-77,66[8]
-88,34[5]
9,50[8]
9,21[5]
-5,00[8]
S o298 ,
J/(moleК)
48,31[8]
48,27[5]
-36,57[8]
-36,18[5]
77,08[8]
79,13[5]
-
(liquid)
o
H 298 ,
S o298 ,
kJ/mole
J/(moleK)
8,16[8]
28,87[8]
17,21[8]
-
-32,20[8]
55,47[8]
-
-
14,00[5]
-
4,00[5]
-
In this study the values of the standard entropy of formation
obtained by using statistical methods (O.V. Dorofeeva et al. [2-4, 9])
for 17 isomers of PCBs, PCDDs and PCDFs are in good agreement
with the values calculated by other investigators [8, 10, 12, 13] and
with the values calculated by us.
Liquid PCBs
It should be noted that ample literature data on the
thermochemical properties of liquid ecotoxicants is only available for
biphenyl (C12H10) [8, 14], dibenzo-n-dioxin (C12H8O2) [11, 15] and
dibenzofuran (C12H8O) [5, 17]. The only study dealing with
calculation of thermodynamic functions for the whole series of liquid
PCDD and PCDF homologues was published by V.S. Iorish et al.
[11]. As to liquid PCB compounds, the literature data on their
thermochemical properties are scarce [8, 14].
The thermochemical properties, namely the standard enthalpy
and entropy of formation of liquid PCBs were calculated using the
group additivity method due to Domalski [8]. Values of the group
increments (Table 3) were adopted from [8]. It is seen from Table 3
84
that the energy contribution of the group Св-Св is unavailable for the
o
entropy calculation. However, if one uses known values of S 298 for
liquid biphenyl (C12H10) [14] and the data on the contribution of the
o
Св-H and Св-Cl groups [8], it is possible to calculate S 298 for the
whole series of PCBs:
S o298 (PCB) = S o298 (BP) - (10-n) S o298 (Св-H) + n S o298 (Св-Cl) +
+(m*orto corr Cl- Cl ) +(p*meta corr Cl- Cl)
(1)
where n is the number of chlorine atoms in a PCBs molecule,
m (p) - spatial amendments, number Cl (from two and more), being
in orto - (meta-) position rather each other.
o
The enthalpy of formation ( H 298 ) for the PCBs series
compounds was calculated by two options: using the group additivity
method due to Domalski [8] and from the equation
H o298 (PCB) = H o298 (BP) - (10 - n) H o298 (Св-H) +
o
+ n H 298 (Св -Cl) +(m*orto corr Cl-Cl )+(p*meta corr Cl-Cl),
(2)
Table 4 lists values of the standard enthalpy of formation for
the series of liquid PCBs compounds as calculated by the group
additivity method [8] and the equation (2). It is seen that the values of
H o298 , which were calculated by the two methods, are in good
mutual agreement.
The thermochemical properties, which were taken as reliable,
were added to the TERRA database and were used for
thermodynamic simulation of the thermal stability of PCBs, PCDDs
and PCDFs.
85
Table 4. Calculated enthalpy of formation (∆Нo298) for liquid PCBs
compounds.
Compound
C12H9Cl
(3-monochlorbiphenyl)
C12H8Cl2
(4,4’-dichlorbiphenyl)
C12H7Cl3
(3,4,4’- trichlorbiphenyl)
C12H6Cl4
(3,3’,4,4’-tetrachlorbiphenyl)
C12H5Cl5
(3,3’,4,4’,5-pentachlorbiphenyl)
C12H4Cl6
(3,3’,4,4’,5,5’-hexachlorbiphenyl)
C12H3Cl7
(2,3,3’,4,4’,5,5’-heptachlorbiphenyl)
C12H2Cl8
(2,2’,3,3’,4,4’,5,5’-octachlorbiphenyl)
C12HCl9
(2,2’,3,3’,4,4’,5,5’6-nanochlorbiphenyl)
C12Cl10
(2,2’,3,3’,4,4’,5,5’6,6’decachlorbiphenyl)
∆Нo298, kJ/mole
Group
Eq. (5)
increments
method
75.84
76.742
δ, %
1.2
35.30
36.382
3.0
-5.06
-3.978
21.38
-45.42
-44.338
2.38
-85.78
-84.698
1.26
-126.1
-125.058
0.83
-166.5
-165.418
0.65
-206.86
-205.778
0.52
-247.22
-246.138
0.44
-287.58
-286.498
0.38
Conclusions
1.The literature data on the thermochemical properties of 17
most widespread and hazardous isomers of PCBs, PCDDs and
PCDFs in the gaseous state and 11 compounds of liquid PCBs have
been analyzed and systematized for the first time.
2.Methods have been developed for calculating of the
thermodynamic characteristics of organic compounds. Values of the
thermodynamic functions (standard enthalpy and entropy of
formation) of liquid PCBs, PCDDs and PCDFs have been calculated
for the first time.
86
3.The comparison of the calculated values of the
thermodynamic functions with the known literature data
demonstrated their good mutual correlation.
4.The obtained data were added to the TERRA database and
were used for thermodynamic simulation of the thermal stability of
PCBs, PCDDs and PCDFs.
5.The obtained data can be used for simulating of the behavior
of complex heterogeneous systems, including ecotoxicants, over a
wide interval of temperatures and initial compositions.
This study was supported by RFBR (project No. 08-03-00362-a).
References
1. Nagahiro Saito, Akio Fuwa. Chemosphere. 2000, vol.40, p.
131-145.
2. O.V. Dorofeeva, N.F. Moiseeva, V.S. Yungman.L.V., J.Phys.
Chem. A., 2004, vol. 108, p. 8324-8332.
3. O.V. Dorofeeva., Thermodynamica Acta.,2001, vol.374., p.7-11.
4. O.V. Dorofeeva, V.S. Iorish, N.F. Moiseeva., J. Chem. Eng.
Data., 1999, vol. 44, p. 516-523.
5. S.W. Benson, F.R. Cruickshank, D.M. Golden, G.R. Haugen,
H.E. O’Neal, A.S. Rodgers, R. Shaw, and R. Walsh. Chem. Rev.,
1969, vol.69, p. 279 -324.
6. H.K. Eigenmann, D.M. Golden, and S.W Benson. J. Phys.
Chem., 1973, vol. 77, 1687-1691.
7. Jung Eun Lee and Wonyong Choi., J. Phys.Chem. A, 2003,
vol. 107, p. 2693-2699.
8. Domalski E. S. and Hearing E. D., J. of Phys. and Chem. Ref.
Data, 1993, vol. 22, p. 805-1159.
9. L.V. Gurvich, O.V. Dorofeeva, V.S. Iorish., Zh. Fiz. Khimii, 1993,
vol.67, No. 10, p. 2030-2032.
10. W.-Y. Shiu and K.-C. Ma., J. Chem. Ref. Data, 2000, vol.29,
No. 3, p. 387-462.
11. V.S. Iorish, O.V. Dorofeeva, N.F. Moiseeva, J. Chem. Eng. Data.,
2001, vol.46, p. 286-298.
12. V.A. Lukyanova, V.P. Kolesov, Zh. Fiz. Khimii.,1997, vol. 71,
No. 3, p. 406-408(in Russian).
87
13. P. Reid, J. Prausnitz, T. Sherwood.,Leningrad, Khimiya, 1982,
592 p(in Russian).
14. Richard, Laurent and Helgeson Harold C. Geochimica et
Cosmochimica Acta, 1998, vol. 62, No. 23/24, p. 3591 – 3636.
15. I. Barin: “Thermochemical Data of Pure Substances”.
Weinheim,
Federal
Republic
of
Germany:
VCH
Verlagsgesellschaft mbH, 1997.
16. "Cambridgesoft" database, ver. 8.0.6, December 31, 2003.
17. Thompson D., Thermochim. Acta, 1995, vol.261, p.7-20.
88