International Journal of Application or Innovation in Engineering & Management (IJAIEM)
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Volume 2, Issue 5, May 2013
ISSN 2319 - 4847
CALCULATION AND ANALYSIS OF
THERMODYNAMIC PARAMETERS OF
Di-SUBSTITUTED PYRIDINE
PANKAJ VARSHNEY1, PIYUSH GUPTA2, GAURAV SHARMA3
DEPTT. OF PHYSICS1&3, DEPTT OF CHEMISTRY2
SRM UNIVERSITY, NCR CAMPUS, MODINAGAR1&2
MEERUT INSTITUTE OF ENGINEER & TECHNOLOGY, MEERUT3
ABSTRACT
The thermodynamic parameters in the temperature 200 to 1500 K for di-substituted pyridine has been calculated using
Computer Programming. The computation is done for 3N-6 observed vibrational frequencies for the compound 2 hydroxy 6
methyl pyridine. The moment of inertia is also calculated. The variation in thermodynamic parameter is shown graphically by
plotting with help Origin software.
Keywords: Thermodynamic functions, enthalpy, heat capacity, free energy function, entropy.
INTRODUCTION
Pyridine and its related derivatives are found in the structure of many drugs. Pyridine is a very stable compound with a
great deal of aromatic character. In pyridine system, a large amount of intermolecular association is possible because of
its greater polarity. The properties are determined by their hydrogen and bonding systems. The vibrational spectra of
substituted pyridine have been the subject of several investigations1-7. Thio-pyridine have reportedly been used in the
treatment of tuberculosis8 and mental disorder9. They are also known to act as herbicides, insecticides, rodenticides
and plant growth regulators. Recent spectroscopic studies of these compounds have been motivated, because the
vibrational spectra of free base molecules are very useful for understanding of specific biological processes and in the
analysis of relatively complex systems. The vibrational spectra of alkyl, halogens, amino, nitro etc. substituted pyridines
have been studied in detail by several workers10,11. In this paper A molecule 2 hydroxy 6 methyl pyridine has been
chosen. The present paper reports the thermodynamic parameters viz. enthalpy heat capacity, free energy and entropy
functions of this molecule have also been computed statistically on the basis of their assigned frequencies from the
Fourier transform Infrared Raman spectra of 2 hydroxy 6 methyl pyridine, taking into account a single top by using the
computer programming.
Aromatic compounds like benzene, pyridine, cytosine, uracil and their derivatives are of great biological importance
but due to their high complexity and low symmetry very few workers have studied these compound [13]. The
computation in thermodynamic functions appear to be one of most important application of vibrational spectra of the
complex molecules. From the vibrational data obtained from the spectra, Urey [14], Tolman and Badger [15] first
suggested that it is quite possible to calculate the accuracy, the values of various thermodynamic functions. This is of
great practical importance particularly since the direct experimental measurements of these quantities are quite
difficult. The values of thermodynamic functions calculated from spectroscopic data are more accurate than the values
obtained from the thermal measurements. The thermodynamic functions of the molecule 2 hydroxy 6 methyl pyridine
have not been reported so far. With this end in view, the decision to compute the thermodynamic functions namely, the
 E
 T

enthalpy function 
, the heat capacity C p . The free energy function  F  E o  T  and the entropy S 
were taken for the said compound at a pressure of atmosphere in the temperature range 200-1500 K under rigid rotatorharmonic oscillator approximation. The frequencies of the different modes of vibrations are used for the calculation of
the various thermodynamic functions
 H
o
o
o

o
o
o
o
The total energy (E) of a system of molecules is given as
E   trans   rot   vib   elec
… (1)
And total partition (  ) can be expressed as the product of the individual partition function.
Hence,
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International Journal of Application or Innovation in Engineering & Management (IJAIEM)
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Volume 2, Issue 5, May 2013
ISSN 2319 - 4847
Q  Qtrans  Qrot  Qelec
… (2)
Where the subscripts trans, rot, vib and elec stands for translation, rotational, vibrational and electronic respectively.
Also
Q   g i exp   i kT 
… (3)
Where g i is the statistical weight of the ith energy level [16] k is the Boltzmann constant and T is the absolute
temperature. Contribution of each partition function may be evaluated separately and then added to the corresponding
thermodynamic functions to obtain the total values. The electronic contribution is small and hence ignored. This is
because  elec is large in comparison to kT at ordinary temperature. The various equations used in computation of
various partition functions and their contribution to different thermodynamic functions are given by Herzberg [17]. The
entropy function represents the total energy stored in a system and the entropy is regarded as a measure of randomness
a system.
EXPERIMENTAL PROCEDURE
Spec-pure grade sample of 2 hydroxy 6 methyl pyridine (abbreviated as 2,6-HMP) was obtained from M/s Sigma
Aldrich Chemicals, U.S.A. The purity of the sample was confirmed by elemental analysis and boiling point
determination (185-186oC). The FTIR spectra of 4,3-HNP molecule was recorded on Perkin Elmer M-500 FTIR
spectrophotometer in the region 4000-400 cm-1 using KBr pellets .
RESULTS AND DISCUSSION
The labeled molecular structure of 2,6-HMP molecule is shown in Fig.-1 .The structural parameter are listed in Table1.The statistically computed thermodynamic functions viz. enthalpy function  H  E  / T  , free energy function   F  E  / T  ,
o
o
o
o
o
o
p
entropy S and heat capacity C functions with absolute temperature are given in Table-2 for 2,6-HMP molecule. The
variation of enthalpy and heat capacity function with absolute temperature are shown in Fig.-2 while that of free energy
and entropy function are shown in Fig.-3.
o
COMPUTATIONAL DETAILS
The entire calculations were performed on a Pentium IV/1.6 GHz personal computer using C programme.
MOLECULAR GEOMETRY
The labeling of atoms in 2,6-HMP is given in Fig.-1 .
THERMODYNAMIC PARAMETERS
On the basis of the molecular data obtained from the spectra, as was first suggested by Urey18, Tolman and Badger 19, it
is possible to predict with great precision the values of thermodynamic properties, such as the heat capacity, free
energy, enthalpy and entropy of the particular gases. This possibility is of great practical importance, particularly since
the direct experimental measurement of these quantities is usually difficult and tedious and sometimes impossible
also18,19. The values calculated from the spectroscopic data are more accurate than those determined by direct thermal
measurement.
o
Thermodynamic functions viz. enthalpy function   H  E  / T  , heat capacity function C p , free energy function   F  E  / T  and
entropy function S o of 2,6-HMP have been computed using the standard expressions20-24 taking Z-axis perpendicular to
the molecular plane and Y-axis to pass through the para position.
o
o
o
o
o
For determining rotational contribution the Table-1 structural parameters were used25-28.
The thermodynamic functions have been calculated at different temperature between 200-1500 K using 39 fundamental
frequencies in 2,6-HMP. Assuming, the rigid rotor harmonic oscillator approximation, the calculations were performed
for 1 mol of an ideal gas at 1 atmospheric pressure. The symmetric number for overall rotation is 1. The principal
moments of inertia Ix, Iy & Iz were found to be 224.87×10-40 gm cm2, 418.321×10-40 gm cm2, 673.189×10-40 gm cm2 in
2,6-HMP.
The variation of thermodynamic functions viz. enthalpy and heat capacity function with absolute temperature have
been shown in Fig.2, this figure shows that at very high temperature the influence of anharmonicity will make itself felt
and will no longer give an accurate representation. The variation of free energy and entropy function is shown in Fig.3,
which shows that in case of free energy function at temperature as high as 1000 K, the effect is quite small. While in
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Volume 2, Issue 5, May 2013
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case of entropy, at very high temperature the vibrational contribution is very small compared to the other contributions
thus a statistical calculation of the entropy is much less dependent upon vibrational data than the other thermodynamic
functions. The trend of variation of thermodynamic parameters is similar to those reported for similar molecules in
literature29-32
The study has become more relevant in view of its great biological importance because the thermodynamic will be used
as important tools for the field of research.
ACKNOWLEDGEMENT:
The authors are thankful to Sophisticated Analytical Instrument Facility (SAIF), IIT Madras, Chennai and Central
Drug Research Institute, Lucknow for the Spectral measurements.
REFERENCES
[1.] R.E. Handschumacher and A.D. Welch, "The Nucleic Acids", Academic Press, New York, 4 (1960).
[2.] G.T. Martin, "Biological Antoganism", Blakiston, New York, (1961).
[3.] G. Shrama, G. Amembri and S.Califano, Spectrochimica Acta, 22 (1966) 1831.
[4.] H. Susi, J.S. Ard and J.M. Purcell, Spectrochimica Acta, 29A (1973) 725.
[5.] R.C. Lord and (Jr) G.J. Thomas, Spectrochimica Acta, 23A (1967) 2551.
[6.] L. J. Bellamy, "The Infrared Spectra of Complex Molecules", John Willey and Sons Inc; New York, (1975).
[7.] S.P. Gupta, Sangeeta Sharma and R.K. Goel, Indian J Chem, 26A (1987) 220-224.
[8.] N.B. Colthup, L.H. Daly and S.E. Wiberley, "Introduction to Infrared and Raman Spectroscopy", Edition IInd,
Academic Press. New York, San Francisco London, (1975).
[9.] R.M. Silverstein, G.C. Bassler and T.C. Morill, "Spectrometric Identification of Organic Compounds", Edition
IVth, John Wilay and Sons, New York, (1981).
[10.] M.L. Josien and J.M. Lebas, Bull Soc Chim Fr, (1956) pp 53,57 and 62.
[11.] J.M. Lebas, C.Carrigou-Lagrange and M.L. Joisen, Spectrochimica Acta, 15 (1959) 225.
[12.] S.E. Wiberley, S.C. Bunce and W.H. Baner, Analytical Chemistry, 32 (1960) 217.
[13.] S Mohan & V Llengonan, Indian J. Pure Appl. Phys., 32(1994) 91.
[14.] H C Urey, J Am.Chem.Soc., 45, 1455(1923).
[15.] R.C.Tolman and R.M.Badger, J Am. Chem.Soc., 45, 2277 (1923).
[16.] W.J.Moore Physical Chemistry (Englewood Cliffs: prentice Hall) (1962).
[17.] G Herzberg “Molecular Spectra and Molecular Structure” Vol II (Divan Nostrand, Priceton, NJ), 1966.
[18.] Nitish K Sanyal, R. K. Goel and S. N. Sharma, Indian J Phys, 53B (1979) 282.
[19.] J. C. Evans, Spectrochimica Acta, 16 (1960) 428.
[20.] C. Garrigou-Lagrange, J.M. Lebas and M. L. Josien, Spectrochimica Acta, 12 (1958) 305.
[21.] J. Baran, Z. Malarski, I. Sobezyle and E. Greach, Spectrochimica Acta, 44 (1988) 993.
[22.] A.V. Stuart and G.B.B.M. Sutherland, J Chem Phys, 24 (1956) 559.
[23.] J. C. Evans, Spectrochimica Acta, 16 (1960) 1382.
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Volume 2, Issue 5, May 2013
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[24.] A. Depaigne - Delay and J. Lecomte, J Phys Rad, 7 (1946) 33, 38.
[25.] P. Barchewitz, Compt rend S Ac Sci Paris, 237 (1953) 237.
[26.] J.H.S. Green, W. Kynaston and H.A. Gebbie, Spectrochimica. Acta, 19 (1963) 807.
[27.] R.J. Jakobsen and J.W. Brasch, Spectrochimica Acta, 21 (1965) 1753.
[28.] N. Sheppard, Trans Faraday Soc, 51 (1955) 1465.
[29.] N.B. Colthup, J Opt Soc Amer, 40 (1950) 397.
[30.] M.K. Rofouei, E. Fereyduni, N. Sohrabi, M. Shamsipur, J. Attar Gharamaleki, N. Sundaraganesan,
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 78(2011) 88.
[31.] K. Chaitanya, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy,86(2012)159.
[32.] Janaki, V. Balachandran, A. Lakshmi, Journal of Molecular Structure, 1042(2013)15.
Table-1:Bond length & Bond angles of 2,6-HMP
Bond lengths
( A°)
Bond angles
(in degree)
C(12)-H(15)
1.0933
H(15)-C(12)-H(14)
107.04
C(12)-H(14)
1.0933
H(15)-C(12)-H(13)
108.8479
C(12)-H(13)
1.0913
H(15)-C(12)-C(6)
110.1125
O(10)-H(11)
0.963
H(14)-C(12)-H(13)
108.8479
C(2)-O(10)
1.3622
H(14)-C(12)-C(6)
110.1125
C(2)-N(1)
1.3212
H(13)-C(12)-C(6)
111.7507
C(3)-H(8)
1.0846
H(11)-O(10)-C(2)
109.5531
C(3)-C(2)
1.4028
C(12)-C(6)-C(5)
116.0474
C(4)-H(7)
1.0844
C(12)-C(6)-N(1)
121.9045
C(4)-C(3)
1.3864
C(5)-C(6)-N(1)
122.048
C(5)-H(9)
1.0828
H(9)-C(5)-C(6)
120.9439
C(5)-C(4)
1.3942
H(9)-C(5)-C(4)
120.4688
C(6)-C(12)
1.5054
C(6)-C(5)-C(4)
118.5873
C(6)-N(1)
1.3425
H(7)-C(4)-C(5)
120.0192
C(6)-C(5)
1.396
H(7)-C(4)-C(3)
120.4615
C(5)-C(4)-C(3)
119.5193
H(8)-C(3)-C(4)
121.2636
H(8)-C(3)-C(2)
121.3433
C(4)-C(3)-C(2)
117.3931
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O(10)-C(2)-C(3)
114.5101
O(10)-C(2)-N(1)
121.7922
C(3)-C(2)-N(1)
123.6977
C(6)-N(1)-C(2)
118.7546
Table-2: Thermodynamic parameters of 2,6-HMP (All values are in cal./degree/mole)
Temperature
Enthalpy Function
Heat Capacity
Free Energy Function
Entropy
200
8.44
10.289
85.172
93.612
300
9.778
14.872
88.821
98.599
400
11.72
20.251
91.89
103.61
500
13.957
25.503
94.742
108.7
600
16.29
30.315
97.493
113.783
700
18.607
34.633
100.178
118.786
800
20.856
38.481
102.811
123.667
900
23.008
41.9
105.393
128.401
1000
25.052
44.928
107.924
132.976
1100
26.983
47.604
110.403
137.386
1200
28.802
49.965
112.829
141.632
1300
30.511
52.046
115.203
145.715
1400
32.116
53.881
117.524
149.641
1500
33.622
55.489
119.791
153.414
(a) Planar view
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(b) Side view
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Fig.1. Molecular structure of 2,6-HMP along with numbering of atoms.
Fig.2. Temperature vs enthalpy and heat capacity for 2,6-HMP
Fig.3. Temperature vs free energy and entropy for 2,6-HMP
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