51
CHAPTER – VI
A COMPARATIVE STUDY ON VIBRATIONAL,
CONFORMATIONAL AND ELECTRONIC STRUCTURE OF
2–(HYDROXYMETHYL)PYRIDINE AND
3–(HYDROXYMETHYL)PYRIDINE
6.1. Introduction
Pyridine has attracted a lot of attention due to its applications in many areas of
chemistry. In particular, it has been used very frequently as a proton acceptor in
studies involving hydrogen bonded complexes [1–2]. Pyridine derivatives are used as
non–linear materials [3] and photochemicals [4–9]. The nitropyridine derivatives form
an acceptor fragment of 2–adamantylamino–5–nitropyridine (AANP). This crystal
shows a particularly large optical non–linearity [10]. For this reason the knowledge of
spectroscopic properties are crucial for the characterisation of such NLO materials.
Many substituted pyridines are involved in bioactivities with applications in
pharmaceutical drugs and agricultural products [11–13]. Pyridine derivatives act as
anesthetic agents, drugs for certain brain diseases, and prodrugs for treating neuronal
damage caused by stroke. They also underpin analgesics for acute and chronic pain,
treatment for tinnitus, depression, and even diabetic neuropathy. The picoline
derivatives prepared from aminopyridine derivatives have been shown to have
cholesterol lowering properties, anti–cancer and anti–inflammatory agents [11]. The
various studies on pyridine derivatives are monosubstituted halo and methylpyridines
[14], 2–iodopyridine [15], 2,6–dichloropyridine [16], di–, tri–halopyridines [17,18],
5–bromo–2–nitropyridine [19], 2–chloro–5–bromopyridine [20] and 2–fluoro–5–
bromopyridine [21].
The density functional theory studies on the vibrational and electronic spectra
of pyridine derivatives, 2–(hydroxymethyl)pyridine (2HMP) and
3–(hydroxymethyl)pyridine (3HMP) have not been carried out. Thus, in the present
investigation, owing to the industrial and biological importance of substituted
pyridines, an extensive experimental and theoretical studies of
2–(hydroxymethyl)pyridine (2HMP) and 3–(hydroxymethyl)pyridine (3HMP) have
been undertaken by recording their FTIR, FT–Raman spectra and subjecting them to
195
normal coordinate analysis, for the proper assignment of the vibrational fundamentals
and to understand the effect of hydroxymethyl group on the characteristic frequencies
of the pyridyl ring. This could not only help the proper assignment of the
fundamentals but also present a complete picture about the molecular characteristics.
Since the recent studies have shown that the combination of vibrational
spectroscopy with DFT calculations can be a powerful tool for understanding
fundamental modes of vibrations of the molecules and to further investigate the
relative stability, the thermodynamical properties and determine the energy
differences among the compounds under study, theoretical DFT calculations have also
been carried out. In this study, the vibrational fundamentals of the compounds 2HMP
and 2HMP have been studied by applying the DFT calculations based on Becke3–
Lee–Yang–Parr (B3LYP) level with 6–31G(d,p), 6–311++G(d,p) and cc–pVTZ basis
sets, to provide the optimised structural parameters, thermodynamic properties and
vibrational frequencies. To satisfactorily describe the conformation and orientation of
the nitro and methyl groups potential energy surface scan was carried out using the
triple zeta 6–311++G(d,p) basis set.
6.2. Experimental
The compounds 2–(hydroxymethyl)pyridine (2HMP) and
3–(hydroxymethyl)pyridine (3HMP) were purchased from Hanzhou Sida Organic
Chemicals Co., Ltd., China and used as such to record FTIR and FT–Raman spectra.
The FTIR spectra have been recorded in the region between 4000 and 400 cm−1 by
neat liquid using CsI windows with Bruker IFS 66V spectrometer. A KBr beam
splitter and liquid nitrogen cooled MCT detector were used to collect the mid–infrared
spectra. The FT–Raman spectra were also recorded in the range between 4000 and
100 cm−1 by the same instrument with FRA 106 Raman module equipped with
Nd:YAG laser source with 200 mW powers operating at 1.064 µm. The spectral
resolution is 2 cm−1.
6.3. Computational details
The gradient corrected density functional theory (DFT) [22] with the three–
parameter hybrid functional Becke3 (B3) [23] for the exchange part and the Lee–
Yang–Parr (LYP) correlation function [24] level of calculations have been carried out
in the present investigation, using 6–31G(d,p) and 6–311++G(d,p) basis sets with
196
Gaussian–03W [25] program package, invoking gradient geometry optimisation [26]
on a Intel Core i5/3.03 GHz processor. The combination of vibrational spectroscopy
with ab initio calculations is considered to be a powerful tool for understanding the
fundamental mode of vibrations and about the electronic structure of the compounds.
The conformational analyses were performed and the energies of the different
possible conformers were found. To satisfactorily describe orientation of the
hydroxymethyl group, split–valence polarised 6–31G(d,p), triple–ζ 6–311++G(d,p)
and Dunning’s cc–pVTZ basis sets [27,28] were used in the optimisation process to
characterise all stationary points as minima. The optimised structural parameters of
the most stable conformer were used in the vibrational frequency calculations. The
Raman intensities were also determined with B3LYP method using 6–311++G(d,p)
basis sets. The force constants obtained from the B3LYP/6–311++G(d,p) method
have been utilised in the normal coordinate analysis by Wilson’s FG matrix method
[29–31]. The potential energy distributions corresponding to each of the observed
frequencies were calculated with the program of Fuhrer et al. [32].
6.4. Results and discussion
6.4.1 Molecular geometry
The energetically most stable optimised geometry obtained by B3LYP/
6–311++G(d,p) method and the scheme of numbering the atoms of the molecules
2–(hydroxymethyl)pyridine (2HMP) and 3–(hydroxymethyl)pyridine (3HMP) are
shown in Figures 6.1 and 6.2. Molecular symmetry describes the symmetry present
in molecules and the classification of molecules according to their symmetry.
Molecular symmetry is a fundamental concept as it can predict or explain many of a
molecule's chemical properties, such as its dipole moment and its
allowed spectroscopic transitions (based on selection rules such as the Laporte rule).
The geometry of the molecules is considered by possessing Cs point group symmetry.
Under Cs symmetry the 39 fundamental vibrations of 2HMP and 3HMP span the
irreducible representations Γ = 27A' + 12 A". All the vibrations are active in both IR
and Raman.
197
Figure 6.1. The optimised geometry and the scheme of numbering the atoms of
2–(hydroxymethyl)pyridine (2HMP)
Figure 6.2. The optimised geometry and the scheme of numbering the atoms of
3–(hydroxymethyl)pyridine (3HMP)
198
6.4.2. Conformation analysis
Molecular geometry is a sensitive indicator of intra and intermolecular
interactions. The accurate determination of geometrical distortions in substituted pyridyl
rings is an important tool for investigating the nature of the interactions between the ring
and the substituents. Although C–C bond distances and C–C–C angles are both
affected by substitution, the latter undergo more extensive variation (up to several
degrees). Gas–phase electron diffraction, microwave spectroscopy, and X–ray crystal-
lography have been used extensively to determine accurately the geometry of many such
molecules. More recently, the experimental studies have been paralleled by ab initio
molecular orbital (MO) calculations with geometry optimisation. Major experimental and
computational efforts are being devoted to determine and interpret even subtle variations in
structural substituent effects originating from conformational changes [33–35] and from
intermolecular interactions in the crystal [36–40].
Conformation analysis of the compounds 2HMP and 3HMP were carried out
using G03 program. All the possible geometry of the conformers was optimised to
find out the energetically and thermodynamically most stable configuration of the
compound. All Possible conformations of the compound 2HMP under investigation
are shown in the Figure 6.3. The potential energy barrier of 2HMP obtained by the
rotation of the hydroxymethyl group with the dihedral angle N1–C2–C7–O8 is
depicted in Figure 6.4. Similarly, the possible conformations of the compound 3HMP
under investigation are shown in the Figure 6.5. The potential energy barrier of
3HMP obtained by the rotation of the hydroxymethyl group with the dihedral angle
C2–C3–C7–O8 is depicted in Figure 6.6.
The compound 2HMP has three different conformers. The stability of
the stable conformer is in the order I > II > III. The energy difference
between the most stable (I) and the second stable (II) conformations is
2.932 kcal. mol–1 while between I and III of 2HMP is 5.5766 kcal. mol–1.
The most stable conformer I is planar and the stability is due to the
formation of intramolecular O–H∙∙∙∙N hydrogen bond. The conformer II is
obtained by the rotation of C–O–H moiety to 180o. Thus, there is no
possibility of intramolecular hydrogen bonding in conformer II. The
conformer III is non–planar, where the –O–H group is above the molecular
plane.
199
(I)
(II)
(III)
Figure 6.3. Possible conformations of 2–(hydroxymethyl)pyridine (2HMP)
200
Figure 6.4. Potential energy surface of 2–(hydroxymethyl)pyridine calculated by
B3LYP/6–31G(d,p) method
In the case of 3HMP there are also three different conformers. The
stability of the stable conformer is in the order I > II > III. The energy
difference between the most stable (I) and the second stable (II)
conformations is 0.8276 kcal. mol–1 while between I and III of 3HMP is
1.2724 kcal. mol–1. The most stable conformer I and the second stable
conformers of 3HMP are planar and there is possibility of the formation of
intramolecular O–H∙∙∙∙N hydrogen bond. The conformer III is non–planar,
where the –O–H group is above the molecular plane. The potential energy
surface diagram of 2–(hydroxymethyl)pyridine determined by B3LYP/6–31G(d,p)
method are shown in Figures 6.4 shows only 5.766 kcal/mol to enable the
planar –O–H group to have internal rotation perpendicular to the phenyl
ring.
201
(I)
(II)
(III)
Figure 6.5. Possible conformations of 3–(hydroxymethyl)pyridine
202
The conformational analysis of 2HMP and 3HMP obviously reveals the
the intramolecular hydrogen bonding gives more stability to 2HMP molecule.
The potential energy surface diagram of 3–(hydroxymethyl)pyridine determined by
B3LYP/6–31G(d,p) method is shown in Figure 6.6 shows only 1.2724
kcal/mol to enable the planar –O–H group to have internal rotation
perpendicular to the phenyl ring. It is also found that the resonance and
conjugated effects do not play an important role in determining the barrier
height of the hydroxymethyl group of the studied molecules. The energy
difference between the conformers is very small in the case of 3HMP than that
of 2HMP molecule.
Figure 6.6. Potential energy surface of 3–(hydroxymethyl)pyridine calculated
by B3LYP/6–31G(d,p) method
6.4.3 Structural properties
The optimised structural parameters bond length and bond angle for the
thermodynamically preferred geometry of 2HMP and 3HMP determined at B3LYP
method using 6–31G(d,p), cc–pVTZ and 6–311++G(d,p) basis sets are presented in
Table 6.1 in accordance with the atom numbering scheme of the molecules shown in
203
Figures 6.1 and 6.3. From the structural data given in Table 6.1, the parameters
derived from B3LYP/6–311++G(d,p) method were only considered for comparative
discussion of the compounds due to the more reliability of this method. It is observed
that the mean C–C bond distance calculated between the ring carbon atoms of 2HMP
and 3HMP are 1.393 and 1.394 Å, respectively and C–H bond lengths are found to be
not significantly deviated with the –CH2OH substitutions at different positions. Bond
angles are also in excellent agreement in all levels of calculations. In X–ray data of
pyridine [41,42] the mean C–C (ring) bond distances is 1.394 Å. The C–H bond
distances are found to be 1 .081 Å. The computed values of C–C (ring) are well
agreed with that of the experimental values. The C–C(CH2OH) bond distance of the
two compounds is equal to 1.51 Å. The effect of –CH2OH on the C–C bond distances
of 2HMP and 3HMP molecules are not significant.
The presence of –CH2OH substituent leads not a significant distortion in bond
lengths of the phenyl ring while a significant distortion is observed in the ring bond
angles. The interior bond angle at the carbon in 2HMP to which a hydroxymethyl
group is attached exceeds the normal 120°. But the interior bond angle at the
carbon in 3HMP to which a hydroxymethyl group is attached less than the normal
120° [43].
The calculated thermodynamic parameters of 2HMP and 3HMP employing
B3LYP method with 6–31G(d,p), cc–pVTZ and 6–311++G(d,p) basis sets are
presented in Table 6.2. The frequency calculations compute the zero point energies,
thermal correction to internal energy, enthalpy, Gibbs free energy and entropy as well
as the heat capacity for a molecular system. The calculated SCF energy and entropy
of the compounds clearly indicates that stability increases in the order 2HMP
3HMP and this may be due to the weak intramolecular hydrogen bonding between
nitrogen atom and the substituent –OH group.
2HMP is more stable than 3HMP by 3.77 cal. mol–1. Determining the point
group is useful way to predict polarity of a molecule. Thus, all these molecules having
zero dipole moment values in the molecular z–axis. The larger total dipole moment of
3HMP (2.795 D) than 2HMP (0.652 D) molecules is due to more separation between
the ring nitrogen and –CH2OH group.
204
6.4.4. Temperature dependence of Thermodynamic properties
The temperature dependence of the thermodynamic properties heat capacity at
constant pressure (Cp), entropy (S) and enthalpy change (∆H0→T) for all the
compounds were also determined by B3LYP/6–311++G(d,p) method and listed in
Table 6.3. The anharmonicity effects have been eliminated by scaling the
thermodynamic properties by 0.98. The Figures 6.7–6.9 depicts the correlation of heat
capacity at constant pressure (Cp), entropy (S) and enthalpy change (∆H0→T) with
temperature along with the correlation equations. From Table 6.3, one can find that
the entropies, heat capacities, and enthalpy changes are increasing with temperature
ranging from 50 to 1000 K due to the fact that the molecular vibrational intensities
increase with temperature [44]. These observed relations of the thermodynamic
functions vs. temperatures were fitted by quadratic formulas, and the corresponding
fitting regression factors (R2) are all not less than 0.9995. The corresponding fitting
equations for 2HMP are
S = 225.932 + 0.4751 T – 1.0503 x 10–4 T2
Cp = 9.9994 + 0.4284 T – 1.6598 x 10–4 T2
ΔH = –3.1432 + 0.0487 T + 1.2683 x 10–4 T2
For 3HMP the corresponding equations are
S = 214.8863 + 0.4323 T – 8.3211 x 10–4 T2
Cp = 2.702 + 0.4239 T – 1.627 x 10–4 T2
ΔH = –2.9295 + 0.0406 T + 1.2644 x 10–4 T2
The Table 6.3 indicate the all the thermodynamic parameters at different
temperatures increases in the order 2HMP 3HMP. From the Figure 6.7 one can
observe that there is a small difference in the entropy of 2HMP and 3HMP. But the
Figures 6.8 and 6.9 clearly reveals that the difference in heat capacity and enthalpy
change between the compounds is very small and not significant.
205
Figure 6.7. Correlation of the effect of temperature on entropy of 2–(hydroxymethyl)
pyridine (2HMP) and 3–(hydroxymethyl)pyridine (3HMP)
Figure 6.8. Correlation of the effect of temperature on heat capacity (Cp) of
2–(hydroxymethyl)pyridine (2HMP) and 3–(hydroxymethyl)pyridine
(3HMP)
206
Figure 6.9. Correlation of the effect of temperature on enthalpy change (∆H0→T) of
2–(hydroxymethyl)pyridine(2HMP) and 3–(hydroxymethyl)pyridine (3HMP)
6.4.5 Analysis of frontier molecular orbitals (FMOs) and Molecular electrostatic
potential (MESP)
The molecular electrostatic potential surface (MESP) which is a method of
mapping electrostatic potential onto the iso–electron density surface simultaneously
displays electrostatic potential (electron + nuclei) distribution, molecular shape, size
and dipole moments of the molecule and it provides a visual method to understand the
relative polarity [45]. Electrostatic potential maps illustrate the charge distributions of
molecules three dimensionally. These maps allow us to visualize variably charged
regions of a molecule. Knowledge of the charge distributions can be used to
determine how molecules interact with one another. One of the purposes of finding
the electrostatic potential is to find the reactive site of a molecule [46,47]. In the
electrostatic potential map, the semi–spherical blue shapes that emerge from the edges
of the above electrostatic potential map are hydrogen atoms. The equation used to find
the electrostatic potential is,
energy potential ticElectrosta energy potential ticelectrosta Total
207
constant sCoulomb' K ,rqqK energy Potential 21
The total electron density and MESP surfaces of the molecules under
investigation are constructed by using B3LYP/6–311++G(d,p) method. These pictures
illustrates an electrostatic potential model of the compounds, computed at the
0.002a.u isodensity surface. The total electron density isosurface of
2–(hydroxymethyl)pyridine and 3–(hydroxymethyl)pyridine is shown in Figure 6.10.
(a)
(b)
Figure 6.10. The total electron density isosurface of (a) 2–(hydroxymethyl)pyridine
and (b) 3–(hydroxymethyl)pyridine
208
The MESP mapped surface of the compounds and electrostatic potential
contour map for positive and negative potentials are shown in Figures 6.11 and 6.12.
(a)
(b)
Figure 6.11. The total electron density iso surface mapped with molecular
electrostatic potential of (a) 2–(hydroxymethyl)pyridine and
(b) 3–(hydroxymethyl)pyridine
209
(a)
(b)
Figure 6.12. The contour map of molecular electrostatic potential surface of
(a) 2–(hydroxymethyl)pyridine and (b) 3–(hydroxymethyl)pyridine
210
The molecular electrostatic potential surface of 2–(hydroxymethyl)pyridine
and 3–(hydroxymethyl)pyridine are depicted in Figure 6.13.
(a)
(b)
Figure 6.13. The molecular electrostatic potential surface of
(a) 2–(hydroxymethyl)pyridine and (b) 3–(hydroxymethyl)pyridine
211
The colour scheme of MESP is the negative electrostatic potentials are shown
in red, the intensity of which is proportional to the absolute value of the potential
energy, and positive electrostatic potentials are shown in blue while Green indicates
surface areas where the potentials are close to zero. The colour–coded values are then
projected on to the 0.002 a.u isodensity surface to produce a three–
dimensional electrostatic potential model. Local negative electrostatic potentials (red)
signal oxygen atoms with lone pairs whereas local positive electrostatic potentials
(blue) signal polar hydrogens in O–H bonds. Green areas cover parts of the molecule
where electrostatic potentials are close to zero (C–C and C–H bonds).
Highest occupied molecular orbital (HOMO) and lowest unoccupied
molecular orbital (LUMO) are very important parameters for quantum chemistry. The
HOMO is the orbital that primarily acts as an electron donor and the LUMO is the
orbital that largely acts as the electron acceptor [45]. The MOs are defined as eigen
functions of the Fock operator, which exhibits the full symmetry of the nuclear point
group, they necessarily form a basis for irreducible representations of full point–
group symmetry. The energies of HOMO, LUMO, LUMO+1 and HOMO–1 and their
orbital energy gaps are calculated using B3LYP/6–311++G(d,p) method and the
pictorial illustration of the frontier molecular orbitals and their respective positive and
negative regions are shown in Figures 6.14 and 6.15 for 2HMP and 3HMP,
respectively. Molecular orbitals, when viewed in a qualitative graphical
representation, can provide insight into the nature of reactivity, and some of the
structural and physical properties of molecules. Well known concepts such as
conjugation, aromaticity and lone pairs are well illustrated by molecular orbitals.
The positive and negative phase is represented in red and green colour,
respectively. From the plots we can see that the region of HOMO and LUMO levels
spread over the entire molecule and the calculated energy gap of HOMO–LUMO’s
explains the ultimate charge transfer interface within the molecule. The frontier
orbital energy gaps (EHOMO – ELUMO) in case of 2HMP and 3HMP is found to be
6.0921 eV and 6.1683 eV, respectively. GaussView 5.0.8 visualisation program [48]
has been utilized to construct the MESP surface, the shape of highest occupied
molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)
orbitals.
212
Figure 6.14. The frontier molecular orbitals of 2–(hydroxymethyl)pyridine
213
Figure 6.15. The frontier molecular orbitals of 3–(hydroxymethyl)pyridine
6.5. Vibrational analysis
The combined FTIR and FT–Raman spectra of the compounds under
investigation are shown in Figures 6.16 and 6.17. The observed and calculated
frequencies using B3LYP/6–31G(d,p), 6–311++G(d,p) and cc–pVTZ basis sets and
along with their relative intensities, probable assignments and potential energy
distribution (PED) of 2HMP and 3HMP are summarised in Tables 6.4 and 6.5,
respectively.
214
Figure 6.16. FTIR and FT–Raman spectra of 2–(hydroxymethyl)pyridine
Figure 6.17. FTIR and FT–Raman spectra of 3–(hydroxymethyl)pyridine
215
6.5.1. Carbon vibrations
The carbon–carbon stretching modes of the pyridine ring appear in the region
1650–1200 cm−1 are determined not so much by the nature of the substituents but by
the form of substitution around the ring [49,50]. In 2HMP under C2 symmetry the
carbon–carbon stretching bands in the infrared spectrum appeared at 1595, 1575 and
1386 cm–1 and 1596 and 1578 cm–1 in 3HMP. The bands observed at 1592, 1567 and
1381 cm–1 in 2HMP and 1590, 1569 and 1462 cm–1 in 3HMP corresponds to Raman
bands assigned to the ring carbon–carbon stretching vibrations respectively.
Weak peaks observed at 1329 cm–1 in 2HMP and the calculated wavenumber
1274 cm–1 in 3HMP are assigned to the exo C–CH2 stretching vibrations. All other
observed skeletal C–C stretching, CCC in–plane and out of plane bending vibrations
of the compounds are completely assigned and are presented in Tables 6.4 and 6.5.
Normal coordinate analysis shows that significant mixing of CCC in–plane bending
with C–H in–plane bending modes and vice versa occurs. The CCC in–plane bending
vibrations of 2HMP observed in the infrared spectrum at 746 and 622 cm–1 and for
3HMP at 709 and 640 cm–1. At lower frequencies the assignments become more
complex since the bands are no longer corresponds to pure motions and also not
sensitive to position of substitution.
6.5.2. Methylene group vibrations
Usually the CH2 asymmetric stretching vibrations are observed in the aromatic
C–H stretching region 3100–3000 cm–1 [51]. The CH2 asymmetric vibration of 3HMP
is observed at 2926 and 2936 cm–1 in the infrared and in Raman spectra. In 2HMP the
same band is assigned to the mode 2914 and 2924 cm–1 in the infrared and in Raman
spectra.
The CH2 symmetric vibration of 2HMP is observed at 2856 and 2859 cm–1 in
the infrared and in Raman spectra. In 3HMP the same band is assigned to the mode
2858 cm–1 in the infrared and Raman spectra. In infrared spectrum, CH2 deformations
of 2HMP is observed at 1437 and 1434 cm–1. In 3HMP it is observed at 1418 and
1412 cm–1, in the infra red and in Raman spectra, respectively. Peaks at 1019, 1014
and 1030, 1036 cm–1 in infrared and Raman spectra are assigned to CH2 wagging
mode of 2HMP and 3HMP, respectively. The CH2 twisting modes in infrared are
observed at 910 and 952 cm–1 in 2HMP and 3HMP, respectively. The weak peak in
216
infrared at 974 cm–1 in 2HMP and the calculated peaks at 978 cm–1 are assigned to
CH2 rocking modes of 2HMP and 3HMP, respectively.
6.5.3. Aromatic C–H vibrations
Usually the bands in the range 3100–3000 cm−1 are assigned to C–H stretching
vibrations of aromatic compounds. Fundamental mode observed at 3103, 3075 and
3022 cm−1 in 2HMP and 3083, 3032 and 3000 cm−1 in 3HMP in the infrared spectra
are assigned to the aromatic C–H stretching vibrations. The C–H in–plane bending
vibrations are observed in the region 1350–950 cm−1. The frequencies of the C–H out
of plane bending modes depends mainly on the number of the adjacent hydrogen
atoms on the ring and not very much affected by the nature of substituents. The C–H
out of plane bending modes usually medium to strong intensity arises in the region
950–600 cm−1 [52]. The C–H in plane bending modes of 2HMP are observed at 1160
and 1068 cm–1 and in 3HMP at 1191, 1132 and 1063 cm–1. A strong peak at
1007 cm–1 and weak bands seen at 910 and 818 cm–1 in 2HMP and weak peaks at 921
and 824 cm–1 in 3HMP are assigned to C–H out of plane bending modes. The
unresolved wavenumbers are predicted from ab initio calculations. All the C–H
in–plane and out of plane bending modes of the compound are well agreed with the
reported data [53,54].
6.5.4. C–O vibrations
The strong band observed at 1110 cm–1 in 2HMP and 3HMP is assigned C–O
stretching vibration. While in Raman spectra the weak bands observed at 1107 and
1102 cm−1 in 2HMP and 3HMP correspond to C–O stretching vibrations. The other
in–plane and out of plane bending modes of C–O bond have also been assigned and
reported in the Tables.
6.5.5. O–H vibrations
Bands due to OH stretching are of medium to strong intensity in the infrared
spectrum, although it may be broad. In Raman spectra the band is generally weak.
Unassociated hydroxyl groups absorbs strongly in the region 3670–3580 cm−1. The
band due to the free hydroxyl group is sharp and its intensity increases. For solids,
liquids and concentrated solutions a broad band of less intensity is normally observed
[55–57]. A broad stretching of O–H also indicates the presence of intramolecular
hydrogen bonding [57]. The observed band due to O–H stretching is very broad in the
217
case of 2HMP and 3HMP molecules indicates the intermolecular hydrogen bonding
between the –CH2OH groups. The O–H stretching band in 2HMP indicates the
presence of intramolecular hydrogen bonding between the N1 atom and the O–H
group of –CH2OH. The compounds under investigation shows strong and broad
stretching of hydroxyl group at 3400 cm−1 in 2HMP and 3365 cm–1 in 3HMP in the
infrared spectrum are assigned to O–H stretching.
6.6. Sclae factors
The vibrational frequencies calculated using DFT methods are known to be
overestimated probably because of the neglect of anharmonicity of vibrations in the
real systems. Accepted values of scaling factors for DFT 0.96 and it has been used to
correct the frequency values [58]. A better agreement between the theoretical and
experimental frequencies can be obtained by using different scale factors for different
regions of vibrations.
To determine the scale factors, the procedure used previously [59–67] have
been followed that minimises the residual separating experimental and theoretically
predicted vibrational frequencies. The optimum scale factors for vibrational
frequencies were determined by minimising the residual
N
i
2Expti
Theori νλωΔ
where, Theoiω and
Exptiν are the i
th theoretical harmonic frequency and ith
experimental fundamental frequency (in cm–1), respectively and N is the number of
frequencies included in the optimisation which leads to
NΔRMS
The scale factors used in this study minimised the deviations between the
computed and experimental frequencies. A uniform scaling factor is recommended for
all frequencies < 1800 cm–1 at the B3LYP method with 6–31G(d,p) and
6–311++G(d,p) basis sets and is adopted in this study. Due to the large
anharmonicities of C–H and O–H stretching frequencies > 2700 cm–1 were scaled by
two different scale factors [65,66]. Initially, all scaling factors have been kept fixed at
a value of 1.0 to produce the pure DFT calculated vibrational frequencies (unscaled)
which are given in Tables 6.4 and 6.5. A scaling factor of 0.87, 0.96 and 0.98 for
218
O–H stretching, C–H stretching and for other vibrations of 3HMP and 0.88, 0.965 and
0.98 for O–H stretching, C–H stretching and for other stretching vibrations of 2HMP.
The scale factors used in the B3LYP method with 6–311++G(d,p)basis sets are all
much closer to unity and minimised the deviations very much between the computed
and experimental frequencies than with 6–31G(d,p) basis set.
The linear regression between the experimental and theoretical scaled
wavenumbers obtained for B3LYP/6–311++G(d,p) and B3LYP/cc–pVTZ methods
are presented in the Figure 6.18. The RMS deviation between the observed and the
calculated wavenumbers of 2HMP is 9 cm–1, while in the case of 3HMP is 8 cm–1.
This minimal RMS deviation confirms the reliability of the assignments of the
fundamental modes of these isomers.
0 500 1000 1500 2000 2500 3000 3500
0
500
1000
1500
2000
2500
3000
3500
R2=0.998
(a) B3LYP/6-311++G(d,p)
2-(hydroxymethyl)pyridine
Th
eore
tica
l Wav
enu
mb
er (
Cm
-1)
Experimental Wavenumber (Cm-1)
0 500 1000 1500 2000 2500 3000 3500
0
500
1000
1500
2000
2500
3000
3500
(b) B3LYP/cc-pVTZ
R2=0.998
2-(hydroxymethyl)pyridine
Th
eore
tica
l Wav
enu
mb
er (
Cm
-1)
Experimental Wavenumber (Cm-1)
219
0 500 1000 1500 2000 2500 3000 3500 4000
0
500
1000
1500
2000
2500
3000
3500
40003-(hydroxymethyl)pyridine
(a) B3LYP/6-311++G(d,p)
R2=0.999
Theo
retic
al W
aven
umbe
r (C
m-1)
Experimental Wavenumber (Cm-1)
0 500 1000 1500 2000 2500 3000 3500 4000
0
500
1000
1500
2000
2500
3000
3500
4000
3-(hydroxymethyl)pyridine
(b) B3LYP/cc-pVTZ
R2=0.999
Th
eore
tica
l Wav
enu
mb
er (
Cm
-1)
Experimental Wavenumber (Cm-1)
Figure 6.18. Correlation between the calculated and the experimental frequencies of
2–(hydroxymethyl)pyridine and 3–(hydroxymethyl)pyridine.
6.7. Conclusions
The Fourier transform infrared (FTIR) and FT–Raman spectra of
2–(hydroxymethyl)pyridine (2HMP) and 3–(hydroxymethyl)pyridine (3HMP) have
been recorded in the range 4000–400 and 4000–100 cm−1, respectively. The
conformational analyses of these compounds were performed. The complete
vibrational assignment and analysis of the fundamental modes of the most stable
conformer of the compounds were carried out using the experimental FTIR and
FT–Raman data and quantum mechanical studies. The observed vibrational
220
frequencies were compared with the wavenumbers derived theoretically for the
optimised geometry of the compounds from the DFT–B3LYP gradient calculations
employing the standard 6–31G(d,p) and high level and 6–311++G(d,p) cc–pVTZ
basis sets.
The structural parameters and vibrational wavenumbers obtained from the
DFT method are in good agreement with the experimental data. The potential energy
distributions of the fundamental modes were also calculated by Wilson’s FG matrix
method. The effect of –CH2OH groups on the skeletal vibrations have been discussed.
The deviation between the experimental and calculated (both unscaled and scaled)
frequencies were reduced with the use of DFT–B3LYP method using high level
6–311++G(d,p) basis set. In the present study, the complete, precise and reliable
assignment of the fundamental vibrational modes as well as all the molecular
parameters of the industrially significant 2HMP and 3HMP were reported.
221
Table 6.1. Structural parameters of 2–(hydroxymethyl)pyridine and 3–(hydroxymethyl)pyridine calculated by B3LYP method
using 6–311++G(d,p), 6–31G(d,p) and cc–pVTZ basis sets.
Structural Parameters
2–(hydroxymethyl)pyridine 3–(hydroxymethyl)pyridine
Experimentala B3LYP/
6–311++G(d,p)
B3LYP/
6–31G(d,p)
B3LYP/
cc–pVTZ
B3LYP/
6–311++G(d,p)
B3LYP/
6–31G(d,p)
B3LYP/
cc–pVTZ
Internuclear Distance (Ǻ)
C5–C6 1.394 1.396 1.394 1.391 1.394 1.392 1.394
C4–C5 1.392 1.394 1.392 1.393 1.395 1.393 1.394
C5–H11 1.083 1.085 1.084 1.084 1.086 1.084 1.081
C6–N1 1.334 1.337 1.335 1.338 1.34 1.338 1.340
C6–H12 1.087 1.089 1.087 1.086 1.088 1.086 1.081
N1–C2 1.339 1.342 1.334 1.333 1.336 1.333 1.340
C2–C3 1.395 1.397 1.395 1.399 1.4 1.399 1.395
C2–C7/C3–C7 1.51 1.512 1.510 1.51 1.512 1.510
C2–H9/C3–H9 1.081 1.083 1.081 1.089 1.091 1.088
C3–C4 1.392 1.394 1.392 1.393 1.395 1.393 1.394
C4–H10 1.085 1.086 1.085 1.082 1.084 1.082 1.081
C7–O8 1.424 1.419 1.424 1.424 1.419 1.424
C7–H13 1.098 1.101 1.098 1.099 1.103 1.099
222
C7–H14 1.098 1.101 1.098 1.099 1.103 1.099
O8–H15 0.961 0.964 0.961 0.961 0.965 0.961
Bond angle(degree)
C6–C5–C4 118.1 118.1 118.1 118.9 118.8 118.9 118.1
C6–C5–H11 120.4 120.4 120.4 120.2 120.3 120.2
C5–C6–N1 123.5 123.7 123.5 123.1 123.3 123.1 123.3
C5–C6–H12 120.5 120.3 120.5 120.7 120.6 120.7 120.8
C4–C5–H11 121.5 121.5 121.5 120.9 120.9 120.9
C5–C4–C3 119.1 119.0 119.1 118.8 118.8 118.8
C5–C4–H10 120.6 120.7 120.6 121.5 121.6 121.5
N1–C6–H12 116.1 116 116.1 116.2 116.1 116.2
C6–N1–C2 118 117.7 118.0 117.4 117.1 117.4 117.3
N1–C2–C3 122.9 123.1 122.9 124.2 124.4 124.2
N1–C2–C7/N1–C2–H9 114.7 114.8 114.7 115.8 115.8 115.8
C3–C2–C7/ C3–C2–H9 122.3 122.1 122.3 120 119.8 120.0
C2–C3–C4 118.4 118.4 118.4 117.6 117.6 117.6 118.5
C2–C3–H9/C2–C3–C7 119.7 119.6 119.7 119.9 120.2 119.9 120.2
C2–C7–O8 / C3–C7–O8 110 109.8 110.0 122.5 122.2 109.6
C2–C7–H13/ C3–C7–H13 108.3 108.2 108.3 119.8 119.6 109.2
223
C2–C7–H14/ C3–C7–H14 108.3 108.2 108.3 109.2 109.1 109.2
C4–C3–H9/C4–C3–C7 121.9 122 121.9 109.2 109.1 122.5
C3–C4–H10 120.3 120.3 120.3 109.6 109.5 119.8
O8–C7–H13 111.3 111.9 111.3 107.5 106.7 110.6
O8–C7–H14 111.3 111.9 111.3 110.6 111.2 110.6
C7–C8–H15 108.8 108 108.8 110.6 111.2 108.9
H13–C7–H14 107.6 106.8 107.6 108.9 108.1 107.5
Dihedral Angle (degree)
N1–C2–C7–H13 58.2 57.7 58.2
N1–C2–C7–H14 –58.2 –57.6 –58.2
C3–C2–C7–O8 0.001 0.00 0.00
C3–C2–C7–H13 –121.8 –122.3 –121.8
C3–C2–C7–H14 121.8 122.4 121.8
C2–C3–C4–C5 0.0 0.0 0.0
C2–C3–C4–H10 –180.0 180.0 –180.0 –180.0 –180.0 –180.0
H9–C3–C4–C5 –180.0 –180.0 –180.0
H9–C3–C4–H10 0.00 0.00 0.00
C2–C7–O8–H15 180.0 180.0 180.0
H13–C7–O8–H15 –60.0 –59.9 –60.0 59.5 59.4 59.5
224
H14–C7–O8–H15 59.9 59.9 60.0 –59.5 –59.4 –59.5
C7–C3–C4–C5 –180.0 –180.0 –180.0
C7–C3–C4–H10 0.00 0.00 0.00
C2–C3–C7–H13 –58.7 –58.1 –58.7
C2–C3–C7–H14 58.7 58.1 58.7
C2–C3–C7–O8 180.0 180.0 180.0
C4–C3–C7–H13 121.3 121.9 121.3
C4–C3–C7–H14 –121.3 –121.9 –121.3
C4–C3–C7–O8 –0.01 –0.01 –0.01
C3–C7–O8–H15 180.0 –180.0 180.0
a–values taken from Ref. [41,42]
225
Table 6.2. The calculated thermodynamic parameters of 2–(hydroxymethyl)pyridine and 3–(hydroxymethyl)pyridine employing
B3LYP method with 6–311++G(d,p), 6–31G(d,p) and cc–pVTZ basis sets.
Thermodynamic parameters (298K)
2–(hydroxymethyl)pyridine 3–(hydroxymethyl)pyridine
B3LYP/ 6–31G(d,p)
B3LYP/ 6–311++G(d,p)
B3LYP/ cc–pVTZ
B3LYP/ 6–31G(d,p)
B3LYP/ 6–311++G(d,p)
B3LYP/ cc–pVTZ
Total Energy (thermal), Etotal (kcal.mol–1) 80.566 80.174 80.353 80.020 79.572 80.393
Heat Capacity at const. volume, Cv
(cal.mol–1.K–1)
25.821 26.070 25.821 23.773 24.095 25.765
Entropy, S (cal.mol–1.K–1) 83.670 85.273 83.194 78.963 79.963 85.819
Vibrational Energy, Evib (kcal.mol–1) 78.788 78.396 78.576 78.242 77.794 78.615
Zero point Vibrational Energy, Evib
(kcal.mol–1)
76.151 75.642 75.956 76.126 75.566 75.931
SCF (a.u) –362.823 –362.919 –362.948 –362.819 –362.913 –362.944
Rotational Constants (GHz)
X 5.040 5.040 5.088 5.099 5.099 5.115
Y 1.545 1.545 1.551 1.507 1.507 1.507
Z 1.192 1.192 1.197 1.172 1.172 1.173
226
Dipolemoment (Debye)
μx –0.499 –0.349 –0.4262 2.694 2.784 2.650
μy 0.573 0.551 0.5669 0.310 0.247 0.287
μz 0.000 0.000 0.000 0.000 0.000 0.000
μtotal 0.760 0.652 0.709 2.712 2.795 2.665
ELUMO + 1 (eV) –0.5695 –0.7013
ELUMO (eV) –1.0164 –0.9192
EHOMO (eV) –7.1085 –7.0875
EHOMO – 1 (eV) –7.2043 –7.1232
ELUMO – EHOMO (eV) 6.0921 6.1683
227
Table 6.3. Thermodynamic properties of 2–(hydroxymethyl)pyridine and 3–(hydroxymethyl)pyridine determined
at different temperatures with B3LYP/6–311++G(d,p) level.
2–(hydroxymethyl)pyridine 3–(hydroxymethyl)pyridine
T (K) S (J. mol–1. K–1) Cp (J. mol–1. K–1) ΔH0→T (kJ. mol–1) S (J. mol–1. K–1) Cp (J. mol–1. K–1) ΔH0→T (kJ. mol–1)
100 269.83 58.26 4.54 256.04 50.33 3.9
150 295.84 71.1 7.77 278.89 63.39 6.74
200 318.24 85.72 11.68 299.07 77.9 10.27
250 339.13 102.36 16.38 318.18 94.3 14.57
298.15 358.62 119.55 21.72 336.23 111.26 19.51
300 359.36 120.22 21.94 336.92 111.92 19.72
350 379.24 138.16 28.4 355.51 129.68 25.76
400 398.82 155.31 35.74 373.95 146.7 32.67
450 418.04 171.17 43.91 392.15 162.49 40.41
500 436.84 185.56 52.83 410.03 176.86 48.9
600 472.92 210.13 72.66 444.53 201.45 67.86
700 506.85 229.98 94.7 477.13 221.36 89.03
800 538.66 246.24 118.54 507.79 237.7 112.01
900 568.47 259.78 143.86 536.6 251.31 136.48
1000 596.44 271.18 170.42 563.68 262.77 162.2
228
Table 6.4. The observed FTIR, FT–Raman and calculated frequencies determined by B3LYP method with 6–31G(d,p), 6–311++G(d,p) and cc–pVTZ basis sets along
with their relative intensities, probable assignments and potential energy distribution (PED) of 2–(hydroxymethyl)pyridinea.
Spec
ies
Observed
wavenumber (cm–1)
B3LYP/6–311++G(d,p)
Calculated wavenumber
B3LYP/cc–pVTZ
Calculated wavenumber
B3LYP/6–31G(d,p)
Calculated wavenumber
Dep
olar
izat
ion
ratio
Ass
ignm
ent
%PE
D
FTIR
FTR
Uns
cale
d
(cm
–1)
Scal
ed
(cm
–1)
IR in
tens
ity
Ram
an
inte
nsity
Uns
cale
d
(cm
–1)
Scal
ed
(cm
–1)
IR in
tens
ity
Uns
cale
d
(cm
–1)
Scal
ed
(cm
–1)
IR in
tens
ity
A' 3400 s 3861 3398 50.89 1.570 3846 3384 44.81 3843 3382 26.48 0.27 νO–H 92OH
A' 3103 s 3215 3102 1.22 1.127 3218 3105 1.60 3237 3124 1.43 0.18 νC–H 90CH
A' 3075 s 3080 m 3191 3079 16.44 1.864 3193 3081 17.74 3209 3097 20.09 0.18 νC–H 92CH
A' 3170 3059 9.98 0.865 3172 3061 10.48 3187 3075 12.71 0.71 νC–H 91CH
A' 3022 m 3022 w 3147 3037 18.12 1.120 3144 3034 21.30 3160 3049 24.62 0.38 νC–H 93CH
A' 2914 m 2924 m 3025 2919 27.15 0.935 3017 2911 30.51 3017 2911 46.63 0.75 νaCH2 90CH2
A' 2856 s 2859 s 2995 2890 34.65 2.000 2990 2885 35.14 2989 2884 38.76 0.07 νsCH2 94CH2
A' 1595 vs 1592 m 1632 1599 52.46 0.244 1635 1602 51.96 1649 1616 49.65 0.47 νC=C 92CC
A' 1575 vs 1567 m 1614 1582 13.06 0.080 1618 1586 13.13 1632 1599 12.36 0.68 νC=C 90CC
A' 1482 s 1508 1478 7.05 0.027 1513 1483 10.02 1523 1493 3.21 0.18 νC=N 87βCN
A' 1497 1467 17.25 0.118 1502 1472 13.45 1514 1484 16.62 0.66 νC–C 89CC
229
A' 1437 vs 1434 w 1465 1436 35.06 0.028 1473 1444 35.57 1477 1447 35.17 0.28 δCH2 92CH2
A' 1386 m 1381 w 1436 1407 11.99 0.091 1445 1416 12.29 1452 1423 18.70 0.47 νC–C 90CC
A' 1329 m 1327 1300 10.49 0.023 1332 1305 12.53 1336 1309 13.23 0.27 νC–C 89CC
A' 1268 w 1278 w 1303 1277 1.64 0.012 1303 1277 1.59 1320 1294 0.01 0.26 νC–N 85CN
A' 1228 m 1221 m 1254 1229 3.49 0.117 1255 1230 3.80 1261 1236 7.72 0.13 βO–H 70βOH + 14βCO
A' 1249 1224 0.15 0.068 1249 1224 0.45 1247 1222 0.62 0.75 βC–H 69βCH + 16βCCC
A' 1160 m 1153 w 1188 1164 82.58 0.085 1194 1170 79.70 1200 1176 92.90 0.50 βC–H 65βCH + 18βCCC
A' 1170 1147 3.92 0.017 1174 1151 1.22 1176 1152 2.26 0.32 βC–H 62βCH + 12βCCC
A' 1110 s 1107 w 1118 1096 7.83 0.025 1122 1100 8.60 1128 1105 15.90 0.72 νC–O 75CO
A' 1068 vs 1057 vs 1069 1048 37.21 0.143 1074 1053 48.32 1091 1069 50.62 0.08 βC–H 60βCH + 18βCCC
A" 1063 1042 0.09 0.002 1069 1048 0.11 1073 1052 0.00 0.12 γC–H 60γCH+16γCCC
A" 1019 vs 1014 vs 1032 1011 40.65 0.063 1044 1023 26.21 1046 1025 4.85 0.86 ωCH2 65ωCH2 + 18γOH
A" 1007 s 1012 992 6.11 0.254 1023 1003 0.14 1012 992 7.21 0.10 γC–H 65γCH + 16γCCC
A' 974 w 1011 991 0.08 0.000 1014 994 6.90 1012 992 0.08 0.75 ρCH2 64ρCH2+15CC
A" 974 955 0.19 0.000 983 963 0.12 974 955 0.06 0.75 tCH2 55tCH2+21ωCH2
A" 910 w 899 vw 909 891 0.31 0.001 916 898 0.30 913 895 0.51 0.75 γC–H 59γCH+22γCCC
A" 818 w 808 m 813 797 1.01 0.135 814 798 0.97 816 800 1.16 0.08 γC–H 63γCH + 12γCCC
A" 777 vs 768 753 51.82 0.000 774 759 42.78 774 759 33.14 0.75 γO–H 67γOH+18γCH
230
A' 746 m 738 vw 744 729 9.69 0.002 755 740 11.48 744 729 8.61 0.75 βCCC 62CCC+24CH
A' 622 m 617 vw 640 627 4.02 0.045 641 628 4.55 639 626 4.70 0.72 βCCC 59βCCC + 24βCH
A' 594 582 10.77 0.015 594 582 9.44 592 580 9.75 0.34 βC–C 62βCC + 18βOH
A' 469 w 464 m 470 461 2.00 0.005 479 469 1.46 476 466 0.27 0.75 βCNC 70βCNC + 15βCH
A' 426 m 421 vw 440 431 0.60 0.041 441 432 0.51 441 432 0.48 0.37 βC–O 63CO+14CC
A" 389 w 414 406 2.71 0.002 418 410 1.87 416 408 1.67 0.75 γCCC 65γCCC + 12γCH
A" 228 m 227 222 11.08 0.001 228 223 9.26 229 224 72.20 0.23 γCCC 59γCCC + 14γCH
A" 215 m 192 188 0.01 0.025 220 216 56.13 227 222 9.58 0.75 γCNC 57γCNC + 18γCH
A" 136 133 97.74 0.002 181 177 61.26 180 176 58.17 0.75 γC–O 60γCO + 22γCC A" 37 37 49.68 0.035 68 68 11.80 53 53 15.76 0.75 γC–C 63γCC + 18γCCC
aν–stretching; β–in–plane bending; δ–deformation; ρ–rocking; γ–out of plane bending; ω–wagging and τ–twisting/torsion, wavenumbers (cm–1);
IR intensities (km/mol) and Raman intensities (Å)4/(a.m.u).
231
Table 6.5. The observed FTIR, FT–Raman and calculated frequencies determined by B3LYP method with 6–31G**, 6–311++G** and cc–pVTZ basis sets along
with their relative intensities, probable assignments and potential energy distribution (PED) of 3–(hydroxymethyl)pyridinea.
Spec
ies
Observed
wavenumber (cm–1)
B3LYP/6–311++G**
Calculated wavenumber
B3LYP/cc–pVTZ
Calculated wavenumber
B3LYP/6–31G**
Calculated wavenumber
Dep
olar
izat
ion
ratio
Ass
ignm
ent
%PE
D
FTIR
FTR
Uns
cale
d
(cm
–1)
Scal
ed
(cm
–1)
IR in
tens
ity
Ram
an
inte
nsity
Uns
cale
d
(cm
–1)
Scal
ed
(cm
–1)
IR in
tens
ity
Uns
cale
d
(cm
–1)
Scal
ed
(cm
–1)
IR in
tens
ity
A' 3365 b 3857 3356 50.89 1.730 3842 3343 44.69 3840 3341 26.76 0.27 νO–H 90OH
A' 3083 b 3208 3080 2.77 1.124 3211 3083 3.28 3229 3100 3.01 0.16 νC–H 90CH
A' 3056 s 3182 3055 15.60 1.596 3184 3057 16.43 3200 3072 19.05 0.30 νC–H 92CH
A' 3032 b 3152 3026 12.76 1.138 3150 3024 15.68 3166 3039 19.10 0.40 νC–H 94CH
A' 3000 b 2995 w 3122 2997 28.66 1.069 3119 2994 30.64 3136 3011 33.47 0.30 νC–H 93CH
A' 2926 vs 2936 w 3002 2882 32.83 0.969 2995 2875 36.24 2994 2874 55.02 0.75 νaCH2 91CH2
A' 2858 vs 2858 m 2979 2860 42.08 2.000 2974 2855 41.49 2972 2853 45.49 0.07 νsCH2 92CH2
A' 1596 s 1590 m 1633 1600 2.14 0.239 1636 1603 1.92 1652 1619 2.54 0.59 νC=C 89CC
A' 1578 vs 1569 w 1614 1582 21.14 0.081 1618 1586 20.05 1631 1598 20.80 0.60 νC=C 90CC
A' 1480 s 1470 vw 1512 1482 2.79 0.017 1518 1488 6.87 1528 1497 0.15 0.69 νC=N 94CC
232
A' 1462 vw 1507 1477 17.50 0.137 1512 1482 13.24 1523 1493 19.20 0.57 νC–C 92CN
A' 1463 1434 8.92 0.018 1469 1440 5.21 1477 1447 5.58 0.75 νC–C 89CC
A' 1418 vs 1412 vw 1431 1402 26.25 0.115 1439 1410 31.80 1446 1417 35.84 0.44 δCH2 85CH2
A' 1327 m 1363 1336 7.72 0.009 1370 1343 8.28 1371 1344 8.91 0.32 νC–N 86CN
A' 1300 1274 7.28 0.039 1301 1275 8.49 1322 1296 8.69 0.32 νC–C 87CC
A' 1259 1234 0.02 0.081 1262 1237 0.24 1259 1234 0.27 0.75 βC–H 65βCH + 16βCCC
A' 1222 s 1225 w 1245 1220 0.92 0.083 1248 1223 1.41 1253 1228 4.38 0.61 βO–H 70βOH + 16βCO
A' 1191 m 1189 w 1211 1187 3.74 0.072 1213 1189 4.79 1220 1196 4.58 0.12 βC–H 61βCH + 18βCCC
A' 1132 m 1123 vw 1188 1164 78.53 0.048 1195 1171 67.85 1200 1176 81.55 0.31 βC–H 62βCH + 16βCCC
A' 1110 m 1102 w 1139 1116 3.38 0.039 1142 1119 3.21 1146 1123 3.57 0.40 νC–O 73CO
A" 1063 vs 1069 1048 24.37 0.121 1073 1052 30.55 1091 1069 51.17 0.15 βC–H 62βCH + 15βCCC
A' 1030 vs 1036 vs 1057 1036 36.19 0.247 1062 1041 25.62 1069 1048 7.52 0.04 ωCH2 56ωCH2 + 18γOH
A" 1038 1017 28.20 0.144 1053 1032 0.01 1052 1031 0.10 0.06 γC–H 60γCH+14γCCC
A" 1034 1013 0.01 0.001 1043 1022 31.62 1039 1018 18.32 0.75 γC–H 63γCH + 12γCCC
A' 998 978 0.22 0.000 1015 995 0.14 1002 982 0.46 0.75 ρCH2 69ρCH2+15CC
A" 952 vw 943 vw 959 940 0.18 0.000 969 950 0.31 963 944 0.69 0.75 tCH2 55tCH2+22ωCH2
A" 921 vw 928 vw 933 914 0.33 0.002 947 928 0.42 944 925 0.23 0.75 γC–H 59γCH+22γCCC
A" 824 m 814 w 810 794 6.48 0.131 811 795 6.68 812 796 7.72 0.07 γC–H 61γCH + 12γCCC
233
A" 793 vs 790 w 796 780 34.03 0.004 809 793 25.07 806 790 21.75 0.75 γO–H 69γOH+16γCH
A' 709 vs 706 vw 723 709 23.51 0.002 735 720 24.92 728 713 15.90 0.75 βCCC 56CCC+24CH
A' 640 s 631 w 647 634 9.23 0.044 648 635 9.72 646 633 9.88 0.67 βCCC 57βCCC + 18βCH
A' 603 m 598 vw 596 584 3.87 0.028 597 585 2.70 596 584 2.71 0.57 βC–C 60βCC + 16βOH
A' 450 441 0.01 0.002 465 456 0.10 462 453 1.00 0.75 βCNC 67βCNC + 14βCH
A' 406 m 400 w 417 409 3.10 0.040 418 410 2.89 418 410 2.80 0.29 βC–O 63CO+14CC
A" 391 vw 404 396 4.82 0.001 412 404 4.22 410 402 3.25 0.75 γCCC 60γCCC + 12γCH
A" 224 220 7.07 0.001 232 227 67.04 239 234 78.21 0.52 γCCC 55γCCC + 21γCH
A" 195 191 1.12 0.035 225 221 5.71 225 221 6.16 0.75 γCNC 57γCNC + 18γCH
A" 163 vw 141 138 92.72 0.005 186 182 41.06 185 181 41.97 0.75 γC–O 56γCO + 20γCC A" 59 59 48.31 0.026 18 18 15.64 35 33 20.04 0.75 γC–C 58γCC + 16γCCC
aν–stretching; β–in–plane bending; δ–deformation; ρ–rocking; γ–out of plane bending; ω–wagging and τ–twisting, wavenumbers (cm–1);
IR intensities (km/mol) and Raman intensity (Å)4/(a.m.u).
228
Table 6.4. The observed FTIR, FT–Raman and calculated frequencies determined by B3LYP method with 6–31G(d,p), 6–311++G(d,p) and cc–pVTZ basis sets along
with their relative intensities, probable assignments and potential energy distribution (PED) of 2–(hydroxymethyl)pyridinea.
Spec
ies
Observed
wavenumber (cm–1)
B3LYP/6–311++G(d,p)
Calculated wavenumber
B3LYP/cc–pVTZ
Calculated wavenumber
B3LYP/6–31G(d,p)
Calculated wavenumber
Dep
olar
izat
ion
ratio
Ass
ignm
ent
%PE
D
FTIR
FTR
Uns
cale
d
(cm
–1)
Scal
ed
(cm
–1)
IR in
tens
ity
Ram
an
inte
nsity
Uns
cale
d
(cm
–1)
Scal
ed
(cm
–1)
IR in
tens
ity
Uns
cale
d
(cm
–1)
Scal
ed
(cm
–1)
IR in
tens
ity
A' 3400 s 3861 3398 50.89 1.570 3846 3384 44.81 3843 3382 26.48 0.27 νO–H 92OH
A' 3103 s 3215 3102 1.22 1.127 3218 3105 1.60 3237 3124 1.43 0.18 νC–H 90CH
A' 3075 s 3080 m 3191 3079 16.44 1.864 3193 3081 17.74 3209 3097 20.09 0.18 νC–H 92CH
A' 3170 3059 9.98 0.865 3172 3061 10.48 3187 3075 12.71 0.71 νC–H 91CH
A' 3022 m 3022 w 3147 3037 18.12 1.120 3144 3034 21.30 3160 3049 24.62 0.38 νC–H 93CH
A' 2914 m 2924 m 3025 2919 27.15 0.935 3017 2911 30.51 3017 2911 46.63 0.75 νaCH2 90CH2
A' 2856 s 2859 s 2995 2890 34.65 2.000 2990 2885 35.14 2989 2884 38.76 0.07 νsCH2 94CH2
A' 1595 vs 1592 m 1632 1599 52.46 0.244 1635 1602 51.96 1649 1616 49.65 0.47 νC=C 92CC
A' 1575 vs 1567 m 1614 1582 13.06 0.080 1618 1586 13.13 1632 1599 12.36 0.68 νC=C 90CC
A' 1482 s 1508 1478 7.05 0.027 1513 1483 10.02 1523 1493 3.21 0.18 νC=N 87βCN
A' 1497 1467 17.25 0.118 1502 1472 13.45 1514 1484 16.62 0.66 νC–C 89CC
229
A' 1437 vs 1434 w 1465 1436 35.06 0.028 1473 1444 35.57 1477 1447 35.17 0.28 δCH2 92CH2
A' 1386 m 1381 w 1436 1407 11.99 0.091 1445 1416 12.29 1452 1423 18.70 0.47 νC–C 90CC
A' 1329 m 1327 1300 10.49 0.023 1332 1305 12.53 1336 1309 13.23 0.27 νC–C 89CC
A' 1268 w 1278 w 1303 1277 1.64 0.012 1303 1277 1.59 1320 1294 0.01 0.26 νC–N 85CN
A' 1228 m 1221 m 1254 1229 3.49 0.117 1255 1230 3.80 1261 1236 7.72 0.13 βO–H 70βOH + 14βCO
A' 1249 1224 0.15 0.068 1249 1224 0.45 1247 1222 0.62 0.75 βC–H 69βCH + 16βCCC
A' 1160 m 1153 w 1188 1164 82.58 0.085 1194 1170 79.70 1200 1176 92.90 0.50 βC–H 65βCH + 18βCCC
A' 1170 1147 3.92 0.017 1174 1151 1.22 1176 1152 2.26 0.32 βC–H 62βCH + 12βCCC
A' 1110 s 1107 w 1118 1096 7.83 0.025 1122 1100 8.60 1128 1105 15.90 0.72 νC–O 75CO
A' 1068 vs 1057 vs 1069 1048 37.21 0.143 1074 1053 48.32 1091 1069 50.62 0.08 βC–H 60βCH + 18βCCC
A" 1063 1042 0.09 0.002 1069 1048 0.11 1073 1052 0.00 0.12 γC–H 60γCH+16γCCC
A" 1019 vs 1014 vs 1032 1011 40.65 0.063 1044 1023 26.21 1046 1025 4.85 0.86 ωCH2 65ωCH2 + 18γOH
A" 1007 s 1012 992 6.11 0.254 1023 1003 0.14 1012 992 7.21 0.10 γC–H 65γCH + 16γCCC
A' 974 w 1011 991 0.08 0.000 1014 994 6.90 1012 992 0.08 0.75 ρCH2 64ρCH2+15CC
A" 974 955 0.19 0.000 983 963 0.12 974 955 0.06 0.75 tCH2 55tCH2+21ωCH2
A" 910 w 899 vw 909 891 0.31 0.001 916 898 0.30 913 895 0.51 0.75 γC–H 59γCH+22γCCC
A" 818 w 808 m 813 797 1.01 0.135 814 798 0.97 816 800 1.16 0.08 γC–H 63γCH + 12γCCC
A" 777 vs 768 753 51.82 0.000 774 759 42.78 774 759 33.14 0.75 γO–H 67γOH+18γCH
230
A' 746 m 738 vw 744 729 9.69 0.002 755 740 11.48 744 729 8.61 0.75 βCCC 62CCC+24CH
A' 622 m 617 vw 640 627 4.02 0.045 641 628 4.55 639 626 4.70 0.72 βCCC 59βCCC + 24βCH
A' 594 582 10.77 0.015 594 582 9.44 592 580 9.75 0.34 βC–C 62βCC + 18βOH
A' 469 w 464 m 470 461 2.00 0.005 479 469 1.46 476 466 0.27 0.75 βCNC 70βCNC + 15βCH
A' 426 m 421 vw 440 431 0.60 0.041 441 432 0.51 441 432 0.48 0.37 βC–O 63CO+14CC
A" 389 w 414 406 2.71 0.002 418 410 1.87 416 408 1.67 0.75 γCCC 65γCCC + 12γCH
A" 228 m 227 222 11.08 0.001 228 223 9.26 229 224 72.20 0.23 γCCC 59γCCC + 14γCH
A" 215 m 192 188 0.01 0.025 220 216 56.13 227 222 9.58 0.75 γCNC 57γCNC + 18γCH
A" 136 133 97.74 0.002 181 177 61.26 180 176 58.17 0.75 γC–O 60γCO + 22γCC A" 37 37 49.68 0.035 68 68 11.80 53 53 15.76 0.75 γC–C 63γCC + 18γCCC
aν–stretching; β–in–plane bending; δ–deformation; ρ–rocking; γ–out of plane bending; ω–wagging and τ–twisting/torsion, wavenumbers (cm–1);
IR intensities (km/mol) and Raman intensities (Å)4/(a.m.u).
231
Table 6.5. The observed FTIR, FT–Raman and calculated frequencies determined by B3LYP method with 6–31G**, 6–311++G** and cc–pVTZ basis sets along
with their relative intensities, probable assignments and potential energy distribution (PED) of 3–(hydroxymethyl)pyridinea.
Spec
ies
Observed
wavenumber (cm–1)
B3LYP/6–311++G**
Calculated wavenumber
B3LYP/cc–pVTZ
Calculated wavenumber
B3LYP/6–31G**
Calculated wavenumber
Dep
olar
izat
ion
ratio
Ass
ignm
ent
%PE
D
FTIR
FTR
Uns
cale
d
(cm
–1)
Scal
ed
(cm
–1)
IR in
tens
ity
Ram
an
inte
nsity
Uns
cale
d
(cm
–1)
Scal
ed
(cm
–1)
IR in
tens
ity
Uns
cale
d
(cm
–1)
Scal
ed
(cm
–1)
IR in
tens
ity
A' 3365 b 3857 3356 50.89 1.730 3842 3343 44.69 3840 3341 26.76 0.27 νO–H 90OH
A' 3083 b 3208 3080 2.77 1.124 3211 3083 3.28 3229 3100 3.01 0.16 νC–H 90CH
A' 3056 s 3182 3055 15.60 1.596 3184 3057 16.43 3200 3072 19.05 0.30 νC–H 92CH
A' 3032 b 3152 3026 12.76 1.138 3150 3024 15.68 3166 3039 19.10 0.40 νC–H 94CH
A' 3000 b 2995 w 3122 2997 28.66 1.069 3119 2994 30.64 3136 3011 33.47 0.30 νC–H 93CH
A' 2926 vs 2936 w 3002 2882 32.83 0.969 2995 2875 36.24 2994 2874 55.02 0.75 νaCH2 91CH2
A' 2858 vs 2858 m 2979 2860 42.08 2.000 2974 2855 41.49 2972 2853 45.49 0.07 νsCH2 92CH2
A' 1596 s 1590 m 1633 1600 2.14 0.239 1636 1603 1.92 1652 1619 2.54 0.59 νC=C 89CC
A' 1578 vs 1569 w 1614 1582 21.14 0.081 1618 1586 20.05 1631 1598 20.80 0.60 νC=C 90CC
A' 1480 s 1470 vw 1512 1482 2.79 0.017 1518 1488 6.87 1528 1497 0.15 0.69 νC=N 94CC
232
A' 1462 vw 1507 1477 17.50 0.137 1512 1482 13.24 1523 1493 19.20 0.57 νC–C 92CN
A' 1463 1434 8.92 0.018 1469 1440 5.21 1477 1447 5.58 0.75 νC–C 89CC
A' 1418 vs 1412 vw 1431 1402 26.25 0.115 1439 1410 31.80 1446 1417 35.84 0.44 δCH2 85CH2
A' 1327 m 1363 1336 7.72 0.009 1370 1343 8.28 1371 1344 8.91 0.32 νC–N 86CN
A' 1300 1274 7.28 0.039 1301 1275 8.49 1322 1296 8.69 0.32 νC–C 87CC
A' 1259 1234 0.02 0.081 1262 1237 0.24 1259 1234 0.27 0.75 βC–H 65βCH + 16βCCC
A' 1222 s 1225 w 1245 1220 0.92 0.083 1248 1223 1.41 1253 1228 4.38 0.61 βO–H 70βOH + 16βCO
A' 1191 m 1189 w 1211 1187 3.74 0.072 1213 1189 4.79 1220 1196 4.58 0.12 βC–H 61βCH + 18βCCC
A' 1132 m 1123 vw 1188 1164 78.53 0.048 1195 1171 67.85 1200 1176 81.55 0.31 βC–H 62βCH + 16βCCC
A' 1110 m 1102 w 1139 1116 3.38 0.039 1142 1119 3.21 1146 1123 3.57 0.40 νC–O 73CO
A" 1063 vs 1069 1048 24.37 0.121 1073 1052 30.55 1091 1069 51.17 0.15 βC–H 62βCH + 15βCCC
A' 1030 vs 1036 vs 1057 1036 36.19 0.247 1062 1041 25.62 1069 1048 7.52 0.04 ωCH2 56ωCH2 + 18γOH
A" 1038 1017 28.20 0.144 1053 1032 0.01 1052 1031 0.10 0.06 γC–H 60γCH+14γCCC
A" 1034 1013 0.01 0.001 1043 1022 31.62 1039 1018 18.32 0.75 γC–H 63γCH + 12γCCC
A' 998 978 0.22 0.000 1015 995 0.14 1002 982 0.46 0.75 ρCH2 69ρCH2+15CC
A" 952 vw 943 vw 959 940 0.18 0.000 969 950 0.31 963 944 0.69 0.75 tCH2 55tCH2+22ωCH2
A" 921 vw 928 vw 933 914 0.33 0.002 947 928 0.42 944 925 0.23 0.75 γC–H 59γCH+22γCCC
A" 824 m 814 w 810 794 6.48 0.131 811 795 6.68 812 796 7.72 0.07 γC–H 61γCH + 12γCCC
233
A" 793 vs 790 w 796 780 34.03 0.004 809 793 25.07 806 790 21.75 0.75 γO–H 69γOH+16γCH
A' 709 vs 706 vw 723 709 23.51 0.002 735 720 24.92 728 713 15.90 0.75 βCCC 56CCC+24CH
A' 640 s 631 w 647 634 9.23 0.044 648 635 9.72 646 633 9.88 0.67 βCCC 57βCCC + 18βCH
A' 603 m 598 vw 596 584 3.87 0.028 597 585 2.70 596 584 2.71 0.57 βC–C 60βCC + 16βOH
A' 450 441 0.01 0.002 465 456 0.10 462 453 1.00 0.75 βCNC 67βCNC + 14βCH
A' 406 m 400 w 417 409 3.10 0.040 418 410 2.89 418 410 2.80 0.29 βC–O 63CO+14CC
A" 391 vw 404 396 4.82 0.001 412 404 4.22 410 402 3.25 0.75 γCCC 60γCCC + 12γCH
A" 224 220 7.07 0.001 232 227 67.04 239 234 78.21 0.52 γCCC 55γCCC + 21γCH
A" 195 191 1.12 0.035 225 221 5.71 225 221 6.16 0.75 γCNC 57γCNC + 18γCH
A" 163 vw 141 138 92.72 0.005 186 182 41.06 185 181 41.97 0.75 γC–O 56γCO + 20γCC A" 59 59 48.31 0.026 18 18 15.64 35 33 20.04 0.75 γC–C 58γCC + 16γCCC
aν–stretching; β–in–plane bending; δ–deformation; ρ–rocking; γ–out of plane bending; ω–wagging and τ–twisting, wavenumbers (cm–1);
IR intensities (km/mol) and Raman intensity (Å)4/(a.m.u).
234
References
[1] Th. Zeegers–Huyskens, P. Huyskens, H. Ratajczak, W.J.Orville–Thomas (Eds.), Molecular Interactions, vol. 2, Wiley, Chichester, UK, 1981, p. 1.
[2] E.N. Gur'yanova, I.P. Gol'dshtein, T.I. Perepelkova, Rus. Chem. Rev. 45 (1976) 792.
[3] S. Tomaru, S. Matsumoto, T. Kurihara, H. Suzuki, N. Oobara, T. Kaino, Appl. Phys. Lett. 58 (1991) 2583.
[4] C. Kaneko, S. Yamada, I. Yokoe, N. Hata, Y. Ubata, Tetrahedron Lett. 7 (1966) 4729.
[5] C. Kaneko, I. Yokoe, S. Yamada, Tetrahedron Lett. 8 (1967) 775.
[6] N. Hata, E. Okutsu, I. Tanaka, Bull. Chem. Soc. Jpn 41 (1968) 1769.
[7] N. Hata, I. Ono, T. Tuchiya, Bull. Chem. Soc. Jpn 45 (1972) 2386.
[8] I. Ono, N. Hata, Bull. Chem. Soc. Jpn 45 (1972) 2951.
[9] D. Dop1p, in: Topics in Current Chemistry, Davidson (Ed.) Vol. 55, Springer, Berlin, 1975, p. 49.
[10] K.C. Medhi, R.N. Medhi, Spectrochim. Acta 49A (1993) 1024.
[11] S.P. Jose, S. Mohan, Spectrochim. Acta 64A (2006) 240.
[12] Kirk–Othmer Encyclopedia of Chemical Technology, 4th Ed. 1997, p. 20.
[13] P. Pierrat, P.C. Gros, Y. Fort, J. Comb. Chem. 7 (2005) 879.
[14] J.H.S. Green, W. Kynaston, H.M. Paisley, Spectrochim. Acta 19A (1963) 549.
[15] V. Sortur, J. Yenagi, J. Tonannavar, Spectrochim. Acta 69A (2008) 604.
[16] S. Mohan, R. Murugan, Ind. J. Pure Appl. Phys. 30 (1992) 283.
[17] V. Krishnakumar, R. John Xavier, Spectrochim. Acta 61A (2005) 253.
[18] V. Krishnakumar, S. Dheivamalar, R.J. Xavier, V. Balachandran, Spectrochim. Acta 65A (2006) 147.
[19] N. Sundaraganesan, S. Ilakiamani, H. Saleem, P.M.Wojciechowski, D. Michalska, Spectrochim. Acta 61A (2005) 2995.
[21] R.N. Medhi, R. Barman, K.C. Medhi, S.S. Jois, Spectrochim. Acta 56A (2000) 1523.
[23] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
[24] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[22] P. Hohenberg, W. Kohn, Phys. Rev. 136 (1964) B864.
[25] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, J.A. Montgomery, Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G.
235
Scalmani, N. Rega, G.A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al–Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson,W. Chen, M.W.Wong, C. Gonzalez, J.A. Pople, Gaussian Inc.,Wallingford, CT, 2004.
[26] H.B. Schlegel, J. Comput. Chem. 3 (1982) 214.
[27] Z. Dega–Szafran, A. Katrusiak, M. Szafran, J. Mol. Struct. 741 (2005) 1.
[28] W.J. Hehre, L. Radom, P.V.R. Schleyer, A.J. Pople, Ab initio Molecular Orbital Theory, Wiley, New York, 1989.
[29] E.B. Wilson Jr., J. Chem. Phys. 7 (1939) 1047.
[30] E.B. Wilson Jr., J. Chem. Phys. 9 (1941) 76.
[31] E.B. Wilson Jr., J.C. Decius, P.C. Cr oss, Molecular Vibrations, McGraw Hill, New York, 1955.
[32] H. Fuhrer, V.B. Kartha, K.L. Kidd, P.J. Kruger, H.H. Mantsch, Computer Program for Infrared and Spectrometry, Normal Coordinate Analysis, Vol. 5, National Research Council, Ottawa, Canada, 1976.
[33] A. Domenicano, A. Vaciago, Acta Crystallogr. B 35 (1979) 1382.
[34] C.W. Bock, M. Trachtman, P. George, J. Mol. Struct.(Theochem.) 139 (1986) 63.
[35] G.H. Penner, P. George, C.W. Bock, J. Mol. Struct.(Theochem.) 152 (1987) 201.
[36] M. Colapietro, A. Domenicano, G. Portalone, Gy. Schultz, I. Hargittai, J. Mol. Struct. 112 (1984) 141.
[37] M. Colapietro, A. Domenicano, G. Portalone, I. Torrini, I. Hargittai, Gy. Schultz, J. Mol. Struct. 125 (1984) 19.
[38] M. Colapietro, A. Domenicano, G. Portalone, Gy. Schultz, I. Hargittai, J. Phys. Chem. 91 (1987) 1728.
[39] G. Portalone, A. Domenicano, Gy. Schultz, I. Hargittai, J. Mol. Struct. 160 (1987) 97.
[40] A. Domenicano, I. Hargittai, G. Portalone, Gy. Schultz, Acta Chem. Scand. Ser. 42A (1988) 460.
236
[41] L.M. Sverdlav, M.A. Kovner, E.P. krainov, Vibrational Spectra of Polyatomic Molecules, Nauka, Moscow, 1970.
[42] S.D. Sharma, S. Doraiswamy, Chem. Phys. Lett. 41 (1976) 192.
[43] P.C. Chen, Y.C. Chieh, J. Mol. Struct. (Theochem) 583 (2002) 173.
[44] A.E. Reed, F. Weinhold, J. Chem. Phys. 83 (1985) 1736.
[45] J.M. Seminario, Recent Developments and Applications of Modern Density Functional Theory, Vol.4, Elsevier, pp. 800–806, 1996.
[46] R.H. Petrucci, W.S. Harwood, F.G. Herring, J.D. Madura, General Chemistry: Principles & Modern Applications, 9th Ed. New Jersey: Pearson Education, Inc., 2007.
[47] I.G. Csizmadia, Theory and Practice of MO Calculations on Organic Molecules, Elsevier, Amsterdam, 1976.
[48] A.E. Frisch, H.P. Hratchian, R.D. Dennington II, etal., GaussView, Version 5.0.8, Gaussian Inc., 235 Wallingford CT, 2009.
[49] L.J. Bellamy, The Infrared Spectra of Complex Molecules, 3rd Ed., Wiley, New York, 1975.
[50] G. Varsanyi, Assignments for Vibrational Spectra of Seven Hundred Benzene Derivatives, Vol. I, Adam Hilger, London, 1974.
[51] W.J. Balfour, D. Ristic−Petrovic, J. Phys. Chem. 97 (1993) 11643.
[52] F.S. Mortimer, R.B. Blodgett, F. Daniels. J. Am. Chem. Soc. 69 (1947) 822.
[53] N. Puviarasan, V. Arjunan, S. Mohan, Turk. J. Chem. 26 (2002) 323.
[54] V. Arjunan, N. Puviarasan, S. Mohan, Spectrochim. Acta 64A (2006) 233.
[55] V. Arjunan, M. Kalaivani, P. Ravindran, S. Mohan, Spectrochim. Acta 79A (2011) 1886.
[56] V. Arjunan, S. Mohan, P. Ravindran, C.V. Mythili, Spectrochim. Acta 72A (2009) 783.
[57] R.M. Silverstein, G.C. Bassler, T.C. Morrill, Spectrometric Identification of Organic Compounds, 5th Ed., John Wiley & Sons, Inc., New York, 1981.
[58] J.A. Pople, H.B. Schlegel, R. Krishnan, D.J. Defrees, J.S Binkley, M.J. Frish, R.A. Whitside, R.H. Hout, W.J. Hehre, Int. J. Quantum Chem. Quantum Chem. Symp. 15 (1981) 269.
[59] V. Arjunan, S. Mohan, J. Mol. Struct. 892 (2008) 289.
[60] V. Arjunan, S. Mohan, Spectrochim. Acta 72A (2009) 436.
[61] H.F. Hameka, J.O. Jensen, J. Mol. Struct. (Theochem.) 362 (1996) 325.
[62] J.O. Jensen, A. Banerjee, C.N. Merrow, D. Zeroka, J.M. Lochner, J. Mol. Struct. (Theochem.) 531 (2000) 323.
237
[63] A.P. Scott, L. Radom, J. Phys. Chem. 100 (1996) 16502.
[64] M.P. Andersson, P. Uvdal, J. Chem. Phys. A 109 (2005) 2937.
[65] M. Alcolea Palafox, M. Gill, N.J. Nunez, V.K. Rastogi, Lalit Mittal, Rekha Sharma, Int. J. Quant. Chem. 103 (2005) 394.
[66] M. Alcolea Palafox, Int. J. Quant. Chem. 77 (2000) 661.
[67] V. Arjunan, P. Ravindran, T. Rani, S. Mohan, J. Mol. Struct. 988 (2011) 91.
