A thermal study of some Schiff bases derivative of α-napthylamine

Article abstract of DOI:10.1134/S0036024408090355

Thermal analyses of some Schiff bases, derivative of α-napthylamine, were performed by the DSC, TG and DTA techniques. The thermograms were used to determine various kinetic parameters, such as the order of degradation (n), energy of activation (E), frequ

Full text of DOI:10.1134/S0036024408090355

ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2008, Vol. 82, No. 9, pp. 1601–1604. © Pleiades Publishing, Ltd., 2008.
SHORT
COMMUNICATIONS
A Thermal Study of Some Schiff Bases Derivative
of a-Napthylamine1
Shipra Baluja, Nirmal Pandya, and Nayan Vekariya
Department of Chemistry, Saurashtra University Gujarat, India
e-mail: shkundal_ad1@sancharnet.in
Received September 3, 2007
Abstract—Thermal analyses of some Schiff bases, derivative of α-napthylamine, were performed by the DSC,
TG and DTA techniques. The thermograms were used to determine various kinetic parameters, such as the order
of degradation (n), energy of activation (E), frequency factor (A), and entropy change (∆S), by the Freeman-
Carroll method.
DOI: 10.1134/S0036024408090355
INTRODUCTION
All these compounds were characterized by their IR,
NMR, and mass spectra.
Thermal analysis has become an established method
in studies of the thermal behavior of materials and finds
wide applications in diverse industrial and research
fields [1–5]. Thermal analysis of a number of materials
such as drugs, ceramics, composites, geologic materi-
als, biological materials, polymers, polyurethanes, and
other organic and inorganic compounds has been
reported [6–12]. Varied kinetic information can also be
obtained from differential thermal analysis [13, 14]. In
the present paper, the thermal properties of some Schiff
bases of α-naphthylamine are reported.
The differential scanning calorimetry (DSC), ther-
mogravimetric analysis (TG), and differential thermal
analysis (DTA) measurements of all the Schiff bases
were taken on a Universal V 2.6D TA Instrument unit at
a heating rate of 10 K/min in the nitrogen atmosphere.
RESULTS AND DISCUSSION
The figure shows the TG/DTA and DSC thermo-
grams for NDP-1. Various thermal properties such as
the initial decomposition temperature (IDT), the
decomposition temperature range, and maximum deg-
radation along with the percentage weight loss and exo-
thermic/endothermic transitions of all the synthesized
Schiff bases are reported in Table 1. The experimental
melting points are also given for comparison.
EXPERIMENTAL
Various Schiff bases were synthesized by the con-
densation of α-napthylamine with aldehydes,
It follows from Table 1 that the initial decomposi-
tion temperature is minimum for NDP-1 and maximum
for NDP-8. However, weight loss is minimum for
NDP-3 and NDP-7. Maximum weight loss is observed
for NDP-8. Only NDP-8 decomposes in two steps. The
weight loss values decrease in the series NDP-8 >
NDP-6 > NDP-10 > NDP-1 > NDP-5 > NDP-9 >
NDP-2 > NDP-4 > NDP-3, NDP-7. Thus, NDP-8,
which appears to be thermally stable, loses maximum
weight when decomposes. The temperature of maxi-
mum degradation is highest for NDP-5 followed by
NDP-8. NDP-7 and NDP-9 have the lowest maximum
degradation temperatures. On the whole, all Schiff
bases show maximum degradation between 274.7 and
342.2°C. The thermal stability of a compound depends
on the type of groups and structure. In the Schiff bases
studied, the central moiety is the same, but side chains
are different. In NDP-8, side chain is furfuraldehyde,
whereas it is benzaldehyde in NDP-1. Hence, the pres-
ence of benzaldehyde decreases stability.
NH2
N CH R
+ RCHO
where R =
NDP-1
NDP-2
NDP-3
NDP-4
NDP-5
OH O
CH3
NDP-8
O N
2
O2N
NDP-6
NDP-7
NDP-9
NDP-10
F
O
HO
Cl
NO2
1
The text was submitted by the authors in English.
1601

1602
BALUJA et al.
100
0.4
0.2
TGA–DTA
26.04°C
100.0 %
172.12°C
98.52 %
80
60
232.20°C
0.2807°C min/mg
83.13°C
0.2021°C min/mg
0
696.90°C
40
20
87.85°C
–0.2
299.37°C
4.448%
–0.4
0
0.5
100
200
300
400
500
600
T, °C
DSC
62.15°C
85.20 J/g
0
–0.5
–1.0
–1.5
–2.0
–2.5
67.92°C
0
100
200
300
T, °C
TGA/DTA and DSC graph for NDP-1.
A = (kBT/h)e∆S/R
,
(3)
The experimental melting points are also compared
with those observed by the DSC and DTA methods. It
was found that, for some Schiff bases, the experimental
values were in close agreement with the results of DSC
and DTA measurements.
The following Freeman–Carroll equation [15] was dation (n), activation energy (E), frequency factor (A),
used to determine the kinetic parameters:
where kB is the Boltzmann constant and h is the Planck
constant. Other symbols have their usual meanings.
The kinetic parameters, such as the order of degra-
and entropy change (∆S), are reported in Table 2 along
with the correlation coefficients (γ). Table 2 shows that,
for all the Schiff bases, the order of the reaction (n) is
larger than one and is maximum for NDP-2. The activa-
tion energy decreases in the series NDP-3 > NDP-7 >
NDP-9 > NDP-10 > NDP-2 > NDP-5 > NDP-8 (first
step) > NDP-6 > NDP-4 > NDP-1. The frequency fac-
tor A is also maximum for NDP-3 and NDP-7 and min-
imum for NDP-1. On the whole, A varies over a wide
range. It decreases in the same order as activation
energy. Entropy changes (∆S) are positive for all the
Schiff bases, which indicates that the transition state is
a less ordered state. The entropy of Schiff bases
decreases in the series NDP-7 > NDP-3 > NDP-9 >
ln(dC/dt)/ln(1 – C) = n – E/R[(1/T)/(∆ln(1 – C)], (1)
where dC/dT is the rate of conversion of the initial
material, C is the degree of conversion, n is the order of
degradation reaction, E is the activation energy, and T
is the absolute temperature. A plot of the left-hand side
of (1) against ∆(1/T)/[∆ln(1 – C)] gives a straight line
with a slope of –E/R, and the intercept gives n.
The frequency factor (A) and entropy change (∆S)
are determined by the equations
lnE – ln(RT2s ) = lnA – lnβ – E/RT2s ,
(2)
where Ts is the temperature of maximum decomposi- NDP-10 > NDP-2 > NDP-5 > NDP-8 (first step) >
tion and β is the rate of heating;
NDP-6 > NDP-4 > NDP-1.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 82 No. 9 2008

A THERMAL STUDY OF SOME SCHIFF BASES DERIVATIVE OF α-NAPTHYLAMINE
Table 1. Thermal data for the Schiff bases
1603
Residual Temp. of
DSC
temp.,
°C
DTA
temp.,
°C
Exp.
Comp. Amt., IDT,
Decomp.
Transi-
tion
% wt loss Wt. loss, max. deg-
I.M.P,
code
NDP-1
NDP-2
NDP-3
NDP-4
NDP-5
mg
°C
range, °C
mg
radation
°C
11.84 139.81 139.81–279.06
13.04 172.12 172.12–299.37
10.77 186.41 186.41–298.07
10.38 207.40 207.40–321.82
13.02 192.90 192.90–342.22
13.29
4.45
1.5736
279.06 Endo
Endo
67.92
68.19
270.97
85
0.5799
0.0890
0.0931
1.6374
299.37 Endo
Endo
85.94
87.85
296.90
89
0.83
298.07 Endo
Endo
148.37
82.10
148.93
296.77
144
80
0.90
321.82 Endo
Endo
85.20
320.11
12.58
342.22 Endo
Endo
138.88
141.20
334.65
130
NDP-6
NDP-7
10.48 212.38 212.38–295.48
10.36 163.04 163.04–274.70
64.94
0.83
6.8088
0.0860
295.48 Endo
214.77
126.69
217.70
204
122
274.70 Endo
Endo
127.50
273.81
NDP-8
NDP-9
10.13 220.17 220.17–333.13
12.04 173.42 173.42–274.70
76.76
8.94
7.7776
1.0757
2.9421
333.13 Endo
179.73
89.85
78.10
215.08
193
85
274.70 Endo
Endo
98.71
269.26
NDP-10 13.18 179.91 179.91–311.06
22.32
311.06 Exo
Endo
83.48
82.21
104
Table 2. Kinetic parameters for Schiff bases
Compound
n
E, kJ
A, s–1
∆S
γ
NDP-1
NDP-2
NDP-3
NDP-4
NDP-5
NDP-6
NDP-7
NDP-8
2.44
5.57
3.64
3.41
3.25
3.11
1.56
8.85
266.26
494.78
14.23
0.11
9.07 × 1023
1.52 × 1045
0.40
231.92
708.97
1115.26
243.15
621.32
290.82
1137.90
0.95
0.98
1.00
0.97
0.98
0.99
1.00
233.30
36.09
2.23 × 1019
131.05
2.41 × 1046
486.83
Step-I 3.72
Step-II 2.31
105.24
33.47
1.9 × 108
409.29
266.48
0.99
0.98
5.06
NDP-9
1.25
3.16
423.32
288.66
1.85 × 1040
3.1 × 1025
1020.82
738.51
1.00
0.99
NDP-10
Thus, the thermal properties suggest that thermal
stability depends on the type of substituents present.
The presence of benzaldehyde as a side chain decreases
stability, whereas the presence of 4-hydroxybenzalde-
hyde increases it.
REFERENCES
1. S. R. Bharadwaj, R. Mishra, M. Ali, et al., J. Nucl. Mater.
275, 201 (1999).
2. L. Bond, S. Allen, M. C. Davis, et al., Int. J. Pharm. 243,
71 (2002).
3. K. Six, J. Murphy, I. Wents, et al., Pharm. Res. 20, 135
ACKNOWLEDGMENTS
(2003).
The authors are thankful to Head of Chemistry
Department for providing the necessary facilities.
4. M. Gaber, M. M. Ayad, and Y. S. Y. El Sayad, Spectro-
chim. Acta, Part A 62, 694 (2005).
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 82 No. 9 2008

1604
BALUJA et al.
5. P. G. Avaji, S. A. Patil, and P. S. Badami, J. Trans. Met. 10. R. K.Verma, L. Verma, M. Chandra, and A. Bhusan,
Chem. 32, 379 (2007).
J. Therm. Anal. Calorimetry 80, 351 (2005).
11. I. Cianga and M. Ivanolu, Eur. Polym. J. 42, 1922
6. D. F. Giron, C. Goldbronn, and P. Piechon, J. Pharm.
(2006).
Boimed. Anal. 7, 1421 (1989).
12. Z. Chu and W. Huang, J. Mol. Struct. 837, 15 (2007).
7. H. Y. Low and H. Ishida, J. Polym. Sci., Part B: Polym.
Phys. Mech. 36, 1935 (1998).
13. M. D. Taylor and R. Panayappan, J. Therm. Anal. 6, 673
(1974).
8. N. Ozpozan, H. Arslan, T. Ozpozan, et al., J. Therm.
Anal. Calorimetry 61, 955 (2000).
14. R. H. Still, Br. Polym. J. 11, 101 (1979).
9. R. Mandali, J. Gangopadhyay, and S. C. Lahiri, Z. Phys. 15. E. S. Freeman and B. Carroll, J. Phys. Chem. 62, 394
Chem. 218, 551 (2004).
(1958).
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 82 No. 9 2008