International Journal of ChemTech Research
CODEN( USA): IJCRGG ISSN : 0974-4290
Vol.1, No.4, pp 1182-1185, Oct-Dec 2009
Microwave assisted synthesis of some Schiff bases on
NaY zeolite: A green chemical approach
Manish K. Rawal, Amit Sahu, Rakshit Ameta#, V.K. Sharma and Pinki B. Punjabi1*
*Microwave Chemistry Laboratory, Department of Chemistry, University College of
Science, Mohanlal Sukhadia University,Udaipur – 313 001 (Raj.), INDIA
# Department of Chemistry, Kota University, Kota (Raj.), India
*E-mail- pb_punjabi@yahoo.com
ABSTRACT: An efficient, extremely fast and ecofriendly method for the synthesis of some Schiff bases of p-
aminobenzoic acid over NaY zeolite under microwave irradiation has been reported. A considerable increase in the
reaction rate has been observed with reasonable good yield. Zeolite acts as a solid support as well as catalyst for the
synthesis of Schiff bases.
Key Words: NaY zeolite, Schiff bases, p-aminobenzoic acid, microwave.
INTRODUCTION
Zeolites are micro porous, crystalline aluminosilicates For example; it avoids use of expensive and toxic
made up of corner-sharing SiO4 and AlO4 tetrahedra. By solvents which are hazardous and causes severe health
virtue of their structure, crystalline and variable problems. On the other hand, solvent free conditions
stoichiometry, zeolite catalysts have well defined pore offer green chemical route for synthesis of organic
size distribution, high and adjustable acidity, very high compounds. This paper describes the synthesis of some
surface area and good thermal stability1. Due to presence Schiff bases of p-aminobenzoic acid using NaY zeolite as
of high surface area, thermal stability and tunable a solid support and an efficient acid catalyst under
acidity2-5, zeolites can potentially replace solvents and microwave irradiation. The work is solvent free and
conventional corrosive liquid acids in many of their therefore, environment benign and operationally simple
applications6-11. The utility of zeolites as selective method for synthesis.
adsorbents and as catalysts for petrochemical processes
has also been reported12-13. EXPERIMENTAL
Schiff bases derived from aromatic amines and aromatic General Procedure:
aldehydes have a wide variety of applications in many All the reactions were carried out in a domestic
fields e.g., biological, inorganic and analytical microwave oven (Kenstar, Model No. OM-26 E 60,
chemistry14-18. In recent years, the acceleration of a wide Power-1200 W). Melting points were determined in open
range of chemical reactions using microwave dielectric capillaries and are uncorrected. Reactions were
heating has been reported19. The solvent free conditions monitored by thin layer chromatography using silica gel-
under microwave irradiation offer several advantages. G as adsorbent. TLC plates were prepared by spreading
*Corres.author: method. These were dried in the air and then activated by
Dr. Pinki B. Punjabi heating in hot air oven at 110°C for 30 min. Iodine
Asstt. Professor, vapours were used for visualization of TLC plates. IR
Department of Chemistry, spectra (KBr pellets) were recorded on perkin-Elmer
University College of Science, 1800 (FTIR) Spectrometer. 1HNMR spectra were
recorded on Jeol JNM FX 100 FTNMR Spectrometer
M. L. Sukhadia University, Udaipur- 313 001 (Raj.)
India (chemical shifts in d) in DMSO-d6 using TMS as internal
reference. Mass spectra were recorded on a Jeol SX-
E-mail- pb_punjabi@yahoo.com
102/DA 6000 mass spectrometer.
Pinki B. Punjabi et al /Int.J. ChemTech Res.2009,1(4) 1183
HOOC NH2 OHC R
+
1
2a-f
MW Zeolite NaY
4-5 min.
HOOC N CH R
3a-f
R = H, OH, NO2, Cl, F, OCH3
Typical procedure for the synthesis of Schiff bases: zeolite), the reaction time is reduced, but still solvent and
Benzaldehyde (0.01mol) and 4.0g zeolite NaY were acetic acid have to be used, which are expensive, toxic
mixed together using a pastel and mortar. Then p- and create the problem of waste disposal of solvent.
aminobenzoic acid (0.01mol) was added and transferred However, present work making the use of NaY zeolite,
in an Erlenmeyer flask with a funnel as loose top and both the acetic acid and solvent have been avoided and
irradiated under microwave irradiation for 5 minutes. reaction time has also been found to be reduced as
After irradiation product was separated from zeolite using compared to conventional and microwave (without using
ethanol by stirring for 15 minutes on magnetic stirrer. NaY zeolite) methods. The yield of products was also
Then the reaction mixture was filtered and product was increased. Therefore, the present work may be regarded
obtained by evaporating the filtrate. The resulting solid as a green approach under solvent free conditions. The
was recrystallized from ethanol. Catalyst was reused after reaction has been carried out by grinding appropriate
washing with ethanol, drying in air overnight. Similarly, reactants with zeolite NaY and then exposing the reaction
other compounds (3b-f) were also synthesized. mixture under microwave irradiation. The progress of
reaction was monitored by thin layer chromatography.
RESULTS AND DISCUSSION Structures of compounds were characterized by IR, NMR
and mass spectral data (Table - 3). A comparison of time
Conventional method for the synthesis of these required for synthesis and yield of products in
compounds requires 10-15 hours reflux and suitable conventional and microwave method (with and without
solvents with catalytic amount of acetic acid. Thus, use of zeolite NaY) has been reported in Table-1. Zeolite
conventional method is time taking and therefore, these catalyst can be reused by simple washing it with ethanol
are not ecofriendly. However, when the same reaction and drying in air overnight.
was carried out in microwave (without using NaY
Pinki B. Punjabi et al /Int.J. ChemTech Res.2009,1(4) 1184
Table-1 Physical data of synthesized compounds
Yield (%) & Yield (%) & Mol. Formula
Com Yield (%)
[ Time] [ Time] Mol.
p. R M. P. [ Time]
(Conventiona (MW Weight
N0. (NaY zeolite)
l) Solvent)
3a H 178 0C 75 (6 hr.) 85 [9 min] 90 [5 min] 225 C14H11NO2
3b OH 190 0C 65 (6 hr.) 72 [9 min] 80 [5 min] 241 C14H11NO3
3c NO2 167 0C 80 (5 hr.) 88 [8 min] 95 [4 min] 270 C14H10N2O4
3d Cl 1850C 77 (6 hr.) 88 [9 min] 92 [5 min] 259 C14H10Cl NO2
3e F 1550C 77 (5 hr.) 90 [8 min] 95 [4 min] 243 C14H10FNO2
3f OCH3 198 0C 75 (6 hr.) 86 [9 min.] 92 [5 min] 255 C15H13NO3
Table 2: Elemental Analysis of Synthesized Compounds
Compd. No. Calculated /Found (%)
C H N
3a 74.65/74.62 4.92/4.88 6.22/6.15
3b 69.70/69.67 4.60/4.58 5.81/5.77
3c 62.22/62.20 3.73/3.70 10.37/10.38
3d 64.75/64.69 3.88/3.82 5.39/5.36
3e 69.13/69.11 4.14/4.11 5.76/5.73
3f 70.58/70.57 5.13/5.11 5.49/5.45
Table 3: Spectral data of synthesized compounds
Comp.
Spectral Data
No.
-1
IR (cm ): 3450 (-OH str., COOH), 1690 (C=O str.), 1631 (C=N str.), 3020 (Ar-H str.)
3a
1
H NMR (d): 10.22 (s,1H, OH), 8.31 (s,1H, CH==N), 7.0-8.0 (m, 4H, Ar-H)
MS(m/z): 225 (M+), 148, 135, 104
3b IR (cm-1): 3456 (-OH str.), 1698 (C=O str.), 1625 (C=N str.), 3025 (Ar-H str.)
1
HNMR (d): 10.22 (s, 1H, OH), 8.30 (s, 1H, CH==N), 7.0-8.1 (m, 4H, Ar-H)
MS(m/z): 241 (M+), 148,135,120
3c IR (cm-1): 3440 (-OH str., COOH), 1685 (C=O str.), 1640 (C=N str.), 3030 (Ar-H str.), 1550,
1390 (-NO2 symm. and asymm. Str.)
1
H NMR (d): 10.22 (s, 1H, OH), 8.32 (s, 1H, CH==N), 6.9-8.0 (m, 4H, Ar-H)
MS(m/z): 270(M+), 148, 135, 149
3d IR (cm-1): 3444 (-OH str., COOH), 1694 (C=O str.), 1635 (C=N str.), 3025 (Ar-H str.), 742 (C-
Cl str.)
1
H NMR (d): 10.22 (s, 1H, OH), 8.28 (s, 1H, CH==N), 7.1-8.1 (m, 4H, Ar-H)
MS(m/z): 260 (M +1), 259 (M+), 148, 135, 138
3e IR (cm-1): 3445 (-OH str., COOH), 1691 (C=O str.), 1625 (C=N str.), 3015 (Ar-H str.), 1095 (C-
F str.)
1
H NMR (d): 10.22 (s, 1H, OH), 8.30 (s, 1H, CH==N), 7.2-8.0 (m, 4H, Ar-H)
MS(m/z): 243(M+),148, 135, 118
3f IR (cm-1): 3454 (-OH str., COOH), 1696 (C=O str.), 1628 (C=N str.), 3025 (Ar-H str.), 1181 (C-
O-CH3 str.)
1
H NMR (d): 10.22 (s, 1H, OH), 8.30 (s, 1H, CH==N), 7.0-8.1 (m, 4H, Ar-H), 3.74 (-OCH3)
MS(m/z): 255 (M+), 148, 135, 143.
Pinki B. Punjabi et al /Int.J. ChemTech Res.2009,1(4) 1185
ACKNOWLEDGEMENTS 9. Bllini R.; Bordono M; Bosica G.; Maggi R.and Sartori
The authors are thankful to Head, Department of G.; Tetrahedron Lett., 1998, 39, 6049.
Chemistry, Mohanlal Sukhadia University, Udaipur 10. (a) Ballini R.; Bosica G.; Frullanti B.; Maggi R.;
(Raj.) for providing necessary laboratory facilities. Sartori G.and Schroce F.; 1998, 39, 1615.
Authors also pay their thanks to the Director, RSIC, (b) Corma A.; Climent M. I.; Carcia H.and Primo J.;
CDRI, Lucknow for analytical and spectral studies. Applied Catalysis, 1990, 59, 333.
11.Ballini R.; Bordani M.; Bosica G.; Maggi R.and
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