Der Pharma Chemica
Journal for Medicinal Chemistry, Pharmaceutical Chemistry, Pharmaceutical Sciences and Computational Chemistry

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Research Article - Der Pharma Chemica ( 2018) Volume 0, Issue 0

Microwave Assisted Synthesis, Physicochemical & Spectral Characterization of Common Molecules

Ambatkar MP1*, Rathi LG2, Rokde VV1, Danao KR1 and Mahajan UN1

1Dadasaheb Balpande College of Pharmacy, Besa, Nagpur (MS), India

2Institute of Pharmaceutical Education and Research, Borgaon (Meghe), Wardha (MS), India

*Corresponding Author:
Ambatkar MP
Dadasaheb Balpande College of Pharmacy
Besa, Nagpur (MS), India

Abstract

Some common molecules like antipyrine and toluene-p-sulphonamide have been synthesized by Microwave Assisted method i.e. “Green Synthesis”. The reaction yields were compared with reported conventional method. The purpose of this study was increasing practical yield, lowering the reaction time and reducing pollution. The products were characterized by various techniques like melting point, Thin Layer Chromatography (TLC), partition coefficients, dissociation constants, % ionization, Fourier Transform Infrared (FTIR) spectroscopy, Mass and Proton Nuclear Magnetic Resonance (1H-NMR) spectroscopy.

Keywords

Synthesis, Antipyrine, Toluene-p-sulphonamide, Microwave

Introduction

Synthesis of organic and pharmaceutical compounds require more than 2-3 h heating for completion of reaction. So, there is no sufficient time for purification, drying and evaluation of the synthesized product. Thus, new technique was developed for synthesis i.e. microwave assisted organic synthesis which completed the reaction in minutes only. Microwaves are electromagnetic waves containing electric and magnetic field components. The electric field applies a force on charged particles as a result of which the charged particles start to migrate or rotate. Due to movement of charged particles further polarization of polar particles takes place. This method is beneficial because of several advantages including high percentage practical yields, reduced reaction time and reduced pollution [1-3]. Keeping this in view, the newly developed microwave assisted method is applied for synthesis of antipyrine and toluene-p-sulphonamide. In this paper, synthesized products were characterized by the physico-chemical studies like melting point, TLC, partition coefficients, dissociation constants and % ionization. The structures of synthesized compounds were confirmed by Ultraviolet (UV), Fourier Transform Infrared (FTIR) spectroscopy, Mass and Nuclear magnetic resonance (NMR) spectroscopy [4-9].

Materials and Methods

All the reagents were of analytical purity, and were used without further purification. CATA’s Scientific Microwave Synthesis System was used in our experiments. A refluxing system was connected with the microwave oven. DBK programmed melting point apparatus was used for determination of melting point. The purification of synthesized products was done by thin layer chromatography. Shimadzu FT-IR - 8400 S using KBr pellets in the region of 4000-500 cm-1 was used for recording IR spectrum. Bruker Avaze II (400 MHz) and QP- 2010 PLUS GC-MS were used for NMR and Mass spectrum respectively.

Synthesis of antipyrine

The mixture of 0.5 ml of ethyl acetoacetate and 0.3 ml of phenylhydrazine was refluxed for 15 min in microwave oven (power input: 245 W, 3 P). The reddish syrup was cooled and 0.9 ml ether was added. The syrup was solidified within 15 min. The product was filtered off and washed with ether to remove coloured impurities. The product was recrystallized from a mixture of ethanol and water [10]. The product was purified by thin layer chromatography using chloroform: ethyl acetate (8:2) (Scheme 1).

derpharmachemica-synthesis-antipyrine

Scheme 1: Reaction of synthesis of antipyrine

Synthesis of toluene-p-sulphonamide

The mixture of fine uniform powder of toluene-p-sulphonyl chloride (0.632 g) and 1.27 g of ammonium carbonate was refluxed by microwave irradiation in oven for 15 min (Power input: 280 W, 4 P). The mixture was cooled and extracted with a little cold water to remove the excess of ammonium salts. The recrystallization was done from hot water [10]. The purity of product was checked by thin layer chromatography using Chloroform: Ethyl acetate (7:3) (Scheme 2).

derpharmachemica-Reaction-synthesis

Scheme 2: Reaction of synthesis of toluene-p-sulphonamide

Results and Discussion

Table 1 shows reaction time taken by microwave irradiation and conventional method, the compounds were obtained in good yields, also the compounds were compared for spectral characterization.

Synthesized compound Conventional method [10] Microwave method
Time (min) Yield (%) Time (min) Output (Watt) Yield (%)
Antipyrine 120 80 15 245 87.29
Toluene-p-sulphonamide 120 88 25 280 95.78

Table 1: Reaction time and yield (%) of products by conventional and MWI method

Characterization

The structure of antipyrine and toluene-p-sulphonamide have been established on the basis of IR, NMR and Mass spectral data. The spectral characterization of the compounds has been given as below:

Antipyrine: IR (KBr) (cm-1): 3100 cm-1 (SP2 C-H stretching), 1785.96 cm-1 (C=O stretching of cyclic ketone), 2900 cm-1 (aliphatic C-H stretching), 3400 (w) & 1525.59 cm-1 (N-H stretching & def. respectively). GC-MS (m/z)=174 (M+); 1H-NMR (400 MHz, CDCl3): δ=2.20 (s, 3H), 3.43 (s, 1H), 7.26 (s, 1H), 7.37-7.41 (m, Ar-H), 7.84-7.86 (m, Ar-H).

Toluene-p-sulphonamide: IR (KBr) (cm-1): 3326.98 & 3240.19 cm-1 (asymmetric & symmetric N-H stretch), 3050 & 1596.95 cm-1 (aromatic C-H & C=C stretching respectively), 2950-2900 cm-1 (Aliphatic C-H stretch), 1325.01 & 1151 cm-1 (Anti & sym S=O stretching). GC-MS (m/z)=171 (M+); 1H-NMR (400 MHz, CDCl3): δ=7.45-7.47 (m, J=1.96, Ar-H), 7.34-7.36 (m, J=3.00, Ar-H), 7.25 (s, 2H of NH2), 1.25 (s, 3H of CH3).

Table 2 shows melting point, Rf value [11-13] and physicochemical parameter of antipyrine and toluene-p-sulphonamide.

Compound Molecular formula (Mol. Wt.) Nature Melting point (°C) Rf value Partition coefficient [12]
(P)
Dissociation constant [13]
(pKa)
% Ionization
Antipyrine C10H10N2O (174) Yellow crystals 126-129 0.50 4.63 1.61 20.45%
Toluene-p-sulphonamide C7H9NO2S (171) White crystals 137-140 0.63 3.81 5.65 12.36%

Table 2: Physicochemical data of synthesized products

Conclusion

In summary, a microwave assisted organic synthesis was developed which was beneficial because of several advantages including high percentage practical yields, reduced reaction time and reduced pollution. antipyrine and toluene-p-sulphonamide have successfully synthesized with this hydrothermal procedure. All the synthesized compounds were subjected to physico-chemical and spectral analysis. In conclusion, microwave technique was successfully developed for routine practical classes for UG students in chemistry laboratories.

References

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