Lemon Juice Catalysed Green Synthesis of Triazole Based Schiff Base, Its Physico-Chemical & Spectral Characterisation and Determination of its Binding Stoichiometry with Cu2+ ion

Abstract

In the recent years Environmental Pollution has emerged as a major challenge for human society. Since the start of Industrial Revolution in England, the amount of chemical waste and toxic substances are increasing exponentially in the environment. The traditional synthesis of chemical substances is accompanied by use of large amount of energy, harmful solvents and release of toxic substances in environment. The green synthesis aims to minimise the release and use of harmful toxic material in synthesis. In the present paper we have prepared a triazole derivative, 4-[(E)-Benzylideneamino]-5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-thione through green synthetic route. The reaction was catalysed by lemon juice and it was carried out in solvent-free condition through mechano-chemical stirring method. The physico-chemical properties were studied. The FT-IR spectral analysis confirmed the structure of Schiff base. The stoichiometry of binding with Cu2+ was determined through Method of Continuous Variation. The Schiff base- metal ratio was found to be 1:1.

Introduction

I. INTRODUCTION

Green chemistry involves elimination of use and generation of hazardous material in production of chemical products and methods [1]. Economic goal of the human society can be achieved through green methods without damaging environment [2]. The organic solvents which are used in synthesis of various chemical compounds have adverse effect on environment [3]. Green solvents are biodegradable and obtained from natural occurring product [4,5]. In 1864, Schiff base was prepared by Hugo Schiff by condensation of an aldehyde and amine [6]. Schiff base are chemical compounds with general formula R1R2C=NR (R≠H) [7]. Schiff bases are easy to synthesize and show variety of biological activity like Antioxidant [8], Anti-Inflammatory [9], Anti-Microbial, Antifungal, Antiviral, Synergistic action on Insecticides, Plant growth Regulator, Allergy inhibitor, Analgesic [10]. The naturally occurring fruit juices have been used as biocatalyst in organic synthesis recently [11]. Lemon juice. Grape juice, Extract of raw Mango have been used to synthesize Schiff base [12,13,14]. In the present research, a Triazole derived Schiff base have been prepared through Green synthetic method using Lemon juice as catalyst.

II. EXPERIMENTAL

A. Materials and Methods

All the chemicals used were either of Merck, Finar, Nice, BDH or Loba. The melting point was determined by open-capillary method. The molar mass was calculated using Rast Method using Camphor as solvent [15]. The metal binding property of the Schiff base was studied using Method of Continuous Variation [16]. The absorbance value were taken using Systronic Photoelectric Colorimeter 112. The FT-IR Spectra was recorded by Agilent Cary 630 FTIR instrument in the range 4000-450 cm-1.

B. Synthesis of Schiff base

1. Preparation of Lemon Juice : The lemons were bought from local market. They were pressed manually and juice was filtered using filter paper to obtain clear lemon juice.
2. Synthesis of 4-amino-5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-thione : The compound was synthesized by reported method [17] and recrystallised using ethanol.

3. Green Synthesis of Schiff Base : 0.002 mole of compound A and 0.002 mole of Benzaldehyde was taken in a beaker. 0.5 ml of lemon juice was added. The reaction mixture was stirred for 30 minutes at 50°C on hot plate. The reaction mixture colour turns yellow. 25ml of distilled water was added and product was filtered, washed with distilled water and recrystallised with ethanol. The yield of the product was 71.3 %.

III. RESULTS AND DISCUSSION

A. Physico-Chemical Analysis

The yield of the synthesized Triazole based Schiff Base through green synthetic route is 71.3%. It was recrystallised using minimum amount of ethanol. Pale-Yellow coloured crystalline solid was obtained. The prepared compound was stable in air. The melting point of the synthesized compound was found 195-197°C. The value of molar mass is 220.56 which was calculated  using Rast Method. Physico-Chemical properties of the Schiff Base is given in Table I.

The solubility of the synthesized Schiff Base was checked in various organic solvents. The Triazole based Schiff Base is completely soluble in DMSO, partially soluble in ethanol, chloroform and insoluble in acetone and water. The solubility of the compound in various organic solvents is given in Table II.

B. FT-IR Spectral Analysis

The FT-IR spectra of the Triazole based Schiff Base was recorded using Agilent Cary 630 FTIR instrument in the frequency range  4000-450cm-1. The IR spectral frequency bands of the compound is mentioned in Table III.

The analysis of Job’s Plot revealed that slope changes from positive to negative at mole-fraction 0.5 which is called turning point. The turning point at 0.5 indicates the formation of 1:1 complex. Hence, the binding stoichiometry between Cu2+ and ligand is 1:1.

IV. ACKNOWLEDGMENT

Vivek Kumar wishes to acknowledge CSIR-HRDG, New Delhi for providing financial support to carry out the research work under CSIR-NET-JRF Scheme ( File No.- 09/138(0078)/2019-EMR-I ). We also want to acknowledge The Head, DST-SAIF, CDRI Lucknow for recording FT-IR Spectra of the compound.

Conclusion

In summary we have synthesized a Triazole based Schiff base through green synthetic method. The synthesis was accomplished using mechano-chemical stirring and lemon juice was used as catalyst. The synthesized Schiff Base was characterized by physico-chemical properties and FT-IR Spectra. The stoichiometry of binding of Schiff base with Cu2+ was determined using the Method of Continuous Variation. The analysis of Job’s Plot indicates the formation of 1:1 complex.

References

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Copyright

Copyright © 2022 Vivek Kumar, Abhay Kumar, Rajesh Kumar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.