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Summer Research Fellowship Programme of India's Science Academies

Synthesis of aromatic esters, imines and azines

Subhashree Kar

MSc Chemistry, Central University of South Bihar, Gaya, PO- Fatehpur 824236

Dr. Chidambaram Gunanathan

Associate Professor, Department of Chemical Sciences, NISER, Khurda 752050

Chapter

Synthesis of Aromatic Esters

Introduction

Esters are non-hydrocarbon organic compounds that contain carbon, hydrogen and oxygen. The organic compound mentioned below is the product of “esterification” reaction occurring between an acid and an alcohol. A molecule of water is eliminated once an acid combines with associate degree alcohol to make associate degree organic compound1.Esters are an important class of compounds made by replacing the hydrogen of carboxylic acid by any alkylgroup. These are very important chemicals having wide applications in chemical industry such as perfumes, flavours, pharmaceuticals, plasticisers, solvents and intermediates1. Esters are generally synthesized by esterification method. 

General synthetic rocedure for synthesis of aromatic esters

To a mixture of benzoic acid (2 mmol) and isopropanol (10 mL) in a round bottomed flask, few drops of concentrated H2SO4 was added. The resulting mixture was heated to reflux and the reaction progress was monitored by TLC. On completion of the reaction, the reaction mixture was cooled to room temperature and the organic solvent was evaporated under reduced pressure.The corresponding ester compounds were purified using column chromatography with EtOAc/hexane as eluent. The purity of the compounds were analysed by NMR analysis.

Chapter

Synthesis of Imines

Introduction

Imines are such a functional group that are comprised of carbon atom double bonded to nitrogen atom. It is sometimes called Schiff base. The nitrogen atom may be attached to a hydrogen or an organic group. Imines and their derivatives have been recognized as key intermediates for the synthesis of nitrogen heterocycles and alkaloids.Imines represent a class of biological reactive intermediates that has been the focus of intensive toxicological research in recent years. Several imines have been reported for their significant biological activities like antitumor, anti-inflammatory agents, insecticidal, antibacterial, antimicrobial and anticonvulsant activity2.

General synthetic procedure for imine synthesis

To a mixture of benzaldehyde (1.05 eq) and aniline (1eq) in a round bottomed flask, 10 mL THF was added as solvent. Further, 2g of molecular sieves (4Å) was added to the reaction mixture as the dehydrating agent3. The resulting mixture was allowed to stir at room temperature and the reaction progress was monitored by TLC. After completion of reaction, the solvent was evaporated under reduced pressure. Then the round bottomed flask kept under high vacuum for one hour to remove excess aldehyde. The resulting imine was further purified by recrystallization using ethanol as a solvent.

Chapter

Synthesis of Azines

Introduction

Azines that are N–N-linked diimines are 2,3-diaza analogs of 1,3-butadiene. They are a class of compounds with interesting chemical properties and undergo a wide variety of chemical processes. Azines have special applications in chemistry. The use of azines as starting materials in organic synthesis is well documented. These readily available compounds have been widely used as substrates in the synthesis of substituted hydrazonesand heterocyclic compounds such as pyrazoles, purines, and pyrimidines. As dipolarophils, they can undergo 1,3-cycloadditions and thus provide an efficient route to afford 1,5-diazabicyclo[3.3.0]octanes by crisscross addition. Azines constitute an important class of stereochemically significant nitrogen donor ligands in organometallic complexes with pharmacological and biological activity4.

General synthetic procedure for azine synthesis

To a mixture of benzaldehyde (5 mmol) and ethanol (20 mL) in a round bottomed flask, hydrazine hydrate (1.5eq) was added. The resulting mixture was heated to reflux and the reaction progress was monitored by TLC. On completion of the reaction, the reaction mixture was cooled to room temperature and the organic solvent was evaporated under reduced pressure. The corresponding azine compounds were purified by recrystallization using ethanol. The purity of the compounds were analysed by NMR analysis4.

REFERENCES

1) Sun, X.; Zhang, Y.; Niu, F.; Jiang, L.; Jia, M.R. Soc. open sci. 2018, 5, 171988.

2) Martin, S. F. Pure Appl Chem. 2009, 81, 195–204.

3) Li, C.; Chu, Guobiao. Org. Biomol. Chem. 2010, 8, 4716–471.

4) Safari, J.; Ravandi, S.G. RSC Adv. 2014, 4, 46224.

ACKNOWLEDGEMENTS

I owe my sincere thanks and deepest sense of gratitude to Dr. C. GUNANATHAN who has been the source of inspiration and support throughout the period of the project, for his kind guidance, critical suggestions and constant encouragement.

I thank Prof. SUDHAKAR PANDA,Director, National Institute of Science Education and Research for providing the necessary facilities at the School of Chemical Sciences. I acknowledge my sincere gratitude to Mr. C.S. RAVIKUMAR, Assistant Executive secretary, Indian Academy of Sciences, Bangalore, for giving me opportunity to work on this project in the School of Chemical Sciences, National Institute of Science Education and Research, Bhubaneswar.

I would also like to extend my heartiest thanks to Dr. C. Gunanathan’s Research group, especially Mr. Biplab K Pandia (Ph.D. Scholar)without whom it would have been difficult for me to complete the work within the stipulated time, for their inspirational guidance, timely help, valuable suggestions and discussions throughout my project.

I owe my deepest gratitude to Mr.SuhasGawali (Ph.D. Scholar), Mr. S.Thiyagarajan(Ph.D. Scholar), Mr. Sandip Patnaik (Ph.D. Scholar), Mr. Prakash Sahoo (M.Sc. Student), Mr. Jugal Kishore (M.Sc. Student), Mr. Deepak Behera (M.Sc Student), Mr. Shubham Jaiswal (M.Sc. Student), Mr. AmlanSubhadarshi for their cooperation and help during the project work.

I would like to thank Indian Academy of Sciences, Bangalore for providing me this opportunity to work and get fellowship under Summer Research Fellowship Program 2019.

 

    

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