Question

PRE-LABORATORY EXERCISES NAME: Isolation of Caffeine Draw the structure of caffeine. what are the chemical and biological properties of caffeine? What are tannins? Draw some representative structures. How are tannins removed using sodium carbonate? What other phytochemicals are found in tea and coffee? 4. 109

Answer 1

Answer 1):- Structure of coffee:-

CH3 1: N. 0 N 0 chs

Answer 2):- Chemical and biological properties of coffee:- Coffee is xanthine alkaloid containing a pyrimidinedione ring (6-membered ring containing two nitrogen atoms) and a five-membered imidazole ring. Molecular formula C_{8​​​​​​​}H_{10​​​​​​​}N​​​​​​​_{4​​​​​​​}O​​​​​​​₂ . Molar mass = 194.19 g/mol. It is central nervous system (CNS) stimulant and increases brain alertness. Caffeine increases the amount of acid in stomach. Caffeine constricts the blood vessels and increases the blood pressure.

​​​​​​Answer 3):- Tannins are the class of water-soluble polyphenols , astringent found in tea and coffee. Tannins are removed by converting them to their sodium phenolate salts by adding sodium bicarbonate. These salts are water -soluble and immiscible in dichloromethane (solvent in which mixture is dissolved) and are easily removed.

Representative of tannins are:-

​​​​​​​

oH ой HO 0H Gallic Aud C=O HO C O OH oH HO OH OH OH Ellagitanun oH IJ C HO -0H PH D Ho HO HOHO oH MO HO Gallotannin CO

Answer 4):- Typical phytochemicals found in tea: epigallocatechin gallate, flavonoids, tannins, caffeine, polyphenols, boheic acid, theophylline, theobromine, anthocyanins, gallic acid.

Phytochemicals found in coffee: Chlorogenic acid (polyphenol), quinic acid , cafestol, kahweol, caffeine ,tannins,etc.