Caffeine’s chemical structure

Caffeine belongs to the group of substances called alkaloids. It is produced in plants such as coffee and tea from adenosine, which is found in DNA and RNA. In plants which biosynthesize caffeine theobromine is also found. Theobromine is therefore found in, e.g. coffee, tea and extracts of plants. Theobromine and caffeine are very similar, both physically and chemically. Therefore, it may be difficult to separate them after analysis. Caffeine has a stronger stimulating effect on the CNS than theobromine.

Figure: Chemical structure of caffeine and theobromine. Caffeine is called 1,3,7-trimethylxanthine, or 1,3,7-trimethylpurine-2,6-dione. Theobromine is called 3,7-dimethylxanthine, or 3,7-dimethylpurine-2,6-dione.

The figure shows that caffeine is built up in two ring systems. These ring systems, named purines, are constructed from a pyrimidine (6 membered ring) and an imidazole ring (5 membered ring). Purines are heterocyclic aromatic compounds. Caffeine is built up of two carbonyl groups and 4 tertiary amines. Both caffeine and theobromine also include an amide group, which is a functional group consisting of a carbonyl group bound to a C atom and a N atom, and an alkene, an unsaturated hydrocarbon containing at least one carbon-carbon double bond. The only difference between caffeine and theobromine is an additional methylene group in position 1 of caffeine. The functional groups of the caffeine are alkene, amide, and amine.