Question

What are the steric properties of the molecule Caffeine?

Answer 1

Caffeine is a xanthine alkaloid compound that acts as a stimulant in humans.

Soluble in ethyl acetate, chloroform, pyrimidine, pyrrole, tetrahydrofuran solution; moderately soluble in alcohol, acetone; slightly soluble in petroleum ether, ether, benzene.

The xanthine core of caffeine contains two fused rings, a pyrimidinedione and imidazole. The pyrimidinedione in turn contains two amide functional groups that exist predominately in a zwitterionic resonance the location from which the nitrogen atoms are double bonded to their adjacent amide carbons atoms. Hence all six of the atoms within the pyrimidinedione ring system are sp² hybridized and planar. Therefore, the fused 5,6 ring core of caffeine contains a total of ten pi electrons and hence according to Hückel's rule is aromatic.