Structure Determination of Santonin

1. Molecular formula: C₁₅H₁₈O₃
2. Detection of Unsaturation: Santonin contains two double bond and behave like an α-unsaturated Ketone. The presence of this group in the molecule is confirmed by its UV absorption spectrum.
3. Hydrogenation of Santonin from Tetrahydro-Santonin: Catalytic hydrogenation of santonin forms tetrahydro-santonin (C₁₅H₂₂O₃), thus, confirming the presence of two double bonds.
4. Nature of Oxygen (Lactone Ring): Santonin dissolves in alkali to form the salt of the hydroxy acid, santonic acid. Hence, santonin is a lactone and its IR spectra shows a carbonyl bond at 1770 cm^–1 and its characteristic of saturated &gama;-lactone.
5. Presence of Naphthalene Skeleton: On distillation with zinc dust, santonin gives a mixture of 1, 4 dimethylnapthaline, propene and 1, 4 dimethylnapthol.
6. Confirmation of Structure of Santonin

In 1930, Clemo proposed the correct structure of santonin (I). He suggested the structure santonin, on the basis of the following reactions: (i) Santonin(I) on reduction with phosphorous and hydraiodic acid gives santonous acid.

Related Topic
Synthesis of Santonin