Menthol

Chemistry - Terpenoids

1. N.GOKILA III B.Sc Chemistry S.B.K COLLEGE

2. Menthol

3. Menthol is obtained by reduction of pulegol pulego l Menthol

4. Physical Properties It is a colourless solid with strong minty odour and cooling taste. It is found in the oil of pepermint. It is laevorotatory.

5. Chemical properties Oxidation on oxidation menthol give menthone . menthone menthol

6. Reduction menthol give menthane on reduction.

7. Dehydration On degradation menthol gives menthene.

8. Structure 1. Molecular formula Molecular formula of menthol was determined as C 10 H 20 O. 2. Presence of –OH On treatment with phosphorous pentachloride and phosphorous pentoxide menthol gave a chloride and hydrocarbon respectively , interfering that it is an alcohol.

9. menthene

10. 3. Nature of –OH group Menthol was oxidised by cromic acid to a ketone , menthone to proved that menthol contained a secondary hydroxyl group . Menthol

11. 4). Menthol was converted into p-cymene by dehydration and dehydrogenation which was also obtained by dehydrogenation of pulegone. There for menthol must possess the same skeleton as pulegone.