Chemistry - Terpenoids

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

2. Menthol

4. Menthol is obtained by reduction of
pulegol
pulegol Menthol

5. 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.

6. Chemical properties
• Oxidation
on oxidation menthol give menthone.
menthonementhol

7. • Reduction
menthol give menthane on reduction.

8. Dehydration
On degradation menthol gives menthene.

9. Structure
1. Molecular formula
Molecular formula of menthol was
determined as C10H20O.
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.

10. menthene

11. 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

12. 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.