TERPENOIDS : TERPENOIDS MENTHOL CAMPHOR Presented
M.Pharm 2nd semester MENTHOL : MENTHOL SOURCE: Oil obtained by steam distillation of
fresh flowering tops of peppermint,
Mentha piperita under the family
Limonene. Isolation of peppermint oil : Isolation of peppermint oil Extraction of oil by steam distillation Peppermint or mentha oil : Peppermint or mentha oil Colour colourless to yellow.
Odour characteristic & pleasant
Taste pungent followed by cooling sensation
Menthol from mentha oil
The oil is chilled to a temperature of -40°C to separate the menthol, which is later crystallized by slow cooling. Physical properties : Physical properties Menthol is an optically active compound; only (-)-form occurs naturally in peppermint oil.
Melting point is 430C Structure Elucidation : Structure Elucidation Molecular formula of menthol & menthone : [ C10H20O];[C10H18O].
Menthol forms ester readily with acids, indicating the presence of alcoholic group; the oxidation of menthol yields a ketone indicating hydroxyl group in menthol is secondary alcoholic.
C10H20O [O] C10H18O Slide 7: Menthol yields Para cymene on dehydration followed by dehydrogenation, suggesting the presence of paramenthane skeleton in the molecule.
Menthone on oxidation with KMnO4 gives a keto acid, which on further oxidation forms acetone & 3-methyladepic acid. Slide 9: Finally pulgeone gives menthol on reduction.
Hence the structure of menthol will be one which explains all its reaction, i.e. its formation from pulgeone & its aromatization to thymol via menthone by means of bromine & quinoline. Slide 10: Thymol Ultimately the structure of menthol established by synthesis : Ultimately the structure of menthol established by synthesis Menthol Reactions of Menthol : Reactions of Menthol STRUCTURE OF MENTHOL : STRUCTURE OF MENTHOL Slide 14: Examination of the menthol structure shows that 3 dissimilar chiral centers are present;thus eight optically active forms (four racemic modification) are possible theoretically.
All eight enantiomers are known and their configurations are as follows. Enantiomers of Menthol : Enantiomers of Menthol USES : USES Flavoring agent
Used in toothpaste
Tooth powder and other cosmetics CAMPHOR : CAMPHOR SOURCE: Solid ketone obtained from volatile oil of Cinnamomum camphora under the family Lauraceae.
Industrially obtained from α pinene i.e. turpentine oil. Physical properties : Physical properties Camphor is solid with characteristic smell and burning taste.
Melting point: 1800C.
Boiling point: 2040C.
It is optically active.
(-) &(+) form occur naturally.
± racemic form is found in synthetic product. Biosynthesis of camphor : Biosynthesis of camphor REACTIONS : REACTIONS Camphor forms substitution product like monobromocamphor,monochlorocamphor,camphor-sulphonic acid. The formation of these product shows that camphor is a saturated compound. Reactions : Reactions Camphor on oxidation with nitric acid gives Camphoric acid,C10H1604. Camphoric acid contains the same number of carbon atom as camphor, the keto group must be in one of the rings in camphor. Slide 22: Presence of keto group in camphor is confirmed as it forms oxime with hydroxylamine, and phenylhydrazone with phenylhydrazine.
C10H16O +H2NOH C10H16=NOH Camphor Hydroxylamine Camphor oxime Slide 23: Presence of- COCH2- group in camphor is confirmed by its formation to isonitroso derivative with amyl nitrite & HCl Camphor Slide 24: Camphor is distilled with zinc chloride/P2O5, forms P-cymene. This shows presence of one six member ring in camphor. Camphor P-cymene Slide 25: Oxidation of camphor with HNO3 produces camphoric acid & camphoronic acid.
C10H16O C10H16O4 C9H14O6 camphor Camphoric acid Camphoronic acid Structure of Camphoronic acid : Structure of Camphoronic acid Molecular formula C9H14O6
It is saturated tricarboxylic acid C6H11(COOH)3
Its hydrocarbon C6H14 corresponds to CnH(2n+2) i.e. acyclic.
Since camphoric acid is not easily decarboxylated, its 3 carboxyl groups are attached to 3 different carbon Slide 27: The exact structure is established;
By distillation under atmospheric-pressure gives, isobutyric acid trimethyl succinic acid and CO2. Slide 28: Molecular formula of camphoric acid is C10H16O4.
It is found to be saturated dicarboxylic acid.
It forms monoester very easily but diester with difficulty indicating two dissimilar carboxyl group.
It is found to be ring substituted glutaric acid on the basis of Blanc rule. Slide 29: Finally structure of camphoronic acid & camphoric acid is established by synthesis Structure of Camphor : Structure of Camphor Molecular formula C10H16O, & the general reactions & molecular refraction of camphor show that it is saturated.
The functional nature of the oxygen atom was shown to be oxo as camphor formed an oxime.
It was a keto group since camphor gives a dicarboxylic acid containing 10 carbon.
From the foregoing facts it can be seen that the parent hydrocarbon of camphor has the molecular formula C10H18 ;this corresponds to CnH2n-2 Structure confirmed by synthesis by (Haller1896) : Structure confirmed by synthesis by (Haller1896) Camphoric acid Camphoric anhydride campholide Homocamphoric acid Camphor Slide 32: Industrially camphor is obtained from α-pinine i.e. from turpentine oil.
Α-pinine Bornyl chloride Camphene Isobornyl acetate
Isoborneol Camphor. USES : USES Used as plasticizer for celluloid & photographic film
Mild disinfectant & stimulant for heart muscle
Used as insect repellant
Used as counter irritant
As flavor in soaps & cosmetics.