Volatile oil
Jan 20, 2018
Volatile oil
Volatile oils• different from fixed– secreted in oil cells in specialised structures
• ducts, gland, cell or glandular hairs– frequently associated with other substances
• gums, resins (resinify on exposure to air)
• mainly terpenoid– some phenol ethers and phenols
• Terpenoids– based on the 5C isoprene unit
– Monoterpenes• most important, most volatile
– di-, tri-, sesquiterpenes also important
• contain 2 condensed 5C units head-tail
Monoterpene components
• Hydrocarbons
• Alcohols
• Aldehydes
– all produced via the terpenoid pathway
• Ketones
Citral
• Esters
• Oxides
Sesquiterpenes (C15)
Hydrocarbons Phenols Phenolic esters
Anethole
Chemical and physical properties
• volatile liquids with no colour– keep in amber bottles with minimum air
• odour• asymetric centres, isomers with optical activity
– only one isomer occurs naturally• refractive index normally high
– is a means to characterise the oil• miscible in water and soluble in organic solvents
– more soluble if contains –OH fatty acids• reasonably heat stable
– can be steam distilled• tend to be used as solvents for resins
Families• Economically only a few family groups are
commercially useful
[1] LabiataeLavender, Mentha Sp.
• oil occurs in special organs – synthesized in glandular trichomes (mint)
[2] UmbelliferaeFruits (best if ripe): anise, caraway, fennel, coriander
• found in “vittae” in the outer layer is characteristic
[3] PinaceaePine, juniper
• found in resin ducts in outer old xylem or bark• released when bark removed
[4] RutaceaeCitrus fruits
• typical ductless sacs in outer part of fruit – rind• less stable, need more care
[5] LauraceaeCinnamon, camphor
• from region immediately below bark
Usesas inhalations, orally, gargles, mouthwashes, trans-dermally
[1] Flavours & carminatives[2] Local stimulants and antiseptics
(containing phenols)[3] Perfumes[4] Insect repellant, antimating device[5] Starting materials