TERPENES

TERPENE

A class of naturally occurring compounds mainly in plants as constituents of essential oils whose carbon skeletons are composed exclusively of isoprene C5 units (CH₂=C(CH₃)-CH=CH₂). Most terpenes are hydrocarbons having molecular formula (C₅H₈)_n in a cyclic or acyclic, saturated or unsaturated structure, while the terpenoids are oxygen-containing analogues of the terpenes such as alcohols, aldehydes or ketones containing hydroxyl groups or carbonyl groups. Several vitamines, hormones, flavour and flagrances and latex are terpenoids. Terpenes containing 30 or more carbons are usually formed by the fusion of two terpene precursors in a regular pattern, usually head-to-tail appears to be violated. They are differ from one another not only in functional groups but also in their basic carbon skeletons. Terpenes are employed mainly the fragrance and flavour purpose, as well as in the pharmaceutical and chemical industries. They are classified by the number of isoprene units:

Class	number of isoprene	Examples
Hemiterpene	1 (C₅H₈)	Found in associated with Alkaloids, Coumarins and Flavonoids.
Monoterpenes	2 (C₁₀H₁₆)	Geraniol, Citronellol, Pinene, Nerol, Citral, Camphor, Menthol, Limonene, Thujone
Sesquiterpenes	3 (C₁₅H₂₄)	Nerolidol, Farnesol
Diterpenes	4 (C₂₀H₃₂)	Phytol, Vitamin A1
Triterpenes	6 (C₃₀H₄₈)	Squalene
Tetraterpenes	8 (C₄₀H₈₄)	Carotene (Provitamin A1)
Polyterpenes	>10 (C₅H₈)_n

PRIMARY COMPOUNDS OF TERPENE (TERPENOIDS)


MENTHANES	MENTHENES	MENTHADIENES	LIMONENE

ALPHA-TERPINENE	Beta-TERPINENE	Alpha-PHELLANDRENE	Beta-PHELLANDRENE

THUJONE	Alpha-PINENE	Bete-PINENE	Beta-MYRCENE

P-CYMENE	Gamma-TERPINENE	TERPINOLENE	LINALOOL

CITRONELLAL	Alpha-TERPINEOL	NERAL (Citral + Geranial)	2-CARENE

CAMPHOR	CAMPHENE	MENTHOL	NEROLIDOL

FARNESOL	PHYTOL	RETINOL	SQUALENE

Beta-CAROTENE