Isoprenoid compounds having 10-40 carbon atoms are called terpenes. Two or more five-carbon isoprene units (C5H8) join to form terpenes (C5H8)n. Two, three, four, five, six, and numerous isoprene units join to form monoterpenes, diterpenes, triterpenes, tetraterpenes, pentaterpenes, hexaterpenes, and polyterpenes, respectively. Monoterpenes are volatile oils. The plant is fragrant due to its presence. Basil leaves, mint leaves (menthol), pinus cells (pinene), lemon (lemnin) etc. contain terpenes. Examples – geraniol, menthol, limonim, proline, camphor, thymol, systrol, pinene, limonene etc.
The action of turpentine
(i) Turpentine is used in the manufacture of varnishes.
(ii) It is used in the preparation of medicines.
(iii) Used in making soft drinks.
(iv) It has extensive use in the manufacture of perfumery and cosmetics.