Borneol
bornyl alcohol, a secondary alcohol of the bicyclic terpene group. Borneol has an endo configuration; its isomer, called isoborneol, has an exo configuration. [The (CH3)2C group is located outside the plane of the ring.]
Borneol and isoborneol contain an asymmetric carbon atom (denoted by an asterisk), and therefore each of them exists in two optically active forms and one inactive racemic form (−, +, and ±). Borneo camphor, (+)-borneol, is contained in the secretions of the tree Dryobanalops camphora, which grows on the islands of Borneo and Sumatra, as well as in rosemary, lavender, and camphor oils. The acetate form, ( − )-borneol, is contained in the coniferous needle of the Siberian pine. Both (+)-borneol and (−)-borneol have a melting point Tm = 208.5° C, boiling point Tb = 212° C, and angle of rotation of the plane of polarization [α]D20 = ±37.9°; and both sublimate. The racemate (±)-borneol melts at 210.3° C. Both (−)-borneol and (±)-borneol are components of valerian oil.
Borneol is converted into camphor upon oxidation and catalytic dehydrogenation; the dehydration of borneol leads to camphene. The primary method of obtaining borneol is the hydration of pinene, which is contained in turpentine. Borneol is used in the production of camphor.
Isoborneol (Tm= 214° C) is not found in nature; it is obtained from camphene.
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