Limonene, also known by its IUPAC name 1-Methyl-4-(prop-1-en-2-yl)cyclohex-1-ene, is an natural product which is found in the oil of citrus fruits and is used in perfume industry.
Formula and structure: The chemical formula of limonene is C10H16; the structure is a cyclic monoterpene, which means it is a molecule formed by two units of isoprene (-CH=C(CH3)−CH=CH2). It molecular mass is 136.24 g mol-1. The structure is a 6 member rings very rigid due to the presence of double bonds. The chemical structures can be written as below, in the common representations used for organic molecules.
Occurrence: Limonene is found in many sources in nature. It is a component if the essential oil of citrus fruit peels; it is more common in oranges. It is produced via cyclization of geranyl pyrophosphate.
Preparation: Limonene is mostly extracted from natural sources as oranges peel and turpentine gum.
Physical properties: Limonene is a colorless to pale-yellow liquid with a pleasant orange-like smell. Its melting point is -74.35 °C and its boiling point is 176 °C. The density is 0.8411 g mL-1. It is insoluble with water but it is miscible in ethanol, methanol, chloroform, ether, benzene e carbon tetrachloride.
Chemical properties: Limonene is formed, as the same those other terpenes, by isoprene units that are alkene, so thus heat can cause the break of limonene to isoprene units. Differently to other alkenes, terpenes are stable and less reactive. It is also important to notice, limonene en nature is found as a pure D-(or R) enantiomer. This means, all the limonene found in oranges and other natural sources has a chiral carbon with configuration R.
Uses: It is used in the flavor and fragrance industry, it is approved by FDA as a safe ingredient for cosmetic purposes. It can be used as a solvent for cleaning products. Limonene also has been said as having medicinal purposes.
Health effects/safety hazards: Limonene is a flammable liquid. It can cause irritation and allergy in skin. It can also cause serious eyes irritation.