limonene

Limonene is a natural monocyclic monoterpene hydrocarbon with the formula C10H16. It occurs widely in the essential oils of citrus fruits and is one of the principal components of orange oil. It exists as two enantiomers, D-limonene and L-limonene; natural citrus oils are enriched in D-limonene, which has a citrusy orange odor, while the L-enantiomer has a pine- or turpentine-like scent. Limonene is a volatile, lipophilic compound with low water solubility and a boiling point around 176°C.

Commercially, limonene is extracted from citrus peels by cold pressing or steam distillation, and is recovered as a component of orange, lemon, lime, and grapefruit essential oils. It is also produced synthetically from terpenes. Limonene is widely used as a fragrance and flavoring ingredient and as a renewable solvent in various industrial applications.

Uses include its role as a solvent in cleaners, degreasers, paints, and inks, and as a flavor and fragrance ingredient in foods, beverages, cosmetics, and perfumes. It also serves as a chemical building block for the synthesis of other terpenes such as carvone and for certain biobased polymers. Its pleasant odor and solvency properties contribute to its popularity in consumer and industrial products.

Safety and regulation: Limonene is generally considered safe in small amounts for flavoring and fragrance use, but its oxidized forms, such as limonene hydroperoxide, can be potent allergens and may cause contact dermatitis in cosmetics. Occupational exposure can irritate the skin, eyes, and respiratory tract. It is biodegradable and has relatively low acute toxicity to aquatic life, though effects can vary by enantiomer and oxidation state.