Hydroxy Citronellal Aroma Chemical
CAS# 107-75-5

Hydroxycitronellal (CAS 107-75-5) is a highly valued synthetic fragrance compound that plays an indispensable role in the perfume and cosmetics industries. Its most defining characteristic is a sweet, pure, and elegant lily-of-the-valley (muguet) scent, accompanied by nuances of lilac, linden blossom, fresh green notes, tropical melon, and citrus. Although it has a medium odor strength, this compound boasts excellent tenacity. When properly blended with modifiers, its fragrance diffuses significantly and develops a powerful, radiant floral tone over time.

Chemically, hydroxycitronellal is a medium-chain aldehyde that appears as a clear, colorless to pale yellow viscous liquid. It is primarily synthesized through the hydration of naturally occurring citronellal. The molecule features an asymmetric carbon center, resulting in two enantiomers with distinct properties. The (S)-(-)-enantiomer is highly preferred in fine perfumery because it yields a cleaner, greener lily-of-the-valley note and is significantly less allergenic than its (R)-(+) counterpart. Because the natural scent of lily of the valley cannot be successfully extracted from the flower, hydroxycitronellal has served as a foundational building block for legendary 20th-century perfumes, including Diorissimo, L'Air du Temps, and Chanel N°5.

The versatility of hydroxycitronellal makes it ubiquitous across various product categories. In perfumery, it acts as an outstanding fixative, helping to round out and diffuse white floral compositions such as peony, sweet pea, and narcissus. Beyond fine fragrances, it is widely utilized in personal care products (such as lotions, shampoos, and deodorants) and household cleaners, particularly because it demonstrates good stability in high-resistance, alkaline environments like soap. Additionally, in minute trace amounts (typically 0.3 to 15 ppm), hydroxycitronellal is employed as a flavoring agent in the food industry to add "richness" and body to fruit flavors like berry, cherry, and melon.

When formulating with hydroxycitronellal, manufacturers must strictly adhere to international safety regulations, as it is a known skin sensitizer and potential contact allergen for some individuals. The International Fragrance Association (IFRA) has established maximum acceptable concentration limits depending on the product category; for example, it is restricted to 2.1% in fine fragrances, 0.53% in body lotions, and 4.1% in rinse-off toiletries like shower gels. In the European Union, the Cosmetics Regulation caps its maximum concentration in finished cosmetic products at 1.0%. Furthermore, to protect sensitized consumers, EU law mandates that hydroxycitronellal must be explicitly declared on the ingredient (INCI) label if its concentration exceeds 0.001% in leave-on products and 0.01% in rinse-off products.