Мускус-кетон

Identity and properties

Musk ketone is a nitro musk with the IUPAC name 1-(4-tert-butyl-2,6-dimethyl-3,5-dinitrophenyl)ethanone. Its molecular weight is 294.30. It is classed as an aromatic ketone. It is insoluble in water, with a solubility of 0.46 mg/L at 25 °C, and very soluble in chloroform. Musk ketone is one of the five most commercially relevant nitro musks, together with musk ambrette, musk moskene, musk tibetene and musk xylene. Nitro musks are structurally related, synthetic alkylated nitrobenzene compounds. Nitro musks have octanol-water partition coefficients between 4.3 and 4.9, which shows that they are lipophilic. When heated to decomposition, musk ketone emits toxic nitrogen oxide vapors.

Regulation and safety

The IFRA Standard for musk ketone is a specification; an Australian assessment of nitro musks quotes it as saying that musk ketone should only be used if it contains less than 0.1% of musk xylene. A restricted use warning was placed on musk ketone. On 8 December 1999 the SCCNFP adopted an opinion on musk ketone. That opinion was requested while limits for musk xylene in cosmetic products were being set. It found that musk ketone can be safely used in cosmetic products, excluding oral care products, up to a maximum daily absorbed dose. It held that consumer exposure should be reduced because the substance is retained for a long time in human fat and excreted in human milk. The SCCNFP added that long term toxicity studies are needed. Musk moskene and musk tibetene have been prohibited from use in fragrant products because of adverse outcomes from structurally similar compounds. Musk ambrette has been discontinued because its consumption was associated with hind limb weakness in rats and with neuropathologic changes in the brain, spinal cord and peripheral nerves.

Behaviour in the body and the environment

Synthetic musks are lipophilic compounds and tend to deposit and persist in fat tissues. Toxicokinetic studies show that musk ketone and musk xylene are distributed to nearly all tissues, with the highest levels in the gastrointestinal tract, liver, adipose tissue, adrenals, thyroid and kidneys. Both were found in rat and human milk. Nitro musks are retained in human adipose tissue and excreted in breast milk, and personal care and household products are the major route of human exposure. Use of these products leads to direct exposure through the skin and through inhalation of contaminated dust and volatilized fragrances. After personal use, these persistent pollutants pass through sewage treatment plants and their effluent into the environment. Nitro musk compounds do not degrade easily, which makes them highly stable and ubiquitous in the environment. The median lethal dose of musk ketone and musk xylene in rats and mice is above 2000 mg/kg body weight. Both the acute oral LD50 in rats and the acute dermal LD50 in rabbits for musk ketone exceeded 10 g/kg. In a guinea pig skin test, mild redness appeared in 5 of 20 animals at the highest challenge dose after 24 hours but not at 48 hours, and the effect was not judged to meet the classification criteria. In an animal test, musk ketone was concluded to be weakly photoallergenic.

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