Ethylene Brassylate

Chemistry and classification

Ethylene brassylate has the IUPAC name 1,4-dioxacycloheptadecane-5,17-dione. Its molecular formula is C₁₅H₂₆O₄ and its molecular weight is 270.36. It is a macrolide, the cyclic ethylene ester of tridecanedioic acid. It belongs to the synthetic musks, a class of aroma compounds that emulate the scent of deer musk and other animal musks. In the narrower sense, synthetic musks are modelled on muscone of deer musk and civetone of civet, which are macrocyclic ketones. The macrocyclic musks extracted from plants are large-ringed lactones, whereas all animal-derived macrocyclic musks are ketones. Within the synthetic musks, ethylene brassylate is one of the macrocyclic lactones. It is insoluble in water and soluble in alcohol. One millilitre of ethylene brassylate dissolves in one millilitre of ethanol. Its melting point is 0 to 7 °C and its Kovats retention index is 1988.6.

Raw materials: brassylic acid and erucic acid

Brassylic acid, the C13 dicarboxylic acid with the formula C₁₃H₂₄O₄, is a white solid that melts at 114 °C. In industry it is used to produce specialty nylons such as nylon 1313, as well as polymers, biodegradable solvents, lubricants, perfumes and plastics. It was first made in the nineteenth century by the oxidative ozonolysis of erucic acid. Erucic acid is a monounsaturated omega-9 fatty acid, denoted 22:1ω9. It is prevalent in wallflower seed and other plants of the family Brassicaceae, at a reported 20 to 54% in high erucic acid rapeseed oil and 42% in mustard oil. Erucic acid is produced by elongation of oleic acid. A low-erucic rapeseed, canola, has been developed for food, and food-grade rapeseed oil is limited to 2% erucic acid by weight in the US and Europe.

Place among the musks

The name musk first meant a strong-smelling substance from a gland of the musk deer, which has served as a perfume fixative since ancient times. The term now covers a wide variety of aromatic substances with similar odours, despite their often differing chemical structures and molecular shapes. Nearly all musk fragrance used in perfumery today is synthetic, since obtaining deer musk requires killing the endangered animal. Synthetic musks can be divided into three major classes: aromatic nitro musks, polycyclic musk compounds and macrocyclic musk compounds. Nitro musks and polycyclic musks, used for 100 years, have low biodegradability and accumulate in the environment. Macrocyclic musk compounds are expected to replace the nitro and polycyclic musks, since they appear to be safer. The nitro and polycyclic musks have broad industrial uses, from cosmetics to detergents. Their detection in human and environmental samples, together with their carcinogenic properties, prompted a public debate about their use and a ban or reduction of it in many regions of the world. Synthetic musks are lipophilic and tend to deposit and persist in fat tissues.

Hazard classification

Ethylene brassylate does not meet GHS hazard criteria for 73.8% of the 2061 reports on record. These reports come from 12 notifications to the ECHA classification and labelling inventory. In 23.3% of reports it is classified H411, toxic to aquatic life with long lasting effects. Its hazard classes are acute and long-term hazard to the aquatic environment, both in category 2. It is a REACH registered substance. It is on the EPA's Chemical Data Reporting list, so manufacturers and importers in the United States must report its production and use under the Toxic Substances Control Act. It is listed among potential endocrine disrupting compounds.