Iso E Super

Iso E Super is a fragrance ingredient with the chemical name octahydro-tetramethyl-naphthalenyl-ethanone, abbreviated OTNE. The beta isomer, CAS 54464-57-2, has the IUPAC name 1-(2,3,8,8-tetramethyl-1,3,4,5,6,7-hexahydronaphthalen-2-yl)ethanone. The formula is C₁₆H₂₆O and the molar mass is 234.38 g/mol. It is formed as a mixture of isomers with a basic unsaturated alkyl cyclic ketone structure. The commercial product comprises more than twenty isomeric ketones. The main isomer is the beta isomer, and the alpha and gamma isomers are two other predominant isomers of the mixture. The dominant isomer makes up most of the mixture yet is nearly odorless. The characteristic scent comes instead from a minor constituent, commonly known as Arborone, which typically represents only a few percent of the mixture. An impurity of about 5%, now called Iso E Super Plus, was held responsible for the characteristic smell. That impurity was analysed thoroughly and finally secured in a patent as Iso E Super Plus. The olfactory active form is (2R,3R)-Iso E Super. Georgywood, a second minor component with a higher odor threshold but better odor characteristics, was patented later.

Iso E Super is in a wide variety of commercial products with differing scents. It may cause allergic reactions detectable by patch tests in humans, and chronic exposure to it from perfumes may result in permanent hypersensitivity. In 3-month dermal studies in rats and mice, the major target was the skin at the site of application. It was not mutagenic in Salmonella typhimurium strains TA98, TA100 or TA102 or in Escherichia coli strain WP2 uvrA pKM101. Lesions at the site of application were more prominent in mice than in rats, liver lesions were seen in mice but not in rats, and OTNE showed potential to be a reproductive toxicant in male and female mice.

OTNE is the abbreviation for the fragrance material registered under the CAS numbers 68155-66-8, 54464-57-2 and 68155-67-9 and EC number 915-730-3.

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