Дамаскон

The damascones are derived from the degradation of carotenoids. They are components of a variety of essential oils. The rose ketone family also includes damascenones and ionones.

The alpha, beta, gamma, delta and epsilon forms each have their own CAS number. Beta-damascone has the formula C13H20O and a molecular weight of 192.30. Its density is 0.934 g/mL. Its IUPAC name is (E)-1-(2,6,6-trimethylcyclohexen-1-yl)but-2-en-1-one. Alpha-damascone also has the formula C13H20O and a molecular weight of 192.30. Its IUPAC name is 1-(2,6,6-trimethylcyclohex-2-en-1-yl)but-3-en-1-one. The FEMA number of beta-damascone is 3243.

Beta-damascenone is not the same compound as beta-damascone: its formula is C13H18O and its molecular weight is 190.28. Beta-damascenone has a cyclohexadiene ring with two double bonds, where beta-damascone has a cyclohexene ring with one.

Beta-damascone carries the hazard statements H315, H317 and H411. Alpha-damascone is classed as an irritant that may cause sensitisation by skin contact.

Isomers and identification

The CAS numbers are 43052-87-5 for alpha-damascone, 23726-91-2 for beta, 35087-49-1 for gamma, 57378-68-4 for delta and 57350-34-2 for epsilon. The trans isomer of alpha-damascone is listed under 24720-09-0 and is named 1-(2,6,6-trimethyl-2-cyclohexen-1-yl)but-2-en-1-one. In beta-damascone, a 2,6,6-trimethylcyclohexene ring is joined to the carbonyl of a but-2-en-1-one chain, and the double bond of the chain has the E configuration. The EC number of beta-damascone is 245-842-1.

Delta-damascone is indexed as 1-(2,6,6-trimethyl-3-cyclohexen-1-yl)but-2-en-1-one, and its FEMA number is 3622.

Alpha-damascone

The trans isomer of alpha-damascone is estimated to be a colourless to pale yellow clear liquid; the grade listed assays at 95 to 100 %. Its specific gravity is 0.937 to 0.943 at 25 °C and its refractive index is 1.493 to 1.499 at 20 °C. It boils at 266 to 267 °C at 760 mm Hg, and its flash point is above 93.33 °C. Its estimated vapour pressure is 0.008 mmHg at 25 °C, its estimated logP is 3.436 and its estimated solubility in water is 10.31 mg/L at 25 °C. Its FEMA number is 4088, and it is not listed in the Food Chemicals Codex.

Occurrence in rose

The damask rose, Rosa × damascena, is a hybrid derived from Rosa gallica and Rosa moschata. Rose oil holds many molecules, and the ones that matter most to its smell are scarce but intensely odorous: beta-damascenone makes up 0.14 % of the oil, beta-ionone 0.03 %, and beta-damascone and rose oxide also contribute strongly. Citronellol, by contrast, is over a third of the oil studied, but its odour threshold is high, so its contribution is small.

Use levels and flavour

A solution of 1 % or less is recommended for smelling alpha-damascone. As a flavour, alpha-damascone is described as fruity, green, seedy, tropical, spicy, apple and woody.

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