Ebanol

Ebanol, also known as Matsunol, is a synthetic high-impact sandalwood odorant of the trisubstituted cyclopentenol chemical class. It is a complex mixture of four diastereomeric secondary alcohols not found in nature. The molecules have three asymmetric carbon centres and one carbon-carbon double bond, which gives rise to both E and Z geometric isomers.

Chemistry and properties

Its odour value exceeds 2 × 10⁵. Ebanol maintains reasonable stability, though prolonged exposure to extreme alkaline conditions such as liquid bleach may cause some olfactory degradation. Its water solubility is 34 mg/L at 20°C. Its EINECS number is 267-140-4 and its FEMA number is 4775. Ebanol has the molecular formula C₁₄H₂₄O and a molecular weight of 208.34. The (Z) isomer is named (Z)-3-methyl-5-(2,2,3-trimethylcyclopent-3-en-1-yl)pent-4-en-2-ol. It boils at 287 °C, with a range of 283–288 °C also recorded, and its flash point is 103 °C. Its density is 0.896–0.906 at 20 °C, its refractive index is 1.481–1.486, and its vapour pressure is 0.89 Pa at 25 °C. Its JECFA number is 2220; it is listed under the US Toxic Substances Control Act, falls in German water-hazard class 2 and is classified as Aquatic Chronic 2.

Sandalwood substitutes

Ebanol is one of the common synthetic substitutes for sandalwood oil. The wood is rare and expensive, so cosmetic companies use synthetic substitutes of similar structure and scent. Ebanol may also serve as an analytical standard for determining the analyte in sandalwood oil, cosmetics and personal care products. Synthetic odorants with a scent similar to sandalwood oil serve as lower-cost alternatives for perfumes, emollients and skin cleaning agents. Brahmanol, Firsantol, Sandalore and Sandaxol are named alongside Ebanol among the common substitutes.

Natural sandalwood oil is steam-distilled from chips and billets cut from the heartwood of sandalwood trees, mainly Santalum album and Santalum spicatum. It contains more than 90% sesquiterpenic alcohols, of which 50-60% is α-santalol. Its composition depends on the species, the region, and the age of the tree.

Structure and solubility

Ebanol is classed as an α,β-unsaturated alcohol with a cyclopentene ring system. It is a colourless to pale yellow liquid that dissolves in ethanol. Its octanol-water partition coefficient, given as logP, is 4.2, and its predicted pKa is 14.96.

Use in compositions

In fragrance concentrates Ebanol works from 0.1%, and typical levels run from 0.5% for a slight gain in volume to 3–5% for a sandalwood core in woody-oriental compositions. At 0.1–0.5% it gives subtle warmth and improves the perceived quality of woody accords, and at 1–3% it sets a clear sandalwood signature while staying transparent. At 3–5% it can serve as the main woody-musky base, but too much may bring out the aromatic-anisic facets and overwhelm subtler effects.

Its tenacity is exceptional and far exceeds that of most natural sandalwood oils, which makes it a fixative for more volatile components. A single molecule can hardly reproduce the scent of sandalwood oil, so a mixture of several synthetic substitutes is needed to obtain its full profile.

Natural sandalwood oil

Sandalwood oil is used in perfumes, cosmetics, sacred unguents and as a mild food flavouring. Its scent is woody-floral, and under some conditions it can smell creamy or even pickled. β-Santalol makes up 20–25% of the oil, and the ISO standard for Santalum album oil sets 41–55% α-santalol and 16–24% β-santalol. Australian sandalwood does not need its white sapwood removed before distilling, whereas Indian sandalwood does.