Sandela

Isobornyl cyclohexanol (IBCH) is an organic compound with the molecular formula C₁₆H₂₈O. It is not found in nature. Sandalwood trees are endangered due to overharvesting, leading to a high cost for the natural oil. IBCH is therefore produced as an economical alternative to the natural product.

Chemistry

Its IUPAC name is 3-(5,5,6-trimethylbicyclo[2.2.1]heptan-2-yl)cyclohexanol. Its chemical structure is closely related to that of α-santalol and β-santalol, which are the primary constituents of sandalwood oil. Its EC number is 222-294-1. In the products of hydrogenating bornylguaiacol, the polycyclic alcohol alone is responsible for the sandalwood-type odour. Mixtures containing less than 50% of this alcohol were judged to be of little value as perfume materials, with deficiencies in diffusiveness of the top note, stability of odour in the dry-out, harmony and persistence. Complete hydrogenolysis of the starting material gives a practically odourless hydrocarbon as a by-product. At least 3.5 moles of hydrogen per mole of bornylguaiacol are essential, with 4 to 5 moles preferred. Amounts up to about 3.3 moles give materially inferior products. Raney nickel, supported nickel catalysts and copper chromite are all operable hydrogenation catalysts.

Sandalwood oil

Sandalwood oil is an essential oil obtained by steam distillation of chips and billets cut from the heartwood of sandalwood trees, mainly Santalum album. It contains more than 90% sesquiterpenic alcohols, of which 50 to 60% is α-santalol, while β-santalol makes up 20 to 25%. Because the wood is rare and expensive, synthetic odorants of similar structure and scent are used as lower-cost alternatives.

Safety

Its GHS labelling carries the signal word Warning, with hazard statements H315, H319, H411 and H412. An older European classification marks it as an irritant to the eyes. No FEMA number is given for it, and it is not meant for flavour use. Its cosmetic use is as a perfuming agent.

Use in Deodorants

The recommended level in the final product should ideally be between 0.3% to 0.6%. If the perfume level in a deodorant or antiperspirant product is 1%, the perfume should contain between 30% and 60% of Sandela. If the perfume level in the product is 1.5%, the perfume preferably consists of 20 to 40% Sandela. For stronger effects the level in the finished deodorant or antiperspirant may be raised to 1%, and in combination with other antibacterial fragrance materials it may be lowered to 0.1%. Sandela can also be added directly to the deodorant or antiperspirant formula, as an ingredient separate from the perfume, at a level of 0.1 to 1%. Sandela can partly replace farnesol in antibacterial fragrance compositions, and its price is four times lower than that of farnesol. The two can be combined in any ratio, adding up their antibacterial effect. The preferred levels are 10 to 80% Sandela and 5 to 50% farnesol. The test strains came from the axilla of 8 human volunteers. The intensity of its antibacterial effect against Corynebacteria and Staphylococcus is equal, which is not the case for Triclosan.

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