Benzyl Alcohol and β‐Phenethyl Alcohol

Abstract

AbstractBenzyl alcohol and β‐phenethyl alcohol (2‐phenylethanol) are the simplest of the aromatic alcohols, and, as such, are chemically similar. Benzyl alcohol occurs widely in essential oils both as the free alcohol, and, more importantly from a fragrance standpoint, in the form of various esters. Although benzyl alcohol itself is rather bland in odor, combined with its much more fragrant esters it is an important part of the odor of jasmine, ylang‐ylang, gardenia, some rose varieties, narcissus and peony, as well as castoreum, balsams of peru and tolu, and propolis. Benzyl alcohol occurs primarily in flower oils and tree exudates. Benzyl alcohol readily undergoes the reactions characteristic of a primary alcohol, such as esterification and etherification, as well as halide formation. In addition, it undergoes ring substitution. Today benzyl alcohol is almost universally manufactured from toluene which is first chlorinated to give benzyl chloride. This is then hydrolyzed to benzyl alcohol by treatment with aqueous sodium carbonate. In the soap, perfume, and flavor industries benzyl alcohol is primarily used in the form of its aliphatic esters. Benzyl alcohol is commercially available in five grades. The largest proportion of benzyl alcohol is for use in the photographic and textile industries although the latter use has been declining. The textile grade is used as a dyeing assistant for wool and nylon. The pharmaceutical industry makes use of benzyl alcohol's local anesthetic, antiseptic, and solvent properties. The technical grade of benzyl alcohol is used in rug cleaners as a degreasing agent, in leather dyeing, in ballpoint inks, as a cleaner for soldering, and as an extractive distillation solvent for xylenes and cresols. In addition, benzyl alcohol is used extensively in the polymer industry and in the manufacture of automobile tires. This material has a Generally Recognized As Safe (GRAS) status indicated by the Flavor and Extract Manufacturers' Association for use in flavors and by the Council of Europe for use as a flavor. Benzyl alcohol satisfies the most current guidelines published by the International Fragrance Association (IFRA). Of all the aromatic organic molecules β‐phenethyl alcohol (PEA) is probably the most prestigious aroma chemical in the world of perfumery. This is because of its exquisite odor of natural rose petals. The compound undergoes the usual chemical reactions of alcohols or aromatic compounds. In insect control, PEA has been considered as a mosquito repellant. The alcohol also has antifungicidal properties. Because of factors of low cost, stability, and odor quality, PEA is ideally suited for use in bar soap fragrances. Current commercial methods for making PEA include Grignard synthesis, Friedel‐Crafts process, and catalytic hydrogenation of styrene oxide. Approximately 85% of the PEA is employed for fragrance use. The use of β‐phenethyl alcohol generally presents no health problems.