Benzyl alcohol (also known as α-

cresol Cresols (also known as hydroxytoluene, toluenol, benzol or cresylic acid) are a group of aromatic organic compounds. They are widely-occurring phenols (sometimes called ''phenolics'') which may be either natural or manufactured. They are also c ...

) is an

aromatic In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

with the formula C₆H₅CH₂OH. The benzyl group is often abbreviated "Bn" (not to be confused with "Bz" which is used for benzoyl), thus benzyl alcohol is denoted as BnOH. Benzyl alcohol is a colorless liquid with a mild pleasant aromatic odor. It is useful as a solvent for its polarity, low toxicity, and low

vapor pressure Vapor pressure or equilibrium vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. The equilibrium vapor pressure is an indicat ...

. Benzyl alcohol has moderate

solubility In chemistry, solubility is the ability of a chemical substance, substance, the solute, to form a solution (chemistry), solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form su ...

in water (4 g/100 mL) and is miscible in alcohols and

diethyl ether Diethyl ether, or simply ether, is an organic compound with the chemical formula , sometimes abbreviated as . It is a colourless, highly Volatility (chemistry), volatile, sweet-smelling ("ethereal odour"), extremely flammable liquid. It belongs ...

. The

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

produced by deprotonation of the alcohol group is known as benzylate or benzyloxide.

Natural occurrences

Benzyl alcohol is produced naturally by many plants and is commonly found in fruits and teas. It is also found in a variety of

essential oil An essential oil is a concentrated hydrophobic liquid containing volatile (easily evaporated at normal temperatures) chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetheroleum, or simply as the ...

s including

jasmine Jasmine (botanical name: ''Jasminum'', pronounced ) is a genus of shrubs and vines in the olive family of Oleaceae. It contains around 200 species native to tropical and warm temperate regions of Eurasia, Africa, and Oceania. Jasmines are wid ...

, hyacinth and ylang-ylang. It is also found in

castoreum Castoreum is a yellowish exudate from the castor sacs of mature beavers used in combination with urine to territorial marking, scent mark their territory. Both beaver sexes have a pair of castor sacs and a pair of anal glands, located in two c ...

from the castor sacs of beavers. Benzyl esters also occur naturally.

Preparation

Benzyl alcohol is produced industrially from

toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon with the chemical formula , often abbreviated as , where Ph stands for the phenyl group. It is a colorless, water Water is an inorganic compound with the c ...

via benzyl chloride, which is hydrolyzed: : C₆H₅CH₂Cl + H₂O → C₆H₅CH₂OH + HCl Another route entails hydrogenation of

benzaldehyde Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is among the simplest aromatic aldehydes and one of the most industrially useful. It is a colorless liquid with a characteristic almond-li ...

, a by-product of the oxidation of toluene to benzoic acid. For laboratory use, Grignard reaction of phenylmagnesium bromide (C₆H₅MgBr) with formaldehyde and the Cannizzaro reaction of benzaldehyde also give benzyl alcohol. The latter also gives benzoic acid, an example of an organic disproportionation reaction.

Reactions

Like most alcohols, it reacts with

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

s to form

ester In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

s. In organic synthesis, benzyl esters are popular protecting groups because they can be removed by mild hydrogenolysis. Benzyl alcohol reacts with acrylonitrile to give ''N''-benzylacrylamide. This is an example of a Ritter reaction: :C₆H₅CH₂OH + NCCHCH₂ → C₆H₅CH₂N(H)C(O)CHCH₂

Applications

Benzyl alcohol is used as a general

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

for inks, waxes, shellacs, paints,

lacquer Lacquer is a type of hard and usually shiny coating or finish applied to materials such as wood or metal. It is most often made from resin extracted from trees and waxes and has been in use since antiquity. Asian lacquerware, which may be c ...

s, and epoxy resin coatings. Thus it can be used in paint strippers, especially when combined with compatible

viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...

enhancers to encourage the mixture to cling to painted surfaces. It is a precursor to a variety of

s and ethers, used in the soap, perfume, and flavor industries. E.g. benzyl benzoate, benzyl salicylate, benzyl cinnamate, dibenzyl ether, benzyl butyl phthalate. It can be used as a local anesthetic, especially with epinephrine. As a dye solvent, it enhances the process of dying wool, nylon, and leather.

Use in health care

Benzyl alcohol is used as a bacteriostatic preservative at low concentration in intravenous medications, cosmetics, and topical drugs. Benzyl alcohol, sold under the brand name Ulesfia, was approved by the U.S.

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...

(FDA) in 2009, as a 5% solution for the treatment of head lice in people 6 months of age and older. It affects the louse's spiracles, preventing them from closing. These then become clogged with water or mineral oil or other matter and cause the insect to die from

asphyxiation Asphyxia or asphyxiation is a condition of deficient supply of oxygen to the body which arises from abnormal breathing. Asphyxia causes generalized hypoxia, which affects all the tissues and organs, some more rapidly than others. There are ...

. Benzyl alcohol is used effectively for treating lice infestations as the active ingredient in lotion shampoo with 5% benzyl alcohol. Benzyl alcohol is an ingredient used in the manufacture of soaps, topical creams, skin lotions, shampoos, and facial cleansers and is popular due to its anti-bacterial and anti-fungal properties. It is a common ingredient in a variety of household products.

Safety

Sensitization to benzyl alcohol occurs very rarely, mainly in patients with stasis dermatitis. Benzyl alcohol is not considered to be a carcinogen, and no data are available regarding teratogenic or reproductive effects. Benzyl alcohol has low acute toxicity with an of 1.2 g/kg in rats. It oxidizes rapidly in healthy individuals to benzoic acid, conjugated with glycine in the liver, and excreted as

hippuric acid Hippuric acid (Greek language, Gr. ''hippos'', horse, ''ouron'', urine) is a carboxylic acid and organic compound. It is found in urine and is formed from the combination of benzoic acid and glycine. Levels of hippuric acid rise with the consumpt ...

. Very high concentrations can result in toxic effects including respiratory failure, vasodilation, hypotension, convulsions, and paralysis. Benzyl alcohol is toxic to neonates and is associated with the gasping syndrome...

References

External links

* {{Authority control Flavors Primary alcohols Alcohol solvents Perfume ingredients Aromatic solvents Benzyl compounds E-number additives Antimicrobials