Benzyl Alcohol
CAS Number: 100-51-6
EC Number: 202-859-9
Chemical formula: C7H8O
Preferred IUPAC name: Phenylmethanol
Benzyl alcohol is an aromatic alcohol with the formula C6H5CH2OH. The benzyl group is often abbreviated as "Bn" (not to be confused with "Bz" for benzoyl), so benzyl alcohol is abbreviated as BnOH.
Benzyl alcohol is a colorless liquid with a slightly pleasant aromatic odor.
Benzyl alcohol is a useful solvent because of its polarity, low toxicity, and low vapor pressure. Benzyl alcohol has moderate solubility in water (4 g/100 mL) and is miscible in alcohols and diethyl ether.
The anion produced by deprotonation of the alcohol group is known as benzylate or benzyloxide.
Natural events
Benzyl alcohol is produced naturally by many plants and is often found in fruits and teas.
Benzyl alcohol is also found in various essential oils, including jasmine, hyacinth, and ylang-ylang.
Benzyl alcohol is also found in castoreum, the castor sacs of beavers.
Benzyl esters also occur naturally.
Preparation
Benzyl alcohol is produced industrially from toluene via hydrolysis to benzyl chloride:
C6H5CH2Cl + H2O → C6H5CH2OH + HCl
Another route requires hydrogenation of benzaldehyde, a byproduct of the oxidation of toluene to benzoic acid.
For laboratory use, the Grignard reaction of phenylmagnesium bromide (C6H5MgBr) with formaldehyde and the Cannizzaro reaction of benzaldehyde also yield benzyl alcohol.
The latter also gives benzoic acid, which is an example of organic disproportionation reaction.
Reactions
Like most alcohols, it reacts with carboxylic acids to form esters. 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 for inks, waxes, shellacs, paints, varnishes and epoxy resin coatings.
For this reason, benzyl alcohol can be used in paint strippers, especially when combined with compatible viscosity enhancers to promote the adhesion of the mixture to painted surfaces.
Benzyl alcohol is a precursor to various esters and ethers used in the soap, perfume and flavor industries, e.g. benzyl benzoate, benzyl salicylate, benzyl cinnamate, dibenzyl ether, benzyl butyl phthalate.
Benzyl alcohol can be used as a local anesthetic, especially with epinephrine.
As a dye solvent, it improves the dyeing process of wool, nylon and leather.
Use in healthcare
Benzyl alcohol is used at low concentrations as a bacteriostatic preservative in intravenous drugs, cosmetics, and topical medications.
Some caution is required if high levels of Benzyl alcohol are used as benzaldehyde derived from benzyl alcohol is used as a preservative in an injectable formulation solution.
Benzyl alcohol, sold under the brand name Ulesfia, was approved by the U.S. Food and Drug Administration (FDA) in 2009 as a 5% solution to treat head lice in people 6 months of age and older.
It affects the pointed ends of the lice and prevents them from closing.
These then become blocked with water or mineral oil or other substances, causing the insect to suffocate and die.
Benzyl alcohol is used effectively in the treatment of lice infestation as an active ingredient in lotion shampoos containing 5% benzyl alcohol.
Contact dermatitis
Allergic contact dermatitis illustration
Benzyl alcohol is an ingredient used in the manufacture of soaps, topical creams, skin lotions, shampoos, and facial cleansers and is popular for its antibacterial and antifungal properties. Benzyl alcohol is a common ingredient in a variety of household products and can cause severe allergic contact dermatitis in a significant percentage of the population.
Safety
Benzyl alcohol has low acute toxicity with an LD50 of 1.2 g/kg in rats.
Benzyl alcohol is rapidly oxidized to benzoic acid in healthy individuals, conjugated with glycine in the liver, and excreted as hippuric acid.
Very high concentrations may cause toxic effects such as respiratory failure, vasodilation, hypotension, convulsions, and paralysis.
Benzyl alcohol is toxic to neonates and is associated with gasping syndrome.
Benzyl alcohol is severely toxic and extremely irritating to the eyes.
Pure benzyl alcohol produces corneal necrosis.
Benzyl alcohol is not considered a carcinogen and no data are available regarding teratogenic or reproductive effects.
Molar mass: 108.140 g mol−1
Appearance: Colorless liquid
Smell: Lightly aromatic
Density: 1.044 g/cm3
Melting point: -15.2 °C (4.6 °F; 257.9 K)
Boiling point: 205.3 °C (401.5 °F; 478.4 K)
Solubility in water: 3.50 g/100 mL (20 °C) 4.29 g/100 mL (25 °C)
Solubility in other solvents: Soluble in benzene, methanol, chloroform, ethanol, ether, acetone[unclear]
daily S: 1.10
Vapor pressure: 0.18 kPa (60 °C)
Acidity (pKa): 15.40
Magnetic susceptibility (χ): −71.83 10−6 cm3/mol
Refractive index (nD): 1.5396
Viscosity: 5.474 cP
Dipole moment: 1.67 D
XLogP3: 1.1
Number of Hydrogen Bond Donors: 1
Number of Hydrogen Bond Acceptors: 1
Number of Rotatable Bonds: 1
Exact Mass: 108.057514874
Monoisotopic Mass: 108.057514874
Topological Polar Surface Area: 20.2 Ų
Heavy Atom Number: 8
Official Fee: 0
Complexity: 55.4
Isotope Atomic Number: 0
Number of Atom Stereocenters Defined: 0
Undefined Atom Stereocenter Count: 0
Number of Defined Bond Stereocenters: 0
Undefined Bond Stereocenter Count:0
Number of Covalently Bonded Units: 1
Compound Canonicalized: Yes
Benzyl alcohol is under review for use as a biocide in the EEA and/or Switzerland for the following purposes: crop protection.
Consumer Uses
Benzyl alcohol is used in the following products: washing and cleaning products, coating products, adhesives and sealants, polishes and waxes, inks and toners, air care products, and perfumes and fragrances.
Benzyl alcohol has an industrial use that results in the production of another substance (use of intermediates).
Other releases of benzyl alcohol to the environment are likely to occur from: indoor use (e.g., machine wash fluids/detergents, automotive care products, paints and coatings or adhesives, fragrances and air fresheners) and outdoor use.
Article service life
Release of benzyl alcohol into the environment may occur from industrial use: industrial abrasion processes with low release rates (e.g. textile cutting, metal cutting, machining or grinding).
Other releases of benzyl alcohol into the environment are likely to occur from: outdoor use in low release rate long-life materials (e.g. metal, wood and plastic building and construction materials) and indoor use in low release rate long-life materials (e.g. flooring, furniture, toys, building materials, curtains, footwear, leather goods, paper and cardboard products, electronic equipment).
Benzyl alcohol can be found in material-based products: fabrics, textiles and garments (e.g. clothing, bedding, curtains or carpets, textile toys), leather (e.g. gloves, shoes, wallets, furniture), paper used for large surface area products (e.g. construction and building materials for insulation panels, wallpapers), paper (e.g. wipes, feminine hygiene products, diapers, books, magazines, wallpapers) and paper used for articles with extensive direct skin (skin) contact during normal use (e.g. hygiene items (e.g. diapers, feminine hygiene products, adult incontinence products, tissues, towels, toilet paper).
Commonly used by professional workers
Benzyl alcohol is used in the following products: coatings, fillers, putties, plasters, modeling clay, metal surface treatment products, non-metal surface treatment products and laboratory chemicals.
Benzyl alcohol is used in the following areas: building and construction work, healthcare, scientific research and development, and formulation and/or repackaging of mixtures.
Benzyl alcohol is used in the manufacture of chemicals.
Other releases of this substance into the environment are likely to occur from: indoor use (e.g. machine wash fluids/detergents, automotive care products, paints and coatings or adhesives, fragrances and air fresheners) and outdoor use.
Uses in industrial sites
Benzyl alcohol is used in the following products: polymers, coating products, adhesives and sealants, fillers, putties, plasters, modeling clay, metal surface treatment products, non-metal surface treatment products, washing and cleaning products, paper chemicals and paints, oils and greases, photochemicals, textile treatment products and dyes, inks and toners, and cosmetics and personal care products.
Benzyl alcohol is used in the following areas: construction and building works.
Benzyl alcohol is used in the manufacture of chemicals, textiles, leather or fur, pulp, paper and paper products, rubber products and plastic products.
Release of this substance into the environment may occur from industrial use: in processing aids on industrial sites, as an intermediate step in the further manufacturing of another substance (use of intermediates) and substances in closed systems with minimal release.
Benzyl alcohol is most commonly known as benzyl alcohol, the aromatic alcohol is also known by several other names such as benzenemethanol or phenylcarbinol.
Benzyl alcohol is derived from the fruit, comes in the form of a colorless liquid and has a slightly sweet odor.
As a multifunctional ingredient, you can find benzyl alcohol on the ingredient labels of many different skin care, cosmetic and personal products, including moisturizers, lip balms, face washes and even makeup.
According to Wong, it is primarily used as a preservative in product formulation to stop microorganisms from overgrowing on products, which could then lead to an infection.
“Benzyl alcohol is mostly used because of the scare about parabens,” Wong says.
"Since many consumers are concerned about parabens, alternative preservatives need to be used for marketing reasons. It occurs naturally, so companies can use it in products and still market them as 'natural.'"
Benefits of Benzyl Alcohol
Aside from possibly having antioxidant effects in some formulas, benzyl alcohol doesn't have any specific benefits for your skin, but instead helps optimize skin care formulas so they perform better for your skin. Here are a few key ways benzyl alcohol helps your products work more effectively:
Preserves the product: Benzyl alcohol acts as a preservative in skin care and cosmetic products due to its ability to kill microbes, especially parasites, according to Krant.
“Any cosmetic or personal care product that does not contain preservatives (for example, preservative-free eye drops) usually comes in single-use containers to prevent contact or airborne contamination,” she says. Benzyl alcohol allows products to be bottled in larger packages designed for multiple uses.
Stabilizes the formula: Krant adds that the ingredient also acts as a stabilizing agent against oxidative degradation of the product, allowing your products to work more effectively for longer.
Has antioxidant activity: Benzyl alcohol also has antioxidant properties, and antioxidants protect against free radical damage, Krant says.
Dissolves ingredients: Benzyl alcohol acts as a solvent and helps dissolve other ingredients in the product formula.
Reduces viscosity: Benzyl alcohol also reduces viscosity, which allows products to flow more easily.
Gives off a pleasant odor: As an aromatic alcohol, benzyl alcohol is naturally fragrant and gives off a slightly sweet odor.