Benzyl alcohol

Benzyl alcohol

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Benzyl alcohol is an organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 with the formula C6H5CH2OH. The benzyl
Benzyl
In organic chemistry, benzyl is the term used to describe the substituent or molecular fragment possessing the structure C6H5CH2-. Benzyl features a benzene ring attached to a CH2 group.-Nomenclature:...

 group is often abbreviated "Bn", thus benzyl alcohol is denoted as BnOH. Benzyl alcohol is a colorless liquid with a mild pleasant aromatic odor. It is a useful solvent due to its polarity, low toxicity, and low vapor pressure
Vapor pressure
Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...

. Benzyl alcohol is partially soluble in water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 (4 g/100 mL) and completely miscible in alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

s and diethyl ether
Diethyl ether
Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...

.

Occurrence and preparation


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
Essential oil
An essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile oils, ethereal oils or aetherolea, or simply as the "oil of" the plant from which they were extracted, such as oil of clove...

s including jasmine
Jasmine
Jasminum , commonly known as jasmines, is a genus of shrubs and vines in the olive family . It contains around 200 species native to tropical and warm temperate regions of the Old World...

, hyacinth, and ylang-ylang
Ylang-ylang
Cananga odorata, commonly called Ylang-ylang , cananga tree, ilang-ilang, kenanga , fragrant cananga, Macassar-oil plant or perfume tree),is a tree valued for its perfume...

.

Benzyl alcohol is prepared by the hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...

 of benzyl chloride
Benzyl chloride
Benzyl chloride, or α-chlorotoluene, is an organic compound with the formula C6H5CH2Cl. This colourless liquid is a reactive organochlorine compound that is a widely used chemical building block.-Preparation:...

 using sodium hydroxide:
C6H5CH2Cl + NaOH → C6H5CH2OH + NaCl


It can also be prepared via a Grignard reaction
Grignard reaction
The Grignard reaction is an organometallic chemical reaction in which alkyl- or aryl-magnesium halides add to a carbonyl group in an aldehyde or ketone. This reaction is an important tool for the formation of carbon–carbon bonds...

 by reacting phenylmagnesium bromide
Phenylmagnesium bromide
Phenylmagnesium bromide, with the simplified formula , is a magnesium-containing organometallic compound. It is so commonly used that it is commercially available as a solution in diethyl ether or tetrahydrofuran . Phenylmagnesium bromide is a Grignard reagent...

 (C6H5MgBr) with formaldehyde
Formaldehyde
Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

, followed by acidification.

Reactions


Like most alcohols, it reacts with carboxylic acid
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...

s to form ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

s. In organic synthesis, benzyl esters are popular protecting group
Protecting group
A protecting group or protective group is introduced into a molecule by chemical modification of a functional group in order to obtain chemoselectivity in a subsequent chemical reaction...

s because they can be removed by mild hydrogenolysis
Hydrogenolysis
Hydrogenolysis is a chemical reaction whereby a carbon–carbon or carbon–heteroatom single bond is cleaved or undergoes "lysis" by hydrogen. The heteroatom may vary, but it usually is oxygen, nitrogen, or sulfur. A related reaction is hydrogenation, where hydrogen is added to the molecule, without...

.

Benzyl alcohol reacts with acrylonitrile
Acrylonitrile
Acrylonitrile is the chemical compound with the formula C3H3N. This pungent-smelling colorless liquid often appears yellow due to impurities. It is an important monomer for the manufacture of useful plastics. In terms of its molecular structure, it consists of a vinyl group linked to a nitrile...

 to give N-benzylacrylamide. This is an example of a Ritter reaction
Ritter reaction
The Ritter reaction is a chemical reaction that transforms a nitrile into a N-alkyl amide using various alkylating reagents, for example, strong acid and isobutylene....

:
C6H5CH2OH + NCCHCH2 → C6H5CH2N(H)C(O)CHCH2

Applications


Benzyl alcohol is used as a general solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

 for ink
Ink
Ink is a liquid or paste that contains pigments and/or dyes and is used to color a surface to produce an image, text, or design. Ink is used for drawing and/or writing with a pen, brush, or quill...

s, paint
Paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

s, lacquer
Lacquer
In a general sense, lacquer is a somewhat imprecise term for a clear or coloured varnish that dries by solvent evaporation and often a curing process as well that produces a hard, durable finish, in any sheen level from ultra matte to high gloss and that can be further polished as required...

s, and epoxy resin coatings. It is also a precursor to a variety of esters, used in the soap
Soap
In chemistry, soap is a salt of a fatty acid.IUPAC. "" Compendium of Chemical Terminology, 2nd ed. . Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford . XML on-line corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN...

, perfume
Perfume
Perfume is a mixture of fragrant essential oils and/or aroma compounds, fixatives, and solvents used to give the human body, animals, objects, and living spaces "a pleasant scent"...

, and flavor industries. It is often added to intravenous medication solutions as a preservative due to its bacteriostatic and antipruritic
Antipruritic
Antipruritics, also known as anti-itch drugs, are medications that inhibit the itching that is often associated with sunburns, allergic reactions, eczema, psoriasis, chickenpox, fungal infections, insect bites and stings like those from mosquitoes, fleas, and mites, and contact dermatitis and...

 properties. It is also used as a photographic developer.

Nanotechnological uses


Benzyl alcohol has been used as a dielectric solvent for the dielectrophoretic
Dielectrophoresis
Dielectrophoresis is a phenomenon in which a force is exerted on a dielectric particle when it is subjected to a non-uniform electric field. This force does not require the particle to be charged. All particles exhibit dielectrophoretic activity in the presence of electric fields...

 reconfiguration of nanowires.

Use in health care


Benzyl alcohol is used as a bacteriostatic preservative at low concentration in intravenous medications. It is oxidized rapidly in healthy individuals to benzoic acid
Benzoic acid
Benzoic acid , C7H6O2 , is a colorless crystalline solid and the simplest aromatic carboxylic acid. The name derived from gum benzoin, which was for a long time the only source for benzoic acid. Its salts are used as a food preservative and benzoic acid is an important precursor for the synthesis...

, conjugated with glycine in the liver, and excreted as hippuric acid
Hippuric acid
Hippuric acid is a carboxylic acid found in the urine of horses and other herbivores. Hippuric acid crystallizes in rhombic prisms which are readily soluble in hot water, melt at 187 °C and decompose at about 240 °C...

. High concentrations can result in toxic effects including respiratory failure, vasodilation, hypotension, convulsions, and paralysis. Newborns, especially if critically ill, may not metabolize benzyl alcohol as readily as adults. Reports in the early 1980s of sixteen neonatal deaths associated with the use of saline flush solutions containing benzyl alcohol preservative led to recommendations to avoid its use in neonates.

The use of benzyl alcohol as a 5% solution has been approved by the U.S. FDA in the treatment of head lice
Head-louse infestation
Pediculosis capitis is a human medical condition caused by the colonization of the hair and skin by the parasitic insect Pediculus humanus capitis—the head louse. Typically, only the head or scalp of the host is infested...

 in children older than 6 months and in adults. The product is sold in the United States (prescription-only) as Ulesfia lotion. The benzyl alcohol prevents the lice from closing their respiratory spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...

s: the spiracles become blocked with the other products in the lotion, and the lice asphyxia
Asphyxia
Asphyxia or asphyxiation is a condition of severely deficient supply of oxygen to the body that arises from being unable to breathe normally. An example of asphyxia is choking. Asphyxia causes generalized hypoxia, which primarily affects the tissues and organs...

te. The lotion is not effective against louse eggs, and so two applications with an interval of seven days are required to treat a case of louse infestation.

Other uses


Benzyl alcohol has nearly the same refraction index of quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

 and wool fibre. If a clear quartz object is immersed in benzyl alcohol, it becomes almost invisible. This has been used as a method to non-destructively recognize if an object is made of true quartz or not (see crystal skull
Crystal skull
The crystal skulls are a number of human skull hardstone carvings made of clear or milky quartz rock, known in art history as "rock crystal", claimed to be pre-Columbian Mesoamerican artifacts by their alleged finders. However, none of the specimens made available for scientific study have been...

). Similarly, white wool immersed in benzyl alcohol also becomes almost invisible clearly revealing contaminants such as dark and medullated fibres and vegetable matter.