Benzyl alcohol

Benzyl alcohol is an organic compound with the formula C6H5CH2OH. The benzyl 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. Benzyl alcohol is partially soluble in water (4 g/100 mL) and completely miscible in alcohols and diethyl ether.

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 oils including jasmine, hyacinth, and ylang-ylang.

Benzyl alcohol is prepared by the hydrolysis of benzyl chloride using sodium hydroxide:
 * C6H5CH2Cl + NaOH → C6H5CH2OH + NaCl

It can also be prepared via a Grignard reaction by reacting phenylmagnesium bromide (C6H5MgBr) with formaldehyde, followed by acidification.

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 &rarr;  C6H5CH2N(H)C(O)CHCH2

Applications
Benzyl alcohol is used as a general solvent for inks, paints, lacquers, and epoxy resin coatings. It is also a precursor to a variety of esters, used in the soap, perfume, and flavor industries. It is often added to intravenous medication solutions as a preservative due to its bacteriostatic and antipruritic properties. It is also used as a photographic developer.

Nanotechnological uses
Benzyl alcohol has been used as a dielectric solvent for the dielectrophoretic 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, conjugated with glycine in the liver, and excreted as hippuric acid. 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 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 spiracles: the spiracles become blocked with the other products in the lotion, and the lice asphyxiate. 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 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). Similarly, white wool immersed in benzyl alcohol also becomes almost invisible clearly revealing contaminants such as dark and medullated fibres and vegetable matter.