Benzyl alcohol

Benzyl alcohol is an organic compound with the formula C₆H₅CH₂OH. The benzyl group is commonly abbreviated "Bn", thus BnOH, for benzyl alcohol. Benzyl alcohol is a colorless liquid with a mild pleasant aromatic odor. It is a natural constituent of a variety of essential oils including jasmine, hyacinth, and ylang-ylang.^[1] Benzyl alcohol is also 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 ether. It 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. Like most alcohols, it reacts with carboxylic acids to form esters.

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Applications

Benzyl alcohol is used as a general solvent for inks, paints, lacquers, and epoxy resin coatings.^[2] It is also a precursor to a variety of esters, used in the soap, perfume, and flavor industries, as well as for pharmaceuticals. It exhibits bacteriostatic and antipruritic properties. It is also used as a photographic developer.

Illustrative organic synthetic uses

In organic synthesis, benzyl esters are popular protecting groups because they can be removed by mild hydrogenolysis.^[3]

BnOH reacts with acrylonitrile to give N-benzylacrylamide. This is an example of a Ritter reaction:^[4]

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

Nanotechnological uses

Benzyl alcohol has been used as a dielectric solvent for the dielectrophoretic reconfiguration of nanowires.^[5]

Health & safety

Benzyl alcohol is used as a bacteriostatic preservative in parenteral (IV) medications. Benzyl alcohol is also known for its toxic effects including respiratory failure, vasodilation, hypotension, convulsions, and paralysis. Sixteen Neonatal deaths have been associated with the use of benzyl alcohol as a preservative in saline flush solutions.^[6] Preservative free solutions are now being used for the infant population.^{[citation needed]}

Benzyl alcohol should be avoided by people with perfume allergy.^{[citation needed]}

References

1. ^ Merck Index, 11th Edition, 1138.
2. ^ Benzyl alcohol at chemicalland21.com
3. ^ Furuta, K.; Gao, Q.-Z.; Yamamoto, H. (1998). "Chiral (Acyloxy)borane Complex-Catalyzed Asymmetric Diels-Alder Reaction: (1R)-1,3,4-Trimethyl-3-Cyclohexene-1-Carboxaldehyde". Org. Synth.; Coll. Vol. 9: 722. 
4. ^ Parris, C. L. (1973). "N-benzylacrylamide". Org. Synth.; Coll. Vol. 5: 73. 
5. ^ Alexander Wissner-Gross (19 Oct 2006). "Nanowires get reconfigured". Nanotechweb.org.
6. ^ (11 Jun 1982) "Neonatal Deaths Associated With Use Of Benzyl Alcohol — United States". Morbidity and Mortality Weekly Report 31 (22): 290-1.