Benzyl alcohol

Benzyl alcohol
Names
IUPAC name
Phenylmethanol
Other names
Phenylcarbinol
Identifiers
100-51-6 Yes
ChEBI CHEBI:17987 Yes
ChEMBL ChEMBL720 Yes
ChemSpider 13860335 Yes
EC number 202-859-9
Jmol-3D images Image
Image
KEGG D00077 Yes
PubChem 244
RTECS number DN3150000
UNII LKG8494WBH Yes
Properties[1]
Molecular formula
 C7H8O
Molar mass 108.14 g·mol−1
Appearance colorless liquid
Odor slightly aromatic
Density 1.044 g cm−3
Melting point −15.2 °C (4.6 °F; 257.9 K)
Boiling point 205.3 °C (401.5 °F; 478.4 K)
3.50 g/100 mL (20 °C)
4.29 g/100 mL (25 °C)
Solubility soluble in benzene, methanol, chloroform, ethanol, ether, acetone
log P 1.10
Vapor pressure 0.18 kPa (60 °C)
Acidity (pKa) 15.40
1.5396
Viscosity 5.474 cP
Dipole moment 1.67 D
Thermochemistry
217.8 J/K mol
Std enthalpy of
formation (ΔfHo298)
 -352 kJ/mol
Hazards
MSDS External MSDS
EU Index 603-057-00-5
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
1
1
0
Flash point 101 °C (214 °F; 374 K)
436 °C (817 °F; 709 K)
Explosive limits 1.3–13%
1250 mg/kg (rat, oral)
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Benzyl alcohol is an aromatic alcohol 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 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.

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 oils including jasmine, hyacinth, and ylang-ylang.[2]

It is also one of the chemical compounds found in castoreum. This compound is gathered from the beaver plant food.[3]

Preparation

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.[4]

Benzyl alcohol reacts with acrylonitrile to give N-benzylacrylamide. This is an example of a Ritter reaction:[5]

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

Applications

Benzyl alcohol is used as a general solvent for inks, paints, lacquers, and epoxy resin coatings.[6] It is also a precursor to a variety of esters, used in the soap, perfume, and flavor industries. 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.[7][8]

Use in health care

Benzyl alcohol is used as a bacteriostatic preservative at low concentration in intravenous medications, cosmetics and topical drugs.

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.[9]

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.

Safety

Benzyl alcohol is only a mild acute toxin with an LD50 of 1.2 g/kg in rats.[10] It oxidizes rapidly in healthy individuals to benzoic acid, conjugated with glycine in the liver, and excreted as hippuric acid. Very high concentrations can result in toxic effects including respiratory failure, vasodilation, hypotension, convulsions, and paralysis.

Benzyl alcohol is toxic to neonates, it is associated with the gasping syndrome.[11][12]

Benzyl alcohol has been reported to cause skin allergy.[13]

Benzyl alcohol is severely toxic and highly irritating to the eye.[10] Pure benzyl alcohol produces corneal necrosis.[14]

Benzyl alcohol is not considered to be a carcinogen and no data are available regarding teratogenic or reproductive effects.[10]

References

  1. ↑ benzyl alcohol.
  2. ↑ The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (11th ed.), Merck, 1989, ISBN 091191028X, 1138.
  3. ↑ The Beaver: Its Life and Impact. Dietland Muller-Schwarze, 2003, page 43 (book at google books)
  4. ↑ Furuta, Kyoji; Gao, Qing-Zhi; Yamamoto, Hisashi (1995). "Chiral (Acyloxy)borane Complex-Catalyzed Asymmetric Diels-Alder Reaction: (1R)-1,3,4-Trimethyl-3-Cyclohexene-1-Carboxaldehyde". Org. Synth. 72: 86.; Coll. Vol. 9, p. 722.
  5. ↑ Parris, Chester L. (1962). "N-benzylacrylamide". Org. Synth. 42: 16.; Coll. Vol. 5, p. 73.
  6. ↑ Benzyl alcohol, chemicalland21.com.
  7. ↑ A. D. Wissner-Gross, "Dielectrophoretic reconfiguration of nanowire interconnects", Nanotechnology 17, 4986–4990 (2006).
  8. ↑ Nanowires get reconfigured, Nanotechweb.org, 19 October 2006.
  9. ↑ Prescribing Information for Ulesfia Lotion (PDF), Sciele Pharmaceuticals, Inc., April 2009, retrieved 2009-08-29.
  10. ↑ 10.0 10.1 10.2 Friedrich Brühne; Elaine Wright (2007), "Benzyl Alcohol", Ullmann's Encyclopedia of Industrial Chemistry (7th ed.), Wiley, pp. 7–8
  11. ↑ Carl R. Baum (2008), "Examples of mass exposures involving the pediatric population", in Jerrold B. Leikin; Frank P. Paloucek, Poisoning and Toxicology Handbook (4th ed.), Informa, p. 726
  12. ↑ Juan Gershanik et al. (1982), "The gasping syndrome and benzyl alcohol poisoning.", N Engl J Med 307: 1384–8, doi:10.1056/nejm198211253072206
  13. ↑ EJ Curry; EM Warshaw (2005), "Benzyl alcohol allergy: importance of patch testing with personal products.", Dermatitis (16): 203–8
  14. ↑ Swarupa G Kulkarni; Harihara M Mehendale (2005), "Benzyl Alcohol", Encyclopedia of Toxicology 1 (2nd ed.), Elsevier, pp. 262–264

External links