Benzyl chloride

Not to be confused with benzoyl chloride, chlorotoluene, or chlorobenzene.
Benzyl chloride
Benzyl chloride
Benzyl chloride
Names
Preferred IUPAC name
(Chloromethyl)benzene
Other names
α-Chlorotoluene
Benzyl chloride
alpha-chlorophenylmethane
Identifiers
3D model (JSmol)
Abbreviations BnCl
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.002.594
EC Number
  • 202-853-6
KEGG
UNII
  • InChI=1S/C7H7Cl/c8-6-7-4-2-1-3-5-7/h1-5H,6H2 checkY
    Key: KCXMKQUNVWSEMD-UHFFFAOYSA-N checkY
  • InChI=1/C7H7Cl/c8-6-7-4-2-1-3-5-7/h1-5H,6H2
    Key: KCXMKQUNVWSEMD-UHFFFAOYAV
  • ClCc1ccccc1
Properties
C7H7Cl
Molar mass 126.58 g·mol−1
Appearance Colorless to slightly yellow, toxic liquid
Odor Pungent, aromatic[1]
Density 1.100 g/cm3
Melting point −39 °C (−38 °F; 234 K)
Boiling point 179 °C (354 °F; 452 K)
very slightly soluble (0.05% at 20 °C)[1]
Solubility soluble in ethanol, ethyl ether, chloroform, CCl4
miscible in organic solvents
Vapor pressure 1 mmHg (20 °C)[1]
−81.98·10−6 cm3/mol
1.5415 (15 °C)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Toxic and carcinogenic; lachrymator
GHS labelling:[3]
GHS05: CorrosiveGHS06: ToxicGHS08: Health hazard
Danger
H302, H315, H318, H331, H335, H350, H373
P203, P260, P264, P264+P265, P270, P271, P280, P301+P317, P302+P352, P304+P340, P305+P354+P338, P316, P317, P318, P319, P321, P330, P332+P317, P362+P364, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
3
2
1
Flash point 67 °C (153 °F; 340 K)
585 °C (1,085 °F; 858 K)
Explosive limits ≥1.1%[1]
Lethal dose or concentration (LD, LC):
121 mg/kg (rat, oral)
150 ppm (rat, 2 hr)
80 ppm (mouse, 2 hr)[2]
380 ppm (dog, 8 hr)[2]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 1 ppm (5 mg/m3)[1]
REL (Recommended)
 C 1 ppm (5 mg/m3) [15-minute][1]
IDLH (Immediate danger)
 10 ppm[1]
Safety data sheet (SDS) External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)
Infobox references

Benzyl chloride, or α-chlorotoluene, is an organic compound with the formula C6H5CH2Cl. This colorless liquid is a reactive organochlorine compound that is a widely used alkylating agent.[4] Its strong alkylating tendency renders it hazardous.

Preparation

Benzyl chloride is prepared industrially by the gas-phase photochemical reaction of toluene with chlorine:[4]

C6H5CH3 + Cl2 → C6H5CH2Cl + HCl

In this way, approximately 100,000 tonnes are produced annually. The reaction proceeds by the free radical process, involving the intermediacy of free chlorine atoms.[5] Side products of the reaction include benzal chloride and benzotrichloride.

Other methods of production exist, such as the Blanc chloromethylation of benzene. Benzyl chloride was first prepared from treatment of benzyl alcohol with hydrochloric acid.

Uses and reactions

Industrially, benzyl chloride is precursor to benzyl esters, which are used as plasticizers, flavorants, and perfumes. Quaternary ammonium salts, such as the benzalkonium chlorides used as surfactants, are produced by alkylation of tertiary amines with benzyl chloride.[4]

Benzyl chloride is more electrophilic and a stronger alkylating agent than typical alkyl chlorides. This behavior is the basis of its lachrymatory nature.

Some of the extensive use of benzyl chloride as a reagent is documented in Organic syntheses, which describes procedures for the alkylation of thiourea,[6] indoles and amines,[7][8] and carbanions and enolates.[9][10][11][12] Cyanide displaces chloride from benzyl chloride.[13] The resulting benzyl cyanide is a precursor to phenylacetic acid, a precursor to pharmaceuticals and commercial fragrances. Phenols and alcohols are common oxygen-containing substrates, the product being benzyl ethers.[14] In organic synthesis, these ethers serve as protecting groups. Debenzylation of such ethers can be achieved by hydrogenolysis using palladium on carbon.

C6H5CH2OR + H2 → C6H5CH3 + HOR

Benzyl chloride undergoes hydrolysis to form benzyl alcohol:

C6H5CH2Cl + H2O → C6H5CH2OH + HCl

When treated with aqueous sodium hydroxide, benzyl chloride converts to benzyl alcohol and dibenzyl ether, depending on conditions.

Benzyl chloride also reacts readily with magnesium to produce a Grignard reagent.[15] It is preferable over benzyl bromide for the preparation of this reagent, since the reaction of the bromide with magnesium tends to form the Wurtz coupling product 1,2-diphenylethane.

Benzyl chloride is used to install benzyl groups on aromatic substrates. For example, when benzyl chloride is treated with benzene and aluminium trichloride under the conditions of Friedel-Crafts alkylation, it gives diphenylmethane.[16] Heating benzyl chloride in the presence of aluminium trichloride gives poly(p-phenylene methylene):[17]

n C6H5CH2Cl → (C6H4CH2)n + n HCl

Safety and regulations

Benzyl chloride is a lachrymator and has been used in chemical warfare.[18] It is also very irritating to the skin.

It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.[19]

Benzyl chloride may be used in the synthesis of amphetamine-class drugs, and for this reason, sales of benzyl chloride are monitored as a List II drug precursor chemical by the US Drug Enforcement Administration.

See also

References

  1. ^ a b c d e f g NIOSH Pocket Guide to Chemical Hazards. "#0053". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ a b "Benzyl chloride". Immediately Dangerous to Life or Health Concentrations. National Institute for Occupational Safety and Health.
  3. ^ "Benzyl Chloride". pubchem.ncbi.nlm.nih.gov. Retrieved 24 December 2025.
  4. ^ a b c Lipper, Karl-August; Löser, Eckhard (2011). "Benzyl Chloride and Other Side-Chain Chlorinated Aromatic Hydrocarbons". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.o04_o01. ISBN 978-3-527-30385-4.
  5. ^ Furniss, B. S.; Hannaford, A. J.; Smith, P. W. G.; Tatchell, A. R. (1989), Vogel's Textbook of Practical Organic Chemistry (5th ed.), Harlow: Longman, p. 864, ISBN 0-582-46236-3
  6. ^ Yang, Zhanhui; Xu, Jiaxi (2014). "Preparation of Alkanesulfonyl Chlorides from S-Alkyl Isothiourea Salts via N-Chlorosuccinimide Mediated Oxidative Chlorosulfonation". Org. Synth. 91: 116. doi:10.15227/orgsyn.091.0116.
  7. ^ Batcho, Andrew D.; Leimgruber, Willy (1985). "Indoles from 2-Methylnitrobenzenes by Condensation with Formamide Acetals Followed by Reduction: 4-Benzyloxyindole". Org. Synth. 63: 214. doi:10.15227/orgsyn.063.0214.
  8. ^ Rubottom, George M.; Chabala, John C. (1974). "N-Alkylindoles from the Alkylation of Sodium Indolide in Hexamethylphosphoric Triamide: 1-Benzylindole". Org. Synth. 54: 60. doi:10.15227/orgsyn.054.0060.
  9. ^ Hauser, Charles R.; Dunnavant, W. R. (1960). "α,β-Diphenylpropionic Acid". Org. Synth. 40: 38. doi:10.15227/orgsyn.040.0038.
  10. ^ Uff, Barrie C.; Kershaw, John R.; Neumeyer, John L. (1977). "Alkylation of Isoquinolines via 2-Benzoyl-1,2-dihydroisoquinaldonitriles: 1-Benzylisoquinoline". Org. Synth. 56: 19. doi:10.15227/orgsyn.056.0019.
  11. ^ Marvel, C. S. (1941). "dl-Phenylalanine". Org. Synth. 21: 99. doi:10.15227/orgsyn.021.0099.
  12. ^ Willson, F. G.; Wheeler, T. S. (1928). "Benzylaniline". Org. Synth. 8: 38. doi:10.15227/orgsyn.008.0038.
  13. ^ Adams, Roger; Thal, A. F. (1922). "Benzyl Cyanide". Org. Synth. 2: 9. doi:10.15227/orgsyn.002.0009.
  14. ^ Enders, D.; von Berg, S.; Jandeleit, B. (2002). "Synthesis of (−)-(E,S)-3-(Benzyloxy)-1-butenyl Phenyl Sulfone via a Horner-Wadsworth-Emmons Reaction of (−)-(S)-2-(Benzyloxy)propanal". Org. Synth. 78: 177. doi:10.15227/orgsyn.078.0177.
  15. ^ Gilman, Henry; Catlin, W. E. (1925). "n-Propylbenzene". Organic Syntheses. 4: 59. doi:10.15227/orgsyn.004.0059.
  16. ^ Hartman, W. W.; Phillips, Ross (1934). "Diphenylmethane". Org. Synth. 14: 34. doi:10.15227/orgsyn.014.0034.
  17. ^ Brühne, Friedrich; Wright, Elaine (2000). "Benzyl Alcohol". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a04_001. ISBN 978-3-527-30385-4.
  18. ^ Sartori, Mario (1939). The War Gases. D. Van Nostrand. p. 129.
  19. ^ "40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities" (PDF) (July 1, 2008 ed.). Government Printing Office. Archived from the original (PDF) on February 25, 2012. Retrieved October 29, 2011.
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