Benzyl chloride

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Not to be confused with benzoyl chloride.

Benzyl chloride

IUPAC name chlorophenylmethane
Other names α-Chlorotoluene
Identifiers
CAS number	100-44-7^Y
PubChem	7503
ChemSpider	13840690^Y
UNII	83H19HW7K6^Y
EC-number	202-853-6
KEGG	C19167^Y
ChEBI	CHEBI:615597^Y
ChEMBL	CHEMBL498878^Y
Jmol-3D images	Image 1 Image 2
SMILES ClCc1ccccc1 c1ccc(cc1)CCl
InChI InChI=1S/C7H7Cl/c8-6-7-4-2-1-3-5-7/h1-5H,6H2^Y Key: KCXMKQUNVWSEMD-UHFFFAOYSA-N^Y InChI=1/C7H7Cl/c8-6-7-4-2-1-3-5-7/h1-5H,6H2 Key: KCXMKQUNVWSEMD-UHFFFAOYAV
Properties
Molecular formula	C₇H₇Cl
Molar mass	126.58 g/mol
Appearance	colorless to slightly yellow liquid
Density	1.100 g/cm³
Melting point	−39 °C; −38 °F; 234 K
Boiling point	179 °C; 354 °F; 452 K
Solubility in water	very slightly soluble
Solubility	soluble in ethanol, ethyl ether, chloroform, CCl₄ miscible in organic solvents
Refractive index (n_D)	1.5415 (15 °C)
Hazards
MSDS	External MSDS
EU Index	602-037-00-3
NFPA 704	2 3 1
Flash point	67 °C; 153 °F; 340 K
Autoignition temperature	585 °C; 1,085 °F; 858 K
LD₅₀	1231 mg/kg (rat, oral)
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

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

Benzyl chloride is prepared industrially by the gas-phase photochemical reaction of toluene with chlorine:^[1]

C₆H₅CH₃ + Cl₂ → C₆H₅CH₂Cl + HCl

In this way, approximately 100,000 tonnes are produced annually. The reaction proceeds via free radical, involving the intermediacy of the chlorine atoms.^[2] Side products of the reaction include benzal chloride and benzotrichloride.

Other methods 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 the precursor to benzyl esters which are used as plasticizer, flavorants, and perfumes. Phenylacetic acid, a precursor to pharmaceuticals, arises via benzyl cyanide, which is generated by treatment of benzyl chloride with sodium cyanide. Quaternary ammonium salts, used as surfactants, are readily formed by alkylation of tertiary amines with benzyl chloride.^[1]

In organic synthesis, benzyl chloride is used for the introduction of the benzyl protecting group for alcohols, yielding the corresponding benzyl ether, and carboxylic acids, yielding the corresponding benzyl ester. Benzoic acid (C₆H₅COOH) can be prepared by oxidation of benzyl chloride in the presence of alkaline KMnO₄

C₆H₅CH₂Cl + 2 KOH + 2 [O] → C₆H₅COOK + KCl + H₂O

It 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.

Benzyl chloride also reacts readily with metallic magnesium to produce a Grignard Reagent.^[3] It is preferable over benzyl bromide for the preparation of benzylic Grignard reagent, since the reaction of the bromide with magnesium tends to form the Wurtz-coupling product 1,2-diphenylethane.

Safety

Benzyl chloride is an alkylating agent. Indicative of its high reactivity (relative to alkyl chlorides), benzyl chloride reacts with water in a hydrolysis reaction to form benzyl alcohol and hydrochloric acid. Since benzyl chloride is quite volatile at room temperature, it can easily reach the mucous membranes where the hydrolysis takes place with production of hydrochloric acid. This explains why benzyl chloride is a lachrymator and has been used as a war gas. It is also very irritating to the skin.

References

↑ 1.0 1.1 M. Rossberg et al. “Chlorinated Hydrocarbons” in Ullmann’s Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a06_233.pub2
↑ 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 .
↑ Henry Gilman and W. E. Catlin (1941), "n-Propylbenzene", Org. Synth. ; Coll. Vol. 1: 471

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