Benzyl chloride

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Not to be confused with benzoyl chloride.
Benzyl chloride
Benzyl chloride Benzyl-chloride-3D-vdW.png
Identifiers
CAS number 100-44-7 YesY
PubChem 7503
ChemSpider 13840690 YesY
UNII 83H19HW7K6 YesY
EC-number 202-853-6
KEGG C19167 YesY
ChEBI CHEBI:615597 YesY
ChEMBL CHEMBL498878 YesY
Jmol-3D images Image 1
Image 2
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 (nD) 1.5415 (15 °C)
Hazards
MSDS External MSDS
EU Index 602-037-00-3
NFPA 704
Flammability code 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 fuel Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point 67 °C (153 °F; 340 K)
LD50 1231 mg/kg (rat, oral)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
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[edit]

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[edit]

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[edit]

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[edit]

  1. ^ a b M. Rossberg et al. “Chlorinated Hydrocarbons” in Ullmann’s Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a06_233.pub2
  2. ^ 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 .
  3. ^ Henry Gilman and W. E. Catlin (1941), "n-Propylbenzene", Org. Synth. ; Coll. Vol. 1: 471 

External links[edit]