Difference between revisions of "Benzyl chloride"

Latest revision as of 09:59, 20 September 2010

Benzyl chloride
Benzyl chloride	File:Benzyl-chloride-3D-vdW.png
IUPAC name (Chloromethyl)benzene
Other names α-Chlorotoluene
style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers
CAS number	100-44-7 Y
PubChem	7503
ChemSpider	7222
EC-number	202-853-6
SMILES	Script error: No such module "collapsible list".
InChI	Script error: No such module "collapsible list".
InChI key	KCXMKQUNVWSEMD-UHFFFAOYAV
style="background: #F8EABA; text-align: center;" colspan="2" | Properties
Molecular formula	C7H7Cl
Molar mass	126.58 g/mol
Density	1.100 g/cm3
Melting point	−39 °C
Boiling point	179 °C
style="background: #F8EABA; text-align: center;" colspan="2" | Hazards
MSDS	External MSDS
EU Index	602-037-00-3
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 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 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

External links

• International Chemical Safety Card 0016
• SIDS Initial Assessment Report for benzyl chloride from the Organisation for Economic Co-operation and Development (OECD)de:Benzylchlorid

et:Bensüülkloriid fr:Chlorure de benzyle nl:Benzylchloride ja:塩化ベンジル pt:Cloreto de benzila ru:Бензилхлорид fi:Bentsyylikloridi

1. ↑ ^{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
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 CS1 maint: Multiple names: authors list (link) .
3. ↑ Henry Gilman and W. E. Catlin (1941), "n-Propylbenzene", Org. Synth. ; Coll. Vol., 1: 471  Missing or empty |title= (help)