Chlorotoluene

Not to be confused with Benzyl chloride.

Chlorotoluenes are aryl chlorides based on toluene in which at least one aromatic hydrogen atom is replaced with a chlorine atom. They have the general formula C₇H_8–nCl_n, where n = 1–5 is the number of chlorine atoms.

Monochlorotoluene

Monochlorotoluenes are chlorotoluenes containing one chlorine atom. There are three isomers, each with the formula C₇H₇Cl.

Properties

The isomers differ in the location of the chlorine, but have the same chemical formula. All have very similar boiling points, although p-chlorotoluene has a much higher melting point due to a more tightly packed crystal structure.

Monochlorotoluene isomers
Common name	o-chlorotoluene	m-chlorotoluene	p-chlorotoluene
Structure
Systematic name	1-chloro-2-methylbenzene	1-chloro-3-methylbenzene	1-chloro-4-methylbenzene
Molecular formula	C7H7Cl (C6H4ClCH3)
Molar mass	126.586 g/mol
Appearance	colorless liquid
CAS number	[95-49-8]	[108-41-8]	[106-43-4]
Properties
Density and phase	1.073 g/ml, liquid	1.072 g/ml, liquid	1.069 g/ml, liquid
Solubility in water	practically insoluble
Other solubilities	Soluble in non-polar solvents such as aromatic hydrocarbons
Melting point	−35 °C (−31 °F; 238 K)	−47 °C (−52.6 °F; 226 K)	7 °C (44.6 °F; 280 K)
Boiling point	159 °C (318.2 °F; 432 K)	162 °C (323.6 °F; 435 K)	162 °C (323.6 °F; 435 K)
Magnetic susceptibility	−81.98·10−6 cm3/mol	−80.07·10−6 cm3/mol	−80.07·10−6 cm3/mol

Benzyl chloride is an isomer, which has a chlorine substituted for one of the hydrogens of toluene's methyl group, and it is sometimes named α-chlorotoluene.

Preparation

A laboratory route to 2- and 4-chlorotoluene proceeds from 2- and 4-toluidines (i.e. 2- and 4-aminotoluene). These compounds are diazotized followed by treatment with cuprous chloride.^[1] Industrially, the diazonium method is reserved for 3-chlorotoluene. The industrial route to 2- and 4-chlorotoluene entails direct reaction of toluene with chlorine. The more valuable 4-chlorotoluene is separated from 2-chlorotoluene by distillation. Distillation cannot be applied to separating 3-chlorotoluene from 4-chlorotoluene.^[2]

Uses

2- and 4-chlorotoluene are precursors to the corresponding benzyl chloride (ClC₆H₄CH₂Cl), benzaldehyde (ClC₆H₄CHO), and benzoyl chloride (ClC₆H₄C(O)Cl).^[2] 2- and 4-chlorotoluenes are converted to 2-chlorobenzonitrile and 4-chlorobenzonitrile, respectively.^[3] Chlorotoluenes are precursors to dichlorotoluenes.

See also

• Bromotoluene
• Iodotoluene