Iodotoluene

They have the general formula C7H8–nIn, where n = 1–5 is the number of iodine atoms.

The isomers differ in the location of the iodine, but have the same chemical formula.

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

A laboratory route to o- and p-iodotoluene proceeds from toluene, which is treated with a mixture of iodine and nitric acid in an electrophilic aromatic substitution.

The resulting mixture of o and p-iodotoluene is then separated by fractional freezing; cooling the mixture in an ice bath results in solidification of p-iodotoluene, which can then be isolated by filtration, while the o-iodotoluene remains behind as a liquid.