4-Ethyltoluene is an organic compound with the formula CH<sub>3</sub>C<sub>6</sub>H<sub>4</sub>C<sub>2</sub>H<sub>5</sub>. It is one of three isomers of ethyltoluene, the other two isomers being 3-ethyltoluene and 2-ethyltoluene. All are colorless liquids and all are used for the production of specialty polystyrenes.
Ethyltoluene is produced by ethylation of toluene:
Over typical acid catalysts, this process gives a mixture of the 2-, 3-, and 4- isomers. Using a modified zeolite catalyst, the alkylation is shape-selective for the 4- isomer.
4-Ethyltoluene is subjected dehydrogenation to give 4-vinyltoluene.