Diethylbenzenes

Diethylbenzene (DEB) refers to any of three isomers with the formula C6H4(C2H5)2. Each consists of a benzene ring and two ethyl substituents. The meta and para have the greater commercial significance. All are colorless liquids.

2 ==Nomenclature==
 * Ortho: known as 1,2-diethylbenzene and o-diethylbenzene.
 * Meta: known as 1,3-diethylbenzene and m-diethylbenzene.
 * Para: known as 1,4-diethylbenzene and p-diethylbenzene.

Production and applications
Diethylbenzenes arise as side-products of the alkylation of benzene with ethylene, which can be described as two steps. The first step is the industrial route to ethylbenzene, which is produced on a large scale as a precursor to styrene.
 * C6H6 +  C2H4   →   C6H5C2H5

The diethylbenzene is an inadvertent side product.
 * C6H5C2H5 +  C2H4   →   C6H4(C2H5)2

Using shape-selective zeolite catalysts, the para isomer can be produced in high selectivity.

Much diethylbenzene is recycled by transalkylation to give ethylbenzene:
 * C6H4(C2H5)2 +  C6H6   →   2 C6H5C2H5

Uses
Diethylbenzene is used in a mixture with methyl and/or ethyl biphenyls as a low temperature heat transfer fluid.

Diethylbenzene is dehydrogenated to give divinylbenzene (DVB):
 * C6H4(C2H5)2  →   C6H4(C2H3)2  +  2 H2

DVB is used in the production of crosslinked polystyrene.