Dicyclopentadiene, abbreviated DCPD, is a
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one ele ...
with formula C
10H
12. At room temperature, it is a white brittle wax, although lower purity samples can be straw coloured liquids. The pure material smells somewhat of soy wax or
camphor
Camphor () is a waxy, colorless solid with a strong aroma. It is classified as a terpenoid and a cyclic ketone. It is found in the wood of the camphor laurel ('' Cinnamomum camphora''), a large evergreen tree found in East Asia; and in the k ...
, with less pure samples possessing a stronger acrid odor. Its
energy density is 10,975
Wh/l.
Dicyclopentadiene is a co-produced in large quantities in the steam cracking of
naphtha
Naphtha ( or ) is a flammable liquid hydrocarbon mixture.
Mixtures labelled ''naphtha'' have been produced from natural gas condensates, petroleum distillates, and the distillation of coal tar and peat. In different industries and regions ...
and
gas oils to
ethylene
Ethylene ( IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds).
Ethylene ...
. The major use is in
resin
In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on n ...
s, particularly, unsaturated polyester resins. It is also used in inks, adhesives, and paints.
The top seven suppliers worldwide together had an annual capacity in 2001 of 179 kilotonnes (395 million pounds).
Synthesis and structure
The spontaneous dimerization of cyclopentadiene at room temperature to form dicyclopentadiene proceeds to around 50% conversion over 24 hours and yields the ''endo'' isomer in better than 99:1 ratio as the kinetically favored product (about 150:1 ''endo'':''exo'' at 80 °C). However, prolonged heating results in
isomerization to the ''exo'' isomer. The pure ''exo'' isomer was first prepared by base-mediated elimination of hydroiodo-''exo''-dicyclopentadiene. Thermodynamically, the ''exo'' isomer is about 0.7 kcal/mol more stable than the ''endo'' isomer. The ''exo'' isomer also has a lower reported melting point of 19°C.