Diene

In organic chemistry a diene (/ˈdaɪ.iːn/ DY-een) (diolefin (/daɪˈoʊləfɪn/ dy-OH-lə-fin) or alkadiene) is a covalent compound that contains two double bonds, usually among carbon atoms. They thus contain two alkene units, with the standard prefix di of systematic nomenclature. As a subunit of more complex molecules, dienes occur in naturally occurring and synthetic chemicals and are used in organic synthesis. Conjugated dienes are widely used as monomers in the polymer industry. Polyunsaturated fats are of interest to nutrition. In organic chemistry a diene (/ˈdaɪ.iːn/ DY-een) (diolefin (/daɪˈoʊləfɪn/ dy-OH-lə-fin) or alkadiene) is a covalent compound that contains two double bonds, usually among carbon atoms. They thus contain two alkene units, with the standard prefix di of systematic nomenclature. As a subunit of more complex molecules, dienes occur in naturally occurring and synthetic chemicals and are used in organic synthesis. Conjugated dienes are widely used as monomers in the polymer industry. Polyunsaturated fats are of interest to nutrition. Dienes can be divided into three classes, depending on the relative location of the double bonds: According to the Gold Book definition, a 'diene' could include one or more heteroatoms which replace unsaturated carbon atoms, giving structures that could more specifically be called heterodienes. Compounds that contain more than two double bonds are called polyenes. Polyenes and dienes share many properties. On an industrial scale, butadiene is prepared by thermal cracking of butanes. In a similarly non-selective process, dicyclopentadiene is obtained from coal tars. In the laboratory, more directed and more delicate processes are employed such as dehydrohalogenations and condensations. Myriad methods have been developed, such as the Whiting reaction. Families of nonconjugated dienes are derived from the oligomerization and dimerization of conjugated dienes. For example, 1,5-cyclooctadiene and vinylcyclohexene are produced by dimerization of 1,3-butadiene. Diene-containing fatty acids are biosynthesized from acetyl CoA. α,ω-Dienes have the formula (CH2)n(CH=CH2)2. They are prepared industrially by ethenolysis of cyclic dienes. For example, 1,5-hexadiene and 1,9-decadiene, useful crosslinking agents and synthetic intermediates, are produced from 1,5-cyclooctadiene and cyclooctene, respectively. The catalyst is derived from Re2O7 on alumina. The most heavily practiced reaction of alkenes, dienes included, is polymerization. 1,3-Butadiene is a precursor to rubber used in tires, and isoprene is the precursor to natural rubber. Chloroprene is related but it is a synthetic monomer.