What is Diene?
[[File:1,3-butadiene.svg|thumb|150px|[[1,3-butadiene]]]] In [[organic chemistry]], a '''diene''' ({{IPAc-en|ˈ|d|aɪ|.|iː|n}} {{respell|DY|een}}) or '''diolefin''' ({{IPAc-en|d|aɪ|ˈ|oʊ|l|ə|f|ᵻ|n}} {{respell|dy|OH|lə-fin}}) is a [[hydrocarbon]] that contains two carbon [[pi bond]]s. [[Conjugated system|Conjugated]] dienes are [[functional group]]s, with a general formula of C<sub>n</sub>H<sub>2n-2</sub>. Dienes and alkynes are functional [[isomer]]s. Dienes occur occasionally in nature but are widely used in the [[polymer]] industry. ==Classes== Dienes can be divided into three classes, depending on the relative location of the double bonds: #'''Cumulated dienes''' have the double bonds sharing a common atom as in a group of compounds called [[allene]]s. #'''Conjugated dienes''' have [[Conjugated system|conjugated]] double bonds separated by one single bond. #'''Unconjugated dienes''' have the double bonds separated by two or more single bonds. They are usually less stable than isomeric conjugated dienes. Compounds that contain more than two double bonds are called [[polyene]]s. Polyenes and dienes, share many of their properties. [[Image:Diene.png|thumb|center|650 px|Some dienes: '''A''': 1,2-Propadiene, also known as [[allene]], is the simplest cumulated diene. '''B''': [[Isoprene]], also known as 2-methyl-1,3-butadiene, the precursor to natural rubber. '''C''': 1,3-[[Butadiene]], a precursor to synthetic polymers. '''D''': [[1,5-Cyclooctadiene]], an unconjugated diene (notice that each double bond is two carbons away from the other). '''E''': [[Norbornadiene]], a strained bicyclic and unconjugated diene. '''F''': [[Dicyclopentadiene]]. '''G''': [[Linoleic acid]], a fatty acid that is required in the human diet.]] ===Cycloadditions=== An important reaction for conjugated dienes is the [[Diels–Alder reaction]]. Many specialized dienes have been developed to exploit this reactivity for the synthesis of [[natural product]]s, e.g. [[Danishefsky’s diene]]. ==Other websites== *[[IUPAC]]s [[Gold Book]] defi