Editing Alkene (section)

===Synthesis from alkenes===
The formation of longer alkenes via the step-wise polymerisation of smaller ones is appealing, as [[ethylene]] (the smallest alkene) is both inexpensive and readily available, with hundreds of millions of tonnes produced annually. The [[Ziegler–Natta process]] allows for the formation of very long chains, for instance those used for [[polyethylene]]. Where shorter chains are wanted, as they for the production of [[surfactant]]s, then processes incorporating a [[olefin metathesis]] step, such as the [[Shell higher olefin process]] are important. 
 
Olefin metathesis is also used commercially for the interconversion of ethylene and 2-butene to propylene. Rhenium- and molybdenum-containing [[heterogeneous catalysis]] are used in this process:<ref name=KO>{{cite encyclopedia|encyclopedia=Kirk-Othmer Encyclopedia of Chemical Technology |first1=Lionel |last1=Delaude |first2=Alfred F. |last2=Noels|year=2005| doi=10.1002/0471238961.metanoel.a01|place=Weinheim|publisher=Wiley-VCH|isbn = 978-0-471-23896-6|chapter = Metathesis|pages=metanoel.a01 }}</ref>
:CH<sub>2</sub>=CH<sub>2</sub>  +  CH<sub>3</sub>CH=CHCH<sub>3</sub>   →   2 CH<sub>2</sub>=CHCH<sub>3</sub>

Transition metal catalyzed [[hydrovinylation]] is another important alkene synthesis process starting from alkene itself.<ref name=Vogt2010>{{cite journal  | last = Vogt |first=D.  | year = 2010  | pages = 7166–8  | title = Cobalt-Catalyzed Asymmetric Hydrovinylation  | issue = 40  | pmid = 20672269  | journal = Angew. Chem. Int. Ed.  | volume = 49  | doi = 10.1002/anie.201003133 }}</ref> It involves the addition of a hydrogen and a vinyl group (or an alkenyl group) across a double bond.