Inorganic chemistry,terminal alkenes (alpha-olefins,α-olefins, or1-alkenes) are a family oforganic compounds which arealkenes (also known as olefins) with achemical formulaCxH2x, distinguished by having adouble bond at the primary,alpha (α), or1- position.[1] This location of a double bond enhances the reactivity of the compound and makes it useful for a number of applications.[2]
There are two types of alpha-olefins,branched andlinear (or normal). The chemical properties of branched alpha-olefins with a branch at either the second (vinylidene) or the thirdcarbon number are significantly different from the properties of linear alpha-olefins and those with branches on the fourth carbon number and further from the start of the chain.
Examples of linear alpha-olefins arepropene,but-1-ene anddec-1-ene. An example of a branched alpha-olefin isisobutylene.
A variety of methods are employed for production of alpha-olefins. One class of methods starts with ethylene which is eitherdimerized or oligomerized. These conversions are respectively effected by thealphabutol process, giving 1-butene, and theShell higher olefin process which gives a range of alpha-olefins. The former is based ontitanium-based catalysts, and the latter relies on nickel-basedcatalysts. A whole other approach to alpha-olefins, especially long chain derivatives, involves cracking ofwaxes:[2]
In thePACOL process (paraffin conversion to olefins), linear alkanes are dehydrogenated over a platinum-based catalyst.
Alpha-olefins are valued building blocks for other industrial chemicals.
A major portion of medium or long chain derivatives are converted todetergents andplasticizers. A common first step in making such products ishydroformylation followed by hydrogenation of the resultingaldehydes. Long chain alpha-olefins are also oligomerized to give medium molecular weight oils that serve as lubricants. Alkylation of benzene with alpha-olefins followed by ring-sulfonation giveslinear alkylbenzene sulfonates (LABS) which are biodegradable detergents. Competing often with these petroleum-derived products are derivatives offatty acids, such asfatty alcohols andfatty amines.[2]
Low molecular weight alpha-olefins (butenes, hexenes, etc.) are used ascomonomers, which are incorporated intopolyethylene. Some are subjected toolefin metathesis as a route topropylene.