Alkenes



Alkenes are chemical compounds with one or more sets of carbon double bonds. Examples of Alkenes include ethene (the simplest of the alkenes), propene, butene, and pentene. The names are based upon the longest chain of carbons that has a double bond and the name given to the chain is based on the name of the similar alkane.


Ethene:
external image ethene01.png


Naming Alkenes

Specific numbers are assigned to alkenes, which are determined by the number of the carbon atom that is part of the double bond. For example: since butene has more than 2 carbons, the double bond can be located 2 different areas. Numerical prefixes and other suffexes like -diene and -triene are used to show the number of double bonds in the molecule. When the molecules have geometric isomers they use two prefixes, cis- and trans-, to show if the double bond is on the same side of the methyl group or the opposite respectively.

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Reactions of Alkenes

-Reactions of Alkenes are typically addition reactions, where the double bonded carbons are broken apart to bond with another atom.
-Hydrogen halides (like HBr) can break the double bond
-If hydrogen gas is added to an Alkene it will form a new Alkane, which is referred to as hydrogenation (this usually does not occur in standard conditions because the bonds between the two hydrogen atoms in the gas are hard to break apart)
-If water is added to the Alkene it can break the double bond with the help of an acid acting as a catalyst

Chemsitry: The Central Science
Brown, LeMay, Bursten

(By Ellen Varner)