Alkenes area class of HYDROCARBONS which contain only carbon and hydrogen. Two other terms which describe alkenes are unsaturated and olefins. UNSATURATED hydrocarbons contain either double or triple bonds. Since the compound is unsaturated with respect to hydrogen atoms, the extra electrons are shared between 2 carbon atoms forming double bonds in alkenes. Alkenes are also called OLEFINS because they form oily liquids on reaction with chlorine gas. The example compounds of ethene or ethylene and pentene are shown on the LEFT.

Ethylene is the number one organic chemical synthesized in the U. S. and the world. The small quantities of ethane, propane, and butane found in natural gas are converted into ethene. It can be produced by thermal cracking of ethane to produce ethene and a hydrogen molecule. Alkenes are the raw materials for a number of plastics such as polyethylene, PVC, polypropylene, and polystyrene. Alkene chemistry is found in unsaturated fats, beta-carotene, and seeing light through vision.

Properties
Structure	Physical Properties	Chemical Reactivity
CnH2n Example: CH2CH2	Boiling points depend on chain length, slightly less than alkanes. Non polar Insoluble in water Less dense than water	Alkenes are quite reactive because of the presence of the double bond. Many small compounds react by addition i.e. molecules add to the alkene to form one product. All compounds: Combustion Reaction

ALKENE NAMES Root names give the number of carbons in the longest continuous chain. Alkene names are formed by dropping the "ane" and replacing it with "ene" The following list gives samples: Example: root = propane - drop "ane" = "prop" alkene = "prop" + alkene ending = "ene" = propene
No. of Carbons	Root Name	Formula CnH2n	Structure
2	ethene	C2H4	CH2=CH2
3	propene	C3H6	CH2=CHCH3
4	1-butene	C4H8	CH2=CHCH2CH3
5	1-pentene	C5H10	CH2=CHCH2CH2CH3