Definitions• Hydrocarbons are compounds containing hydrogen and carbon.• Alkenes are hydrocarbons containing a double carbon- carbon bond.• The C=C double bonds have a triganol planar molecular geometry with 120 bond angles.• C=C double bonds have one sigma and one pi bond.• Unlike C-C single bonds, C=C double bonds are unable to rotate freely. This is because of the overlapping of sigma and pi bond orbitals.• If there are four or more carbons in an alkene, the alkene can have isomers.
Ethene• Ethene, C2H4, is an alkene with a double bond in- between the two carbons.• The condensed structure is CH2=CH2.• The H-C-H bond angle is 120°.
Propene• Propene, C3H6, is an alkene because it has a double bond in-between the first two carbons.• The condensed structure for propene is CH2=CHCH3.
Physical States of Alkenes• Ethene, Propene, and Butene are colorless gases.• If an alkene has 5 or more carbons, it is a liquid.• Alkenes with fifteen or more carbons exist as solids.
Summary• In conclusion, alkenes are unsaturated hydrocarbons with one or more carbon- carbon double bond. Their double bond is made up of one sigma bond and one pi bond. The pi bond is what differentiates an alkene from an alkane.