AlkenesBy: Elly Terry

• 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.

Definitions

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.