1. SCH4C Ms. Richardson

2. Alkenes  Alkenes contain less hydrogen than alkanes and are considered to be unsaturated.  All alkenes contain at least one carbon- carbon double bond Two carbons share two pairs of electrons. ethene

3. Alkenes  When only one double bond is present, the general formula for an alkene is C n H 2n.  For butene and larger alkenes, the double bond can have different positions. We indicate the position of the bond(s) using a number as a prefix. 1-butene2-butene

4. Geometric Isomers  2-butene can be represented two ways structurally.  When the two surrounding hydrogens (or methyl groups) are on the same plane, it is a cis- isomer.  When the two surrounding groups are on opposite sides of the plane, it is a trans- isomer. cis-butenetrans-butene

5. Naming Alkenes  Alkenes are named the same way as alkanes, but the ending is –ene.  Some important points about naming alkenes: The main chain must contain the double bond The position of the double bond(s) is indicated using numbers, with the double bond getting the lowest number possible A prefix indicates how many double bonds are present 2-ethyl-3-methyl-1-pentene

6. Alkynes  Alkynes contain at least one carbon-carbon triple bond.  Alkynes with only one triple bond have the general formula C n H 2n-2.  Alkynes are named like alkenes, but the suffix is changed to –yne. ethyne