Alkenes and Alkynes

Naming Alkenes and Alkynes

1. Name the longest carbon chain that contains the double or triple bond (see table).
1. The name for the alkenes ends in ene instead of –ane.
2. The name for the alkynes ends in –yne instead of –ane. 
2. Number the main chain from the end nearest the double or triple bond.
1. Indicate the position of the double or triple bond with the number of the first unsaturated carbon.
3. Place the number and names of substituents in front of the alkene or alkyne name.
4. Cyclic alkenes are named as cycloalkenes.

 

Names of carbon chains:

Number of C atoms	Alkane Name	Alkene Name	Alkyne Name
1	Methane	--------	--------
2	Ethane	Ethene	Ethyne
3	Propane	Propene	Propyne
4	Butane	Butene	Butyne
5	Pentane	Pentene	Pentyne
6	Hexane	Hexene	Hexyne
7	Heptane	Heptene	Heptyne
8	Octane	Octene	Octyne
9	Nonane	Nonene	Nonyne
10	Decane	Decene	Decyne

 

Reactions of Alkenes and Alkynes

Reactant	Name of Reaction	Example
H2	Hydrogenation (catalyzed by metals)	CH2=CH2 → H-CH2-CH2-H
H2O	Hydration (catalyzed by acid)	CH2=CH2 → H-CH2-CH2-OH
X2	Halogenation	CH2=CH2 → Cl-CH2-CH2-Cl
HX	Hydrohalogenation	CH2=CH2 → Cl-CH2-CH2-H
KmnO4, H2O, and OH- or OsO4 and Na2SO3	Oxidation	CH2=CH2 → OH-CH2-CH2-OH

 

Naming Aromatic Compounds:

1. Base name is benzene.  Some benzene derivatives have common names (see below).
2. Number ring to give lowest numbers to substituents.
3. Name the substituents alphabetically.

 

Benzene Derivatives with Common Names:

 

 

Aromatic Substituents: