Alkenes and Alkynes? Really now? Do Intelligent Chemists Really Not Know How to Make Up More Exciting Names?

Alkenes, Alkynes, who cares? They're the same thing.

WRONG.

Even though they both form bonds that contain fewer Hydrogen atoms attached to Carbon atoms, THEY ARE VERY DIFFERENT!
Naming these compounds are relatively easy, as they follow the same rules as naming Alkanes. Just remember to change the ENDING to the appropriate one!

Let's start with Alkenes.

Alkenes-->contain one or more double bonds
-->classified as unsaturated hydrocarbons
-->CHANGE ENDING TO "-ENE"

eg. CH3-CH2-C=CH-CH3
                               |
                             CH3-CH3-CH3
            
                 2-propyl-2-pentene

*notice how the ending of the parent chain changed

Alkenes have a many possible structures (same), BUT have different geometrical shape
-->this is special to ONLY ALKENES called geometric insomers

Geometric insomers-->occur when double bond is formed, having side chains attached (top & bottom)
-->2 types:
                  -trans: (top&bottom, bottom&top)
                  -cis: same side (top&top, bottom&bottom)


So, practice what you've learned!
Draw these structures:

4-methyl-2-pentene
3-propyl-2-heptene

Now, for the Alkynes!
Alkynes-->contain one or more triple bonds (yes, now you use 3 LINES!!)
-->also unsaturated hydrocarbons
-->naming rules are still the same, but CHANGE ENDINGS to "-YNE"


 eg. CH3-CH-CH3-C(insert triple bond here)C-CH3
        |         |
       C    CH3
  
                   5,6-methyl-2-heptyne


It's simple...REALLY!


Make sure you do some extra practice from the textbook!!
Memorize all the prefixes (it'll help)!




Jialynn.