1. Alkenes At least one double bond present in the main chain
General formula is CnH2n
Form a trigonal planar shape
Note: more on shapes in the next unit
Create a 120° angle between bonds
Considered “unsaturated” because other hydrogen atoms can be added
Always end in “~ene”

2. Nomenclature
Identify and name the longest carbon chain that CONTAINS THE DOUBLE BOND(S).
Number the carbons in the chain so that the two carbons involved in the double bond have the lowest possible numbers.
If the double bond is equidistant from both ends, number the chain so that the substituent(s) have the lowest possibly number.
Follow same rules for identifying and naming prefixes.

3. Nomenclature
Try naming this…
2-ethyl 1-pentene

4. Nomenclature
Now let’s draw 1-butene and 2-butene…
1-butene 2-butene

5. Nomenclature Let’s try a structure with more than one double bond…
1,3-pentadiene

6. Nomenclature Let’s put everything together and name…
4-ethyl-3,6-dimethyl 1,2,4-octatriene

7. Diastereomers Consider the following compounds…
cis-2-butene trans-2-butene 2-methyl-
1-propene

8. Alkynes At least one triple bond present in the main chain
General formula is CnH2n-2
Form a linear shape
Note: more on shapes in the next unit
Create a 180° angle between bonds
Considered “unsaturated” because other hydrogen atoms can be added
Always end in “~yne”

9. Nomenclature
Identify and name the longest carbon chain that CONTAINS THE TRIPLE BOND(S).
Number the carbons in the chain so that the two carbons involved in the triple bond have the lowest possible numbers.
If the triple bond is equidistant from both ends, number the chain so that the substituent(s) have the lowest possibly number.
Follow same rules for identifying and naming prefixes.

10. Nomenclature
Try naming this…
3,4-dimethyl 1-hexyne

11. Nomenclature
Now let’s draw 1-butyne and 2-butyne…
1-butyne 2-butene

12. Nomenclature Let’s try a structure with more than one triple bond…
2,4-hexadiyne

13. Nomenclature Let’s put everything together and name…
4-ethyl-4,5-dimethyl 2,6-octadiyne