1. CH 7-2: Alkene & Alkyne Nomenclature
Identify longest carbon chain containing the double bond
Drop the –ane ending and add –ene
Numbering is fixed by location of the double bond
Alkene location defined by two carbons; use lowest number to indicate position.
2,4-dimethyl-2-pentene

2. Nomenclature: cis/trans Geometry
Identify longest carbon chain containing the double bond
Drop the –ane ending and add –ene
Numbering is fixed by location of the double bond
Cis/trans geometry: used when same atom or group is found on each sp2 carbon:
trans-(S)-
5-bromo-3-methyl-2-hexene

3. Nomenclature: E/Z Geometry
Can the compound below be designated cis or trans?
Alternative to cis/trans is the E/Z nomenclature: used if all four sp2 substituents are different (cis/trans can not be used).
Determine highest priority atom at each sp2 carbon. If on same side of double bond use (Z), if on opposite sides of double bond use (E).
(Z)-
3-bromo-4-methyl-3-heptene

4. Alkyne Nomenclature – similar to alkenes
Alkane …………Alkyne
butane
2-butyne
1-butyne
The “dots” are to help locate the linear, sp carbons of the alkyne triple bond.

5. Alkane …………Alkyne Alkyne Nomenclature 4-methylpentyne
(S)-4-bromo-4,5-dimethyl-2-hexyne