Alkenes and Alkynes (Double & Triple bonds)
-Each carbon can have 4 bonds:
Carbon can form double & triple bonds with carbon atoms, when multiple bonds form, fewer hydrogen will attach the carbon atom
-The position of the double/triple bonds always has the lowest number and is put in front of the parent chain. Ex.
2-pentene-Naming rules are almost same as Alkanes, just change –ane to –ene foe Alkenes
For example CH2=CH2 ehene CH2=CH–CH3 1-propene or propene
-as we know, the general formula for Alkanes is CnH2n+2 , here have another formula for Alkenes is CnH2n
Naming rules:
1) Find the longest chain and place it at the end of the name
2) Number the carbon atoms to get the lowest number for the start of the double bond and place that number before the parent name.
3) Assign names and numbers for all side groups and assemble the name alphabetically (videos)http://www.youtube.com/watch?v=KWv5PaoHwPA
Alkenes: some molecules will have the same structure, but have different geometry.-these called geometric isomers
- trans & cis butane eample:
.
1. If the larger groups are both above H or below R the plane of the bond, the double bond is termed a “cis” double bond
2. If the larger groups are across the plane of the bond (H or R), the double bond is termed a “trans” double bond
3. If there are two identical groups on either end of the double bond (H or R), there are no geometric isomers, and no need for cis or trans in the name
Alkynes (hydrocarbons)- triple bonds between carbon atom (-yne for alkynes)
-Naming rules: (general formula: CnH2n-2)
The naming rules are “mostly” the same as the alkenes (with no cis or trans!)
1) Find the longest chain (and write at the end)
2) Number the carbon atoms to get the lowest number for the start of the triple bond and write that number before the parent name
3) Assign names and numbers for all side groups and assemble the name alphabetically
Double bonds (Alkenes) end in –ene Triple bonds (Alkynes) end in -yne
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