Fun. group formula → C = C
Name of fun. group → carbon - carbon double bond or olefinic double bond.
Definition : The aliphatic, unsaturated, hydrocarbons containing Carbon = Carbon double bond is called alkenes.
General Formula : CnH2n [ n = 2,3,4,....]
Nomenclature :
Common name system :
The common names of Alkenes are derived as using following steps.
1. Count the total number of carbon atoms in alkene molecule, Find the name of parent alkane.
2. Replace 'ane' suffix of an alkane with suffix 'ene' hence it becomes Alkylene.
3. Use the prefixes n, Iso & Neo whenever needed.
4. Now the position of double bond by using α, β, γ letters to normal carbon chain. These letters can be given from that terminal carbon nearest to C = C bond.
IUPAC system :
Following are the Rules can be employed to find the IUPAC names of alkanes.
Rule 1 :
Select the longest carbon chain containing C = C bond functional, find the name of parent alkane.
Replace ending 'ane' suffix to alkane with suffix 'ene'. This it becomes alkene.
Rule 2 :
Give numbering from that terminal carbon atom nearest to C = C bond.
Rule 3 :
Give name & position of branched group.
Give the location of C = C functional group.
Rule 4 :
If alkene contains 2,3,4 similar branched groups use the prefixes di, tri & tetra respectively.
Rule 5 :
If alkene contains different branched groups, suggest their names by alphabetical order.
| SL. No | Formula | Common name | IUPAC name | ||
| 1 | CH2 = CH2 | Ethylene | ethene | ||
| 2 | CH3-CH = CH2 | Propylene | propene | ||
| 3 | CH3-CH2-CH = CH2 | n,α -Buty-lene | 1-butene or but-1-ene | ||
| 4 | CH3 - CH = CH - CH3 | n,β-Buty-lene | 2-butene or but-2-ene | ||
| 5 |  |
Iso α- Butylene | 2-methyl-1-propene OR 2-methylprop-1-ene |
||
| 6 |  |
Neo-Pentylene | 2,2-dimethylbut-1-ene |