Everything Science Grade 12

CHAPTER 1. ORGANICMOLECULES 1.7

Naming the alkenes ESCP

Similar rules will applyin naming the alkenes, as for the alkanes.

See video: VPmqj at http://www.everythingscience.co.za

Example 5: Naming the alkenes

QUESTION

Give the IUPAC name for the following compound:

H C(1)

H

H

C(2)

H

C(3)

H

C(4)

H

H

H

SOLUTION

Step 1 : Identify the functionalgroup

The compound is an alkene and will have the suffix -ene.

Step 2 : Find the longest carbonchain

There are four carbon atoms in the longest chainand so the prefix

for this compound will be ’but’.

Step 3 : Number the carbon atoms

Remember that when there is a double or triplebond, the car-

bon atoms must be numbered so that the double or triple bond

is at the lowest numbered carbon. In this case,it doesn’t matter

whether we number thecarbons from the left toright, or from the

right to left. The double bond will still fall between C 2 and C 3.

The position of the bond will come just beforethe suffix in the

compound’s name.

Step 4 : Look for any branchedgroups, name them andgive their posi-

tion on the carbon chain