Splitting the number of carbons into two groups

R–O–R
ether


ester
For some functional groups there are two carbon chains. 

All ethers have two carbon chains.
Most esters have two carbon chains. 
The exception is esters that have H bonded to the C=O.

When drawing all constitutional isomers for a specified number of carbons, split the number of carbons in all of the possible ways.

C5 can be split into C4 and C1 or C2 and C3.

Then consider branched isomers for chains longer than C2. 
 
There are for example, two arrangements of carbons for C3. 
Dr Sheila Woodgate
© The University of Auckland 2002