I kinda learned this from hard experiences… I think for this class (bio organic chemistry) we do not worry about double bonds since these molecules are unstable. The most important part of finding the possible structures given one formula is to focus on the functional group of interest and work around that in a step by step approach. I decided to show all the carbon atoms to make this much easier but with practice you won’t need to. I do draw small dashes to remind me of the hydrogens i’ve counted.

Formula: C4H11N

Notes: Start with the longest carbon chain with the functional group of interest at first. Keep consistency.


1. List all of the possible locations that functional group can switch the carbon with.

1. NCCCC
2. CNCCC
3. CCNCC
4. CCCNC
5. CCCCN

2. On each possibility add exactly the amount of hydrogens the formula contains. If not enough hydrogens are present then the molecule might be saturated and this will cause an additional slew of possibilities…

If not enough hydrogens are present then the molecule might be saturated and this will cause an additional slew of possibilities...

3. Label the longest carbon chains on each possibility.

1. NCCCC, LC=4 
2. CNCCC, LC=3 3. CCNCC, LC=2 4. CCCNC, LC=3 (duplicate) 5. CCCCN, LC=4 (duplicate)

5. Remove the duplicates.

7. Repeat this process with each formula above that was not a duplicate. (ie 1,2 and 3 were not duplicates.)

8. Now repeat, but this time check for rings. The long round arrows mean that the atom connects to this atom (in this molecule 6=#1, 7=#2.. and 8=#3 not shown since it cannot form a ring. sorry to confuse. ).