For a doublet of doublet, how many neighbors does it have?

1 Answer
Shulgin
Apr 20, 2018

2

Explanation:

For a doublet of doublet you would see 4 peaks. When drawing the splitting tree this becomes obvious. So a splitting tree of a doublet of doublet would look like the following:
![https://useruploads.socratic.org/tYJUvD7zT0uS1ZGM18ww_doublet_of_doublet.jpg)
Here the proton what we look at in the molecule is the upper line. This proton has two neighbors with different coupling constants #(J)#.

So we start with the proton who has the highest #J#, which follows the #n+1# rule. Meaning we would see two peaks, shown between the arrow #J_(ba)#.

Now we take the proton with the lower #J#, which from each peak will make two doublets shown as #J_(bc)#.

This gives a signal with a doublet of doublets. Since we use #n+1# rule twice the amount of neighbors is 2.

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