HL
NMR Splitting Patterns
High-resolution NMR reveals "spin-spin coupling".
The n+1 Rule
If a proton has n neighbors on adjacent carbons, its signal
splits into n + 1 peaks.
1
Singlet
0 Neighbors
1:1
Doublet
1 Neighbor
1:2:1
Triplet
2 Neighbors (−CH₂−)
1:3:3:1
Quartet
3 Neighbors (−CH₃)
Examiner Tip: The Ethyl Group Fingerprint
One of the most common patterns in IB Chemistry exams is the Ethyl Group (\(-CH_2CH_3\)).
\(-CH_3\) protons see 2 neighbors:
Triplet
\(-CH_2-\) protons see 3 neighbors:
Quartet
If you see a Triplet and a Quartet in the same spectrum, think Ethyl.