Structure 3.2.11

NMR Splitting Patterns

High-resolution NMR reveals "spin-spin coupling", where signals are split into clusters of peaks.

The n+1 Rule

If a proton has n neighbors on adjacent carbons, its signal will split into n + 1 peaks.

0 Neighbors

1:1

1 Neighbor

1:2:1

2 Neighbors (e.g., -CH₂-)

1:3:3:1

3 Neighbors (e.g., -CH₃)

Deep Think Concept

One of the most common patterns in IB Chemistry exams is the Ethyl Group ( $-CH_2CH_3$ ).

The $-CH_3$ protons see 2 neighbors:

Triplet

The $-CH_2-$ protons see 3 neighbors:

Quartet

If you see a Triplet and a Quartet in the same spectrum, think Ethyl.