1H NMR: Proton Counting and Spin–Spin Splitting
Start with the big picture
Integration trace area is proportional to the number of equivalent protons represented by a signal. Normalize integral values against the smallest and scale the ratios to whole-number proton counts, while treating OH, NH, and SH integrations cautiously because exchange can make them unreliable. Splitting, by contrast, arises from spin–spin coupling: in first-order cases, n equivalent vicinal protons produce n + 1 lines, with relative intensities described by Pascal’s triangle. The total area of a multiplet—not each individual line—corresponds to its proton count. Coupling constants measure spacing between adjacent lines and help link coupled nuclei. When chemical-shift separation is not large relative to J, second-order patterns can distort line ratios without changing overall integration. Combining integration, splitting, and chemical shift helps assign fragments and complete proton accounting.
What you'll learn
- Normalize integration values to estimate proton counts, noting why exchangeable protons may be unreliable.
- Distinguish multiplet integration from splitting and apply the first-order n + 1 rule.
- Interpret line intensities and coupling constants in first-order spectra.
- Recognize when second-order effects or chemical exchange complicate signal patterns.
- Combine integration, splitting, and chemical shift to support proton assignment.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
