Nuclear magnetic resonance (NMR) is the most powerful structure-determination tool in organic chemistry, because it maps out the carbon–hydrogen framework in detail. Proton (¹H) NMR reports on hydrogen atoms in a molecule, and it delivers four independent pieces of information, each answering a different question:

1. Number of signals = the number of chemically distinct types of hydrogen. Equivalent protons (related by symmetry) produce one signal; each different chemical environment produces its own. Counting signals tells you how many kinds of H the molecule has.

2. Chemical shift (δ, in ppm) = the electronic environment of each hydrogen — essentially, how much nearby electronegative atoms or pi systems pull electron density away ("deshielding" the proton and shifting it downfield, to higher ppm). Rough anchors: alkane C–H near 0.9–1.5 ppm; H next to a carbonyl or electronegative atom around 2–4 ppm; vinyl (C=C–H) around 5–6.5 ppm; aromatic H around 7–8 ppm; aldehyde H near 9–10 ppm; carboxylic acid O–H around 10–12 ppm. Chemical shift tells you what kind of environment each hydrogen sits in.

3. Integration = the relative number of hydrogens giving each signal. The area under a peak is proportional to how many protons it represents, so a 3:2 integration ratio might mean a CH₃ next to a CH₂. Integration tells you how many of each type.

4. Spin–spin splitting (multiplicity) = the number of hydrogens on adjacent carbons. Neighboring nonequivalent protons split a signal according to the n+1 rule: a proton with n equivalent neighbors appears as a peak split into n+1 lines (a singlet = 0 neighbors, doublet = 1, triplet = 2, quartet = 3). This is the "count the neighbors" feature that lets you stitch fragments together — a triplet and a quartet in a 3:2 ratio, for instance, is the unmistakable signature of an ethyl group (–CH₂CH₃).

Interpreting a ¹H NMR spectrum is a synthesis of all four: signals tell you how many H environments exist, shift tells you their nature, integration tells you their headcount, and splitting tells you how they connect — together enough to assemble a structure.

"Read the Peaks"