¹H NMR by region
0–2 ppm — alkyl hydrogens, the routine workhorse signals. 2–3 ppm — α to a carbonyl, allylic to a double bond, or benzylic next to an aromatic ring. 3–4.5 ppm — H on a carbon attached to O or N (CH–OH, CH–OR, CH–NR₂). 5–7 ppm — vinyl H (on a C=C). 6.5–8 ppm — aromatic H. 9–10 ppm — aldehyde H. 10–13 ppm — carboxylic acid OH (broad).
¹³C NMR by region
Roughly twice as wide as ¹H. 0–50 ppm — alkyl carbons. 50–90 ppm — C attached to O or N. 90–160 ppm — sp² (alkene, aromatic). 160–180 ppm — ester, amide, carboxylic acid carbonyls. 180–220 ppm — ketones and aldehydes (the highest carbonyl region).
Splitting (n+1 rule)
In ¹H NMR, a hydrogen with n neighboring hydrogens on adjacent carbons splits into n+1 peaks: singlet, doublet, triplet, quartet. A CH₃ next to a CH appears as a doublet; a CH next to a CH₃ appears as a quartet. Equivalent neighbors don't split each other; only inequivalent neighbors count.
Integration
The area under each peak (the integral) is proportional to the number of H atoms generating that peak. A 3:2:1 ratio of integrals across three peaks means 3 H : 2 H : 1 H. Combined with shift and splitting, integration usually nails the structure.
Draw this on the whiteboard
Open the OChem Board whiteboard — benzene rings, wedge/dash bonds, and a clickable periodic table built in. No account needed.