simple alkyl
0.8-1.8 ppm
Usually shielded; overlap is common.
NMR reference
1H NMR chemical shifts
Approximate shift ranges overlap and depend on molecular environment, solvent, concentration, and instrument conditions.
allylic
1.6-2.4 ppm
Adjacent to C=C, shifted downfield from simple alkyl.
benzylic
2.2-3 ppm
Adjacent to aromatic ring.
alpha to carbonyl
2-3 ppm
Deshielded by nearby C=O.
attached to heteroatom
3-4.5 ppm
O, N, halogens, and sulfur shift protons downfield.
vinylic
4.5-6.5 ppm
Directly attached to alkene carbon.
aromatic
6.5-8.5 ppm
Ring-current effects dominate.
aldehydic
9-10.5 ppm
Strongly deshielded aldehyde proton.
carboxylic acid
10-13 ppm
Broad, exchangeable, concentration-dependent.
alcohol/amine exchangeable
0.5-6 ppm
Variable; often broad and solvent dependent.
Splitting practice
CH3 next to CH2 in a simple ethyl group
The n+1 rule assumes simple first-order coupling to equivalent neighboring hydrogens. Real spectra can show overlap, second-order effects, exchange, and long-range coupling.