Chapter 13: Spectroscopy

H-NMR Chemical shifts

• The chemical shift is the position on the δ scale (in ppm) where the peak occurs.
• Typical δ /ppm values for protons in different chemical environments are shown in the schematic figure below.
• There are two major factors that influence chemical shifts

(a) deshielding due to reduced electron density (due electronegative atoms) and
(b) anisotropy (due to magnetic fields generated by π bonds).

© Dr. Ian Hunt, Department of Chemistry