Alkene NMR

A vinyl hydrogen is attached directly to a double bond, an allyl hydrogen is attached to a carbon attached to the double bond.

C=C-H: 4.5-6.5 ppm, deshielded by anisotropy

C=C-C-H: 1.6-1.2 ppm, also deshielded. The anisotropy effect falls rapidly with distance.

Vinyl protons are rarely equivalent, becausce no rotation happens around the double bond. This can make the spectra of alkenes quite complicated. Another difficulty is that alkenes have noticeable ⁴J coupling - which can be even longer if the molecule is conjugated.

2-methyl-1-pentene