Ester NMR

Isobutyl acetate

O-C-H: 3.5 - 4.8 ppm. Deshielded by the O atom, but without the extra anisotropy effect.

O=C-CH: 2.1 - 2.5 ppm. This has a slightly higher range compared to the typical O=C-CH, since there is extra induction from the other oxygen atom.

A methyl ester would show a tall 3-proton singlet around 4 ppm. Induction falls rapidly with distance, so an ethyl group would show a 4 ppm quartet and a 1.3 ppm triplet - they will tend to merge into multiplets as more carbons are added.