Isocyanides exhibit a strong absorption in their IR spectra in the range of 2165–2110 cm.
The electronic symmetry about the isocyanide N nucleus results in a slow quadrupolar relaxation so that C-N nuclear spin coupling can be observed, with coupling constants of ca. 5 Hz for the isocyanide C nucleus and 5–14 Hz for the C nucleus which the isocyanide group is attached to.