Structures and relative energies of the four different isomers of butyl cyanide. Here, the lowest energy conformers are shown. Panel a: the lowest energy isomer is tertiary butyl cyanide (0.0 kJ mol⁻¹). Panel b: 3-methylbutyronitrile (here the anti-conformer is shown) has an energy difference of 3.7 kJ mol⁻¹. Both conformers, the anti- and gauche-conformer, are essentially isoenergetic. Panel c: 2-cyano-anti-butane is about 6.6 kJ mol⁻¹ higher in energy. Panel d: the highest energy isomer is the straight-chain butyl cyanide (here the anti–anti-conformer is shown) with an energy of 11.0 kJ mol⁻¹ higher than the lowest energy isomer tertiary butyl cyanide. Blue and grey spheres indicate N and C atoms, respectively, and white spheres indicate H atoms.