The conformers of n-butyl cyanide. Those investigated in the present work are given in the upper row: a) anti-anti, b) gauche-anti, and c) anti-gauche; the others are in the lower row: d) gauche-gauche’ and e) gauche-gauche. The ordering is from a) being lowest to e) being highest in energy. The C and N atoms are indicated by gray and violet “spheres”, respectively, and the H atoms by small, light gray “spheres”.