The cyanate ion, OCN−, is a linear ion known to possess multiple resonance structures in which the negative charge and multiple-bond character are delocalized among the three atoms.
(a) Draw all valid resonance structures for OCN− and assign formal charges to each atom in every structure.
(b) Assuming the resonance structures contribute equally, calculate the average bond order for the N–C bond and for the C–O bond in the resonance hybrid.
(c) Infrared spectroscopy of OCN− shows an N–C stretching frequency at 2080 cm−1 and a C–O stretching frequency at 1370 cm−1. Relate these vibrational data to the bond orders obtained in part (b).
(d) Using electronegativity considerations and the formal charges in the resonance structures, argue which single resonance structure most accurately reflects the dominant contributor to the resonance hybrid.