Question

Methyl isocyanate, which was involved in the disaster in Bhopal, India, in 1984, has the chemical formula ${\mathbf{CH}}_{\mathbf{3}}\mathbf{NCO}$. Draw its Lewis diagram, including resonance forms. (Note: The N atom is bonded to the two C atoms.)

Short answer

The Lewis diagram of methyl isocyanate is,

Step-by-step solution

Resonance forms

When two or multiple Lewis structures can be collectively represented for a particular ion or molecule, the structures are termed as resonance structures. The phenomenon is called resonance or mesomerism.

Lewis structure of methyl isocyanate

The given formula$\left({\mathrm{CH}}_3\mathrm{NCO}\right)$can be represented with a structure bearing no formal charges.

However, there are also resonance forms because the delocalization on the linear part of the molecule allows both the oxygen and nitrogen atoms to "grab" a formal negative charge, while the other bears the positive one.

The structure on the left is considered less plausible (because of the positively charged oxygen). However, the structure on the right justifies why this molecule can be protonated on the oxygen atom.

Resonance forms of methyl isocyanate