Question

Methyl isocyanate, \(\mathrm{CH}_{3}-\ddot{\mathrm{N}}=\mathrm{C}=\ddot{\mathrm{O}}:,\) is an intermediate in the manufacture of many pesticides. In \(1984,\) a leak from a manufacturing plant resulted in the death of more than 2000 people in Bhopal, India. What are the hybridizations of the \(\mathrm{N}\) atom and the two \(\mathrm{C}\) atoms in methyl isocyanate? Sketch the molecular shape.

Short answer

N: sp2; First C: sp2; Second C: sp

Step-by-step solution

Determine Hybridization of N Atom

Examine the structure of the \(\mathrm{N}\) atom in methyl isocyanate. The \(\mathrm{N}\) atom forms sigma bonds with two groups and has one lone pair of electrons. With three electron groups around it, the hybridization of the \(\mathrm{N}\) atom is \(\mathrm{sp}^2\).

Determine Hybridization of the First C Atom

Look at the \(\mathrm{C}\) atom bonded to the methyl group (\(\mathrm{CH}_3\)). This carbon is double-bonded to an oxygen atom and single-bonded to the nitrogen atom, making a total of three electron groups around it. Therefore, the hybridization of this carbon is \(\mathrm{sp}^2\).

Determine Hybridization of the Second C Atom

Consider the \(\mathrm{C}\) atom in the carbonyl group (connected to oxygen with a double bond). This carbon is triple-bonded to the nitrogen atom and single-bonded to the first carbon atom via a sigma bond, leading to two electron groups. Consequently, the hybridization of this carbon is \(\mathrm{sp}\).

Sketch the Molecular Shape

Using the determined hybridizations, sketch the molecular shape of methyl isocyanate. The \(\mathrm{N}\) with \(\mathrm{sp}^2\) hybridization will be in a trigonal planar arrangement. The first \(\mathrm{C}\) atom (also \(\mathrm{sp}^2\)) will have a trigonal planar geometry around it, and the second \(\mathrm{C}\) atom with \(\mathrm{sp}\) hybridization will be linear. Draw this structure accordingly.

Key concepts

Methyl Isocyanate

Methyl isocyanate, with the chemical formula \(\text{CH}_{3}-\text{N}=\text{C}=\text{O}\), is a highly dangerous compound. It is used as an intermediate in the production of pesticides.
Unfortunately, it became infamous for the tragic Bhopal disaster in \(1984\), where a leak caused over \(2,000\) deaths. Understanding its molecular structure helps us grasp the shape and reactivity of this compound.

Molecular Shape

The shape of a molecule is dictated by the arrangement of atoms around a central atom and the hybridization states of these atoms. Let's break down the shape of methyl isocyanate.
The \( \text{N} \) atom is \( \text{sp}^2 \) hybridized. It forms \(2\) sigma bonds and has \(1\) lone pair, taking on a trigonal planar shape.
The first \( \text{C} \) atom (attached to the methyl group) is also \( \text{sp}^2 \) hybridized. It makes \(3\) sigma bonds, adopting a trigonal planar geometry.
The second \( \text{C} \) atom in the carbonyl group is \( \text{sp} \) hybridized. It forms \(2\) sigma bonds in a linear shape. Together, these hybridizations give us a clear picture of how the molecule is structured.

Electronic Configuration

The electronic configuration of each atom in a molecule influences its hybridization and, consequently, the molecular shape.
For nitrogen (\text{N}), we have \(1s^2 2s^2 2p^3\), which leads to the \( \text{sp}^2 \) hybridization forming \(2\) sigma bonds and retaining a lone pair.
For carbon atoms, the configuration is \(1s^2 2s^2 2p^2\). In the first \( \text{C} \) atom, the \(2p\) electrons participate in \( \text{sp}^2 \) hybridization, while for the second \( \text{C} \), the same electrons participate in \( \text{sp} \) hybridization.