Q10.42P - Chemistry: Molecular Nature Of Matter And Change

Question

Determine the shape around each central atom in each molecule, and explain any deviation from ideal bond angles: (a) ${\mathbf{CH}}_3{\mathbf{OH}}_{}$  (b)   ${\mathbf{N}}_2{\mathbf{O}}_4\mathbf{\left(}{\mathbf{O}}_2{\mathbf{NNO}}_2\mathbf{\right)}$

Step-by-Step Solution

Answer

The shapes and bond angles of molecules can be determined from the VSEPR theory. The deviations arise mainly due to lone pair-lone pair repulsions.

Step 1: Methanol

The methyl carbon atom is ${\mathbf{sp}}^3$ hybridised with a bond angle of  $\mathbf{109}\mathbf{.}\mathbf{5}\mathbf{°}$ .

The oxygen of the OH group is ${\mathbf{sp}}^3$  hybridised with an expected bond angle of  $\mathbf{109}\mathbf{.}\mathbf{5}\mathbf{°}$ , but the lone pairs on oxygen decrease the bond angle from  $\mathbf{109}\mathbf{.}\mathbf{5}\mathbf{°}$ . The shape around the oxygen atom is Bent or V-Shaped.

Step 2:Dinitrogen tetraoxide

The nitrogen atoms are ${\mathbf{sp}}^2$   hybridized and the geometry around the nitrogen atoms is planar. The expected bond angles are  $\mathbf{120}\mathbf{°}$ each. Since no lone pairs are present on the nitrogen atom, the bond angle is as expected.