Q10.70CP - Chemistry: Molecular Nature Of Matter And Change

Question

Propylene oxide is used to make many products, including plastics such as polyurethane. One method for synthesizing it involves oxidizing propene with hydrogen peroxide:

${\mathbf{CH}}_3{\mathbf{CH}}_2\mathbf{=}{\mathbf{CH}}_2\mathbf{+}{\mathbf{H}}_2{\mathbf{O}}_2\mathbf{\to }{\mathbf{CH}}_3{\mathbf{CHCH}}_2\mathbf{O}\mathbf{+}{\mathbf{H}}_2\mathbf{O}$

(a) What is the molecular shape and ideal bond angle around each carbon atom in propylene oxide? 

(b) Predict any deviation from the ideal for the actual C-C-C bond angles (assume the three atoms in the ring form an equilateral triangle).

Step-by-Step Solution

Answer

1.  ${\mathbf{sp}}^3$hybridized carbon and the bond angle are $\mathbf{109}\mathbf{.}\mathbf{5}\mathbf{°}$ .
2. Deviation from an ideal bond angle is  $\mathbf{60}\mathbf{°}$.

Step 1: Concept

Mixing two atomic orbitals to give rise to a new type of hybridized orbital with the same energy and different shape is known as hybridization.

 

In propylene oxide, each carbon atom is forming 4 bonds using 1s and 3p orbitals, hence the hybridization of each carbon atom is ${\mathbf{sp}}^3$  which forms a tetrahedral geometry, in which the bond angle in every two bonds is $\mathbf{109}\mathbf{.}\mathbf{5}\mathbf{°}$  .

 

Step 2: Ideal bond angles

Each carbon atom in propylene oxide is  ${\mathbf{sp}}^3$ hybridized. The ideal bond angles are 

Step 3: Deviations

The reaction and answer are as follows:

 

In this reaction, propene reacted with hydrogen peroxide and formed propylene oxide.

In propylene oxide, the bond angle C-O-C deviated from the ideal bond angle due to the ring formation.

The carbon atoms forming the three-membered ring have a deviation from an ideal angle. The angle around these carbon atoms is  $\mathbf{60}\mathbf{°}$.