Q69. - Organic Chemistry

Question

Question: Two useful organic compounds that contain Cl atoms are vinyl chloride $\left({\mathrm{CH}}_2=\mathrm{CH}-\mathrm{Cl}\right)$   and chloroethane $\left({\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{Cl}\right)$ . Vinyl chloride is the starting material used to prepare poly (vinyl chloride), a plastic used in insulation, pipes, and bottles. Chloroethane (ethyl chloride) is a local anesthetic. Why is the bond of vinyl chloride stronger than the bond in chloroethane?

Step-by-Step Solution

Answer

Answer

The $\mathrm{C}-\mathrm{Cl}$  bond of vinyl chloride is stronger due to the higher percentage of s character in the bonding orbital of the carbon atom.

Step-by-Step Solution Step 1: Percentage of s character

The percent s character of the hybridized orbitals is useful to determine the strength of a covalent bond. With the increase in the s character of the orbital forming the bond, the strength of the bond increases.

 

The ${\mathrm{sp}}^3$  -hybridized orbitals have 25% s character. On the other hand, the ${\mathrm{sp}}^2$ -hybridized orbitals have 33.33% s character. The sp-hybridized orbital-hybridized orbitals have the maximum s character, which is about 50%.

Step 2: Strength of bonds based on s character

The vinyl chloride has the following structure:

                                               

                                                                    Vinyl chloride

The ethyl chloride or chloroethane has the following structure:

                                               

                                                                         Ethyl chloride

 

 

The  $\mathrm{C}-\mathrm{Cl}$ bond in vinyl chloride is formed by the ${\mathrm{sp}}^2$ -hybridized orbital of the carbon atom. It has more s character, due to which the bond is stronger as compared to the  $\mathrm{C}-\mathrm{Cl}$ bond in chloroethane or ethyl chloride.

 

The $\mathrm{C}-\mathrm{Cl}$  bond in ethyl chloride is formed by the ${\mathrm{sp}}^3$ -hybridized orbital of the carbon atom. The s character of the ${\mathrm{sp}}^3$  -hybridized orbital is less due to which the bond is weaker.