Q. 6.132 - An Introduction to General, Organic, and Biological Chemistry

Question

Select the more polar bond in each of the following pairs.$\left(6.7\right)$

a. $\mathrm{C}-\mathrm{C} \mathrm{or} \mathrm{C}-\mathrm{O}$

b. $\mathrm{P}-\mathrm{Cl} \mathrm{or} \mathrm{P}-\mathrm{Br}$

c. $\mathrm{Si}-\mathrm{S} \mathrm{or} \mathrm{Si}-\mathrm{Cl}$

d. $\mathrm{F}-\mathrm{Cl} \mathrm{or} \mathrm{F}-\mathrm{Br}$

e. $\mathrm{P}-\mathrm{O} \mathrm{or} \mathrm{P}-\mathrm{S}$

Step-by-Step Solution

Answer

a. In the pair $\mathrm{C}-\mathrm{C} and \mathrm{C}-\mathrm{O}$, $\mathrm{C}-\mathrm{O}$ is a more polar bond.

b. In the pair  $\mathrm{P}-\mathrm{Cl} and P-\mathrm{Br}$, $\mathrm{P}-\mathrm{Cl}$is a more polar bond.

c. In the pair $\mathrm{Si}-\mathrm{S} \mathrm{or} \mathrm{Si}-\mathrm{Cl}$, $\mathrm{Si}-\mathrm{Cl}$is a more polar bond.

d. In the pair $\mathrm{F}-\mathrm{Cl} \mathrm{or} \mathrm{F}-\mathrm{Br}$, $\mathrm{F} -\mathrm{Br}$is a more polar bond.

e. In the pair $\mathrm{P}-\mathrm{O} \mathrm{or} \mathrm{P}-\mathrm{S}$,  $\mathrm{P}-\mathrm{O}$is a more polar bond.

Part (a) step 1: Given Information

We need to find the more polar bond from $\mathrm{C}-\mathrm{C} \mathrm{or} \mathrm{C}-\mathrm{O}$.

Part (a) step 2: Explanation

A bond is more polar if the electronegativity difference is more in the elements forming bonds.

$\mathrm{C}-\mathrm{C}$ in non-polar due to zero electronegativity difference bond and $\mathrm{C}-\mathrm{O}$ is a polar bond.

Part (b) step 1: Given Information

We need to find the more polar bond from $\mathrm{P}-\mathrm{Cl} \mathrm{or} \mathrm{P}-\mathrm{Br}$.

Part (b) step 2: Explanation

A bond is more polar if the electronegativity difference is more in the elements forming bonds.

Electronegativity 

$\mathrm{P} -- 2.1$

$\mathrm{Cl}--3$

$\mathrm{Br}--2.8$

$\mathrm{P}-\mathrm{Cl}$ difference is $3-2.1=0.9$

$P-\mathrm{Br}$  difference is $2.8-2.1=0.7$

So, $\mathrm{P}-\mathrm{Cl}$ more polar.

Part (c) step 1: Given Information

We need to find the more polar bond from $\mathrm{Si}-\mathrm{S} \mathrm{or} \mathrm{Si}-\mathrm{Cl}$.

Part (c) step 2: Explanation

A bond is more polar if the electronegativity difference is more in the elements forming bonds.

Electronegativity 

$\mathrm{Si}--1.8$

$\mathrm{S}--2.5$

$\mathrm{Cl}--3$

$\mathrm{Si}-\mathrm{Cl}$ difference is $3-1.8=1.2$

$\mathrm{Si}-\mathrm{S}$ difference is $2.5-1.8=0.7$

Therefore, $\mathrm{Si}-\mathrm{Cl}$ is the bond is more polar.

Part (d) step 1: Given Information

We need to find the more polar bond from $\mathrm{F}-\mathrm{Cl} \mathrm{or} \mathrm{F}-\mathrm{Br}$.

Part (d) step 2: Explanation

A bond is more polar if the electronegativity difference is more in the elements forming bonds.

Electronegativity 

$$\begin{gathered} \mathrm{F}--4 \\ \mathrm{Cl} --3 \\ \mathrm{Br}--2.8 \end{gathered}$$

$\mathrm{F}-\mathrm{Cl}$ difference is $4-3=1$

$\mathrm{F} -\mathrm{Br}$ difference is $4-2.8=1.2$

So, $\mathrm{F} -\mathrm{Br}$ is the bond is more polar.

Part (e) step 1: Given Information

We need to find the more polar bond from $\mathrm{P}-\mathrm{O} \mathrm{or} \mathrm{P}-\mathrm{S}$.

Part (e) step 2: Explanation

A bond is more polar if the electronegativity difference is more in the elements forming bonds.

Electronegativity 

$$\begin{gathered} \mathrm{P}--2.1 \\ \mathrm{O} --3.5 \\ \mathrm{S}--2.5 \end{gathered}$$

$\mathrm{P}-\mathrm{O}$ difference is $3.5-2.1=1.4$

$\mathrm{P}-\mathrm{S}$ difference is $2.5-2.1=0.4$

So, $\mathrm{P}-\mathrm{O}$ is the bond is more polar.