Chapter 2, Problem 2.1P

a. Which compounds are Bronsted-Lowry acids: ${\text{HBr, NH}}_{\text{3}}{\text{, CCl}}_{\text{4}}$?

b. Which compounds are Bronsted-Lowry bases: ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{3}}\text{, }{\left({\text{CH}}_{\text{3}}\right)}_{\text{3}}{\text{CO}}^{-},\text{HC}\equiv \text{CH}$?

c. Classify each compound as an acid, a base, or both:

${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{OH, CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_2{\text{CH}}_3{\text{, CH}}_{\text{3}}{\text{CO}}_2{\text{CH}}_{\text{3}}$.

Interpretation Introduction

(a)

Interpretation: Among the given compounds, Bronsted-Lowry acids are to be identified.

Concept introduction: Bronsted-Lowry acids are those species which donate proton. They are also known as proton donor. The net charge on Bronsted-Lowry acids can be zero or negative or positive.

Answer to Problem 2.1P

The Bronsted-Lowry acid is $\text{HBr}$.

Explanation of Solution

All Bronsted-Lowry acids donate proton.

Hydrogen bromide contain hydrogen atom. Hence, it is a Bronsted-Lowry acid.

Ammonia contains a lone pair of electrons which can be easily donated to form a new bond. Hence, it is a Bronsted-Lowry base.

No hydrogen is present in the ${\text{CCl}}_{\text{4}}$. Hence, it is not a Bronsted-Lowry acid.

Conclusion

In the given set of compounds, Bronsted-Lowry acid is $\text{HBr}$.

Interpretation Introduction

(b)

Interpretation: Among the given compounds, Bronsted-Lowry bases are to be identified.

Concept introduction: Bronsted-Lowry bases are those species which can accept a proton. The Base must contain a lone pair or pi bond that could be easily donated to an acid to form a new bond. Bronsted-Lowry base are proton acceptor. The net charge on Bronsted-Lowry base can be zero and negative.

Answer to Problem 2.1P

The Bronsted-Lowry acids are $\text{CH}\equiv \text{CH}$ and ${\left({\text{CH}}_{\text{3}}\right)}_{\text{3}}{\text{CO}}^{-}$.

Explanation of Solution

All Bronsted-lowry bases contain lone pair of electrons or pi bond. In ${\left({\text{CH}}_{\text{3}}\right)}_{\text{3}}{\text{CO}}^{-}$, oxygen atom possess negative charge. It means that it can accept a proton. Hence, ${\left({\text{CH}}_{\text{3}}\right)}_{\text{3}}{\text{CO}}^{-}$ is a Bronsted-Lowry base.

Figure 1

The molecule $\text{HC}\equiv \text{CH}$ contains pi bonds. Hence, $\text{HC}\equiv \text{CH}$ is a Bronsted-Lowry base.

Figure 2

There is neither a pi bond nor a negative charge present in ${\text{CH}}_3{\text{CH}}_3$. Hence, it is not a Bronsted-Lowry base.

Conclusion

In the given set of compounds, Bronsted-Lowry acids are $\text{CH}\equiv \text{CH}$ and ${\left({\text{CH}}_{\text{3}}\right)}_{\text{3}}{\text{CO}}^{-}$.

Interpretation Introduction

(c)

Interpretation: Among the given compounds, Bronsted-lowry bases are to be identified.

Concept introduction: Bronsted-Lowry bases are those species which can accept a proton. The Base must contain a lone pair or pi bond that could be easily donated to an acid to form a new bond. Bronsted-Lowry base are proton acceptor. The net charge on Bronsted-Lowry base can be zero and negative.

Answer to Problem 2.1P

The Bronsted-Lowry acids are ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_2{\text{CH}}_3$. The compounds which are both Bronsted-Lowry acid and Bronsted-Lowry base are ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{OH, CH}}_{\text{3}}{\text{COOCH}}_{\text{3}}$.

Explanation of Solution

All Bronsted-Lowry bases contain lone pairs of electrons or pi bond. Bronsted-Lowry acids contain proton.

Ethanol contains hydrogen atom and lone pairs on oxygen atom. Hence, it is a Bronsted-Lowry base as well as a Bronsted-Lowry acid.

Figure 3

Propane contains only hydrogen atoms. Hence, it is a Bronsted-Lowry acid.

Figure 4

${\text{CH}}_{\text{3}}{\text{COOCH}}_{\text{3}}$ contains hydrogen atom and lone pairs on oxygen atom. Hence, it is a Bronsted-Lowry base as well as a Bronsted-Lowry acid.

Figure 5

Conclusion

The Bronsted-Lowry acids are ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_2{\text{CH}}_3$. The compounds which are both Bronsted-Lowry acid and Bronsted-Lowry bases are ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{OH, CH}}_{\text{3}}{\text{COOCH}}_{\text{3}}$.