Chapter 18, Problem 18.49AP

Interpretation Introduction

(a)

Interpretation:

The increasing order of acidity with the reason for the given compounds is to be stated.

Concept introduction:

Brønsted bases are those species which accept a proton. Base accepts a proton and forms conjugate acid. Brønsted acids are those species which donate a proton. Acid loses a proton and forms conjugate base. The acidity of the compound depends upon the stability of its conjugate base. The more stable the conjugate base, the more acidic the given compound. It also depends on the charge, inductive effects, the role of atom present.

Answer to Problem 18.49AP

The acidity of the given compounds in increasing order is shown below.

$\text{Cyclohexanol}<\text{cyclohexyl}\text{mercaptan}<\text{benzenethiol}$

This is because of the conjugate base stability and resonance stabilization of benzene thiol.

Explanation of Solution

The acidity of the compound depends upon the stability of its conjugate base. The greater the stability of the conjugate base more acidic the given compound. The structure of the conjugate base of the given compounds is shown below.

Figure 1

The conjugate base of benzene thiol is stabilized by the resonance that is why its acidity is greater among the given compounds. The cyclohexyl mercaptan contains sulfur atom which is larger than the oxygen atom, due to this it is more capable of diffusing negative charge. Therefore, the cyclohexyl mercaptan conjugate base is more stable than the cyclohexanol. This results in greater acidity of the cyclohexyl mercaptan compound.

The increasing order of acidity of the given compound is shown below.

$\text{Cyclohexanol}<\text{cyclohexyl}\text{mercaptan}<\text{benzenethiol}$

Conclusion

The increasing order of acidity is $\text{Cyclohexanol}<\text{cyclohexyl}\text{mercaptan}<\text{benzenethiol}$ due to the conjugate base stability and resonance stabilization of benzene thiol.

Interpretation Introduction

(b)

Interpretation:

The increasing order of acidity with the reason for the given compounds is to be stated.

Concept introduction:

Brønsted bases are those species which accept a proton. Base accepts a proton and forms conjugate acid. Brønsted acids are those species which donate a proton. Acid loses a proton and forms conjugate base. The acidity of the compound depends upon the stability of its conjugate base. The more stable the conjugate base, the more acidic the given compound. It also depends on the charge, inductive effects, the role of the atom present, resonance, orbitals.

Answer to Problem 18.49AP

The acidity of the given compounds in increasing order is shown below. $\text{Cyclohexanol}<\text{benzyl}\text{alcohol}<\text{phenol}$

This is because of the conjugate base stability and resonance stabilization of phenol and $-\text{I}$ effect of benzyl alcohol.

Explanation of Solution

The acidity of the compound depends upon the stability of its conjugate base. The greater the stability of the conjugate base more acidic the given compound. The structure of the conjugate base of the given compounds is shown below.

Figure 2

The conjugate base of phenoxide ion is stabilized by the resonance that is why its acidity is greater among the given compounds. The conjugate base of benzyl alcohol exerts $-\text{I}$ effect, due to this its conjugate base is more stable than cyclohexanol which exerts $+\text{I}$ effect. Therefore, the acidity of the given compounds is arranged in the order as shown below.

$\text{Cyclohexanol}<\text{benzyl}\text{alcohol}<\text{phenol}$

Conclusion

The increasing order of acidity is $\text{Cyclohexanol}<\text{benzyl}\text{alcohol}<\text{phenol}$ due to the conjugate base stability and resonance stabilization of benzene thiol and $-\text{I}$ effect of benzyl alcohol.

Interpretation Introduction

(c)

Interpretation:

The increasing order of acidity with the reason for the given compounds is to be stated.

Concept introduction:

Brønsted bases are those species which accept a proton. Base accepts a proton and forms conjugate acid. Brønsted acids are those species which donate a proton. Acid loses a proton and forms conjugate base. The acidity of the compound depends upon the stability of its conjugate base. The more stable the conjugate base, the more acidic the given compound. It also depends on the charge, inductive effects, electronegativity, resonance, orbitals.

Answer to Problem 18.49AP

The acidity of the given compounds in increasing order is shown below.

$p-\text{chlorophenol}<p-\text{nitrophenol}<\text{nitric acid}$

This is because of the conjugate base stability and equivalent resonance stabilization of nitric acid.

Explanation of Solution

The acidity of the compound depends upon the stability of its conjugate base. The greater the stability of the conjugate base more acidic the given compound. The structure of the conjugate base of the given compounds is shown below.

Figure 3

The equivalent resonance structures are more stable as compared to nonequivalent resonance structures. The nitric acid conjugate base shows equivalent resonance structures. Also, it is stabilized by the negative charge on the two oxygen atoms. It also exerts $-\text{I}$ effect. That is why it is more acidic compound among other compounds. The compound $p-\text{nitrophenol}$ exerts $-\text{R}$ effect which is stronger than $-\text{I}$ effect which is shown by $p-\text{chlorophenol}$. Therefore the increasing acidity of the given compounds is shown below.

$p-\text{chlorophenol}<p-\text{nitrophenol}<\text{nitric acid}$

Conclusion

The increasing order of acidity is $p-\text{chlorophenol}<p-\text{nitrophenol}<\text{nitric acid}$ due to the conjugate base stability and equivalent resonance stabilization of nitric acid. Also, the $-\text{R}$ effect of $p-\text{nitrophenol}$ is stronger than $-\text{I}$ effect of $p-\text{chlorophenol}$.

Interpretation Introduction

(d)

Interpretation:

The increasing order of acidity with the reason for the given compounds is to be stated.

Concept introduction:

Brønsted bases are those species which accept a proton. Base accepts a proton and forms conjugate acid. Brønsted acids are those species which donate a proton. Acid loses a proton and forms conjugate base. The acidity of the compound depends upon the stability of its conjugate base. The more stable the conjugate base, the more acidic the given compound. It also depends on the charge, inductive effects, electronegativity, resonance, orbitals.

Answer to Problem 18.49AP

The acidity of the given compounds in increasing order is shown below.

$\text{Phenol}<4-\text{nitrophenol}<\text{4}-\text{nitrobenzothiol}$

This is because of the conjugate base stability and resonance stabilization of $4-\text{nitrobenzenethiol}$ and it also contains heavier sulfur atom. Along with that the compound $4-\text{nitrophenol}$ stabilized by $-\text{R}$ effect and $-\text{I}$ effect of the nitro group.

Explanation of Solution

The acidity of the compound depends upon the stability of its conjugate base. The greater the stability of the conjugate base more acidic the given compound. The structure of the conjugate base of the given compounds is shown below.

Figure 4

The conjugate base of $4-\text{nitrobenzenethiol}$ is more stable. It contains a sulfur atom which is larger than the oxygen atom, due to this it is more capable of diffusing negative charge. It is also stabilized by $-\text{R}$ effect and $-\text{I}$ effect of the nitro group. Similarly, the conjugate base of $4-\text{nitrophenol}$ stabilized by $-\text{R}$ effect and $-\text{I}$ effect of the nitro group as compared to phenol which is only stabilized by $-\text{R}$ effect of the phenyl ring. Therefore the increasing order of acidity of the given compounds is shown below.

$\text{Phenol}<4-\text{nitrophenol}<\text{4}-\text{nitrobenzothiol}$

Conclusion

The increasing order of acidity is $\text{Phenol}<4-\text{nitrophenol}<\text{4}-\text{nitrobenzothiol}$ due to the conjugate base stability and resonance stabilization of $\text{4}-\text{nitrobenzothiol}$, it also contains heavy sulfur atom. The compound $4-\text{nitrophenol}$ is stabilized by $-\text{R}$ effect and $-\text{I}$ effect of the nitro group.

Interpretation Introduction

(e)

Interpretation:

The increasing order of acidity with the reason for the given compounds is to be stated.

Concept introduction:

Brønsted bases are those species which accept a proton. Base accepts a proton and forms conjugate acid. Brønsted acids are those species which donate a proton. Acid loses a proton and forms conjugate base. The acidity of the compound depends upon the stability of its conjugate base. The more stable the conjugate base, the more acidic the given compound. It also depends on the charge, inductive effects, electronegativity, resonance, orbitals.

Answer to Problem 18.49AP

The acidity of the given compounds in increasing order is shown below.

$C<A<D<B$

This is because of the conjugate base stability, $-\text{R}$ effect and $-\text{I}$ effect of the phenyl rings and the nitro group.

Explanation of Solution

The acidity of the compound depends upon the stability of its conjugate base. The greater the stability of the conjugate base more acidic the given compound. The structure of the conjugate base of the given compounds is shown below.

Figure 5

The conjugate base of the compound B stabilized by $-\text{R}$ effect and $-\text{I}$ effect of the two phenyl rings and nitro group. It is the most acidic compound among the given compounds. Also, the conjugate base of the compound D stabilized by $-\text{R}$ effect and $-\text{I}$ effect of the two phenyl rings and $-\text{I}$ effect of the nitro group. It is less stable than the conjugate base of the compound B. The conjugate base of compound A stabilized by $-\text{R}$ effect and $-\text{I}$ effect of the two phenyl rings only. The conjugate base of compound C stabilized by $-\text{R}$ effect and $-\text{I}$ effect of the one phenyl ring only. Therefore the increasing order of the given compound is shown below.

$C<A<D<B$

Conclusion

The increasing order of acidity is $C<A<D<B$ due to the conjugate base stability, $-\text{R}$ effect, and $-\text{I}$ effect of the phenyl rings and the nitro group.