Chapter 6, Problem 6.50P

Interpretation Introduction

(a)

Interpretation:

The most acidic proton, in the given species, is to be identified, and its pKa value is to be estimated.

Concept introduction:

An Acidic proton is one which is directly bonded to an electronegative atom. The acidity of a compound is governed largely by the functional group on which the acidic proton is found. Nearby structural features such as highly electronegative substituent or presence of a double or triple bond can alter the acidity significantly. The pKa value for a particular compound is explained based on structural similarities of the compound and the compounds listed in Table 6-1.

Answer to Problem 6.50P

The most acidic proton in the given species along with its estimated pKa value is:

Explanation of Solution

The structure for the given compound is:

There are three protons that could be acidic. The proton attached to the carbon in methyl group, to the oxygen atom in alcohol, and the proton directly attached to the oxygen atom in phenol functional group are the protons that could be acidic.

According to Table 6-1, the relative pKa value of each of the protons is:

The pKa value for the compound having $\text{C-H}$ adjacent to the carbon atom, which is a characteristic of alkanes, is $\text{50}$.

The pKa value for the compound having $\text{O-H}$ adjacent to the carbon atom, which is a characteristic of primary alcohols, is $\text{16}$.

The pKa value for the compound having $\text{O-H}$ adjacent the benzene ring, which is a characteristic of phenols, is $\text{10}$.

Lower the pKa value, stronger is the acid, and the proton associated with it is the most acidic proton. The lowest pKa value is for $\text{O-H}$ in phenol. Thus, it is the most acidic proton. The most acidic proton in the structure is circled along with its pKa value as:

Conclusion

The most acidic proton in the given structure is identified along with its estimated pKa value using Table 6-1.

Interpretation Introduction

(b)

Interpretation:

The most acidic proton in the given species is to be identified and its pKa value is to be estimated.

Concept introduction:

An Acidic proton is the one which is directly bonded to an electronegative atom. The acidity of a compound is governed largely by the functional group on which the acidic proton is found. Nearby structural features such as highly electronegative substituent or presence of a double or triple bond can alter the acidity significantly. The pKa value for a particular compound is explained based on structural similarities of the compound and the compounds listed in Table 6-1.

Answer to Problem 6.50P

The most acidic proton in the given species along with its estimated pKa value is:

Explanation of Solution

The structure for the given compound is:

In the given structure, the proton attached to the nitrogen atom, and to the carbon atom next to the carbonyl group, could be the acidic protons.

According to Table 6-1, the relative pKa value of each of the protons is:

The pKa value for the compound having $\text{N-H}$ adjacent to one carbon atom, which is a characteristic of primary amines, is $\text{36}$.

The pKa value for the compound having $\text{C-H}$ adjacent to the carbonyl group, which is a characteristic of ketones, is $\text{20}$.

Lower the pKa value, stronger is the acid, and the proton associated with it is the most acidic proton. The lowest pKa value is for $\text{C-H}$ proton in ketones. Thus, it is the most acidic proton. The most acidic proton in the structure is circled along with its pKa value as:

Conclusion

The most acidic proton in the given structure is identified along with its estimated pKa value using Table 6-1.

Interpretation Introduction

(c)

Interpretation:

The most acidic proton in the given species is to be identified and its pKa value is to be estimated.

Concept introduction:

An Acidic proton is the one which is directly bonded to an electronegative atom. The acidity of a compound is governed largely by the functional group on which the acidic proton is found. Nearby structural features such as highly electronegative substituent or presence of a double or triple bond can alter the acidity significantly. The pKa value for a particular compound is explained based on structural similarities of the compound and the compounds listed in Table 6-1.

Answer to Problem 6.50P

The most acidic proton in the given species along with its estimated pKa value is:

Explanation of Solution

The structure for the given compound is:

There are two protons that could be acidic. The proton attached to the oxygen atom which is directly bonded to the carbonyl group, and to the sulfur atom are the protons that could be acidic.

According to Table 6-1, the relative pKa value of each of the protons is:

The pKa value for the compound having $\text{O-H}$ adjacent to the carbonyl group, which is a characteristic of carboxylic acids, is around $\text{4}\text{.75}$.

The pKa value for the compound having $\text{S-H}$ adjacent to the carbon atom, which is a characteristic of thiols, is around $\text{7}\text{.2}$.

Lower the pKa value, stronger is the acid and the proton associated with it is the most acidic proton. The lowest pKa value is for $\text{O-H}$ proton in carboxylic acid group. Thus, it is the most acidic proton. The most acidic proton in the structure is circled along with its pKa value as:

Conclusion

The most acidic proton in the given structure is identified along with its estimated pKa value using Table 6-1.

Interpretation Introduction

(d)

Interpretation:

The most acidic proton in the given species is to be identified and its pKa value is to be estimated.

Concept introduction:

An Acidic proton is the one which is directly bonded to an electronegative atom. The acidity of a compound is governed largely by the functional group on which the acidic proton is found. Nearby structural features such as highly electronegative substituent or presence of a double or triple bond can alter the acidity significantly. The pKa value for a particular compound is explained based on structural similarities of the compound and the compounds listed in Table 6-1.

Answer to Problem 6.50P

The most acidic proton in the given species along with its estimated pKa value is:

Explanation of Solution

The structure for the given compound is:

In the given structure, the proton attached to the nitrogen atom and to the triple bonded carbon atom could be the acidic protons.

According to Table 6-1, the relative pKa value of each of the protons is:

The pKa value for the compound having $\text{N-H}$ adjacent to two carbon atoms, which is a characteristic of secondary amines, is $\text{38}$.

The pKa value for the compound having $\text{C-H}$ adjacent to the triple bonded carbon atom, which is a characteristic of alkynes or nitriles, is $\text{25}$.

Lower the pKa value, stronger is the acid and the proton associated with it is the most acidic proton. The lowest pKa value is for $\text{C-H}$ proton in alkynes or nitriles. Thus, it is the most acidic proton. The most acidic proton in the structure is circled along with its pKa value as:

Conclusion

The most acidic proton in the given structure is identified along with its estimated pKa value using Table 6-1.

Interpretation Introduction

(e)

Interpretation:

The most acidic proton in the given species is to be identified and its pKa value is to be estimated.

Concept introduction:

An Acidic proton is the one which is directly bonded to an electronegative atom. The acidity of a compound is governed largely by the functional group on which the acidic proton is found. Nearby structural features such as highly electronegative substituent or presence of a double or triple bond can alter the acidity significantly. The pKa value for a particular compound is explained based on structural similarities of the compound and the compounds listed in Table 6-1.

Answer to Problem 6.50P

The most acidic proton in the given species along with its estimated pKa value is:

Explanation of Solution

The structure for the given compound is:

There are two protons that could be acidic. The proton attached to the carbon in methyl group, to the oxygen atom in alcohol, and the proton directly attached to the oxygen atom in phenol functional group are the protons that could be acidic.

According to Table 6-1, the relative pKa value of each of the protons is:

The pKa value for the compound having $\text{O-H}$ adjacent the benzene ring, which is a characteristic of phenols is around $\text{10}$.

The pKa value for the compound having $\text{O-H}$ adjacent to sulfur atom, which is a characteristic of sulfonic acid is around $\text{-2}$.

Lower the pKa value, stronger is the acid and the proton associated with it is the most acidic proton. The lowest pKa value is for $\text{O-H}$ in sulfonic acid. Thus, it is the most acidic proton. The most acidic proton in the structure is circled along with its pKa value as:

Conclusion

The most acidic proton in the given structure is identified along with its estimated pKa value using Table 6-1.

Interpretation Introduction

(f)

Interpretation:

The most acidic proton in the given species is to be identified and its pKa value is to be estimated.

Concept introduction:

An Acidic proton is the one which is directly bonded to an electronegative atom. The acidity of a compound is governed largely by the functional group on which the acidic proton is found. Nearby structural features such as highly electronegative substituent or presence of a double or triple bond can alter the acidity significantly. The pKa value for a particular compound is explained based on structural similarities of the compound and the compounds listed in Table 6-1.

Answer to Problem 6.50P

The most acidic proton in the given species along with its estimated pKa value is:

Explanation of Solution

The structure for the given compound is:

There are two protons that could be acidic. The proton attached to the carbon in methyl group, to the oxygen atom in alcohol, and the proton directly attached to the oxygen atom in phenol functional group are the protons that could be acidic.

According to Table 6-1, the relative pKa value of each of the protons is:

The pKa value for the compound having protonated $\text{O-H}$ adjacent the benzene ring, which is a characteristic of protonated phenols, is around $\text{~ -1}\text{.7}$.

The pKa value for the compound having $\text{O-H}$ adjacent to the carbonyl group, which is a characteristic of carboxylic acid, is around $\text{4}\text{.75}$.

Lower the pKa value, stronger is the acid and the proton associated is the most acidic proton. The lowest pKa value is for protonated $\text{O-H}$ group in phenol. Thus, it is the most acidic proton. The most acidic proton in the structure is circled along with its pKa value as:

Conclusion

The most acidic proton in the given structure is identified along with its estimated pKa value using Table 6-1.

Interpretation Introduction

(g)

Interpretation:

The most acidic proton in the given species is to be identified and its pKa value is to be estimated.

Concept introduction:

An Acidic proton is the one which is directly bonded to an electronegative atom. The acidity of a compound is governed largely by the functional group on which the acidic proton is found. Nearby structural features such as highly electronegative substituent or presence of a double or triple bond can alter the acidity significantly. The pKa value for a particular compound is explained based on structural similarities of the compound and the compounds listed in Table 6-1.

Answer to Problem 6.50P

The most acidic proton in the given species along with its estimated pKa value is:

Explanation of Solution

The structure for the given compound is:

In the given structure, the proton attached to both nitrogen atoms could be acidic protons.

According to Table 6-1, the relative pKa value of each of the protons is:

The pKa value for the compound having protonated $\text{N-H}$ adjacent to two carbon atoms, which is a characteristic of ammonium ion, is $\text{~ 9}\text{.4}$.

The pKa value for the compound having $\text{N-H}$ adjacent to the carbonyl group, which is a characteristic of alkynes or nitriles is $\text{~ 15}$.

Lower the pKa value, stronger is the acid and the proton associated with it is the most acidic proton. The lowest pKa value is for protonated $\text{N-H}$ proton in ammonium ions. Thus, it is the most acidic proton. The most acidic proton in the structure is circled along with its pKa value as:

Conclusion

The most acidic proton in the given structure is identified along with its estimated pKa value using Table 6-1.

Interpretation Introduction

(h)

Interpretation:

The most acidic proton in the given species is to be identified and its pKa value is to be estimated.

Concept introduction:

An Acidic proton is the one which is directly bonded to an electronegative atom. The acidity of a compound is governed largely by the functional group on which the acidic proton is found. Nearby structural features such as highly electronegative substituent or presence of a double or triple bond can alter the acidity significantly. The pKa value for a particular compound is explained based on structural similarities of the compound and the compounds listed in Table 6-1.

Answer to Problem 6.50P

The most acidic proton in the given species along with its estimated pKa value is:

Explanation of Solution

The structure for the given compound is:

In the given structure, the protons attached to the terminal triple bonded carbon atom and to the nitrogen atom could be acidic protons.

According to Table 6-1, the relative pKa value of each of the protons is:

The pKa value for the compound having protonated $\text{N-H}$ adjacent to one carbon atom, which is a characteristic of primary amines, is $\text{36}$.

The pKa value for the compound having $\text{C-H}$ adjacent to the triple bonded carbon atom, which is a characteristic of alkynes, is $\text{~ 15}$.

Lower the pKa value, stronger is the acid and the proton associated with it is the most acidic proton. The lowest pKa value is for $\text{C-H}$ proton in terminal alkynes. Thus, it is the most acidic proton. The most acidic proton in the structure is circled along with its pKa value as:

Conclusion

The most acidic proton in the given structure is identified along with its estimated pKa value using Table 6-1.