Chapter 3, Problem 3.60P

Quinapril (trade name Accupril) is a drug used to treat hypertension and congestive heart

failure.

a. Identify the functional groups in quinpril.

b. Classify any alcohol, amide or amine as $1°$ $2°$ or $3^{°}$.

c. At which sites can quinapril hydrogen bond to water?

d. At which sites can quinapril hydrogen bond to acetone $\left[{\left({\text{CH}}_{\text{3}}\right)}_{\text{2}}\text{CO}\right]$ ?

e. Label the most acidic hydrogen atom.

f. Which site is most basic?

Interpretation Introduction

(a)

Interpretation: The functional groups present in the given compound, quinapril are to be identified.

Concept introduction: An atom or a group of atoms that shows characteristic physical and chemical properties are collectively known as functional groups. The functional group is the most reactive part present in the molecule. The main functional groups are $\text{OH}$ (alcoholic group), $\text{COOH(carboxylic}\text{group)}$, $\text{CHO}\left(\text{aldehydic}\text{group}\right)$ and $\text{C=O}\left(\text{ketonic}\text{group}\right)$.

Answer to Problem 3.60P

The functional groups present in the given compound, quinapril are shown below.

Explanation of Solution

The functional groups present in the given compound, quinapril are shown as,

Figure 1

Thus, there are total four functional groups present in quinapril which are ester group, amine group, amide group and carboxylic group as highlighted above. There are two aromatic also present in the given compound, quinapril.

Conclusion

There are total four functional groups present in quinapril which are ester group, amine group, amide group and carboxylic group.

Interpretation Introduction

(b)

Interpretation: The alcohol, amine or amide groups present in the given compound, quinapril are to be classified as $1^{°}$, $2^{°}$, or $3^{°}$.

Concept introduction: The amine, amide or alcoholic groups are identified as primary $\left(1^{°}\right)$, secondary $\left(2^{°}\right)$ and tertiary $\left(3^{°}\right)$. The primary amine, amide or alcoholic groups are the one in which amine, amide or $\text{OH}$ groups are attached to that carbon atom which is bonded with one carbon atom only. The secondary amine, amide or alcoholic groups are the one in which amine, amide or $\text{OH}$ groups are attached to that carbon atom which is bonded with two carbon atoms. The tertiary amine, amide or alcoholic groups are the one in which amine, amide or $\text{OH}$ group are attached to that carbon atom which is bonded with three carbon atoms.

Answer to Problem 3.60P

The classification of alcohol, amine or amide groups present in the given compound, quinapril as $1^{°}$, $2^{°}$, or $3^{°}$ is shown below.

Explanation of Solution

The classification alcohol, amine or amide groups present in the given compound, quinapril are shown as,

Figure 2

The given compound consists of one tertiary amide and one secondary amine as shown above.

Conclusion

The classification of alcohol, amine or amide groups present in the given compound, quinapril as $1^{°}$, $2^{°}$, or $3^{°}$ is shown in Figure 2.

Interpretation Introduction

(c)

Interpretation: The site at which quinapril forms hydrogen bond with water is to be predicted.

Concept introduction: The bonding that takes place between hydrogen atom and hetero atoms like oxygen, nitrogen and fluorine is known as hydrogen bonding. In case of water, hydrogen atom makes bond with each other. Hydrogen bonding is the strongest bonding among the intermolecular forces and covalent bonding.

Answer to Problem 3.60P

The site at which quinapril forms hydrogen bond with water is shown below.

Explanation of Solution

The site at which quinapril forms hydrogen bond with water is shown as,

Figure 3

In the given compound, the sites where the electronegative atoms like, oxygen and nitrogen are present, there only hydrogen bond forms with water as highlighted above.

Conclusion

The site at which quinapril forms hydrogen bond with water is shown in Figure 3.

Interpretation Introduction

(d)

Interpretation: The site at which quinapril forms hydrogen bond with acetone is to be predicted.

Concept introduction: The bonding that takes place between hydrogen atom and hetero atoms like oxygen, nitrogen and fluorine is known as hydrogen bonding. In case of acetone, hydrogen atom makes bond with that electronegative atom which is attached to hydrogen atom only. Hydrogen bonding is the strongest bonding among the intermolecular forces and covalent bonding.

Answer to Problem 3.60P

The site at which quinapril forms hydrogen bond with acetone is shown below.

Explanation of Solution

The site at which quinapril forms hydrogen bond with acetone is shown as,

Figure 4

In the given compound, the sites where the electronegative atoms like, oxygen and nitrogen attached to other hydrogen atom are present, there only hydrogen bond forms with acetone as highlighted above.

Conclusion

The site at which quinapril forms hydrogen bond with acetone is shown in Figure 4.

Interpretation Introduction

(e)

Interpretation: The most acidic hydrogen present in the given compound, quinapril is to be labeled.

Concept introduction: The most acidic hydrogen $\left(\text{H}\right)$ atom or proton is the one which can be easily eliminated from the molecule. This higher acidity of $\text{H-atom}$ is dependent upon the electronegativity of the functional groups that are bonded with carbon atom containing hydrogen. The elimination of a proton leads to the formation of a conjugate base. The higher stability of the conjugate base corresponds to the higher acidity of the proton.

Answer to Problem 3.60P

The labeling of the most acidic hydrogen present in the given compound, quinapril is shown below.

Explanation of Solution

The labeling of the most acidic hydrogen present in the given compound, quinapril is shown as,

Figure 5

The electronegativity increases while moving left to right in the period. Thus, oxygen is more electronegative than nitrogen atom as it is located at the extreme right position. According to the structure of quinapril, hydrogen atom that is bonded with oxygen atom is the most acidic one because oxygen is more electronegative than nitrogen atom. The higher electronegativity corresponds to the greater acidic character of hydrogen atom attached to the electronegative atom.

Conclusion

The labeling of the most acidic hydrogen present in the given compound, quinapril is shown in Figure 5.

Interpretation Introduction

(f)

Interpretation: The most basic site in the compound quinapril is to be labeled.

Concept introduction: According to Bronsted-Lowry theory, the species that easily tends to accept the proton is known as base and the species that easily donate the proton is known as acid. The high delocalization of electron pair corresponds to the high basic character of the atom.

Answer to Problem 3.60P

The labeling of the most basic site in the compound quinapril is shown below.

Explanation of Solution

The labeling of the most basic site in the compound quinapril is shown as,

Figure 6

According to the structure of quinapril, the site at which amide group is present is the most basic site because in amides, the pair of electrons over nitrogen atom gets highly delocalized. Hence, the most basic site is present at tertiary amide.

Conclusion

The labeling of the most basic site in the compound quinapril is shown in Figure 6.