Chapter 11, Problem 56P

(a)

Interpretation Introduction

Interpretation:The complete Lewis structure of lisinopril needs to be drawn.

Concept Introduction: The complete Lewis structure of a molecule can be drawn using the total number of valence electrons present in it. It shows distribution of total number of valence electrons between the atoms of molecules. The bonded electrons are those electrons which are involved in bonding and they are represented as bonds or lines between the bonded atoms. The lone pair of electrons are those electrons which are not involved in bonding they are represented as dots (in pair) on the symbol of the atom.

Explanation of Solution

The given structure is as follows:

Here, O can have maximum of 2 lone pairs of electrons, N can have 1 lone pair of electrons and there is no lone pair of electrons on C and H atoms.

The valence electrons of C, H, N and O is 4, 1, 5 and 6 respectively.

The complete Lewis structure will be as follows:

(b)

Interpretation Introduction

Interpretation:All the bond angles in lisinopril needs to be identified using the valence shell electron-pair repulsion model.

Concept Introduction: Hybridization is defined as mixing of orbital. The geometry of a central atom depends on its hybridization. The shape will be different from geometry if there are lone pair of electrons present on the central atom. The bond angles of central atom can be determined from its hybridization and geometry.

Explanation of Solution

The complete Lewis structure of lisinopril is as follows:

The valence electrons of C, H, N and O atom is 4, 1, 5 and 6 respectively. The C atom with 4 single bonds will have $s{p}^3$ hybridization. The C atom with 2 single bonds and 1 double bond will have $s{p}^2$ hybridization. The O atom with 2 single bonds and 2 lone pair of electrons will have $s{p}^3$ hybridization and nitrogen atom with 3 single bonds and 1 lone pair will have $s{p}^3$ hybridization.

The central atom with $s{p}^3$ hybridization and 0 lone pair of electrons will have tetrahedral geometry with bond angle ${109.5}^o$ , atom with $s{p}^3$ hybridization and 1 lone pair will have tetrahedral geometry and trigonal pyramidal shape with bond angle approx. ${106}^o-{107}^{\text{o}}$ , atom with $s{p}^3$ hybridization and 2 lone pair of electrons will have tetrahedral geometry but bent shape with bond angle approx. ${104}^o$ and atom with $s{p}^2$ hybridization and 0 lone pair is trigonal planar with bond angle ${120}^{\text{o}}$ .

(c)

Interpretation Introduction

Interpretation: The most polar bond in lisinopril needs to be determined.

Concept Introduction: A bond is said to be polar if there is electronegativity difference between the atoms. The most polar bond will be the one with maximum electronegativity difference between the bonded atoms.

Explanation of Solution

The structure is given as follows:

Here, C and H have comparable electronegativity thus, C-H bond is non-polar. The difference in electronegativity can be observed if C or H are bonded with O and N atoms.

Here, H is more electropositive than C thus, the electronegativity difference will be more in case of O-H or N-H bond as compared to O-C or N-C bonds.

Comparing O-H and N-H bond, O atom is more electronegative thus, electronegativity difference will be more in O-H and it is most polar bond in lisinopril.

(d)

Interpretation Introduction

Interpretation: Whether the given molecule is polar or non-polar needs to be determined.

Concept Introduction: If there are polar bonds present in a molecule then it is considered as a polar molecule.

Explanation of Solution

Due to the presence of polar O-H, N-H, C-O and C-N bonds, lisinopril is considered as a polar molecule.

(e)

Interpretation Introduction

Interpretation: This is to be explained whether lisinopril possess resonance or not.

Concept Introduction: Resonance is possessed by a molecule if there is possibility of delocalization of electrons. This can be positive if there is intercation between alternate lone pairs and pi bonds present in a molecule.

Explanation of Solution

The complete structure of lisinopril is as follows:

The above structure shows resonance as lone pair of electrons on oxygen atom is in conjugation with double bond. Similarly, lone pair of electrons on N atom is in conjugation with double bonded oxygen atom.

This is represented as follows:

(f)

Interpretation Introduction

Interpretation: The functional groups present in lisinopril needs to be determined.

Concept Introduction: The functional groups are identity groups of the molecules. Functional groups define the types of chemical reactions a molecule can undergo. In organic chemistry, functional group is responsible for any characteristic reaction of the molecule. Two molecules with same functional groups will show similar type of chemical reactions.

Explanation of Solution

The complete structure of lisinopril is as follows:

Here, -COOH, NH-, -NH₂, CON- and benzene or aromatic functional groups are present.

Functional groups are labelled as follows:

(g)

Interpretation Introduction

Interpretation: The molecular formula of lisinopril needs to be determined.

Concept Introduction: Molecular formula of any compound can be determined by calculating the total number of atoms of each element present in it.

Explanation of Solution

The complete structure of lisinopril is as follows:

There are 4 types of atoms present in the above molecule namely carbon atom, oxygen atom, hydrogen atom and nitrogen atom.

From the above structure, the molecular formula will be ${\text{C}}_{\text{21}}{\text{H}}_{\text{31}}{\text{N}}_{\text{3}}{\text{O}}_{\text{5}}$ .

(h)

Interpretation Introduction

Interpretation: The types of intermolecular forces present in the lisinopril molecules needs to be determined.

Concept Introduction: Intermolecular forces are defined as type of forces present between the two molecules when they come in contact of each other. The type of forces depends on the physical and chemical properties of atoms present in the molecule.

Explanation of Solution

The complete structure is represented as follows:

All the type of molecules containing non-polar bonds exhibits London dispersion forces. Due to the non-polar bonds (C-C and C-H) in the molecule. London dispersion forces are present.

Due to the presence of O-H bond, it also exhibits hydrogen bonding.