Chapter 3, Problem 3.28P

Interpretation Introduction

(a)

Interpretation: The given compounds must be arranged in increasing order of strength of their intermolecular forces.

Concept introduction: Intermolecular forces are those interactions among molecules by which the molecules either attract or repel each other. There are mainly four types of intermolecular interactions these are electrostatic, Van der Waals, dipole-dipole and hydrogen bonding. The electrostatic force is strongest and among the three types of intermolecular forces in covalent compounds van der Waals forces are weakest, dipole-dipole is intermediate and hydrogen bonding is the strongest.

Answer to Problem 3.28P

${\text{CH}}_3{\text{CH}}_3{\text{ CH}}_3{\text{Cl CH}}_3{\text{NH}}_2$

Increasing intermolecular forces

Explanation of Solution

The CH₃CH₃, ethane consists of only C – H and C – C bonds and these bonds are nonpolar thus the ethane has no permanent dipole moment therefore, ethane molecules are attracted to each other only by van der Waals forces.

The CH₃Cl, chloromethane consists of C – H and C – Cl bonds among which C – Cl bond is polar since Cl is highly electronegative atom thus the chloromethane molecule possesses a permanent dipole moment. Therefore, chloromethane molecules are attracted to each other not only by van der Waals forces but also by dipole-dipole interactions.

The CH₃NH₂, methylamine consists of C – H, N – H and C – Cl bonds among which C – N and N – H bonds are polar since N is an electronegative atom thus the methylamine molecule possesses a permanent dipole moment. Therefore, methylamine molecules are attracted to each other not only by van der Waals forces but also by dipole-dipole interactions and since it contains a H-atom attached to an electronegative N-atom so CH₃NH₂ molecules will also be linked through Hydrogen bonding.

Conclusion

${\text{CH}}_3{\text{CH}}_3{\text{ CH}}_3{\text{Cl CH}}_3{\text{NH}}_2$

Increasing intermolecular forces

Interpretation Introduction

(b)

Interpretation: The given compounds must be arranged in increasing order of strength of their intermolecular forces.

Concept introduction: Intermolecular forces are those interactions among molecules by which the molecules either attract or repel each other. There are mainly four types of intermolecular interactions these are electrostatic, Van der Waals, dipole-dipole and hydrogen bonding. The electrostatic force is strongest and among the three types of intermolecular forces in covalent compounds van der Waals forces are weakest, dipole-dipole is intermediate and hydrogen bonding is the strongest.

Answer to Problem 3.28P

${\text{CH}}_3{\text{Cl CH}}_3{\text{Br CH}}_3\text{I}$

Increasing intermolecular forces

Explanation of Solution

The CH₃Br molecule consists of only C – H and C – Br bonds among which C – Br bond is polar thus this molecule has permanent dipole moment therefore; these molecules are attracted towards each other not only by van der Waals forces but also by dipole-dipole interactions.

The CH₃I molecule consists of only C – H and C – I bonds among which C – I bond is polar thus this molecule has permanent dipole moment therefore; these molecules are attracted towards each other not only by van der Waals forces but also by dipole-dipole interactions.

The CH₃Cl molecule consists of only C – H and C – Cl bonds among which C – Cl bond is polar thus this molecule has permanent dipole moment therefore; these molecules are attracted towards each other not only by van der Waals forces but also by dipole-dipole interactions.

All these molecules are attracted to each other by van der Waals forces and dipole-dipole interactions. But with increase in size of the atom here halogen atoms the polarizability increases which results in the increase of intermolecular forces. Here, the size of halogen atoms increase with increase in atomic number that is I > Br > Cl thus, CH₃I molecules will have strongest and CH₃Cl molecules will have weakest intermolecular forces.

Conclusion

${\text{CH}}_3{\text{Cl CH}}_3{\text{Br CH}}_3\text{I}$

Increasing intermolecular forces

Interpretation Introduction

(c)

Interpretation: The given compounds must be arranged in increasing order of strength of their intermolecular forces.

Concept introduction: Intermolecular forces are those interactions among molecules by which the molecules either attract or repel each other. There are mainly four types of intermolecular interactions these are electrostatic, Van der Waals, dipole-dipole and hydrogen bonding. The electrostatic force is strongest and among the three types of intermolecular forces in covalent compounds van der Waals forces are weakest, dipole-dipole is intermediate and hydrogen bonding is the strongest.

Answer to Problem 3.28P

${\left({\text{CH}}_3\right)}_2\text{C = C}{\left({\text{CH}}_3\right)}_2{\left({\text{CH}}_3\right)}_2{\text{CHCOCH}}_3{\left({\text{CH}}_3\right)}_2\text{CHCOOH}$

Increasing intermolecular forces

Explanation of Solution

The ${\left({\text{CH}}_3\right)}_2\text{C = C}{\left({\text{CH}}_3\right)}_2$ molecule consists of only C – H, C = C and C – C bonds and these bonds are nonpolar thus this molecule has no permanent dipole moment therefore, these molecules are attracted towards each other only by van der Waals forces.

The ${\left({\text{CH}}_3\right)}_2{\text{CHCOCH}}_3$ molecule consists of C – H, C – C and C = O bonds among which C = O bond is polar since O is highly electronegative atom thus this molecule possesses a permanent dipole moment. Therefore, these molecules are attracted to each other not only by van der Waals forces but also by dipole-dipole interactions.

The ${\left({\text{CH}}_3\right)}_2\text{CHCOOH}$ molecule consists of C – H, C – C, C = O and O – H bonds among which C = O and O – H bonds are polar since O is an electronegative atom thus these molecules possess a permanent dipole moment. Therefore, these molecules are attracted to each other not only by van der Waals forces but also by dipole-dipole interactions and since it contains a H-atom attached to an electronegative O-atom so ${\left({\text{CH}}_3\right)}_2\text{CHCOOH}$ molecules will also be linked through Hydrogen bonding.

Conclusion

${\left({\text{CH}}_3\right)}_2\text{C = C}{\left({\text{CH}}_3\right)}_2{\left({\text{CH}}_3\right)}_2{\text{CHCOCH}}_3{\left({\text{CH}}_3\right)}_2\text{CHCOOH}$

Increasing intermolecular forces

Interpretation Introduction

(d)

Interpretation: The given compounds must be arranged in increasing order of strength of their intermolecular forces.

Concept introduction: Intermolecular forces are those interactions among molecules by which the molecules either attract or repel each other. There are mainly four types of intermolecular interactions these are electrostatic, Van der Waals, dipole-dipole and hydrogen bonding. The electrostatic force is strongest and among the three types of intermolecular forces in covalent compounds van der Waals forces are weakest, dipole-dipole is intermediate and hydrogen bonding is the strongest.

Answer to Problem 3.28P

${\text{CH}}_3{\text{Cl CH}}_3\text{OH NaCl}$

Increasing intermolecular forces

Explanation of Solution

The CH₃Cl molecule consists of only C – H and C – Cl bonds among which C – Cl bond is polar thus this molecule has permanent dipole moment therefore; these molecules are attracted towards each other not only by van der Waals forces but also by dipole-dipole interactions.

The CH₃OH, methanol consists of C – H and O – H bonds among which O – H bond are polar since O is an electronegative atom thus the methanol molecule possesses a permanent dipole moment. Therefore, methanol molecules are attracted to each other not only by van der Waals forces but also by dipole-dipole interactions and since it contains a H-atom attached to an electronegative O-atom so CH₃OH molecules will also be linked through Hydrogen bonding.

The NaCl molecule consists of only an ionic bond among Na⁺ and Cl^- ions thus, these molecules are attracted towards each other by electrostatic interactions.

Conclusion

${\text{CH}}_3{\text{Cl CH}}_3\text{OH NaCl}$

Increasing intermolecular forces