Chapter 6, Problem 6.9P

Interpretation Introduction

(a)

Interpretation:

It is to be determined whether the given solvent is suitable for a reaction involving $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ as a reactant with respect to leveling effect.

Concept introduction:

Leveling effects refers to the effect of a solvent on the behavior of acids and bases. If the reactant is a very strong acid or base, it can react with the solvent in an undesired proton transfer reaction. At equilibrium, the strongest acid that can occur in solution is the protonated solvent, and the strongest base that can occur in solution is the deprotonated solvent. For the leveling effect, a solvent is unsuitable for a particular reactant if the reactant (lower $\text{pKa}$) is stronger than the solvent’s conjugate acid and if the reactant is a stronger base (higher $\text{pKa}$) than the solvent’s conjugate base.

Answer to Problem 6.9P

With respect to the leveling effect, water is not a suitable solvent for a reaction involving $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ as a reactant.

Explanation of Solution

The reaction of $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ with water is shown below:

Water, ${\text{H}}_{\text{2}}\text{O}$ ($\text{pKa = 15}\text{.7}$), is a stronger acid than acetylene, $\text{HC}\equiv \text{CH}$ ($\text{pKa = 25}$). The product side of the reaction is most favored because the stronger acid, ${\text{H}}_{\text{2}}\text{O}$, is on the reactant side. $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ does not change the properties of the water. Therefore, water, ${\text{H}}_{\text{2}}\text{O}$, is not a suitable solvent for $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ because the equilibrium lies to the product side.

Conclusion

The solvent effect on the reactant is determined with respect to the leveling effect.

Interpretation Introduction

(b)

Interpretation:

It is to be determined whether the given solvent is suitable for a reaction involving $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ as a reactant with respect to leveling effect.

Concept introduction:

Leveling effects refers to the effect of a solvent on the behavior of acids and bases. If the reactant is a very strong acid or base, it can react with the solvent in an undesired proton transfer reaction. At equilibrium, the strongest acid that can occur in solution is the protonated solvent, and the strongest base that can occur in solution is the deprotonated solvent. For the leveling effect, a solvent is unsuitable for a particular reactant if the reactant (lower $\text{pKa}$) is stronger than the solvent’s conjugate acid and if the reactant is a stronger base (higher $\text{pKa}$) than the solvent’s conjugate base.

Answer to Problem 6.9P

With respect to the leveling effect, ethanol is not a suitable solvent for a reaction involving $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ as a reactant.

Explanation of Solution

The reaction of $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ with water is shown below:

Ethanol, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{OH}$ ($\text{pKa = 16}$), is a stronger acid than acetylene, $\text{HC}\equiv \text{CH}$ ($\text{pKa = 25}$). The product side of the reaction is most favored because the stronger acid, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{OH}$, is on the reactant side. $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ does not change the properties of ethanol. Therefore, ethanol, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{OH}$, is not a suitable solvent for $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ because the equilibrium lies to the product side.

Conclusion

The solvent effect on the reactant is determined with respect to the leveling effect.

Interpretation Introduction

(c)

Interpretation:

It is to be determined whether the given solvent is suitable for a reaction involving $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ as a reactant with respect to leveling effect.

Concept introduction:

Leveling effects refers to the effect of a solvent on the behavior of acids and bases. If the reactant is a very strong acid or base, it can react with the solvent in an undesired proton transfer reaction. At equilibrium, the strongest acid that can occur in solution is the protonated solvent, and the strongest base that can occur in solution is the deprotonated solvent. For the leveling effect, a solvent is unsuitable for a particular reactant if the reactant (lower $\text{pKa}$) is stronger than the solvent’s conjugate acid and if the reactant is a stronger base (higher $\text{pKa}$) than the solvent’s conjugate base.

Answer to Problem 6.9P

With respect to the leveling effect, ethanamide is not a suitable solvent for a reaction involving $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ as a reactant.

Explanation of Solution

The reaction of $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ with water is shown below:

Ethanamide, ${\text{CH}}_{\text{3}}{\text{CONH}}_{\text{2}}$ ($\text{pKa = 17}$), is a stronger acid than acetylene, $\text{HC}\equiv \text{CH}$ ($\text{pKa = 25}$). The product side of the reaction is most favored because the stronger acid, ${\text{CH}}_{\text{3}}{\text{CONH}}_{\text{2}}$, is on the reactant side. $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ does not change the properties of ethanamide. Therefore, Ethanamide (${\text{CH}}_{\text{3}}{\text{CONH}}_{\text{2}}$) is not a suitable solvent for $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ because the equilibrium lies to the product side.

Conclusion

The solvent effect on the reactant is determined with respect to the leveling effect.

Interpretation Introduction

(d)

Interpretation:

It is to be determined whether the given solvent is suitable for a reaction involving $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ as a reactant with respect to leveling effect.

Concept introduction:

Leveling effects refers to the effect of a solvent on the behavior of acids and bases. If the reactant is a very strong acid or base, it can react with the solvent in an undesired proton transfer reaction. At equilibrium, the strongest acid that can occur in solution is the protonated solvent, and the strongest base that can occur in solution is the deprotonated solvent. For the leveling effect, a solvent is unsuitable for a particular reactant if the reactant (lower $\text{pKa}$) is stronger than the solvent’s conjugate acid and if the reactant is a stronger base (higher $\text{pKa}$) than the solvent’s conjugate base.

Answer to Problem 6.9P

With respect to the leveling effect, ${\text{CH}}_{\text{3}}{\text{SOCH}}_{\text{3}}$ is a suitable solvent for a reaction involving $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ as a reactant.

Explanation of Solution

The reaction of $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ with water is shown below:

Acetylene, $\text{HC}\equiv \text{CH}$ ($\text{pKa = 25}$) is a stronger acid than dimethyl sulfoxide (${\text{CH}}_{\text{3}}{\text{SOCH}}_{\text{3}}$) ($\text{pKa = 35}$). The reactant side of the reaction is most favored because the stronger acid, $\text{HC}\equiv \text{CH}$, is on the product side. $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ changes the properties of dimethyl sulfoxide. Therefore, dimethyl sulfoxide, ${\text{CH}}_{\text{3}}{\text{SOCH}}_{\text{3}}$, is a suitable solvent for $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ because the equilibrium lies to the reactant side.

Conclusion

The solvent effect on the reactant is determined with respect to the leveling effect.

Interpretation Introduction

(e)

Interpretation:

It is to be determined whether the given solvent is suitable for a reaction involving $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ as a reactant with respect to leveling effect.

Concept introduction:

Leveling effects refers to the effect of a solvent on the behavior of acids and bases. If the reactant is a very strong acid or base, it can react with the solvent in an undesired proton transfer reaction. At equilibrium, the strongest acid that can occur in solution is the protonated solvent, and the strongest base that can occur in solution is the deprotonated solvent. For the leveling effect, a solvent is unsuitable for a particular reactant if the reactant (lower $\text{pKa}$) is stronger than the solvent’s conjugate acid and if the reactant is a stronger base (higher $\text{pKa}$) than the solvent’s conjugate base.

Answer to Problem 6.9P

With respect to the leveling effect, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{OCH}}_{\text{2}}{\text{CH}}_{\text{3}}$ is a suitable solvent for a reaction involving $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ as a reactant.

Explanation of Solution

The reaction of $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ with water is shown below:

Acetylene, $\text{HC}\equiv \text{CH}$ ($\text{pKa = 25}$), is a stronger acid than diethyl ether (${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{OCH}}_{\text{2}}{\text{CH}}_{\text{3}}$) ($\text{pKa = 45}$). The reactant side of the reaction is most favored because the stronger acid, $\text{HC}\equiv \text{CH}$, is on the product side. $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ changes the properties of diethyl ether. Therefore, diethyl ether, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{OCH}}_{\text{2}}{\text{CH}}_{\text{3}}$, is a suitable solvent for $\text{HC}\equiv {\text{C:}}^{\text{Θ}}$ because the equilibrium lies to the reactant side.

Conclusion

The solvent effect on the reactant is determined with respect to the leveling effect.