Chapter 9, Problem 9.13P

Interpretation Introduction

(a)

Interpretation:

The reaction, either ${\text{S}}_{\text{N}}{\text{1, S}}_{\text{N}}\text{2}$, or $\text{E1, E2}$ favored at high concentration of ${\text{HO}}^{\text{-}}$ is to be explained.

Concept introduction:

${\text{S}}_{\text{N}}\text{2}$ reaction rates are highly sensitive to nucleophilicity whereas ${\text{S}}_{\text{N}}\text{1}$ reactions are not. Thus, strong nucleophiles favor ${\text{S}}_{\text{N}}\text{2}$ reactions and weak nucleophiles favor ${\text{S}}_{\text{N}}\text{1}$ reactions.

$\text{E2}$ reaction rates are highly sensitive to the strength of the attacking base whereas $\text{E1}$ reactions are not. Thus, strong bases favor $\text{E2}$ reactions, and weak bases favor $\text{E1}$ reactions.

Answer to Problem 9.13P

Both ${\text{S}}_{\text{N}}\text{2}$ and $\text{E2}$ reactions are favored at high concentration of ${\text{HO}}^{\text{-}}$.

Explanation of Solution

Both ${\text{S}}_{\text{N}}\text{2}$ and $\text{E2}$ reaction rates depend on the concentration of the attacking species. In an ${\text{S}}_{\text{N}}\text{2}$ and $\text{E2}$ reaction, the attacking species forces off the leaving group, so with a higher concentration of attacking species, the rate-determining step occurs more frequently and the rate increases.

${\text{HO}}^{\text{-}}$ is a strong nucleophile as well as a strong base, that is, attacking species. At high concentration of ${\text{HO}}^{\text{-}}$, therefore, ${\text{S}}_{\text{N}}\text{2}$ and $\text{E2}$ reactions are favored over ${\text{S}}_{\text{N}}\text{1}$ or $\text{E1}$.

Conclusion

${\text{S}}_{\text{N}}\text{2}$, $\text{E2}$ reactions are favored at high concentration of nucleophile and strong base.

Interpretation Introduction

(b)

Interpretation:

The reactions, either ${\text{S}}_{\text{N}}{\text{1, S}}_{\text{N}}\text{2}$, or $\text{E1, E2}$ are favored at low concentration of ${\text{HO}}^{\text{-}}$ is to be explained.

Concept introduction:

${\text{S}}_{\text{N}}\text{2}$ reaction rates are highly sensitive to nucleophilicity whereas ${\text{S}}_{\text{N}}\text{1}$ reactions are not. Thus, strong nucleophiles favor ${\text{S}}_{\text{N}}\text{2}$ reactions and weak nucleophiles favor ${\text{S}}_{\text{N}}\text{1}$ reactions.

$\text{E2}$ reaction rates are highly sensitive to the strength of the attacking base, whereas $\text{E1}$ reactions are not. Thus, strong bases favor $\text{E2}$ reactions and weak bases favor $\text{E1}$ reactions.

Answer to Problem 9.13P

Both ${\text{S}}_{\text{N}}1$ and $\text{E1}$ reactions are favored at low concentration of ${\text{OH}}^{\text{-}}$.

Explanation of Solution

The given species ${\text{HO}}^{\text{-}}$ acts as a strong nucleophile and a strong base. If the attacking species is a strong nucleophile and strong base, ${\text{S}}_{\text{N}}\text{2}$ and $\text{E2}$ reactions are favored at high concentration. But the given condition is low concentration of ${\text{HO}}^{\text{-}}$, therefore ${\text{S}}_{\text{N}}1$ and $\text{E1}$ reactions are favored over ${\text{S}}_{\text{N}}\text{2}$ and $\text{E2}$ reaction.

Conclusion

${\text{S}}_{\text{N}}1$, $\text{E1}$ reactions are favored at low concentration of a strong nucleophile and strong base.

Interpretation Introduction

(c)

Interpretation:

The reaction, either ${\text{S}}_{\text{N}}{\text{1, S}}_{\text{N}}\text{2}$, or $\text{E1, E2}$ favored at a high concentration of ${\text{Br}}^{\text{-}}$ is to be explained.

Concept introduction:

${\text{S}}_{\text{N}}\text{2}$ reaction rates are highly sensitive to nucleophilicity, whereas ${\text{S}}_{\text{N}}\text{1}$ reactions are not. Thus, strong nucleophiles favor ${\text{S}}_{\text{N}}\text{2}$ reactions and weak nucleophiles favor ${\text{S}}_{\text{N}}\text{1}$ reactions.

$\text{E2}$ reaction rates are highly sensitive to the strength of the attacking base, whereas $\text{E1}$ reactions are not. Thus, strong bases favor $\text{E2}$ reactions, and weak bases favor $\text{E1}$ reactions.

Answer to Problem 9.13P

${\text{S}}_{\text{N}}\text{2}$ and $\text{E1}$ reactions are favored at high concentration of ${\text{Br}}^{\text{-}}$.

Explanation of Solution

Since the given species ${\text{Br}}^{\text{-}}$ is a strong nucleophile with high concentration, therefore, ${\text{S}}_{\text{N}}\text{2}$ is favored over ${\text{S}}_{\text{N}}1$. ${\text{Br}}^{\text{-}}$ is a weak base, thus, $\text{E1}$ reaction is favored over $\text{E2}$.

Therefore, ${\text{S}}_{\text{N}}\text{2}$ and $\text{E1}$ reactions are favored at high concentration of ${\text{Br}}^{\text{-}}$.

Conclusion

${\text{S}}_{\text{N}}\text{2}$ reaction is favored at high concentration of a strong nucleophile and $\text{E1}$ reaction is favored if a weak base is used.

Interpretation Introduction

(d)

Interpretation:

The reaction, either ${\text{S}}_{\text{N}}{\text{1, S}}_{\text{N}}\text{2}$, or $\text{E1, E2}$ is favored at a low concentration of ${\text{Br}}^{\text{-}}$ is to be explained.

Concept introduction:

${\text{S}}_{\text{N}}\text{2}$ reaction rates are highly sensitive to nucleophilicity whereas ${\text{S}}_{\text{N}}\text{1}$ reactions are not. Thus, strong nucleophiles favor ${\text{S}}_{\text{N}}\text{2}$ reactions and weak nucleophiles favor ${\text{S}}_{\text{N}}\text{1}$ reactions.

$\text{E2}$ reaction rates are highly sensitive to the strength of the attacking base whereas $\text{E1}$ reactions are not. Thus, strong bases favor $\text{E2}$ reactions and weak bases favor $\text{E1}$ reactions.

Answer to Problem 9.13P

Both ${\text{S}}_{\text{N}}1$ and $\text{E1}$ reactions are favored at low concentration of ${\text{Br}}^{\text{-}}$.

Explanation of Solution

Since the given species ${\text{Br}}^{\text{-}}$ is a strong nucleophile with low concentration, therefore, ${\text{S}}_{\text{N}}1$ is favored over ${\text{S}}_{\text{N}}2$. ${\text{Br}}^{\text{-}}$ is a weak base, and thus, $\text{E1}$ reaction is favored over $\text{E2}$.

Therefore, ${\text{S}}_{\text{N}}1$ and $\text{E1}$ reactions are favored at low concentration of ${\text{Br}}^{\text{-}}$.

Conclusion

${\text{S}}_{\text{N}}1$ reaction is favored at low concentration of a strong nucleophile and $\text{E1}$ reaction is favored if a weak base is used.

Interpretation Introduction

(e)

Interpretation:

The reaction, either ${\text{S}}_{\text{N}}{\text{1, S}}_{\text{N}}\text{2}$, or $\text{E1, E2}$ favored at high concentration of ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{3}}{\text{CO}}^{\text{-}}$ is to be explained.

Concept introduction:

${\text{S}}_{\text{N}}\text{2}$ reaction rates are highly sensitive to nucleophilicity whereas ${\text{S}}_{\text{N}}\text{1}$ reactions are not. Thus, strong nucleophiles favor ${\text{S}}_{\text{N}}\text{2}$ reactions and weak nucleophiles favor ${\text{S}}_{\text{N}}\text{1}$ reactions.

$\text{E2}$ reaction rates are highly sensitive to the strength of the attacking base whereas $\text{E1}$ reactions are not. Thus, strong bases favor $\text{E2}$ reactions and weak bases favor $\text{E1}$ reactions.

Answer to Problem 9.13P

$\text{E2}$ reactions are favored at high concentration of ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{3}}{\text{CO}}^{-}$.

Explanation of Solution

The given species ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{3}}{\text{CO}}^{-}$ is a strong nucleophile as well as a strong base. Though ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{3}}{\text{CO}}^{-}$ is a strong nucleophile, $\text{E2}$ is favored over ${\text{S}}_{\text{N}}2$ because it is very bulky.

Therefore, $\text{E2}$ reactions are favored at high concentration of ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{3}}{\text{CO}}^{-}$.

Conclusion

$\text{E2}$ reactions are favored at a high concentration of a strong bulky base.

Interpretation Introduction

(f)

Interpretation:

The reaction, either ${\text{S}}_{\text{N}}{\text{1, S}}_{\text{N}}\text{2}$, or $\text{E1, E2}$ is favored at low concentration of ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{3}}{\text{CO}}^{\text{-}}$ is to be explained.

Concept introduction:

${\text{S}}_{\text{N}}\text{2}$ reaction rates are highly sensitive to nucleophilicity, whereas ${\text{S}}_{\text{N}}\text{1}$ reactions are not. Thus, strong nucleophiles favor ${\text{S}}_{\text{N}}\text{2}$ reactions and weak nucleophiles favor ${\text{S}}_{\text{N}}\text{1}$ reactions.

$\text{E2}$ reaction rates are highly sensitive to the strength of the attacking base, whereas $\text{E1}$ reactions are not. Thus, strong bases favor $\text{E2}$ reactions and weak bases favor $\text{E1}$ reactions.

Answer to Problem 9.13P

Both ${\text{S}}_{\text{N}}1$ and $\text{E1}$ reactions are favored at low concentration of ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{3}}{\text{CO}}^{\text{-}}$.

Explanation of Solution

The given species ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{3}}{\text{CO}}^{-}$ acts as a strong nucleophile and a strong base. If the attacking species is a strong nucleophile and strong base, ${\text{S}}_{\text{N}}\text{2}$ and $\text{E2}$ reactions are favored at high concentration. But the given condition is low concentration of ${{\text{(CH}}_{\text{3}}\text{)}}_{\text{3}}{\text{CO}}^{-}$, therefore ${\text{S}}_{\text{N}}1$ and $\text{E1}$ reactions are favored over ${\text{S}}_{\text{N}}\text{2}$ and $\text{E2}$ reactions.

Conclusion

${\text{S}}_{\text{N}}1$, $\text{E1}$ reactions are favored at low concentration of a strong nucleophile and a strong base.