Chapter 10, Problem 10.53P

Interpretation Introduction

(a)

Interpretation:

The product of the given reaction is to be predicted.

Concept introduction:

Epoxides react readily under neutral, basic, or acidic conditions. Epoxides can undergo ${\text{S}}_{\text{N}}\text{2}$ reactions in neutral or basic reaction conditions so as to relieve the ring strain, and this compensates for the poor leaving group ability of alkoxides (${\text{RO}}^{-}$).

The mechanism for epoxides under neutral or basic conditions consists of an ${\text{S}}_{\text{N}}\text{2}$ step followed by a proton transfer reaction. Under neutral or basic conditions, a nucleophile attacks an epoxide at the least substituted carbon atom (less sterically hindered) of the ring from the side opposite to the oxygen atom. Under acidic conditions, the first step is the protonation of $\text{C}-\text{O}$ bond. This generates a partial positive charge on the carbon atoms in the epoxide. In the second step, a nucleophile attacks the most substituted carbon atom in the epoxide from the side opposite to the $\text{C}-\text{O}$ bond.

Answer to Problem 10.53P

The product of the given reaction is:

Explanation of Solution

The given reaction is:

When the given epoxide is treated with sodium azide (basic conditions), the azide ion in sodium azide acts as a nucleophile and attacks the less substituted carbon atom (highlighted in red) of the epoxide. Due to this, the highly strained epoxide ring opens and the azide gets attached to the less substituted carbon atom. In the presence of a solvent such as water, the negatively charged oxygen atom is protonated resulting in the final product. The product of the reaction when the given epoxide is treated with sodium azide is as below:

Conclusion

Epoxides can undergo nucleophilic substitution reactions under neutral or basic conditions in which the nucleophile attacks the least substituted carbon atom in the epoxide.

Interpretation Introduction

(b)

Interpretation:

The product of the given reaction is to be predicted.

Concept introduction:

Epoxides react readily under neutral, basic, or acidic conditions. Epoxides can undergo ${\text{S}}_{\text{N}}\text{2}$ reactions in neutral or basic reaction conditions so as to relieve the ring strain, and this compensates for the poor leaving group ability of alkoxides (${\text{RO}}^{-}$).

The mechanism for the epoxides under neutral or basic conditions consists of an ${\text{S}}_{\text{N}}\text{2}$ step followed by a proton transfer reaction. Under neutral or basic conditions, a nucleophile attacks an epoxide at the least substituted carbon atom (less sterically hindered) of the ring from the side opposite to the oxygen atom. Under acidic conditions, the first step is the protonation of $\text{C}-\text{O}$ bond. This generates a partial positive charge on the carbon atoms in the epoxide. In the second step, a nucleophile attacks at the most substituted carbon atom in the epoxide from the side opposite to the $\text{C}-\text{O}$ bond.

Answer to Problem 10.53P

The product of the given reaction is:

Explanation of Solution

The given reaction is:

The given reaction conditions are basic as the potassium cyanide is a weak base and nucleophile.

When the given epoxide is treated with potassium cyanide (neutral conditions), the cyanide ion acts as a nucleophile and attacks the least substituted carbon atom of the epoxide. Due to this, the highly strained epoxide ring opens and the cyanide ion gets attached to the carbon. In the presence of a solvent such as ethanediol, the negatively charged oxygen atom is protonated resulting in the final product. The product of the reaction when the given epoxide is treated with sodium azide is as below:

Conclusion

Epoxides can undergo nucleophilic substitution reactions under neutral or basic conditions in which the nucleophile attacks the least substituted carbon atom in the epoxide.

Interpretation Introduction

(c)

Interpretation:

The product of the given reaction is to be predicted.

Concept introduction:

Epoxides react readily under neutral, basic, or acidic conditions. Epoxides can undergo ${\text{S}}_{\text{N}}\text{2}$ reactions in neutral or basic reaction conditions so as to relieve the ring strain and this compensates for the poor leaving group ability of alkoxides (${\text{RO}}^{-}$).

Under acidic conditions, the first step is the protonation of $\text{C}-\text{O}$ bond. This generates a partial positive charge on the carbon atoms in the epoxide. In the second step, a nucleophile attacks the most substituted carbon atom in the epoxide from the side opposite to the $\text{C}-\text{O}$ bond.

Answer to Problem 10.53P

The product of the given reaction is:

Explanation of Solution

The given reaction is:

The given reaction conditions are acidic as hydrogen cyanide is a weak acid.

When the given epoxide is treated with hydrogen cyanide (acidic conditions), the first step is the protonation of the epoxide oxygen atom. Due to this, a partial positive charge is generated on both carbon atoms in the epoxide. Out of the two carbon atoms, the one that is most substituted would be able to stabilize the partially developed charge, and thus, in the second step, the nucleophile, cyanide ion attacks the most substituted carbon atom from the side opposite to the $\text{C}-\text{O}$ bond. This is the ring opening step. In the last step, the acid, $\text{HCN}$ protonates the negatively charged oxygen atom to yield the final product. The product of the reaction when the given epoxide is treated with hydrogen cyanide is as below:

Conclusion

Epoxides can undergo nucleophilic substitution reactions under acidic conditions in which the nucleophile attacks the most substituted carbon atom in the epoxide.

Interpretation Introduction

(d)

Interpretation:

The product of the given reaction is to be predicted.

Concept introduction:

Epoxides react readily under neutral, basic, or acidic conditions. Epoxides can undergo ${\text{S}}_{\text{N}}\text{2}$ reactions in neutral or basic reaction conditions so as to relieve the ring strain, and this compensates for the poor leaving group ability of alkoxides (${\text{RO}}^{-}$).

The mechanism for the epoxides under neutral or basic conditions consists of an ${\text{S}}_{\text{N}}\text{2}$ step followed by a proton transfer reaction. Under neutral or basic conditions, a nucleophile attacks an epoxide at the least substituted carbon atom (less sterically hindered) of the ring from the side opposite to the oxygen atom. Under acidic conditions, the first step is the protonation of $\text{C}-\text{O}$ bond. This generates a partial positive charge on the carbon atoms in the epoxide. In the second step, a nucleophile attacks the most substituted carbon atom in the epoxide from the side opposite to the $\text{C}-\text{O}$ bond.

Answer to Problem 10.53P

The product of the given reaction is:

Explanation of Solution

The given reaction is:

The given reaction conditions are basic as lithium aluminum hydride is a strong base.

${\text{LiAlH}}_4$ is a hydride nucleophile and can open the epoxide ring via an ${\text{S}}_{\text{N}}\text{2}$ reaction. The H- generated from ${\text{LiAlH}}_4$ attacks the least substituted carbon atom in the epoxide. In the next proton transfer step, ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$, which is a strong acid, protonates the negatively charged oxygen in the epoxide to yield the final product. The product of the reaction when the given epoxide is treated with ${\text{LiAlH}}_4$ is as below:

Conclusion

Epoxides can undergo nucleophilic substitution reactions under neutral or basic conditions in which the nucleophile attacks the least substituted carbon atom in the epoxide.

Interpretation Introduction

(e)

Interpretation:

The product of the given reaction is to be predicted.

Concept introduction:

Epoxides react readily under neutral, basic, or acidic conditions. Epoxides can undergo ${\text{S}}_{\text{N}}\text{2}$ reactions in neutral or basic reaction conditions so as to relieve the ring strain and this compensates for the poor leaving group ability of alkoxides (${\text{RO}}^{-}$).

Under acidic conditions, the first step is the protonation the $\text{C}-\text{O}$ bond. This generates a partial positive charge on the carbon atoms in the epoxide. In the second step, a nucleophile attacks the most substituted carbon atom in the epoxide from the side opposite to the $\text{C}-\text{O}$ bond.

Answer to Problem 10.53P

The product of the given reaction is:

Explanation of Solution

The given reaction is:

The given reaction conditions are methanol in sulfuric acid. Sulfuric acid is a strong acid. When it is treated with methanol, it will produce protonated methanol which is a strongest known acid. When the given epoxide is treated with protonated methanol, (highly acidic conditions), the first step is the protonation of the oxygen atom in the epoxide. Due to this, a partial positive charge is generated on both the carbon atoms in the epoxide. Out of the two carbon atoms, the one that is most substituted would be able to stabilize the partially developed positive charge. Thus, in the second step, the nucleophile, methoxide ion attacks the most substituted carbon atom from the side opposite to the protonated $\text{C}-\text{O}$ bond. This is the ring opening step. In the last step, the acid, sulfuric acid protonates the negatively charged oxygen atom to yield the final product. The product of the reaction when the given epoxide is treated with methanol in sulfuric acid is as below:

Conclusion

Epoxides can undergo nucleophilic substitution reactions under acidic conditions in which the nucleophile attacks on the most substituted carbon atom in the epoxide.

Interpretation Introduction

(f)

Interpretation:

The product of the given reaction is to be predicted.

Concept introduction:

Epoxides react readily under neutral, basic, or acidic conditions. Epoxides can undergo ${\text{S}}_{\text{N}}\text{2}$ reactions in neutral or basic reaction conditions so as to relieve the ring strain, and this compensates for the poor leaving group ability of alkoxides (${\text{RO}}^{-}$).

The mechanism for the epoxides under neutral or basic conditions consists of an ${\text{S}}_{\text{N}}\text{2}$ step followed by a proton transfer reaction. Under neutral or basic conditions, a nucleophile attacks an epoxide at the least substituted carbon atom (less sterically hindered) of the ring from the side opposite to the oxygen atom. Under acidic conditions, the first step is the protonation of $\text{C}-\text{O}$ bond. This generates a partial positive charge on the carbon atoms in the epoxide. In the second step, a nucleophile attacks the most substituted carbon atom in the epoxide from the side opposite to the $\text{C}-\text{O}$ bond.

Answer to Problem 10.53P

The product of the given reaction is:

Explanation of Solution

The given reaction is:

When the given epoxide is treated with sodium methoxide in methanol (basic conditions), the methoxide ion acts as a nucleophile and attacks the least substituted carbon atom of the epoxide. Due to this, the highly strained epoxide ring opens and the methoxide ion gets attached to the least substituted carbon atom. The product of the reaction when the given epoxide is treated with sodium methoxide in methanol is as below:

Conclusion

Epoxides can undergo nucleophilic substitution reactions under neutral or basic conditions in which the nucleophile attacks the least substituted carbon atom in the epoxide.

Interpretation Introduction

(g)

Interpretation:

The product of the given reaction is to be predicted.

Concept introduction:

Epoxides react readily under neutral, basic, or acidic conditions. Epoxides can undergo ${\text{S}}_{\text{N}}\text{2}$ reactions in neutral or basic reaction conditions so as to relieve the ring strain and this compensates for the poor leaving group ability of alkoxides (${\text{RO}}^{-}$).

The mechanism for the epoxides under neutral or basic conditions consists of an ${\text{S}}_{\text{N}}\text{2}$ step followed by a proton transfer reaction. Under neutral or basic conditions, a nucleophile attacks an epoxide at the least substituted carbon atom (less sterically hindered) of the ring, from the side opposite to the oxygen atom. Under acidic conditions, the first step is the protonation of $\text{C}-\text{O}$ bond. This generates a partial positive charge on the carbon atoms in the epoxide. In the second step, a nucleophile attacks the most substituted carbon atom in the epoxide from the side opposite to the $\text{C}-\text{O}$ bond.

Answer to Problem 10.53P

The product of the given reaction is:

Explanation of Solution

The given reaction is:

When the given epoxide is treated with benzyl amine in methanol (basic conditions), the nitrogen atom in benzyl amine acts as a nucleophile and attacks the least substituted carbon atom of the epoxide. Due to this, the highly strained epoxide ring opens and the nitrogen atom gets attached to the least substituted carbon atom. The product of the reaction when the given epoxide is treated with benzyl amine in methanol is as below:

Conclusion

Epoxides can undergo nucleophilic substitution reactions under neutral or basic conditions in which the nucleophile attacks on the least substituted carbon atom in the epoxide.

Interpretation Introduction

(h)

Interpretation:

The product of the given reaction is to be predicted.

Concept introduction:

Epoxides react readily under neutral, basic, or acidic conditions. Epoxides can undergo ${\text{S}}_{\text{N}}\text{2}$ reactions in neutral or basic reaction conditions so as to relieve the ring strain, and this compensates for the poor leaving group ability of alkoxides (${\text{RO}}^{-}$).

The mechanism for the epoxides under neutral or basic conditions consists of an ${\text{S}}_{\text{N}}\text{2}$ step followed by a proton transfer reaction. Under neutral or basic conditions, a nucleophile attacks an epoxide at the least substituted carbon atom (less sterically hindered) of the ring, from the side opposite to the oxygen atom. Under acidic conditions, the first step is the protonation of the $\text{C}-\text{O}$ bond. This generates a partial positive charge on the carbon atoms in the epoxide. In the second step, a nucleophile attacks the most substituted carbon atom in the epoxide from the side opposite to the $\text{C}-\text{O}$ bond.

Answer to Problem 10.53P

The product of the given reaction is:

Explanation of Solution

The given reaction is:

Methyl lithium is an inorganic methylating agent. When the given epoxide is treated with methyl lithium (basic conditions), the methyl anion acts as a nucleophile and attacks the least substituted carbon atom of the epoxide. Due to this, the highly strained epoxide ring opens. In the second step, acidic workup is important so as to protonate the negatively charged oxygen atom.

The product of the reaction when the given epoxide is treated with methyl lithium in the acidic workup is as below:

Conclusion

Epoxides can undergo nucleophilic substitution reactions under neutral or basic conditions in which the nucleophile attacks the least substituted carbon atom in the epoxide.