Chapter 10, Problem 10.64P

Devise a synthesis of each product from the given starting material. More than one step is required.

a. d.

b. e.

c. f.

Interpretation Introduction

(a)

Interpretation: The synthesis of each product from the given starting material having more than one step is to be predicted.

Concept introduction: The removal of two substituents from a molecule either in one step or in two steps is called an elimination reaction.

For preparation of alkenes, acid-catalyzed dehydration of alcohols is one of the best methods. Less substituted alkene is the minor product when a mixture of constitutional isomers is possible. The reaction occurs via E1 mechanism or by an E2 mechanism. For primary alcohols, the reaction involves E2 mechanism, whereas for secondary and tertiary alcohols, the reaction occurs via E1 mechanism.

Hydration of alkenes is one the method used for the formation of alcohol.

The general steps involved in the hydration reaction are stated below:

• First protonation of the alkene take place to generate the carbocation.

• Formation of protonated alcohol.

• Deprotonation.

Answer to Problem 10.64P

The synthesis of each product from the given starting material having more than one step is shown below.

Explanation of Solution

For preparation of alkenes, acid-catalyzed dehydration of alcohols is one of the best methods. Less substituted alkene is the minor product when a mixture of constitutional isomers is possible. The reaction occurs via E1 mechanism or by an E2 mechanism. For primary alcohols, the reaction involves E2 mechanism, whereas for secondary and tertiary alcohols, the reaction occurs via E1 mechanism.

The general steps involved in the hydration reaction are stated below:

• First protonation of the alkene take place to generate the carbocation.

• Formation of protonated alcohol.

• Deprotonation.

The given conversion is,

Figure 1

The above diagram shows the conversion of primary alcohol into secondary alcohol. The process involves two steps. The first step is the dehydration of alcohol that results in the formation of alkene. In the next step, hydration of alkene takes place to give secondary alcohol.

The reaction that shows the formation of secondary alcohol is shown below.

Figure 2

Conclusion

The synthesis of each product from the given starting material having more than one step is rightfully stated.

Interpretation Introduction

(b)

Interpretation: The synthesis of each product from the given starting material having more than one step is to be predicted.

Concept introduction: The removal of two substituents from a molecule either in one step or in two steps is called an elimination reaction.

In elimination reaction, abstraction of proton occurs to form an alkene. Elimination reactions are of two types that is $\text{E1}$ and $\text{E2}$. The $\text{E1}$ elimination reaction involves the formation of a carbocation by the loss of leaving group in the first step followed by the abstraction of proton to form alkene. This type of elimination reactions are favored by polar aprotic solvents like acetone. In $\text{E2}$ elimination reaction, the abstraction of proton and loss of the leaving group takes place in a single step to give an alkene as the product. An elimination reaction is favored over a substitution reaction by a strong base.

Hydroboration reaction is a two step reaction, which involves conversion of alkene into alcohol. This type of reaction follows anti-markovnikov’s rule.

Answer to Problem 10.64P

The synthesis of each product from the given starting material having more than one step is shown below.

Explanation of Solution

Hydroboration reaction is a two step reaction, which involves conversion of alkene into alcohol. This type of reaction follows anti-markovinokov’s rule.

Anti markovinokov’s rule states that the positive part of acid attached to that carbon atom in $\text{C=C}$ bond which carries minimum number of hydrogen atoms and the negative part of acid will attach to that carbon atom in $\text{C=C}$ bond which has maximum number of hydrogen atoms.

The given conversion is,

Figure 3

The above diagram shows the conversion of $2-\text{bromopropane}$ into $1-\text{methoxypropane}$. The process involves three steps. The first step is the dehydrohalogenation of $2-\text{bromopropane}$ that result in the formation of alkene. In the next step, hydroboration-oxidation of alkene takes place. This results in the formation of alcohol. In the third step, reaction of methyl iodide and $\text{NaH}$ with alcohol results in the formation of $1-\text{methoxypropane}$.

The reaction that shows the formation of $1-\text{methoxypropane}$ is shown below.

Figure 4

Conclusion

The synthesis of each product from the given starting material having more than one step is rightfully stated.

Interpretation Introduction

(c)

Interpretation: The synthesis of each product from the given starting material having more than one step is to be predicted.

Concept introduction: The removal of two substituents from a molecule either in one step or in two steps is called an elimination reaction. Dehydrohalogenation is the elimination of halogen that results in the formation of alkene.

The reaction of hydrogen halide with alkene results in the formation of alkyl halide. This type of reaction is an electrophilic addition of hydrogen halide.

Electrophilic addition reactions are those in which breaking of pi bond take place to form new sigma bond. In this type of reaction, carbocation is formed during the formation of new bond.

Answer to Problem 10.64P

The synthesis of each product from the given starting material having more than one step is shown below.

Explanation of Solution

The removal of two substituents from a molecule either in one step or in two steps is called an elimination reaction. Dehydrohalogenation is the elimination of halogen that results in the formation of alkene.

The reaction of hydrogen halide with alkene results in the formation of alkyl halide. This type of reaction is an electrophilic addition of hydrogen halide.

Electrophilic addition reactions are those in which breaking of pi bond take place to form new sigma bond. In this type of reaction, carbocation is formed during the formation of new bond.

The given conversion is,

Figure 5

The above diagram shows the conversion of $1-\text{iodo}-2-\text{methylpropane}$ into $2-\text{chloro}-2-\text{methypropane}$ . The process involves two steps. The first step is the dehydrohalogenation that results in the formation of alkene. In the next step, electrophilic addition of $\text{HBr}$ takes place to give $2-\text{chloro}-2-\text{methypropane}$.

The reaction that shows the formation of $2-\text{chloro}-2-\text{methypropane}$ is shown below.

Figure 6

Conclusion

The synthesis of each product from the given starting material having more than one step is rightfully stated.

Interpretation Introduction

(d)

Interpretation: The synthesis of each product from the given starting material having more than one step is to be predicted.

Concept introduction: The general steps followed by the given reaction are as follows:

• Bromination of alkene.

• Reaction of dihalide product with soda amide to form alkyne product.

Answer to Problem 10.64P

The synthesis of each product from the given starting material having more than one step is shown below.

Explanation of Solution

The given conversion is,

Figure 7

The above diagram shows the conversion of allylcycohexane into $\text{prop}-2-\text{yn}-1-\text{ylcyclohexane}$. The process involves two steps. The first step is the bromination of alkene that results in the formation of bromo product. In the next step, reaction of soda amide with dihalide results in the formation of alkynes.

The reaction that shows the formation of alkyne is shown below.

Figure 8

Conclusion

The synthesis of each product from the given starting material having more than one step is rightfully stated.

Interpretation Introduction

(e)

Interpretation: The synthesis of each product from the given starting material having more than one step is to be predicted.

Concept introduction: The removal of two substituents from a molecule either in one step or in two steps is called an elimination reaction. Dehydrohalogenation is the elimination of halogen that results in the formation of alkene.

Bromination of alkene results in the formation of bromo products.

The reaction of dihalide reactant with soda amide results in the formation of alkyne product.

Answer to Problem 10.64P

The synthesis of each product from the given starting material having more than one step is shown below.

Explanation of Solution

The given conversion is,

Figure 9

The above diagram shows the conversion of $1-\text{bromo}-3-\text{methylbutane}$ into $1,2-\text{dibromo}-3-\text{methylbutane}$. The process involves three steps. The first step is the elimination of bromine that results in the formation of alkene. In the next step, reaction of bromination of alkene takes place that results in the dihalide product. In third step, reaction of dihalide product with soda amide results in the formation of alkyne.

The reaction that shows the formation of alkyne is shown below.

Figure 10

Conclusion

The synthesis of each product from the given starting material having more than one step is rightfully stated.

Interpretation Introduction

(f)

Interpretation: The synthesis of each product from the given starting material having more than one step is to be predicted.

Concept introduction: The removal of two substituents from a molecule either in one step or in two steps is called an elimination reaction. Dehydrohalogenation is the elimination of halogen that results in the formation of alkene.

Answer to Problem 10.64P

The synthesis of each product from the given starting material having more than one step is shown below.

Explanation of Solution

The given conversion is,

Figure 11

The above diagram shows the conversion of $\left(2-\text{chloroethyl}\right)\text{cyclopentane}$ into $2-\text{cyclopentyloxirane}$. The process involves two steps. The first step is the elimination of chlorine that results in the formation of alkene. In the next step, reaction of alkene with peroxy acid takes place that results in the formation of epoxides or oxirane.

The reaction that shows the formation of alkyne is shown below.

Figure 12

Conclusion

The synthesis of each product from the given starting material having more than one step is rightfully stated.