(a) Interpretation: Whether an E2 elimination from the given alkyl halide precursor will exclusively produce (E)-anethol or a mixture of stereoisomers is to be determined. Concept introduction: E2 elimination is a single step mechanism involving both the substrate molecule and the reagent molecule. It involves the elimination of a leaving group along with hydrogen from a carbon adjacent to the one with the leaving group. In E2 mechanism, a strong base extracts the proton with the C − H bond pair moving to form a second bond between the two carbon atoms. Simultaneously, the leaving group departs with its pair of bond electrons. This requires that the leaving group and the extracted proton be anti to each other. This generally leads to the formation of only one isomer. However, if there are two hydrogen atoms on the carbon from which the proton is extracted, a mixture of stereoisomers is possible. The product distribution, in this case, depends on the stabilities of the conformers that lead to the two isomers.

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Answer 1

Question

Chapter 8, Problem 8.50P

Interpretation Introduction

(a)

Interpretation:

Whether an E2 elimination from the given alkyl halide precursor will exclusively produce (E)-anethol or a mixture of stereoisomers is to be determined.

Concept introduction:

E2 elimination is a single step mechanism involving both the substrate molecule and the reagent molecule. It involves the elimination of a leaving group along with hydrogen from a carbon adjacent to the one with the leaving group. In E2 mechanism, a strong base extracts the proton with the C−H bond pair moving to form a second bond between the two carbon atoms. Simultaneously, the leaving group departs with its pair of bond electrons. This requires that the leaving group and the extracted proton be anti to each other. This generally leads to the formation of only one isomer. However, if there are two hydrogen atoms on the carbon from which the proton is extracted, a mixture of stereoisomers is possible. The product distribution, in this case, depends on the stabilities of the conformers that lead to the two isomers.

Interpretation Introduction

(b)

Interpretation:

Whether an E1 elimination reaction, from the given precursor, will produce a pure stereoisomer or a mixture is to be determined.

Concept introduction:

E1 elimination is a two-step reaction. The leaving group breaks off in the first step taking its bond pair with it. A trigonal planar carbocation results from this step. Since the carbocation is planar, any one of the hydrogen atoms, on an adjacent carbon, can be removed as a proton. The associated C−H bond pair can then move toward the carbocation to form the second (pi) bond between the two carbon atoms. Since there is no restriction on which hydrogen can be lost, a mixture of stereoisomers is formed.

Interpretation Introduction

(c)

Interpretation:

In each of the two reactions that produce a mixture, which isomer is produced in greater abundance is to be determined.

Concept introduction:

When a reaction produces a mixture of stereoisomers, the product distribution depends on two factors, the stability of the product and the stability of the conformers of the precursor in case of an E2 reaction. An E2 reaction requires that the proton and the leaving group be anti to each other. If there are two protons on the beta carbon, the relative stabilities of the two conformers will influence the product distribution.

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When treated with NaOH, the bromide below gives an alkene by the E2 mechanism, by elimination of the H atom indicated by the arrow: (a) Draw the Newman projection from which elimination takes place. (b) Draw the mechanism. (c) Draw the product with the proper stereochemistry. (d) Assign the proper stereochemical descriptor to the product. (e) Give the rate equation

Q12. (1bremeetblbenzene 1 ydergOesan elimination following an E1 mechanism. Fill in the following synthetic scheme by drawing the structure of intermediate 2 and product 3. The chemical formula of product 3 is provided as guidance.

When 2-bromo-3-phenylbutane is treated with sodium methoxide, two alkenes result (by E2 elimination). The Zaitsevproduct predominates.(a) Draw the reaction, showing the major and minor products.(b) When one pure stereoisomer of 2-bromo-3-phenylbutane reacts, one pure stereoisomer of the major product results.For example, when (2R,3R)-2-bromo-3-phenylbutane reacts, the product is the stereoisomer with the methyl groups cis.Use your models to draw a Newman projection of the transition state to show why this stereospecificity is observed.(c) Use a Newman projection of the transition state to predict the major product of elimination of (2S,3R)-2-bromo-3-phenylbutane

Answer 2

Question

Chapter 8, Problem 8.50P

Interpretation Introduction

(a)

Interpretation:

Whether an E2 elimination from the given alkyl halide precursor will exclusively produce (E)-anethol or a mixture of stereoisomers is to be determined.

Concept introduction:

E2 elimination is a single step mechanism involving both the substrate molecule and the reagent molecule. It involves the elimination of a leaving group along with hydrogen from a carbon adjacent to the one with the leaving group. In E2 mechanism, a strong base extracts the proton with the C−H bond pair moving to form a second bond between the two carbon atoms. Simultaneously, the leaving group departs with its pair of bond electrons. This requires that the leaving group and the extracted proton be anti to each other. This generally leads to the formation of only one isomer. However, if there are two hydrogen atoms on the carbon from which the proton is extracted, a mixture of stereoisomers is possible. The product distribution, in this case, depends on the stabilities of the conformers that lead to the two isomers.

Interpretation Introduction

(b)

Interpretation:

Whether an E1 elimination reaction, from the given precursor, will produce a pure stereoisomer or a mixture is to be determined.

Concept introduction:

E1 elimination is a two-step reaction. The leaving group breaks off in the first step taking its bond pair with it. A trigonal planar carbocation results from this step. Since the carbocation is planar, any one of the hydrogen atoms, on an adjacent carbon, can be removed as a proton. The associated C−H bond pair can then move toward the carbocation to form the second (pi) bond between the two carbon atoms. Since there is no restriction on which hydrogen can be lost, a mixture of stereoisomers is formed.

Interpretation Introduction

(c)

Interpretation:

In each of the two reactions that produce a mixture, which isomer is produced in greater abundance is to be determined.

Concept introduction:

When a reaction produces a mixture of stereoisomers, the product distribution depends on two factors, the stability of the product and the stability of the conformers of the precursor in case of an E2 reaction. An E2 reaction requires that the proton and the leaving group be anti to each other. If there are two protons on the beta carbon, the relative stabilities of the two conformers will influence the product distribution.

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Answer 3

Question

Chapter 8, Problem 8.50P

Interpretation Introduction

(a)

Interpretation:

Whether an E2 elimination from the given alkyl halide precursor will exclusively produce (E)-anethol or a mixture of stereoisomers is to be determined.

Concept introduction:

E2 elimination is a single step mechanism involving both the substrate molecule and the reagent molecule. It involves the elimination of a leaving group along with hydrogen from a carbon adjacent to the one with the leaving group. In E2 mechanism, a strong base extracts the proton with the C−H bond pair moving to form a second bond between the two carbon atoms. Simultaneously, the leaving group departs with its pair of bond electrons. This requires that the leaving group and the extracted proton be anti to each other. This generally leads to the formation of only one isomer. However, if there are two hydrogen atoms on the carbon from which the proton is extracted, a mixture of stereoisomers is possible. The product distribution, in this case, depends on the stabilities of the conformers that lead to the two isomers.

Interpretation Introduction

(b)

Interpretation:

Whether an E1 elimination reaction, from the given precursor, will produce a pure stereoisomer or a mixture is to be determined.

Concept introduction:

E1 elimination is a two-step reaction. The leaving group breaks off in the first step taking its bond pair with it. A trigonal planar carbocation results from this step. Since the carbocation is planar, any one of the hydrogen atoms, on an adjacent carbon, can be removed as a proton. The associated C−H bond pair can then move toward the carbocation to form the second (pi) bond between the two carbon atoms. Since there is no restriction on which hydrogen can be lost, a mixture of stereoisomers is formed.

Interpretation Introduction

(c)

Interpretation:

In each of the two reactions that produce a mixture, which isomer is produced in greater abundance is to be determined.

Concept introduction:

When a reaction produces a mixture of stereoisomers, the product distribution depends on two factors, the stability of the product and the stability of the conformers of the precursor in case of an E2 reaction. An E2 reaction requires that the proton and the leaving group be anti to each other. If there are two protons on the beta carbon, the relative stabilities of the two conformers will influence the product distribution.

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Answer 4

Question

Chapter 8, Problem 8.50P

Interpretation Introduction

(a)

Interpretation:

Whether an E2 elimination from the given alkyl halide precursor will exclusively produce (E)-anethol or a mixture of stereoisomers is to be determined.

Concept introduction:

E2 elimination is a single step mechanism involving both the substrate molecule and the reagent molecule. It involves the elimination of a leaving group along with hydrogen from a carbon adjacent to the one with the leaving group. In E2 mechanism, a strong base extracts the proton with the C−H bond pair moving to form a second bond between the two carbon atoms. Simultaneously, the leaving group departs with its pair of bond electrons. This requires that the leaving group and the extracted proton be anti to each other. This generally leads to the formation of only one isomer. However, if there are two hydrogen atoms on the carbon from which the proton is extracted, a mixture of stereoisomers is possible. The product distribution, in this case, depends on the stabilities of the conformers that lead to the two isomers.

Interpretation Introduction

(b)

Interpretation:

Whether an E1 elimination reaction, from the given precursor, will produce a pure stereoisomer or a mixture is to be determined.

Concept introduction:

E1 elimination is a two-step reaction. The leaving group breaks off in the first step taking its bond pair with it. A trigonal planar carbocation results from this step. Since the carbocation is planar, any one of the hydrogen atoms, on an adjacent carbon, can be removed as a proton. The associated C−H bond pair can then move toward the carbocation to form the second (pi) bond between the two carbon atoms. Since there is no restriction on which hydrogen can be lost, a mixture of stereoisomers is formed.

Interpretation Introduction

(c)

Interpretation:

In each of the two reactions that produce a mixture, which isomer is produced in greater abundance is to be determined.

Concept introduction:

When a reaction produces a mixture of stereoisomers, the product distribution depends on two factors, the stability of the product and the stability of the conformers of the precursor in case of an E2 reaction. An E2 reaction requires that the proton and the leaving group be anti to each other. If there are two protons on the beta carbon, the relative stabilities of the two conformers will influence the product distribution.

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Answer 5

Chapter 8, Problem 8.50P

Interpretation Introduction

(a)

Interpretation:

Whether an E2 elimination from the given alkyl halide precursor will exclusively produce (E)-anethol or a mixture of stereoisomers is to be determined.

Concept introduction:

E2 elimination is a single step mechanism involving both the substrate molecule and the reagent molecule. It involves the elimination of a leaving group along with hydrogen from a carbon adjacent to the one with the leaving group. In E2 mechanism, a strong base extracts the proton with the C−H bond pair moving to form a second bond between the two carbon atoms. Simultaneously, the leaving group departs with its pair of bond electrons. This requires that the leaving group and the extracted proton be anti to each other. This generally leads to the formation of only one isomer. However, if there are two hydrogen atoms on the carbon from which the proton is extracted, a mixture of stereoisomers is possible. The product distribution, in this case, depends on the stabilities of the conformers that lead to the two isomers.

Interpretation Introduction

(b)

Interpretation:

Whether an E1 elimination reaction, from the given precursor, will produce a pure stereoisomer or a mixture is to be determined.

Concept introduction:

E1 elimination is a two-step reaction. The leaving group breaks off in the first step taking its bond pair with it. A trigonal planar carbocation results from this step. Since the carbocation is planar, any one of the hydrogen atoms, on an adjacent carbon, can be removed as a proton. The associated C−H bond pair can then move toward the carbocation to form the second (pi) bond between the two carbon atoms. Since there is no restriction on which hydrogen can be lost, a mixture of stereoisomers is formed.

Interpretation Introduction

(c)

Interpretation:

In each of the two reactions that produce a mixture, which isomer is produced in greater abundance is to be determined.

Concept introduction:

When a reaction produces a mixture of stereoisomers, the product distribution depends on two factors, the stability of the product and the stability of the conformers of the precursor in case of an E2 reaction. An E2 reaction requires that the proton and the leaving group be anti to each other. If there are two protons on the beta carbon, the relative stabilities of the two conformers will influence the product distribution.

Answer 6

Chapter 8, Problem 8.50P

Interpretation Introduction

(a)

Interpretation:

Whether an E2 elimination from the given alkyl halide precursor will exclusively produce (E)-anethol or a mixture of stereoisomers is to be determined.

Concept introduction:

E2 elimination is a single step mechanism involving both the substrate molecule and the reagent molecule. It involves the elimination of a leaving group along with hydrogen from a carbon adjacent to the one with the leaving group. In E2 mechanism, a strong base extracts the proton with the C−H bond pair moving to form a second bond between the two carbon atoms. Simultaneously, the leaving group departs with its pair of bond electrons. This requires that the leaving group and the extracted proton be anti to each other. This generally leads to the formation of only one isomer. However, if there are two hydrogen atoms on the carbon from which the proton is extracted, a mixture of stereoisomers is possible. The product distribution, in this case, depends on the stabilities of the conformers that lead to the two isomers.

Answer 7

Chapter 8, Problem 8.50P

Interpretation Introduction

(a)

Interpretation:

Whether an E2 elimination from the given alkyl halide precursor will exclusively produce (E)-anethol or a mixture of stereoisomers is to be determined.

Concept introduction:

E2 elimination is a single step mechanism involving both the substrate molecule and the reagent molecule. It involves the elimination of a leaving group along with hydrogen from a carbon adjacent to the one with the leaving group. In E2 mechanism, a strong base extracts the proton with the C−H bond pair moving to form a second bond between the two carbon atoms. Simultaneously, the leaving group departs with its pair of bond electrons. This requires that the leaving group and the extracted proton be anti to each other. This generally leads to the formation of only one isomer. However, if there are two hydrogen atoms on the carbon from which the proton is extracted, a mixture of stereoisomers is possible. The product distribution, in this case, depends on the stabilities of the conformers that lead to the two isomers.

Answer 8

Interpretation Introduction

(b)

Interpretation:

Whether an E1 elimination reaction, from the given precursor, will produce a pure stereoisomer or a mixture is to be determined.

Concept introduction:

E1 elimination is a two-step reaction. The leaving group breaks off in the first step taking its bond pair with it. A trigonal planar carbocation results from this step. Since the carbocation is planar, any one of the hydrogen atoms, on an adjacent carbon, can be removed as a proton. The associated C−H bond pair can then move toward the carbocation to form the second (pi) bond between the two carbon atoms. Since there is no restriction on which hydrogen can be lost, a mixture of stereoisomers is formed.

Answer 9

Interpretation Introduction

(b)

Interpretation:

Whether an E1 elimination reaction, from the given precursor, will produce a pure stereoisomer or a mixture is to be determined.

Concept introduction:

E1 elimination is a two-step reaction. The leaving group breaks off in the first step taking its bond pair with it. A trigonal planar carbocation results from this step. Since the carbocation is planar, any one of the hydrogen atoms, on an adjacent carbon, can be removed as a proton. The associated C−H bond pair can then move toward the carbocation to form the second (pi) bond between the two carbon atoms. Since there is no restriction on which hydrogen can be lost, a mixture of stereoisomers is formed.

Answer 10

Interpretation Introduction

(c)

Interpretation:

In each of the two reactions that produce a mixture, which isomer is produced in greater abundance is to be determined.

Concept introduction:

When a reaction produces a mixture of stereoisomers, the product distribution depends on two factors, the stability of the product and the stability of the conformers of the precursor in case of an E2 reaction. An E2 reaction requires that the proton and the leaving group be anti to each other. If there are two protons on the beta carbon, the relative stabilities of the two conformers will influence the product distribution.

Answer 11

Interpretation Introduction

(c)

Interpretation:

In each of the two reactions that produce a mixture, which isomer is produced in greater abundance is to be determined.

Concept introduction:

When a reaction produces a mixture of stereoisomers, the product distribution depends on two factors, the stability of the product and the stability of the conformers of the precursor in case of an E2 reaction. An E2 reaction requires that the proton and the leaving group be anti to each other. If there are two protons on the beta carbon, the relative stabilities of the two conformers will influence the product distribution.

Answer 12

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Answer 15

Ch. 8 - Prob. 8.1P Ch. 8 - Prob. 8.2P Ch. 8 - Prob. 8.3P Ch. 8 - Prob. 8.4P Ch. 8 - Prob. 8.5P Ch. 8 - Prob. 8.6P Ch. 8 - Prob. 8.7P Ch. 8 - Prob. 8.8P Ch. 8 - Prob. 8.9P Ch. 8 - Prob. 8.10P

Solution Summary: The author explains that E2 elimination is a single step mechanism involving both reactants.

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