Chapter 8.SE, Problem 42AP

Interpretation Introduction

a)

Interpretation:

To predict the product of the reaction shown with regiochemistry, if relevant.

Concept introduction:

Catalytic hydrogenation is a heterogeneous process which occurs with syn stereochemistry. Both hydrogens adsorbed on the catalytic surface add to the double bond from the same face.

To predict:

The product of the reaction shown with regiochemistry, if relevant.

Answer to Problem 42AP

The product of the reaction is ethylbenzene.

Explanation of Solution

The addition of hydrogen takes place to the double bond in the side chain with syn stereochemistry. Both hydrogens add to the double bond from the same face to yield ethylbenzene.

Conclusion

The product of the reaction is ethylbenzene.

Interpretation Introduction

b)

Interpretation:

To predict the product of the reaction shown with regiochemistry, if relevant.

Concept introduction:

Addition of bromine to the double bond in alkenes takes place in two steps with anti stereochemistry. In the first step a cyclic bromonium ion is formed by the attack of the π electrons of the double bond with the elimination of bromide ion. In the second step the bromide ion attacks the bromonium ion from the less shielded side to give a dibromo derivative.

To predict:

The product of the reaction shown with regiochemistry, if relevant.

Answer to Problem 42AP

The product of the reaction is

Explanation of Solution

In the first step the addition of bromine to the double bond in 1,2-dimethylcyclohexane results in the formation of a cyclic bromonium ion with the simultaneous elimination of a bromide ion. The large bromonium ion shields one side of the molecule. Hence the attack of the bromide ion occurs from the opposite, unshielded side to yield a trans-product.

Conclusion

The product of the reaction is

Interpretation Introduction

c)

Interpretation:

To predict the product of the reaction shown with regiochemistry, if relevant.

Concept introduction:

Hydroxylation of double bonds can be carried out directly by treating the alkene with osmium tetroxide, O_sO₄, in the presence of N-phenylmorpholine N-oxide. The reaction occurs with syn stereochemistry through the formation of a cyclic intermediate, called osmate, formed by the addition of O_sO₄ to the alkene in a single step. The cyclic osmate is then cleaved to give the cis-1,2-diol by treatment with NaHSO₃.

To predict:

The product of the reaction shown with regiochemistry, if relevant.

Answer to Problem 42AP

The product of the reaction is

Explanation of Solution

O_sO₄ adds to the double bond in the side chain from the same side to yield a cyclic osmate in a single step. When treated with NaHSO₃ the cyclic osmate gets cleaved to give the diol.

Conclusion

The product of the reaction is

Interpretation Introduction

d)

Interpretation:

To predict the product of the reaction shown with regiochemistry, if relevant.

Concept introduction:

The addition of chlorine to alkenes in the presence of water results in the anti addition of the halohydrin, HOCl, to the double bond. In the first step a cyclic chloronium ion is formed by the attack of the π electrons of the double bond on chlorine. In the second step water attacks the chloronium ion from the least shielded side to give an anti addition product. The addition obeys Markovnokov orientation. The negative part (OH) adds to the doubly bonded carbon atom which has more number of substituents.

To predict:

The product of the reaction shown with regiochemistry, if relevant.

Answer to Problem 42AP

The product of the reaction is

Explanation of Solution

The given alkene has an unsymmetrically substituted double bond in the side chain. In the first step a cyclic chloronium ion is formed by the attack of the double bond on chlorine. In the second step water attacks the the chloronium ion from the opposite less shielded side to give an intermediate which then loses a proton to yield the product.

Conclusion

The product of the reaction is

Interpretation Introduction

e)

Interpretation:

The product expected in the reaction shown is to be given.

Concept introduction:

The reaction given is an example of Simmons-Smith reaction. When CH₂I₂ is treated with Zn/Cu couple, iodomethylzinc iodide, ICH₂ZnI, is formed. This ICH₂ZnI transfers a CH₂ group to the double bond in alkene to form a cyclopropane ring in the product.

To give:

The product expected in the reaction shown.

Answer to Problem 42AP

The product expected in the reaction shown is

Explanation of Solution

When CH₂I₂ is treated with Zn/Cu couple, iodomethylzinc iodide, ICH₂ZnI, is formed. This ICH₂ZnI transfers a CH₂ group to the double bond in the side chain to form a cyclopropane ring in the product.

Conclusion

The product expected in the reaction shown is

Interpretation Introduction

f)

Interpretation:

The product expected in the reaction shown is to be given.

Concept introduction:

Alkenes are oxidized to give epoxides or oxiranes when treated with peracids like meta-chloroperoxybenzoic acid. The oxygen transfer from the peroxy acids takes place with syn stereochemistry. Both the C-O bonds are formed from the same face of the double bond through a one step process without the formation of an intermediate. The oxygen atom farthest from the carbonyl group gets transferred.

To give:

The product expected in the reaction shown.

Answer to Problem 42AP

The product expected in the reaction shown is

Where RCO₃H = meta-chloroperoxybenzoic acid

Explanation of Solution

The oxygen transfer from the peroxy acids to the double bond in the side chain takes place with syn stereochemistry. Both the C-O bonds are formed from the same face of the double bond through a one step process without the formation of an intermediate to yield the product.

Conclusion

The product expected in the reaction shown is