Chapter 17.SE, Problem 22VC

Interpretation Introduction

a) PBr₃

Interpretation:

The product obtained when 3-(m-bromophenyl)-2-butanol is treated with PBr₃.

Concept introduction:

Alcohols when reacted with PBr₃ yield the corresponding alkyl bromides along with H₃BO₃. When treated with aqueous H₂SO₄ they undergo dehydration to give alkenes. They react with SOCl₂ to yield the corresponding alkyl halide along with SO₂ and HCl. Dess-Martin periodinate oxidizes 2⁰ alcohols to ketones. In aromatic electrophilic substitution reactions the alkyl group is an ortho and para directing and activating group. Bromine also is an ortho and para directing but deactivating group.

To give:

The products obtained when the alcohol shown is treated with PBr₃.

Answer to Problem 22VC

The product obtained when the alcohol is treated with PBr₃ is

Explanation of Solution

The reaction of the alcohol with PBr₃ is a bimolecular nucleophilic substitution (SN₂) reaction. It takes place with inversion in configuration at the reaction centre to yield an alkyl bromide.

Conclusion

The product obtained when the alcohol is treated with PBr₃ is

Interpretation Introduction

b) H₂SO₄

Interpretation:

The product obtained when 3-(m-bromophenyl)-2-butanol is treated with aqueous H₂SO₄.

Concept introduction:

Alcohols when reacted with PBr₃ yield the corresponding alkyl bromides along with H₃BO₃. When treated with aqueous H₂SO₄ they undergo dehydration to give alkenes. They react with SOCl₂ to yield the corresponding alkyl halide along with SO₂ and HCl. Dess-Martin periodinate oxidizes 2⁰ alcohols to ketones. In aromatic electrophilic substitution reactions the alkyl group is an ortho and para directing and activating group. Bromine also is an ortho and para directing but deactivating group.

To give:

The products obtained when the alcohol shown is treated with aqueous H₂SO₄.

Answer to Problem 22VC

The products obtained when the alcohol is treated with aqueous H₂SO₄ are two isomeric alkenes (E) and (Z). E isomer is obtained as the major product.

Explanation of Solution

The alcohol gets dehydrated when treated with aqueous H₂SO₄ yields the E and Z isomers of an alkene. The E isomer is more stable and obtained as the major product as the bulky groups are far away.

Conclusion

The products obtained when the alcohol is treated with aqueous H₂SO₄ isomeric alkenes (E) and (Z) are produced. E isomer is obtained as the major product.

Interpretation Introduction

c) SOCl₂

Interpretation:

The product obtained when 3-(m-bromophenyl)-2-butanol is treated with SOCl2.

Concept introduction:

Alcohols when reacted with PBr₃ yield the corresponding alkyl bromides along with H₃BO₃. When treated with aqueous H₂SO₄ they undergo dehydration to give alkenes. They react with SOCl₂ to yield the corresponding alkyl halide along with SO₂ and HCl. Dess-Martin periodinate oxidizes 2⁰ alcohols to ketones. In aromatic electrophilic substitution reactions the alkyl group is an ortho and para directing and activating group. Bromine also is an ortho and para directing but deactivating group.

To give:

The products obtained when the alcohol shown is treated with SOCl₂.

Answer to Problem 22VC

The product obtained when the alcohol is treated with SOCl₂ is

Explanation of Solution

The reaction of the alcohol with SOCl₂ is a bimolecular nucleophilic substitution (S_N²) reaction. It takes place with inversion in configuration at the reaction centre to yield an alkyl chloride.

Conclusion

The product obtained when the alcohol is treated with SOCl₂ is

Interpretation Introduction

d) Dess-Martin periodinate

Interpretation:

The product obtained when 3-(m-bromophenyl)-2-butanol is treated with Dess-Martin periodinate.

Concept introduction:

Alcohols when reacted with PBr₃ yield the corresponding alkyl bromides along with H₃BO₃. When treated with aqueous H₂SO₄ they undergo dehydration to give alkenes. They react with SOCl₂ to yield the corresponding alkyl halide along with SO₂ and HCl. Dess-Martin periodinate oxidizes 2⁰ alcohols to ketones. In aromatic electrophilic substitution reactions the alkyl group is an ortho and para directing and activating group. Bromine also is an ortho and para directing but deactivating group.

To give:

The products obtained when the alcohol shown is treated with Dess-Martin periodinate.

Answer to Problem 22VC

The product obtained when the alcohol is treated with Dess-Martin periodinate is

Explanation of Solution

The alcohol is a 2⁰ in nature. Dess-Martin periodinate oxidizes it into a ketone.

Conclusion

The product obtained when the alcohol is treated with Dess-Martin periodinate is

Interpretation Introduction

e) Br₂, FeBr₃

Interpretation:

The product obtained when 3-(m-bromophenyl)-2-butanol is treated Br₂, FeBr₃.

Concept introduction:

Alcohols when reacted with PBr₃ yield the corresponding alkyl bromides along with H₃BO₃. When treated with aqueous H₂SO₄ they undergo dehydration to give alkenes. They react with SOCl₂ to yield the corresponding alkyl halide along with SO₂ and HCl. Dess-Martin periodinate oxidizes 2⁰ alcohols to ketones. In aromatic electrophilic substitution reactions the alkyl group is an ortho and para directing and activating group. Bromine also is an ortho and para directing but deactivating group.

To give:

The products obtained when the alcohol shown is treated Br₂, FeBr₃.

Answer to Problem 22VC

The products obtained when the alcohol is treated with Br₂, FeBr₃ are

Explanation of Solution

The alcohol undergoes bromination in the benzene ring when treated with Br₂, FeBr₃. Both bromine and an alkyl group are attached to the ring. Both alkyl and Br are ortho and para directing, the alkyl is activating while the Br is deactivating. Hence during bromination the bromine enters into the ortho and para positions to yield the products.

Conclusion

The products obtained when the alcohol is treated with Br₂, FeBr₃ are