Chapter 17.SE, Problem 47AP

Interpretation Introduction

a) Styrene (PhCH=CH₂)

Interpretation:

How to prepare styrene from 2-phenylethanol is to be stated.

Concept introduction:

Alcohols undergo dehydration when treated with POCl₃ in pyridine to yield alkenes.

To state:

How to prepare styrene from 2-phenylethanol.

Answer to Problem 47AP

Styrene can be prepared by treating 2-phenylethanol with POCl₃ in pyridine.

Explanation of Solution

2-Phenylethanol when treated with POCl₃ in pyridine eliminates a molecule of water from the side chain to yield styrene.

Conclusion

Styrene can be prepared by treating 2-phenylethanol with POCl₃ in pyridine.

Interpretation Introduction

b) Phenylacetaldehyde (PhCH₂CHO)

Interpretation:

How to prepare phenylacetaldehyde from 2-phenylethanol is to be stated.

Concept introduction:

Dess-Martin periodinate in dichloromethane oxidizes 1⁰alcohols to aldehydes and 2⁰alcohols to ketones.

To state:

How to prepare phenylacetaldehyde from 2-phenylethanol

Answer to Problem 47AP

Phenylacetaldehyde can be prepared by oxidizing 2-phenylethanol with Dess-Martin periodinate in dichloromethane.

Explanation of Solution

2-phenylethanol is a 1⁰ alcohol. It gets oxidized to phenylacetaldehyde when treated with Dess-Martin periodinate in dichloromethane.

Conclusion

Phenylacetaldehyde can be prepared by oxidizing 2-phenylethanol with Dess-Martin periodinate in dichloromethane.

Interpretation Introduction

c) Phenylacetic acid (PhCH₂COOH)

Interpretation:

How to prepare phenylacetic acid from 2-phenylethanol is to be stated.

Concept introduction:

CrO₃ in acidic solutions oxidize 1⁰ alcohols directly into acids and 2⁰ alcohols to ketones. It does not oxidize 3⁰ alcohols.

To state:

How to prepare phenylacetic acid from 2-phenylethanol.

Answer to Problem 47AP

Phenylacetic acid can be prepared by oxidizing 2-phenylethanol with CrO₃ in acidic solutions.

Explanation of Solution

2-phenylethanol is a 1⁰ alcohol. It gets oxidized to phenylacetic acid when treated with CrO₃ in acidic solutions.

Conclusion

Phenylacetic acid can be prepared by oxidizing 2-phenylethanol with CrO₃ in acidic solutions.

Interpretation Introduction

d) Benzoic acid

Interpretation:

How to prepare benzoic acid from 2-phenylethanol is to be stated.

Concept introduction:

KMnO₄ in acidic solutions oxidize aromatic 1⁰ alcohols to carboxylic acids and 2⁰ alcohols to ketones. The aromatic ring remains unaffected.

To state:

How to prepare benzoic acid from 2-phenylethanol.

Answer to Problem 47AP

Benzoic acid can be prepared by oxidizing 2-phenylethanol with KMnO₄ in acidic solutions.

Explanation of Solution

2-phenylethanol is a 1⁰ alcohol. It gets oxidized to benzoic acid when treated with KMnO₄ in acidic solutions.

Conclusion

Benzoic acid can be prepared by oxidizing 2-phenylethanol with KMnO₄ in acidic solutions.

Interpretation Introduction

e) Ethylbenzene

Interpretation:

How to prepare ethylbenzene from 2-phenylethanol is to be stated.

Concept introduction:

Alcohols undergo dehydration when treated with POCl₃ in pyridine to yield an alkene. The alkene upon reduction gives the alkane.

To state:

How to prepare ethylbenzene from 2-phenylethanol.

Answer to Problem 47AP

Ethylbenzene can be prepared from 2-phenylethanol by following the steps shown below.

Explanation of Solution

2-Phenylethanol when treated with POCl₃ in pyridine eliminates a molecule of water from the side chain to yield styrene. When treated with H₂/Pd, the double bond in the side chain gets reduced to yield ethyl benzene.

Conclusion

Ethylbenzene can be prepared from 2-phenylethanol by following the steps shown below.

Interpretation Introduction

f) benzaldehyde

Interpretation:

How to prepare benzaldehyde from 2-phenylethanol is to be stated.

Concept introduction:

Alcohols undergo dehydration when treated with POCl₃ in pyridine to yield an alkene. The alkene upon ozonolyzis followed by reduction will yield the aldehyde required.

To state:

How to prepare benzaldehyde from 2-phenylethanol.

Answer to Problem 47AP

Benzaldehyde can be prepared from 2-phenylethanol by following the steps shown below.

Explanation of Solution

2-Phenylethanol when treated with POCl₃ in pyridine eliminates a molecule of water from the side chain to yield styrene. When styrene is subjected to ozonolysis followed by reduction, the double bond in side chain gets cleaved resulting in the formation of benzaldehyde.

Conclusion

Benzaldehyde can be prepared from 2-phenylethanol by following the steps shown below.

Interpretation Introduction

g) 1-phenylethanol

Interpretation:

How to prepare 1-phenylethanol from 2-phenylethanol is to be stated.

Concept introduction:

Alcohols undergo dehydration when treated with POCl₃ in pyridine to yield an alkene. The alkene adds a molecule of water following oxymercuration-demercuration process. The addition will take place following Markovnikov regiochemistry.

To state:

How to prepare 1-phenylethanol from 2-phenylethanol.

Answer to Problem 47AP

1- Phenylethanol can be prepared from 2-phenylethanol by following the steps shown below.

Explanation of Solution

2-Phenylethanol, when treated with POCl₃ in pyridine eliminates a molecule of water from the side chain to yield styrene. When styrene is subjected oxymercuration-demercuration processes, a molecule of water is added, following Markovnikov regiochemistry, to the double bond. The –OH adds on to the more alkyl substituted carbon and H to the less alkyl substituted carbon in double bond to yield 1-phenylethanol.

Conclusion

1-Phenylethanol can be prepared from 2-phenylethanol by following the steps shown below.

Interpretation Introduction

h) 1-Bromo-2-phenylethane

Interpretation:

How to prepare 1-bromo-2-phenylethane from 2-phenylethanol is to be stated.

Concept introduction:

Alcohols yield the corresponding alkyl bromides when treated with PBr₃.

To state:

How to prepare 1-bromo-2-phenylethane from 2-phenylethanol is to be stated.

Answer to Problem 47AP

1-Bromo-2-phenylethane can be prepared from 2-phenylethanol by following the steps shown below.

Explanation of Solution

When 2-phenylethanol is treated with PBr₃, a bimolecular nucleophilic substitution of –OH by Br takes place to yield 1-bromo-2-phenylethane.

Conclusion

1-Bromo-2-phenylethane can be prepared from 2-phenylethanol by following the steps shown below.