Chapter 16, Problem 67P

17-73 Alcohols can be prepared by the acid-catalyzed hydration of alkenes (Section 12-6B) and by the reduction of aldehydes and ketones (Section 17-4B). Show how you might prepare each of the following alcohols by (1) acid-catalyzed hydration of an alkene and (2) reduction of an aldehyde or a ketone.

(a) Ethanol

(b) Cyclohexanol

(c) 2-Propanol

(d) 1-Phenylethanol

Interpretation Introduction

(a)

Interpretation:

Show the preparation of ethanol by acid-catalyzed hydration of an alkene and by reduction of an aldehyde or a ketone.

Concept Introduction:

Acid-catalyzed hydration of alkenes: In the presence of an acid catalyst $\left({\text{H}}_{2}S{\text{O}}_4\right)$ water adds to the carbon-carbon double bond of an alkene to give an alcohol. Addition of water is called hydration. In the case of simple alkenes, hydration follows Markovnikov’s rule.

Reduction of an aldehyde or a ketone: The C=C double bond of an alkene is reduced by hydrogen in the presence of a transition metal catalyst to a C−C single bond. The same is true for the C=O double bond of an aldehyde or a ketone. Aldehydes are reduced to primary alcohols and ketones are reduced to secondary alcohol.

Answer to Problem 67P

By acid-catalyzed hydration of ethane:

By Reduction of ethanal:

Explanation of Solution

By acid-catalyzed hydration of ethane:

When ethene is allowed to react with water in presence of an acid catalyst it gives ethanol.

By Reduction of ethanal: When ethanal is reduced in the presence of sodium borohydride it gives ethanol.

Interpretation Introduction

(b)

Interpretation:

Show the preparation of cyclohexanol by acid-catalyzed hydration of an alkene and by reduction of an aldehyde or a ketone.

Concept Introduction:

Acid-catalyzed hydration of alkenes: In the presence of an acid catalyst $\left({\text{H}}_{2}S{\text{O}}_4\right)$ water adds to the carbon-carbon double bond of an alkene to give an alcohol. Addition of water is called hydration. In the case of simple alkenes, hydration follows Markovnikov’s rule.

Reduction of an aldehyde or a ketone: The C=C double bond of an alkene is reduced by hydrogen in the presence of a transition metal catalyst to a C−C single bond. The same is true for the C=O double bond of an aldehyde or a ketone. Aldehydes are reduced to primary alcohols and ketones are reduced to secondary alcohol.

Answer to Problem 67P

By acid-catalyzed hydration of ethane:

By Reduction of ethanal:

Explanation of Solution

By acid-catalyzed hydration of ethane: When cyclohexene is allowed to react with water in presence of an acid catalyst it gives cyclohexanol.

By Reduction of ethanal: When cyclohexanone is reduced in the presence of sodium borohydride it gives cyclohexanol.

Interpretation Introduction

(c)

Interpretation:

Show the preparation of 2-propanol by acid-catalyzed hydration of an alkene and by reduction of an aldehyde or a ketone.

Concept Introduction:

Acid-catalyzed hydration of alkenes: In the presence of an acid catalyst $\left({\text{H}}_{2}S{\text{O}}_4\right)$ water adds to the carbon-carbon double bond of an alkene to give an alcohol. Addition of water is called hydration. In the case of simple alkenes, hydration follows Markovnikov’s rule.

Reduction of an aldehyde or a ketone: The C=C double bond of an alkene is reduced by hydrogen in the presence of a transition metal catalyst to a C−C single bond. The same is true for the C=O double bond of an aldehyde or a ketone. Aldehydes are reduced to primary alcohols and ketones are reduced to secondary alcohol.

Answer to Problem 67P

By acid-catalyzed hydration of ethane:

By Reduction of ethanal:

Explanation of Solution

By acid-catalyzed hydration of ethane: When propene is allowed to react with water in presence of an acid catalyst it gives 2-propanol.

By Reduction of ethanal: When acetone is reduced in the presence of sodium borohydride it gives 2-propanol.

Interpretation Introduction

(d)

Interpretation:

Show the preparation of 1-phenylethanol by acid-catalyzed hydration of an alkene and by reduction of an aldehyde or a ketone.

Concept Introduction:

Acid-catalyzed hydration of alkenes: In the presence of an acid catalyst $\left({\text{H}}_{2}S{\text{O}}_4\right)$ water adds to the carbon-carbon double bond of an alkene to give an alcohol. Addition of water is called hydration. In the case of simple alkenes, hydration follows Markovnikov’s rule.

Reduction of an aldehyde or a ketone: The C=C double bond of an alkene is reduced by hydrogen in the presence of a transition metal catalyst to a C−C single bond. The same is true for the C=O double bond of an aldehyde or a ketone. Aldehydes are reduced to primary alcohols and ketones are reduced to secondary alcohol.

Answer to Problem 67P

By acid-catalyzed hydration of ethane:

By Reduction of ethanal:

Explanation of Solution

By acid-catalyzed hydration of ethane: When 1-phenylethene is allowed to react with water in presence of an acid catalyst it gives 1-phenylethanol.

By Reduction of ethanal: When acetophenone is reduced in the presence of sodium borohydride it gives 1-phenylethanol.