Chapter 4, Problem 4.78EP

(a)

Interpretation Introduction

Interpretation:

Structural formula of the organic product formed when propanal undergoes Tollen’s test has to be drawn.

Concept Introduction:

In organic chemistry, oxidation reaction is referred to the number $\text{C}-\text{O}$ bonds increase and/or number of $\text{C}-\text{H}$ bonds decrease.

In organic chemistry, reduction reaction is referred to the number $\text{C}-\text{O}$ bonds decrease and/or number of $\text{C}-\text{H}$ bonds increase.

Alcohols undergo oxidation reaction and reduction reaction.  This depends upon the number of hydrogen atoms that is bonded to the alpha carbon atom.  Primary and secondary alcohol undergoes oxidation reaction while tertiary alcohol does not undergo oxidation reaction.  Primary alcohols undergo oxidation to give aldehyde and carboxylic acid as product.  Secondary alcohol undergoes oxidation to give ketone as the product.

Aldehyde undergoes oxidation to give carboxylic acid as the product while ketone does not undergo oxidation reaction.

Tollen’s test:

This is also known as silver mirror test.  The reagent that is used in Tollen’s test is silver nitrate and ammonia in water.  Aldehyde reacts with Tollen’s reagent, where the silver ion is reduced to silver metal and the aldehyde is oxidized to carboxylic acid.

Ketone does not undergo Tollen’s test to deposit silver metal.

Benedict’s test:

This test is also similar to Tollen’s test.  In this test, ${\text{Cu}}^{\text{2+}}$ metal ion is used as oxidizing agent.  The ${\text{Cu}}^{\text{2+}}$ ion is reduced to ${\text{Cu}}^{\text{+}}$ ion while the aldehyde is oxidized to carboxylic acid.  ${\text{Cu}}_{\text{2}}\text{O}$ is precipitated as brick-red solid.  Ketone does not answer the Benedict’s test.  This is because ketone are not oxidized.

Answer to Problem 4.78EP

The structure of organic product obtained is,

Explanation of Solution

Aldehydes undergo Tollen’s test.  The product formed when aldehyde undergo oxidation is a carboxylic acid.  The general oxidation reaction for aldehyde can be given as,

Given aldehyde is propanal and the structure can be given as shown below,

This on reaction with Tollen’s reagent gives carboxylic acid as the product.  The structure of the organic product formed and the complete reaction can be given as shown below,

Propanoic acid is formed from propanal when it undergoes Tollen’s test.

Conclusion

The structure of the organic product formed is drawn.

(b)

Interpretation Introduction

Interpretation:

Structural formula of the organic product formed when 3-pentanone undergoes Tollen’s test has to be drawn.

Concept Introduction:

In organic chemistry, oxidation reaction is referred to the number $\text{C}-\text{O}$ bonds increase and/or number of $\text{C}-\text{H}$ bonds decrease.

In organic chemistry, reduction reaction is referred to the number $\text{C}-\text{O}$ bonds decrease and/or number of $\text{C}-\text{H}$ bonds increase.

Alcohols undergo oxidation reaction and reduction reaction.  This depends upon the number of hydrogen atoms that is bonded to the alpha carbon atom.  Primary and secondary alcohol undergoes oxidation reaction while tertiary alcohol does not undergo oxidation reaction.  Primary alcohols undergo oxidation to give aldehyde and carboxylic acid as product.  Secondary alcohol undergoes oxidation to give ketone as the product.

Aldehyde undergoes oxidation to give carboxylic acid as the product while ketone does not undergo oxidation reaction.

Tollen’s test:

This is also known as silver mirror test.  The reagent that is used in Tollen’s test is silver nitrate and ammonia in water.  Aldehyde reacts with Tollen’s reagent, where the silver ion is reduced to silver metal and the aldehyde is oxidized to carboxylic acid.

Ketone does not undergo Tollen’s test to deposit silver metal.

Benedict’s test:

This test is also similar to Tollen’s test.  In this test, ${\text{Cu}}^{\text{2+}}$ metal ion is used as oxidizing agent.  The ${\text{Cu}}^{\text{2+}}$ ion is reduced to ${\text{Cu}}^{\text{+}}$ ion while the aldehyde is oxidized to carboxylic acid.  ${\text{Cu}}_{\text{2}}\text{O}$ is precipitated as brick-red solid.  Ketone does not answer the Benedict’s test.  This is because ketone are not oxidized.

Answer to Problem 4.78EP

3-pentanone does not undergo Tollen’s test.

Explanation of Solution

Aldehydes undergo Tollen’s test.  The product formed when aldehyde undergo oxidation is a carboxylic acid.  The general oxidation reaction for aldehyde can be given as,

Given compound is a ketone that is 3-pentanone and the structure can be given as shown below,

This on reaction with Tollen’s reagent does not give oxidized product.  Therefore, no reaction takes place when 3-pentanone reacts with Tollen’s reagent.

3-pentanone does not react with Tollen’s reagent.

Conclusion

No reaction takes place when 3-pentanone undergoes Tollen’s test.

(c)

Interpretation Introduction

Interpretation:

Structural formula of the organic product formed when methylpropanal undergoes Benedict’s test has to be drawn.

Concept Introduction:

In organic chemistry, oxidation reaction is referred to the number $\text{C}-\text{O}$ bonds increase and/or number of $\text{C}-\text{H}$ bonds decrease.

In organic chemistry, reduction reaction is referred to the number $\text{C}-\text{O}$ bonds decrease and/or number of $\text{C}-\text{H}$ bonds increase.

Alcohols undergo oxidation reaction and reduction reaction.  This depends upon the number of hydrogen atoms that is bonded to the alpha carbon atom.  Primary and secondary alcohol undergoes oxidation reaction while tertiary alcohol does not undergo oxidation reaction.  Primary alcohols undergo oxidation to give aldehyde and carboxylic acid as product.  Secondary alcohol undergoes oxidation to give ketone as the product.

Aldehyde undergoes oxidation to give carboxylic acid as the product while ketone does not undergo oxidation reaction.

Tollen’s test:

This is also known as silver mirror test.  The reagent that is used in Tollen’s test is silver nitrate and ammonia in water.  Aldehyde reacts with Tollen’s reagent, where the silver ion is reduced to silver metal and the aldehyde is oxidized to carboxylic acid.

Ketone does not undergo Tollen’s test to deposit silver metal.

Benedict’s test:

This test is also similar to Tollen’s test.  In this test, ${\text{Cu}}^{\text{2+}}$ metal ion is used as oxidizing agent.  The ${\text{Cu}}^{\text{2+}}$ ion is reduced to ${\text{Cu}}^{\text{+}}$ ion while the aldehyde is oxidized to carboxylic acid.  ${\text{Cu}}_{\text{2}}\text{O}$ is precipitated as brick-red solid.  Ketone does not answer the Benedict’s test.  This is because ketones are not oxidized.

Answer to Problem 4.78EP

The structure of organic product obtained is,

Explanation of Solution

Aldehydes undergo Benedicts’s test.  The product formed when aldehyde undergo oxidation is a carboxylic acid.  The general oxidation reaction for aldehyde can be given as,

Given aldehyde is methylpropanal and the structure can be given as shown below,

This on reaction with Tollen’s reagent gives carboxylic acid as the product.  The structure of the organic product formed and the complete reaction can be given as shown below,

2-methylpropanoic acid is formed from methylpropanal when it undergoes Benedict’s test.

Conclusion

The structure of the organic product formed is drawn.

(d)

Interpretation Introduction

Interpretation:

Structural formula of the organic product formed when propanone undergoes Benedict’s test has to be drawn.

Concept Introduction:

In organic chemistry, oxidation reaction is referred to the number $\text{C}-\text{O}$ bonds increase and/or number of $\text{C}-\text{H}$ bonds decrease.

In organic chemistry, reduction reaction is referred to the number $\text{C}-\text{O}$ bonds decrease and/or number of $\text{C}-\text{H}$ bonds increase.

Alcohols undergo oxidation reaction and reduction reaction.  This depends upon the number of hydrogen atoms that is bonded to the alpha carbon atom.  Primary and secondary alcohol undergoes oxidation reaction while tertiary alcohol does not undergo oxidation reaction.  Primary alcohols undergo oxidation to give aldehyde and carboxylic acid as product.  Secondary alcohol undergoes oxidation to give ketone as the product.

Aldehyde undergoes oxidation to give carboxylic acid as the product while ketone does not undergo oxidation reaction.

Tollen’s test:

This is also known as silver mirror test.  The reagent that is used in Tollen’s test is silver nitrate and ammonia in water.  Aldehyde reacts with Tollen’s reagent, where the silver ion is reduced to silver metal and the aldehyde is oxidized to carboxylic acid.

Ketone does not undergo Tollen’s test to deposit silver metal.

Benedict’s test:

This test is also similar to Tollen’s test.  In this test, ${\text{Cu}}^{\text{2+}}$ metal ion is used as oxidizing agent.  The ${\text{Cu}}^{\text{2+}}$ ion is reduced to ${\text{Cu}}^{\text{+}}$ ion while the aldehyde is oxidized to carboxylic acid.  ${\text{Cu}}_{\text{2}}\text{O}$ is precipitated as brick-red solid.  Ketone does not answer the Benedict’s test.  This is because ketones are not oxidized.

Answer to Problem 4.78EP

Propanone does not undergo Benedict’s test.

Explanation of Solution

Aldehydes undergo Benedict’s test.  The product formed when aldehyde undergo oxidation is a carboxylic acid.  The general oxidation reaction for aldehyde can be given as,

Given compound is a ketone.  The name of ketone is propanone and the structure can be given as shown below,

This on reaction with Benedict’s reagent does not give oxidized product.  Therefore, no reaction takes place when propanone undergoes Benedict’s test.

Propanone does not undergo Benedict’s test.

Conclusion

No reaction takes place when propanone undergoes Benedict’s test.