Chapter 16, Problem 16.55P

Interpretation Introduction

(a)

Interpretation:

Whether erythrulose contains an aldehyde or ketone should be identified.

Concept Introduction:

Compounds which contain carbonyl carbon bonded to hydrogen or carbon atom will be considered as aldehydes or ketones.

Aldehydes − at least one H atom bonded to the carbonyl group.

Ketones − has two alkyl groups bonded to the carbonyl group.

Answer to Problem 16.55P

Erythrulose contains a ketone group.

Explanation of Solution

Given:

In the stick and ball structure, C atoms are representing in black color, H atoms in white color and O atoms in red color.

Stick and ball structure can be simplified as below;

In erythrulose there is a carbonyl group that connects to two alkyl groups, thus, the erythrulose contains ketone.

Interpretation Introduction

(b)

Interpretation:

Hydroxyl groups in erythrulose should be classified as $1^0,2^0\text{ or }{3}^0$.

Concept Introduction:

Alcohol- is an organic compound contains the group of $OH$, bonded to a tetrahedral C atom. Alcohols are classified as $1^0,2^0\text{ or }{3}^0$ by the number of C atoms bonded to the C with the OH group.

  $1^0$ alcohols - Consist of an OH group on a carbon bonded to one carbon.

  $2^0$ alcohols - Consist of an OH group on a carbon bonded to two carbons.

  $3^0$ alcohols - Consist of an OH group on a carbon bonded to two carbons.

Answer to Problem 16.55P

Explanation of Solution

  $1^0$ alcohols - Consist of an OH group on a carbon bonded to one carbon.

  $2^0$ alcohols - Consist of an OH group on a carbon bonded to two carbons.

  $3^0$ alcohols - Consist of an OH group on a carbon bonded to two carbons.

In the below stick and ball structure, C atoms are representing in black color, H atoms in white color and O atoms in red color.

Stick and ball structure can be simplified as below;

Bonds that are indicated in red color are the $C-C$ bonds that connect to the OH group boned C in alcohol which makes it as an $1^0$ OH group.

Bond that is indicated in blue color is the one that binds to two carbon atoms which makes an $2^0$ OH group.

Therefore, OH groups in erythrulose can be assigned as below.

Interpretation Introduction

(c)

Interpretation:

The products should be identified by the reaction of erythrulose with Tollens reagent.

Concept Introduction:

Silver oxide in aqueous ammonium hydroxide reagent ( $A{g}_{2}O,N{H}_{4}OH$ ) is called Tollens reagent. Addition of an O atom into a molecule is known as oxidation. If a carbonyl atom consists of a hydrogen atom directly connected to the carbonyl C in an it will be oxidized in the presence of an oxidizing agent such as ( $A{g}_{2}O$ ) in an aqueous medium of ammonium hydroxide ( $N{H}_{4}OH$ ) and give the respective carboxylic acid. But ketones do not contain any hydrogen atom bonded to the carbonyl group; they are not going oxidize to a carboxylic acid. In the below ketone structure, R groups are the alkyl groups.

Answer to Problem 16.55P

No reaction.

Explanation of Solution

Addition of an O atom into a molecule is known as oxidation. If a carbonyl atom consists of a hydrogen atom directly connected to the carbonyl C, it will be oxidized in the presence of an oxidizing agent such as $A{g}_{2}O$ in an aqueous medium of ammonium hydroxide( $N{H}_{4}OH$ ), (this $A{g}_{2}O,N{H}_{4}OH$ is known as Tollens reagent) and give the respective carboxylic acid. But ketones do not contain any hydrogen atom bonded to the carbonyl group; they are not going oxidize to a carboxylic acid. So, there is no reaction of ketones with $A{g}_{2}O,N{H}_{4}OH$. Hence, during the reaction, no silver mirror can be observed.

Interpretation Introduction

(d)

Interpretation:

The products should be identified by the reaction of erythrulose with $K_{2}C{r}_2{O}_7$.

Concept Introduction:

Addition of an O atom into a molecule is known as oxidation. If a carbonyl atom consists of a hydrogen atom directly connected to the carbonyl C, it will be oxidized in the presence of an oxidizing agent such as $K_{2}C{r}_2{O}_7$ and give the respective carboxylic acid. Though ketones do not contain any hydrogen atom bonded to the carbonyl group, they are not going to oxidize to a carboxylic acid.

But, OH groups will be oxidized into respective carboxylic acids, aldehydes or ketones.

  $1^0$ alcohols -can be oxidized to either aldehyde or carboxylic acid.

  $2^0$ alcohols -can be oxidized to ketones.

  $3^0$ alcohols -cannot be oxidized.

Answer to Problem 16.55P

Explanation of Solution

In erythrulose molecule there are two primary alcohol groups and those groups will end up with a carboxylic acid and one secondary alcohol group in the erythrulose molecule will end up with a ketone by oxidation with $K_{2}C{r}_2{O}_7$.

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