Chapter 24, Problem 24.35AP

Interpretation Introduction

(a)

Interpretation:

The products expected when D-ribose is reacted with dilute is to be stated.

Concept introduction:

The aldehyde and alcohols on complete oxidation change into a carboxylic acid. The complete oxidation of the aldoses into the aldaric acid that is carboxylic acid on both ends is done with the help of nitric acid.

Answer to Problem 24.35AP

The product obtained when D-ribose is reacted with dilute is shown below.

Explanation of Solution

The product obtained when D-ribose is reacted with dilute is shown below.

Figure 1

The oxidation of D-ribose into D-ribaric acid occurs in the presence of dilute nitric acid.

Conclusion

The product obtained when D-ribose is reacted with dilute is shown in Figure 1.

Interpretation Introduction

(b)

Interpretation:

The products expected when D-ribose is reacted with is to be stated.

Concept introduction:

Kiliani-Fischer process is is the reaction pathway by which an aldose is extended by one carbon unit. The first step of this reaction is the attack of the cyanide group on the carbonyl carbon of the aldehyde group resulting in the formation of the cyanohydrins. The cyanohydrins thus formed is reduced to imine with catalytic hydrogenation. The imine thus formed can easily be hydrolyzed by into aldose and ammonium ion.

Answer to Problem 24.35AP

The products obtained when D-ribose is reacted with are shown below.

Explanation of Solution

The products obtained when D-ribose is reacted with are shown below.

Figure 2

The D-ribose is converted into cyanohydrins by the nucleophilic attack of the cyanide group on the carbonyl carbon of the aldehyde group.

Conclusion

The products obtained when D-ribose is reacted with are shown in Figure 2.

Interpretation Introduction

(c)

Interpretation:

The products expected when the product of part (b) is reacted with and is to be stated.

Concept introduction:

Kiliani-Fischer process is is the reaction pathway by which an aldose is extended by one carbon unit. The first step of this reaction is the attack of the cyanide group on the carbonyl carbon of the aldehyde group resulting in the formation of the cyanohydrins. The cyanohydrins thus formed is reduced to imine with catalytic hydrogenation. The imine thus formed can easily be hydrolyzed by into aldose and ammonium ion.

Answer to Problem 24.35AP

The products obtained when the product of part (b) is reacted with and are shown below.

Explanation of Solution

The products obtained when the product of part (b) is reacted with and are shown below.

Figure 3

The product of part (b) is the cyanohydrin of D-ribose which is then converted into the extended aldose, altrose and allose. The catalytic hydrogenation of cyanohydrin into imine is done by . The imine then formed is hydrolyzed into the altrose and allose by .

Conclusion

The products obtained when the product of part (b) is reacted with and are shown in Figure 3.

Interpretation Introduction

(d)

Interpretation:

The products expected when D-ribose is reacted with is to be stated.

Concept introduction:

A monosaccharide is converted into cyclic acetals on reaction with alcohols in the presence of acidic conditions. The hydroxide group right to the oxygen atom in the pyranose ring structure is methylated and result in the formation of acetal.

Answer to Problem 24.35AP

The product obtained when D-ribose is reacted with is shown below.

Explanation of Solution

The product obtained when D-ribose is reacted with is shown below.

Figure 4

The D-ribose on reaction with methanol and hydrochloric acid is converted into the acetal. The acetal formed is found in both forms alpha and beta regardless of the configuration of D-ribose.

Conclusion

The product obtained when D-ribose is reacted with is shown in Figure 4.

Interpretation Introduction

(e)

Interpretation:

The product obtained when the product of part (d) is reacted with (excess) and is to be stated.

Concept introduction:

The methylation of the hydroxyl group of sugars is an important reaction. The methylation of hydroxyl groups is done with the help of methylating agent dimethyl sulfate in the presence of strong base sodium hydroxide.

Answer to Problem 24.35AP

The product obtained when the product of part (d) is reacted with (excess) and is shown below.

Explanation of Solution

The product obtained when the product of part (d) is reacted with (excess) and is shown below.

Figure 5

The four products of part (d) are alkylated in the strong base sodium hydroxide. The sodium hydroxide takes up the acidic proton of alcohol groups and converts them to alkoxide ion form. This alkoxide ion then attacks on the dimethyl sulfate (also a methylating agent) and take up the methyl group simultaneously eliminating the methyl sulfate group.

Conclusion

The product obtained when the product of part (d) is reacted with (excess) and is shown in Figure 5.