ORGANIC CHEMISTRY-OWL V2 ACCESS
ORGANIC CHEMISTRY-OWL V2 ACCESS
8th Edition
ISBN: 9781305582422
Author: Brown
Publisher: CENGAGE L
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Chapter 25, Problem 25.24P

(a)

Interpretation Introduction

Interpretation:

The product formed by the reaction of D-galactose with NaBH4 and H2O has to be drawn in Fischer projection and the product is optically active or inactive has to be stated.

Concept Introduction:

The reaction of NaBH4 and H2O with carbohydrates is a reduction reaction.  The carbonyl group in the carbohydrate is reduced to alcoholic group and forms alditols.

(a)

Expert Solution
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Explanation of Solution

The D-galactose is an aldohexose molecule.  The carbonyl group present in D-galactose is aldehyde (-CHO).  When the D-galactose molecule is reacted with NaBH4 and H2O, the aldehyde group is reduced to alcohol group (-CH2OH) forming the alditol product.

ORGANIC CHEMISTRY-OWL V2 ACCESS, Chapter 25, Problem 25.24P , additional homework tip  1

The formed alditol is optically inactive as it is a meso compound and shows plane of symmetry.

ORGANIC CHEMISTRY-OWL V2 ACCESS, Chapter 25, Problem 25.24P , additional homework tip  2

(b)

Interpretation Introduction

Interpretation:

The product formed by the reaction of D-galactose with H2/Pt has to be drawn in Fischer projection and the product is optically active or inactive has to be stated.

Concept Introduction:

The reagent H2/Pt is a reducing agent which reduces the carbonyl group into alcoholic group.  The carbonyl group in the carbohydrate is reduced to alcoholic group and forms alditols.

(b)

Expert Solution
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Explanation of Solution

When the D-galactose molecule is made to react with H2/Pt, the aldehyde group is reduced to alcoholic group forming the alditol.

ORGANIC CHEMISTRY-OWL V2 ACCESS, Chapter 25, Problem 25.24P , additional homework tip  3

The formed alditol is optically inactive as it is a meso compound and it shows plane of symmetry.

ORGANIC CHEMISTRY-OWL V2 ACCESS, Chapter 25, Problem 25.24P , additional homework tip  4

(c)

Interpretation Introduction

Interpretation:

The product formed by the reaction of D-galactose with warm HNO3 has to be drawn in Fischer projection and the product is optically active or inactive has to be stated.

Concept Introduction:

The reaction of warm HNO3 with carbohydrates is a oxidation reaction.  The carbonyl groups and alcoholic groups in the carbohydrate is oxidised to acid groups.

(c)

Expert Solution
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Explanation of Solution

The nitric acid (HNO3) is an oxidising agent.  It oxidises the alcoholic groups and carbonyl groups into acidic groups.  In D-galactose, the aldehyde group and the alcoholic group (C6) are oxidised to acid groups forming D-galactaric acid.

ORGANIC CHEMISTRY-OWL V2 ACCESS, Chapter 25, Problem 25.24P , additional homework tip  5

The product formed is a meso compound and shows plane of symmetry.  So, it is optically inactive.

ORGANIC CHEMISTRY-OWL V2 ACCESS, Chapter 25, Problem 25.24P , additional homework tip  6

(d)

Interpretation Introduction

Interpretation:

The product formed by the reaction of D-galactose with Br2/H2O/CaCO3 has to be drawn in Fischer projection and the product is optically active or inactive has to be stated.

Concept Introduction:

The reaction of Br2/H2O/CaCO3 with carbohydrates is a oxidation reaction.  The carbonyl group in the carbohydrate is oxidised to acid group.  It is a mild oxidising agent compared to HNO3.

(d)

Expert Solution
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Explanation of Solution

When the D-galactose reacts with Br2/H2O/CaCO3, the aldehyde group is oxidised to acid group forming the acidic product, D-galactonic acid.

ORGANIC CHEMISTRY-OWL V2 ACCESS, Chapter 25, Problem 25.24P , additional homework tip  7

The formed product is optically active.

ORGANIC CHEMISTRY-OWL V2 ACCESS, Chapter 25, Problem 25.24P , additional homework tip  8

(e)

Interpretation Introduction

Interpretation:

The product formed by the reaction of D-galactose with H5IO6 has to be drawn in Fischer projection and the product is optically active or inactive has to be stated.

Concept Introduction:

The reaction of H5IO6 oxidises the carbohydrate molecule by cleaving the carbon-carbon bonds.  It forms many cleaved products of the carbohydrate.

(e)

Expert Solution
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Explanation of Solution

The D-galactose molecule consumes 5H5IO6 molecules to cleave the six carbon-carbon bonds.  The aldehyde group (C1) and hydroxyl groups (C2-C5) are reduced to acid groups and the C6 alcohol group is converted to aldehyde group.  It forms six products among which five are formic acid molecules and one is formaldehyde.

ORGANIC CHEMISTRY-OWL V2 ACCESS, Chapter 25, Problem 25.24P , additional homework tip  9

The products formed are achiral and are optically inactive.

(f)

Interpretation Introduction

Interpretation:

The product formed by the reaction of D-galactose with aniline (C6H5NH2) has to be drawn in Fischer projection and the product is optically active or inactive has to be stated.

(f)

Expert Solution
Check Mark

Explanation of Solution

The D-galactose molecule reacts with aniline molecule and the aldehyde group of carbohydrate is reacted with the amine group of aniline.  By the loss of water molecule, it forms Schiff’s base of D-galactose.

ORGANIC CHEMISTRY-OWL V2 ACCESS, Chapter 25, Problem 25.24P , additional homework tip  10

The formed product is a chiral compound and optically active.

ORGANIC CHEMISTRY-OWL V2 ACCESS, Chapter 25, Problem 25.24P , additional homework tip  11

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