Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 25: Problem 38

The trisaccharide raffinose occurs principally in cottonseed meal. Raffinose (a) Name the three monosaccharide units in raffinose. (b) Describe each glycosidic bond in this trisaccharicle. (c) Is raffinose a reducing sugar? (d) With how many moles of periodic acid will raffinose react?

Short Answer

Expert verified
Question: Identify the monosaccharide units, describe the glycosidic bonds, determine if raffinose is a reducing sugar, and calculate the number of moles of periodic acid that raffinose will react with. Answer: Raffinose is a trisaccharide composed of D-galactose, D-glucose, and L-fructose units. The glycosidic bonds are an α-1,6-linkage between D-galactose and D-glucose and an α-1,2-linkage between D-glucose and L-fructose. Raffinose is not a reducing sugar, and it will react with three moles of periodic acid.

Step by step solution

01

Identify the monosaccharide units in raffinose

Raffinose is a trisaccharide made up of three monosaccharide units. The three monosaccharide units in raffinose are: D-galactose, D-glucose, and L-fructose.
02

Describe the glycosidic bonds in raffinose

In raffinose, two glycosidic bonds connect the three monosaccharide units. The first glycosidic bond is an α-1,6-linkage between the D-galactose and D-glucose units. The second glycosidic bond is an α-1,2-linkage between the D-glucose and L-fructose units.
03

Determine if raffinose is a reducing sugar

A reducing sugar is a carbohydrate that can act as a reducing agent because it has a free aldehyde or ketone group. In raffinose, both the D-glucose and D-galactose units have their anomeric carbons involved in glycosidic bonds, and the L-fructose unit has its ketone group at carbon 2. Since none of the monosaccharide units have a free aldehyde or ketone group, raffinose is not a reducing sugar.
04

Calculate the number of moles of periodic acid that raffinose will react with

Periodic acid reacts with vicinal diols (two hydroxyl groups on adjacent carbons) in a carbohydrate molecule, which results in the cleavage of the carbon-carbon bond. In raffinose, there are three such vicinal diols: one in each of the D-galactose, D-glucose, and L-fructose units. Therefore, raffinose will react with three moles of periodic acid. Summary: (a) The three monosaccharide units in raffinose are D-galactose, D-glucose, and L-fructose. (b) The glycosidic bonds in raffinose are an α-1,6-linkage between D-galactose and D-glucose and an α-1,2-linkage between D-glucose and L-fructose. (c) Raffinose is not a reducing sugar. (d) Raffinose will react with three moles of periodic acid.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Hyaluronic acid acts as a lubricant in the synovial fluid of joints. In rheumatoid arthritis, inflammation breaks hyaluronic acid down to smaller molecules. Lnder these conditions, what happens to the lubricating power of the synovial fluid?

Consider Nacetyl-D-glucasamine (Section 25.11)). (a) Draw a chair conformation for the \(\alpha\) - and \(\beta\) pyranose forms of this monosaccharide. (b) Draw a chair conformation for the clisaccharide formed by joining two units of the Pyranose form of Nacety-1-gglucosamaine by a \(\beta-1,4\)-glycosidic bond. If you drew this correctly, you have the structural formula for the repeating dimer of chitin, the structural polysaccharide component of the shell of lobster and other crustalceans.

An important technique for establishing relative configurations among isomeric aldoses and ketoses is to convert both terminal carbon atoms to the same functional group. This can be done either by selective oxidation or reduction. As a specific example, nitric acid oxidation of Derythrose gives meso-tartaric acid (Section 3.4B). Similar oxidation of \(\mathrm{D}\)-threose gives \((2 S, 35)\)-tartaric acid. Gaven this information and the fact that D-erythrose and D-threose are diastereomers, draw Fischer projections for D-erythrose and D-threose. Check your answers aggainst Table 25.1.

How many chiral centers are present in D-glucose? In D-ribose?

Which is the anomeric carbon in a 2-ketohexose?
See all solutions

Recommended explanations on Chemistry Textbooks

Nuclear Chemistry

Read Explanation

Inorganic Chemistry

Read Explanation

Chemistry Branches

Read Explanation

Kinetics

Read Explanation

Chemical Reactions

Read Explanation

Ionic and Molecular Compounds

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free