Concept explainers
Interpretation:
The percent of (R)-glyceraldehyde present in the given mixture has to be calculated.
Concept introduction:
The pair of Enantiomers has different configurations.
Pair of enantiomers has different optical activity, which means if one will show levorotatory then the other will show dextrorotatory.
The direction and magnitude of rotation of plane-polarized light by an optically compound is measured by using polarimeter.
This rotation of polarized light is specific for a compound at specified temperature and wavelength, so it is called as Specific rotation of that compound.
The specific rotation of enantiomers has equal magnitudes and opposite signs.
Racemic mixture (equal amounts of enantiomers) of a compound has zero specific rotation.
If the mixture contain unequal amount of enantiomers of a compound, then the amount of excess of enantiomer is called enantiomeric excess or optical purity. It is calculated by,
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Chapter 4 Solutions
Organic Chemistry
- Like glucose, galactose mutarotates when it dissolves in water. The specific rotation ofa-d-galactopyranose is +150.7°, and that of the b anomer is +52.8°. When either ofthe pure anomers dissolves in water, the specific rotation gradually changes to +80.2°.Determine the percentages of the two anomers present at equilibrium.arrow_forwardThe specific rotation of a-d-glucose is +112.2. Q.) When a-d-glucose is dissolved in water, the specific rotation of the solution changes from +112.2 to +52.7. Does the specific rotation of a-l-glucose also change when it is dissolved in water? If so, to what value?arrow_forwardCarbohydrates. Determination of the extent of branching in glycogen. The amount of branching (number of α 1⟶ 6 glycosidic bonds) in glycogen can be determined by the following procedure. A sample of glycogen is exhaustively methylated-treated with a methylating agent (methyl iodide) that replaces the hydrogen of every sugar hydroxyl with a methyl group, converting –OH to –OCH3. All the glycosidic bonds in the treated sample are then hydrolyzed in aqueous acid, and the amounts of α -D-2,3-di-O-methylglucopyranose and α -D-2,3,6-tri-O-methylglucopyranose formed are measured. 1- Draw the cyclic structure of α-D-glucopyranose, α-D-2,3-di-O-methylglucopyranose and α-D-2,3,6-tri-O-methylglucopyranose, including the numbering of carbon atoms. 2- Which of α-D-2,3-di-O-methylglucopyranose or α-D-2,3,6-tri-O-methylglucopyranose represents a glucose unit in glycogen which was originally carrying a α 1⟶ 6 glycosidic bond? Explain.arrow_forward
- The specific rotation of a-d-glucose is +112.2. Q.) What is the specific rotation of a-l-glucose?arrow_forwardPure cholesterol has a specific rotation of −32. A sample of cholesterolprepared in the lab had a specific rotation of −16. What is the enantiomericexcess of this sample of cholesterol?arrow_forwarda. What is the specific rotation of (R)-(-)-monosodium glutamate? b. What is the specific rotation of a racemic mixture of MSG?arrow_forward
- Identify the configuration of the stereogenic center (R or S)arrow_forwardWhat is the maximum number of stereoisomers for mannuronic acid?arrow_forwardIf the optical rotation of a pure enantiomer A is +10 and the optical rotation of a mixture of two enantiomers (A+B) is -4 (Negative 6), what is the percentage of A and B in that mixture?arrow_forward
- Mannose exists in aqueous solution as a mixture of a-d-mannopyranose and b-d-mannopyranose. Draw Haworth projections for these molecules.arrow_forwardThe following compound has two asymmetric centers and four stereoisomers. Two of these are d-erythrose and d-threose, which are naturally occurring sugars. The configuration of d-erythrose is (2R,3R), and the configuration of d-threose is (2S,3R). a. Which structure represents d-erythrose? b. Which represents d-threose?arrow_forwardThere are three (3) vials labeled A, B, and C known to contain the following monosaccharides. All three samples reduce Tollens and Fehling. By oxidation with dilute HNO3 an optically active aldaric acid is obtained for sample A and the remaining two give products without optical activity. When the three samples were subjected to an alkaline medium, it was observed that, after a certain time, samples A and C reached the same value of the specific rotation [α]. Select the RIGHT alternative: (a) Sample A is Galactose. (b) Sample B is Alosa. (c) Samples A and C are not related to each other by an epimerization process. (d) Sample C is Talose. (e) Samples B and C are epimers.arrow_forward
- Organic And Biological ChemistryChemistryISBN:9781305081079Author:STOKER, H. Stephen (howard Stephen)Publisher:Cengage Learning,General, Organic, and Biological ChemistryChemistryISBN:9781285853918Author:H. Stephen StokerPublisher:Cengage LearningOrganic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning