Textbook Question
If α−galactose is dissolved in water, β−galactose is eventually present. Explain how this occurs.
Ch.13 Carbohydrates
Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353
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Table of contents
- Ch.1 Chemistry in Our Lives11
- Ch.2 Chemistry and Measurements80
- Ch.3 Matter and Energy54
- Ch.4 Atoms and Elements51
- Ch.5 Nuclear Chemistry42
- Ch.6 Ionic and Molecular Compounds57
- Ch.7 Chemical Quantities and Reactions41
- Ch.8 Gases29
- Ch.9 Solutions51
- Ch.10 Acids and Bases and Equilibrium65
- Ch.11 Introduction to Organic Chemistry: Hydrocarbons78
- Ch.12 Alcohols, Thiols, Ethers, Aldehydes, and Ketones83
- Ch.13 Carbohydrates54
- Ch.14 Carboxylic Acids, Esters, Amines, and Amides90
- Ch.15 Lipids61
- Ch.16 Amino Acids, Proteins, and Enzymes84
- Ch.17 Nucleic Acids and Protein Synthesis83
- Ch.18 Metabolic Pathways and ATP Production67
Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353Not the one you use?Change textbook
Chapter 13, Problem 72
D-Erythritol is 70% as sweet as sucrose and contains only hydroxyl functional groups. When d-erythritol is oxidized it forms D-erythrose. Draw the Fischer projection for D-erythritol.
Verified step by step guidance1
Understand the structure of d-erythritol: d-erythritol is a sugar alcohol (polyol) with four carbon atoms, each containing a hydroxyl (-OH) group. It is derived from the reduction of the corresponding aldose sugar, d-erythrose.
Recall the Fischer projection: A Fischer projection is a two-dimensional representation of a molecule where the carbon chain is drawn vertically, with the most oxidized carbon (in this case, the primary alcohol group) at the top. Horizontal lines represent bonds projecting out of the plane (toward the viewer), and vertical lines represent bonds projecting into the plane (away from the viewer).
Determine the stereochemistry of d-erythritol: d-erythritol is a meso compound, meaning it has internal symmetry and is achiral. The hydroxyl groups on the second and third carbons are on opposite sides of the carbon chain, creating a mirror image within the molecule.
Draw the Fischer projection: Start by placing the four carbon atoms in a vertical line. Attach hydroxyl (-OH) groups to each carbon, ensuring that the second carbon has the hydroxyl group on the right, the third carbon has the hydroxyl group on the left, and the first and fourth carbons have hydroxyl groups pointing vertically (up and down, respectively).
Verify the structure: Check that the Fischer projection accurately represents the meso structure of d-erythritol, with the correct placement of hydroxyl groups and the internal symmetry of the molecule.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Fischer Projection
The Fischer projection is a two-dimensional representation of a three-dimensional organic molecule, particularly useful for depicting carbohydrates and amino acids. In this format, the vertical lines represent bonds that are oriented away from the viewer, while horizontal lines indicate bonds that are coming towards the viewer. This method helps in visualizing the stereochemistry of molecules, making it easier to identify chiral centers and their configurations.
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Fischer Projections Example 1
Hydroxyl Functional Groups
Hydroxyl functional groups (-OH) are characterized by the presence of an oxygen atom bonded to a hydrogen atom. They are polar and can form hydrogen bonds, which significantly influence the solubility and reactivity of organic compounds. In sugars like d-erythritol, hydroxyl groups contribute to the molecule's sweetness and its ability to participate in various chemical reactions, including oxidation.
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Oxidation of Alcohols
Oxidation of alcohols involves the conversion of hydroxyl groups into carbonyl groups, resulting in the formation of aldehydes or ketones. In the case of d-erythritol, oxidation leads to the formation of d-erythrose, a sugar with a different structure and properties. This transformation is significant in organic chemistry as it alters the functional groups and can change the biological activity and sweetness of the compound.
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Related Practice
Textbook Question
Use the Fischer projection for D-gulose in problem 13.69 to answer each of the following:
b. Draw the Fischer projection and name the product formed by the oxidation of D-gulose.
Textbook Question
Use the Fischer projection for d-gulose in problem 13.69 to answer each of the following:
a. Draw the Fischer projection and name the product formed by the reduction of D-gulose.
Textbook Question
α−Cellobiose is a disaccharide obtained from the hydrolysis of cellulose. It is quite similar to maltose except it has a β(1→4)−glycosidic bond. Draw the Haworth structure for α−cellobiose.
Textbook Question
The sugar d-gulose is a sweet-tasting syrup.
b. Draw the Haworth structures for α− and β-D-gulose.
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Textbook Question
The disaccharide trehalose found in mushrooms is composed of two α-D-glucose molecules joined by an α(1→1)−glycosidic bond. Draw the Haworth structure for trehalose.