Question

Match the elements of Column I to elements of Column II. There can be single or multiple matches. Column I Column II (a) \(\mathrm{D}(+)\) glucose (p) Lobry de Bruyn-van Ekenstein rearrangement (b) \(\mathrm{D}(-)\) fructose (q) Red precipitate with Fehling's solution (c) \((+)\) Maltose (r) Exhibits mutarotation (d) \((+)\) sucrose (s) oxidized by \(\mathrm{Br}_{2} / \mathrm{H}_{2} \mathrm{O}\) (t) \(\mathrm{C}_{1}-\mathrm{C}_{2}\) glycosidic linkage

Short answer

Question: Match the elements of Column I (a to t) with the elements of Column II (glucose, fructose, maltose, sucrose, Lobry de Bruyn-van Ekenstein rearrangement, red precipitate with Fehling's solution, exhibits mutarotation, oxidized by Br2 / H2O, and C1-C2 glycosidic linkage). Answer: (a) D(+) glucose: (p) Lobry de Bruyn-van Ekenstein rearrangement, (r) exhibits mutarotation, and (s) oxidized by Br2 / H2O (b) D(-) fructose: (p) Lobry de Bruyn-van Ekenstein rearrangement, (q) red precipitate with Fehling's solution, and (r) exhibits mutarotation (c) (+) maltose: (r) exhibits mutarotation, (s) oxidized by Br2 / H2O, and (t) C1-C2 glycosidic linkage (d) (+) sucrose: (s) oxidized by Br2 / H2O

Step-by-step solution

Recalling properties and reactions

Recall the properties and reactions of the given carbohydrates: glucose, fructose, maltose, and sucrose.

Matching Column I elements with Column II elements

Based on our knowledge and understanding of carbohydrates, we can match the given elements in Column I to the appropriate elements in Column II. (a) \(\mathrm{D}(+)\) glucose: - Exhibits mutarotation: (r) - Oxidized by \(\mathrm{Br}_{2} / \mathrm{H}_{2} \mathrm{O}\): (s) - Transforms into fructose via Lobry de Bruyn-van Ekenstein rearrangement: (p) (b) \(\mathrm{D}(-)\) fructose: - Red precipitate with Fehling's solution: (q) - Exhibits mutarotation: (r) - Transforms into glucose via Lobry de Bruyn-van Ekenstein rearrangement: (p) (c) \((+)\) Maltose: - C1-C2 glycosidic linkage: (t) - Oxidized by \(\mathrm{Br}_{2} / \mathrm{H}_{2} \mathrm{O}\): (s) - Exhibits mutarotation: (r) (d) \((+)\) sucrose: - No red precipitate with Fehling's solution (no matching) - No mutarotation (no matching) - Oxidized by \(\mathrm{Br}_{2} / \mathrm{H}_{2} \mathrm{O}\): (s) Once we match column I elements with the appropriate column II elements, we can summarize them: (a) \(\mathrm{D}(+)\) glucose: (p), (r), and (s) (b) \(\mathrm{D}(-)\) fructose: (p), (q), and (r) (c) \((+)\) maltose: (r), (s), and (t) (d) \((+)\) sucrose: (s)

Key concepts

Lobry de Bruyn-van Ekenstein rearrangement

The Lobry de Bruyn-van Ekenstein rearrangement is a fascinating transformation in the chemistry of carbohydrates. It involves the interconversion between aldose and ketose sugars through an enediol intermediate. This process is catalyzed by both acidic and basic conditions and is critical for understanding how simple sugars are able to transform in biological systems. For instance, glucose can interconvert to fructose via this rearrangement. This reaction is vital for the body's metabolism of sugars and highlights the dynamic nature of carbohydrate chemistry.

Understanding this rearrangement helps explain how glucose and fructose, which have different structures (an aldehyde and a ketone group, respectively), can be related and how they can readily convert into one another under certain conditions. This knowledge is particularly important for students studying biochemistry and metabolic pathways.

Mutarotation in carbohydrates

Mutarotation is a term that describes the change in optical rotation that occurs when an equilibrium is established between the alpha and beta anomers of a sugar in aqueous solution. When sugars like glucose dissolve in water, they can switch from their straight-chain form to a cyclic form. This process creates a point of asymmetry at the carbon where the ring closes, typically carbon number 1, leading to two different isomers—alpha and beta. Mutarotation refers to the conversion between these cyclic isomers, which show different light rotation directions, or optical activity.

Students often experiment with mutarotation by measuring the change in optical rotation of a sugar solution over time. The direct relevance of mutarotation can be seen in our bodies, where certain enzymes can only recognize one anomer of a sugar, which is why this topic is crucial for understanding carbohydrate biochemistry.

Fehling's solution test

• Step 1 - Understanding Fehling's Solution: Comprised of two parts, Fehling's solution A and B, this test involves a complex of copper(II) ions in an alkaline solution. Fehling's solution A contains copper(II) sulfate, while Fehling's solution B has potassium sodium tartrate and sodium hydroxide.
• Step 2 - The Redox Reaction: When heated with reducing sugars, such as aldoses that possess a free aldehyde group, the copper(II) ions are reduced to copper(I) oxide, which forms a red or brick-red precipitate, indicating a positive result.
• Step 3 - Non-Reducing Sugars: Sucrose, a non-reducing sugar due to its acetal linkage, does not react with Fehling's solution, leading to no change in color.
• Step 4 - Importance for Students: This test provides a classic example of a qualitative analysis in organic chemistry and aids in differentiating reducing from non-reducing sugars, an important concept in biologically relevant chemistry.

Glycosidic linkage

Glycosidic linkages are the bonds that hold together carbohydrates in larger structures, such as in disaccharides and polysaccharides. These linkages can occur between different carbons in the sugar molecules ('C1-C2', 'C1-C4', etc.) and define the structure and function of the carbohydrate. For example, maltose has a glycosidic linkage between the first carbon of one glucose and the fourth carbon of another glucose, labeled as a α(1→4) bond. Different types of glycosidic linkages result in various properties and digestibility in carbohydrates, such as the difference between starch and cellulose in plants.

The understanding of glycosidic linkages is essential when studying how carbohydrates are broken down by enzymes in digestion or how they are synthesized in biological processes, making it another key concept in both biochemistry and nutrition science.