Question

This section contains multiple choice questions. Each question has 4 choices (a), (b), (c) and (d), out of which ONLY ONE is correct. The oxidation of monosaccharides using periodic acid, will work well (a) in aqueous medium (b) in organic solvent (c) in the presence of a catalyst (d) in the presence of base

Short answer

Answer: (a) In an aqueous medium

Step-by-step solution

Option (a) - Aqueous Medium

Periodic acid (HIO4) is a strong oxidizing agent and is soluble in water. In an aqueous medium, periodic acid can effectively cleave vicinal diol groups present in carbohydrates. The resulting product is a pair of aldehyde or ketone groups. This oxidation process works well in an aqueous medium as the reactants and products are soluble in water, leading to better interaction between them.

Option (b) - Organic Solvent

The use of organic solvents for the oxidation of monosaccharides with periodic acid is not ideal as it might lead to reduced solubility and a retarded reaction. Additionally, organic solvents can sometimes participate in side reactions, causing unwanted products.

Option (c) - Presence of a Catalyst

Generally, periodic acid oxidation reactions do not require the presence of a catalyst. Using a catalyst in such reactions may lead to unnecessary complications or side reactions.

Option (d) - Presence of a Base

Periodic acid is an oxidizing agent, and thus, its strength can be affected by the pH of the reaction medium. The presence of a base can alter the pH, potentially affecting the efficiency of the oxidation reaction. It is not recommended to perform the reaction in basic conditions. Based on the discussion above, the correct choice for the oxidation of monosaccharides using periodic acid is:

Correct Answer

(a) In an aqueous medium

Key concepts

Periodic Acid and Monosaccharides

Periodic acid, often represented as \( \text{HIO}_4 \), is a chemical compound widely known for its strong oxidizing properties. This makes it highly effective in the oxidation of monosaccharides, which are simple sugars and building blocks of carbohydrates. When monosaccharides are exposed to periodic acid, it targets specific structural elements called vicinal diols. These are pairs of hydroxyl groups (- \( -OH \) groups) attached to adjacent carbon atoms. Monosaccharides possess these vicinal diols, wherein periodic acid acts to transform them into smaller aldehyde or ketone groups in the oxidation process, a reaction referred to as cleavage. This action enhances the utility of monosaccharides for varied biochemical applications. This oxidation process is particularly useful in organic chemistry for analyzing and fragmenting complex carbohydrate structures into simpler ones.By effectively breaking down complex structures, periodic acid facilitates a deeper understanding of carbohydrate makeup, which is integral in fields like biochemistry and molecular biology.

Vicinal Diol Cleavage

An intriguing feature of periodic acid is its efficiency at cleaving vicinal diols within monosaccharides. This means that when periodic acid comes into contact with monosaccharides, it oxidizes the hydroxyl groups located on adjacent carbon atoms, resulting in the breaking of the carbon-carbon bond linking these groups. The prominent products of this oxidation are aldehydes or ketones. This cleavage is crucial because it allows chemists to break down and examine the intricate structures of carbohydrates. - The process simplifies the structural analysis - Yields products that provide insights into the original configuration of the molecule For example, suppose a molecule has a sequence of carbon atoms with vicinal diols. Upon treatment with periodic acid, these sections may break down into distinct smaller fragments. The reaction can be harnessed to decompose complex carbohydrates into simpler components, facilitating analysis and identification of their structures. Understanding vicinal diol cleavage is fundamental in mapping complex carbohydrate networks since it offers a method to explore the detailed architecture of sugar molecules.

Oxidation Reaction Medium

The medium in which a chemical reaction occurs can significantly influence its outcome. For periodic acid oxidation of monosaccharides, an aqueous medium (water-based environment) is optimal. This choice of medium supports the solubility required for effective reactions. As periodic acid can fully dissolve in water, it ensures an even dispersion throughout the reaction vessel. This enhances contact between the periodic acid and the monosaccharide, facilitating efficient oxidation. - Aqueous medium promotes uniform reactions - Reduces unwanted side reactions by excluding non-polar solvents Choosing a non-aqueous medium, like organic solvents, may lower this effectiveness due to solubility issues and possible side reactions. Furthermore, periodic acid oxidation does not demand additional catalysts, nor benefits from being carried out in a basic medium, as a basic environment may adversely impact its activity. Hence, keeping a neutral, water-based reaction condition maximizes both the rate and effectiveness of the oxidation. This is one of the reasons why aqueous solutions are preferred for many types of organic reactions, given their minimal impact on reaction dynamics and reliability.