Problem 27 - A Complete Resource Book in Chemistry for JEE Main

Question

Reduction product of glucose is (a) menthol (b) sorbitol (c) mannitol (d) sorbitol and mannitol

Step-by-Step Solution

Answer

The reduction product of glucose is (d) sorbitol and mannitol.

Step 1: Understanding the Question

The exercise is asking which compound is formed when glucose undergoes reduction. This involves converting the aldehyde group in glucose to an alcohol group, which results in a sugar alcohol.

Step 2: Identifying Sugar Alcohols

The sugar alcohols that can be formed from the reduction of glucose are sorbitol and mannitol. Sorbitol is primarily formed, while mannitol can also be produced under specific conditions.

Step 3: Comparing Options

Reviewing the options provided: (a) Menthol is not related to glucose, and (b) Sorbitol is one product. (c) Mannitol can be formed, but only partially, and (d) Both sorbitol and mannitol are formed. Among these, both sorbitol and mannitol are relevant reduction products.

Step 4: Selecting the Best Answer

Given the reasoning above, option (d) "sorbitol and mannitol" includes both sugar alcohols potentially formed from glucose, making it the most comprehensive answer.

Key Concepts

Sugar Alcohols

Sugar alcohols are fascinating compounds that bridge the gap between sugars and alcohols. They are neither sugar nor alcohol in the strictest sense, but rather a hybrid. This combination results from the hydrogenation of sugars. In this process, the aldehyde group of a sugar like glucose is reduced to form an alcohol group.
As a result, sugar alcohols have unique properties:

• They are sweeter than sugars and can be used as sweeteners for people seeking to reduce sugar intake.
• They have fewer calories than regular sugars, making them a favorable choice for calorie-conscious individuals.
• Sugar alcohols do not cause a spike in blood glucose levels, making them suitable for people with diabetes.
• They provide a mouth-cooling effect, often used in sugar-free gums and mints.

Understanding sugar alcohols and their properties help in managing diets better and making informed choices about dietary sugars.

Sorbitol

Sorbitol is one of the most common sugar alcohols, produced predominantly from the reduction of glucose. When glucose is fully hydrogenated, every aldehyde in glucose turns into an alcohol group, producing sorbitol.
It is naturally found in fruits such as apples, pears, and peaches. Sorbitol is widely used in:

• Processed foods as a sugar substitute.
• The cosmetic industry for adding moisture to lotions and creams.
• The pharmaceutical industry, often as a sweetening agent in cough syrups.

Though it is a useful sugar alternative, consuming sorbitol in large quantities might lead to digestive distress for some individuals. It is thus crucial to be mindful of intake levels.

Mannitol

Mannitol is another sugar alcohol that can be derived from the reduction of glucose. However, the formation of mannitol occurs under specific conditions where partial reduction takes place. This makes mannitol less abundant than sorbitol but just as important.
Mannitol is extracted from natural sources like seaweed and is frequently used due to its unique properties:

• As a diuretic in the medical field, helping to reduce swelling and pressure around the brain or eyes.
• In foods low in calories and suitable for people with diabetes.
• As an excipient in making tablets because of its pleasant taste and texture.

Mannitol’s less common occurrence doesn't diminish its significance in both health and industry-focused applications.

Reduction Reaction

A reduction reaction is a chemical process by which a molecule, atom, or ion gains electrons. In the context of glucose reduction, this is primarily observed when the aldehyde group in glucose is reduced to an alcohol group.
This chemical transformation:

• Is facilitated by catalysts and specific conditions, such as the presence of hydrogen or a suitable reducing agent.
• Results in the creation of sugar alcohols like sorbitol and mannitol.
• Is an important technique in both chemical synthesis and food industry.

Such reactions not only illustrate the flexibility of glucose in forming different compounds but also demonstrate its versatility across various applications. Understanding these reactions provides insights into how chemical processes alter the structure and functional group of molecules like glucose.