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

Sorbitol is the reduction product of glucose.

Step 1: Understand the Question

The question is asking about the reduction product of glucose. Glucose is a simple sugar that can undergo reduction, a chemical reaction where oxygen is removed or hydrogen is added to the molecule.

Step 2: Review the Structure of Glucose

Glucose is an aldohexose sugar, meaning it contains an aldehyde group and six carbon atoms. It has the chemical formula C6H12O6.

Step 3: Identify the Reduction Process

When glucose undergoes reduction, the aldehyde group (CHO) is reduced to an alcohol group (CH2OH). This process adds hydrogen atoms to the original aldehyde section of the glucose molecule.

Step 4: Determine the Product of Reduction

The reduction of glucose converts all the carbonyl (aldehyde) group to hydroxyl groups, resulting in a hexitol (sugar alcohol). Sorbitol is the sugar alcohol form of glucose. Mannitol is also related as a reduction product, but specifically, glucose primarily reduces to sorbitol.

Step 5: Choose the Correct Answer

Out of the given options (a) menthol, (b) sorbitol, (c) mannitol, and (d) sorbitol and mannitol, option (b) sorbitol is the correct reduction product of glucose.

Key Concepts

Glucose Structure

Glucose is one of the most important and common sugars in nature. It's a simple sugar, known in scientific terms as a monosaccharide. The structure of glucose is what makes it quite versatile in biochemical reactions. Glucose is characterized as an aldohexose. What does this mean?

• "Aldo" refers to the presence of an aldehyde group, which is a type of functional group consisting of a carbon atom bonded to a hydrogen atom and double-bonded to an oxygen atom, forming a carbonyl group.
• "Hexose" means the molecule comprises six carbon atoms.

This gives glucose the chemical formula of \(C_6H_{12}O_6\). Understanding glucose's structure is essential because it is the starting point for many reactions, including reduction.

Reduction Reaction

A reduction reaction is a type of chemical reaction that involves the gain of hydrogen or the loss of oxygen in a molecule. It is one part of the redox (reduction-oxidation) reactions, which are vital for many biological processes.

• In the reduction of glucose, the aldehyde group (found at the end of the glucose molecule) is reduced to a primary alcohol group (\(CH_2OH\)).
• This changes the functional group in the glucose from a reactive carbonyl group to more stable alcohol groups.

Reduction plays a critical role in transforming glucose into a sugar alcohol called sorbitol, with specific biochemical implications.

Sugar Alcohol

Sugar alcohols are a class of compounds that resemble sugar but are derived from the reduction of sugars. They are often used as low-calorie sweeteners.

• They are not wholly sugars nor pure alcohols but offer properties of both.
• Upon reduction, the carbonyl group in glucose is converted to a hydroxyl group, forming a sugar alcohol.

Sugar alcohols like sorbitol have fewer calories than regular sugar, are slowly absorbed by the body, and do not cause a rapid spike in blood sugar levels. This makes them useful in various dietary products.

Sorbitol

Sorbitol is a specific sugar alcohol formed from the reduction of glucose. It is widely used in the food industry and also occurs naturally in fruits like apples, pears, and berries.

• When glucose is reduced, the aldehyde group becomes an alcohol group, transforming it into sorbitol.
• Sorbitol retains the sweetness of glucose but has different chemical stability and other beneficial properties.

In the context of the reduction of glucose, sorbitol is the direct reduction product, highlighting its significance as both a natural and industrial sweetener.

Aldohexose

An aldohexose, such as glucose, is a simple sugar containing both an aldehyde group and six carbon atoms. This form is important in understanding sugars' chemical and biological properties.

• "Aldo" indicates the presence of an aldehyde group at one end of the sugar.
• "Hexose" acknowledges the structure composed of six carbons.

The classification of glucose as an aldohexose is crucial in predicting its behavior in chemical reactions, such as its tendency to form sugar alcohols through reduction processes. Understanding glucose as an aldohexose explains much about its role and function in different physiological and biochemical processes.