Problem 46 - Arihant Objective Approach to Organic Chemistry for IIT JEE and NEET all Medical Entrances Part 4

Question

Sucrose on treatment with conc. HCl produces: (a) glucose (b) fructose (c) both (a) and (b) (d) laevulinic acid

Step-by-Step Solution

Answer

Sucrose with conc. HCl produces both glucose and fructose.

Step 1: Understanding Sucrose Composition

Sucrose is a disaccharide composed of glucose and fructose. It is a naturally occurring sugar found in many plants.

Step 2: Understanding the Reaction with HCl

When sucrose is treated with concentrated hydrochloric acid (HCl), it undergoes hydrolysis. Hydrolysis is a chemical reaction that involves the breaking of a bond in a molecule using water.

Step 3: Performing Hydrolysis

During hydrolysis of sucrose with HCl, the glycosidic bond between glucose and fructose is cleaved. This reaction yields the two monosaccharides glucose and fructose.

Step 4: Identifying the Products

The products from this hydrolysis reaction are glucose and fructose because the glycosidic bond is broken and the individual sugars are released.

Key Concepts

Glycosidic Bond

A glycosidic bond is a type of covalent bond that connects carbohydrate molecules. Specifically, it joins monosaccharides, like glucose and fructose, to form disaccharides such as sucrose. This bond is crucial in the structure and functionality of carbohydrates.
In sucrose, the glycosidic bond forms between the hydroxyl groups of glucose and fructose. This bond is not just a simple connection, but is also responsible for the sweet taste and the energy-providing properties of sucrose.

• Without glycosidic bonds, the unique properties of sugars such as solubility and sweetness wouldn't exist.
• The stability of these bonds ensures that sucrose remains unchanged until it undergoes specific reactions like hydrolysis.

Glucose and Fructose

Glucose and fructose are two simple sugars, also known as monosaccharides, found in many foods. These sugars are essential in our diets because they provide quick energy to our cells.
Glucose is a primary energy source for our bodies and is crucial for brain function, cell health, and muscular activity. Fructose, on the other hand, is naturally found in fruits and adds sweetness to many processed foods.

• Both of these sugars contribute to the total sugar content in foods, influencing flavor and caloric content.
• In sucrose, glucose and fructose are linked together by a glycosidic bond, making it a disaccharide.

The separation of these sugars in a chemical reaction, such as hydrolysis, releases them back into their simple forms. This reaction is fundamental for human digestion as it helps the body process nutrition.

Hydrochloric Acid Reaction

When sucrose is exposed to concentrated hydrochloric acid (HCl), a special reaction occurs called hydrolysis. This process involves breaking the glycosidic bond with the help of water. Hydrochloric acid acts as a catalyst in this reaction, speeding up the breakdown.
In hydrolysis, HCl donates a hydrogen ion to assist in cleaving the bond between glucose and fructose. This reaction transforms sucrose back into its original components, glucose and fructose

• Initially, sucrose is a stable compound, but the presence of HCl and water disrupts the glycosidic bond.
• This cleavage is a classic example of acid-catalyzed hydrolysis, common in both laboratory and biological systems.

Understanding this reaction is vital, as it plays a crucial role in various digestive processes and industrial applications.