Glucose - Structure of Glucose, Preparation, Uses, Properties, Osazone Formation, Practice Problems, Frequently Asked Questions - FAQs

Look at this picture. Have you ever seen this at your home or at shops or in TV ads? Of course yes. Have you ever drunk it? Of course yes. Each one of us has had Glucon D. But what does? Why do we drink it, especially in summer? Why do we start feeling energetic after having it?  As it contains 99.4% glucose which is a carbohydrate that fulfils the energy that the body needs, Glucon-D gives instant energy when we got tired on a summer day.  If you’re now thinking that how glucose gives us energy let’s try to understand more about it.

Table of content

• Glucose
• Structure of Glucose
• Preparation of Glucose
• Uses of Glucose
• Properties of Glucose
• Osazone formation
• Practice problems
• Frequently asked question:

Glucose:

Glucose is a carbohydrate and a vital biomolecule that contributes to the body's metabolism. It has a chemical formula C₆H₁₂O₆ and is a simple sugar. It is made up of six carbon atoms, twelve hydrogen atoms, and six oxygen atoms in simple terms.

Glucose, often known as dextrose or blood sugar, is an easily accessible monosaccharide. Glucose is primarily produced by plants and the majority of algae during the photosynthesis process.

To put it precisely, Glucose is a type of sugar. We don't only mean the white crystals we sprinkle on our cuisine when we say sugar. These sugars are a subgroup of carbohydrates, which are energy-giving chemicals found in food.

Structure of Glucose:

Have a look at the structure given below. Are you wondering how this structure would have been derived? Let’s find the answer together.

We know that the molecular formula of Glucose is C₆H₁₂O₆ . 

Let’s look at how the structure of glucose was elucidated.

A:  On prolonged heating with red 𝑃 and 𝐻𝐼, it forms n-hexane, suggesting that all the six carbon atoms are linked in a straight chain.

B: Glucose reacts with hydroxylamine to form an oxime and adds a molecule of hydrogen cyanide to give cyanohydrin. These reactions confirm the presence of a carbonyl group  ( >𝑪 = 𝑶 ) in glucose.

C:  Glucose gets oxidised to six carbon carboxylic acid (gluconic acid) on reaction with a mild oxidising agent like bromine water. This indicates that the carbonyl group is present as an aldehydic group.

D:  Acetylation of glucose with acetic anhydride gives glucose pentaacetate which confirms the presence of five –𝑂𝐻 groups. Since it exists as a stable compound, five –𝑂𝐻 groups should be attached to different carbon atoms.

E: On oxidation with dilute nitric acid, both glucose and gluconic acid yield a dicarboxylic acid, i.e., saccharic acid. This indicates the presence of a primary alcoholic ( –𝑂𝐻 ) group in glucose.

Point to remember: Dilute nitric acid is a stronger oxidising agent than bromine water, oxidises both the −𝑪𝑯𝑶 group and the terminal CH₂OH group of an aldose to −𝑪𝑶𝑶𝑯 groups, forming dicarboxylic acids. 

F:  Emil Fischer was able to establish the stereochemical configuration of glucose, the most  abundant monosaccharide.

Preparation of glucose: 

Glucose can be prepared by two different methods.

Let’s see each of the given methods one by one.

• From sucrose:

Cane sugar, which is a disaccharide, on acid hydrolysis gives glucose and fructose in the equal amount. This can be explained by the given reaction.

• From starch

Starch, which is a polysaccharide, by the enzymatic action of the Diastase enzyme gives Maltose which is a disaccharide. Maltose on further gives Glucose, a monosaccharide, by the enzymatic action of the Maltase enzyme. This equation can be represented as below.

Uses of Glucose:

• It is used in the treatment of hypoglycemia (low blood sugar)
• It is given to patients who are unable to eat because it contains carbohydrate calories.
• It is used in the treatment of increased potassium levels in the blood (hyperkalemia)
• It is utilised in the synthesis of substances as a precursor.

Properties of Glucose:

• Glucose is a crystalline white solid with a melting point of 1460⁰C. 
• When a glucose molecule is crystallised with cold water, glucose monohydrate is formed, with the chemical formula C₆H₁₂O₆ .H₂O with a melting point of 86O⁰C. 
•  It's highly soluble in water, only slightly soluble in ethanol, and completely insoluble in ether. 
• Sucrose is roughly three-quarters as sweet as cane sugar. 

Osazone formation:

1,2-biarylhyrazone is formed by the reaction of an aldose or ketose with three molar equivalents of arylhydrazone. Most common are phenylosazones, formed by reaction with phenylhydrazine, and 2,4-dinitrophenylhydrazones.

Mechanism for the formation of phenylhydrazone formation:

Practice problems

Q 1. Which of the following indicates the presence of five –𝑂𝐻 groups in glucose?

A. Penta-acetyl derivative of glucose

B. Cyanohydrin formation of glucose

C. Reaction with Fehling's solution

D. Reaction with Tollens' reagent

Answer: Acetylation of glucose with acetic anhydride gives glucose pentaacetate which confirms the presence of five –𝑂𝐻 groups as given in the reaction.

So, option A is the correct answer.

Q 2. Which of the following is correct regarding glucose?

A. The molecular formula of glucose is C₆H₈O₆.

B. It can be obtained by base-catalyzed hydrolysis of cane sugar.

C. It is a mono-saccharide.

D. It can’t be oxidized

Answer: We know that the molecular formula of Glucose is   C₆H₁₂O₆ and it is an easily

accessible monosaccharides. Glucose is a non-oxidizing substance. Furthermore, glucose is classified as a lowering sugar (a sugar that has the ability to act as a reducing agent owing to its free aldehyde group or free ketone group) and can undergo oxidation to form gluconic acid HCOH₂ - (CHOH)₄ - COOH.

So, option C is the correct answer.

Q 3. Glucose is known as _______

A. Aldopentose

B. Aldohexose

C. Ketopentose

D. Ketohexose

Answer: The structure of glucose can be represented as HCOH₂ - (CHOH)₄ - COOH.. It is a molecule containing six carbons in which an aldehyde functional group is present. So we can call such a molecule aldohexose

Option B is the correct answer. 

Q 4. How fructose is different from glucose?

Answer: Glucose is a monosaccharide that contains six carbon atoms and an aldehyde group. Therefore, it is a hexose and an aldose. It has four hydroxyl groups and has the following structure.

On the other hand, fructose is a type of sugar known as hexose. It also contains a keto group, making it a ketose. Fruits, sugar cane, sugar beets, corn, and other foods contain fructose. The structure of fructose is as follows. 

Frequently asked questions :

Q 1. How many carbon atoms are present in glucose?

Answer: We know that the molecular formula of Glucose is C₆H₁₂O₆, so it has 6 carbon atoms.

Q 2. Is glucose a reducing sugar?

Answer: Glucose is a reducing sugar because it is an aldose, which means it has an aldehyde group in its open-chain form. In general, carboxylic acids are quickly oxidised from aldehydes.

Q 3. What exactly are the components of glucose?

Answer: Carbon, hydrogen, and oxygen are the three elements that makeup glucose. 6 carbon atoms are bound together like a chain, with oxygen and hydrogen.

Q 4. What is the source of glucose?

Answer: Glucose or sugar is found in the foods we eat. Carbohydrates including fruit, bread, pasta, and cereals are common sources of glucose. These foods are broken down into sugar in our stomachs and then absorbed into the bloodstream.

Q 5. What is the chemical name of glucose?

Answer: With six carbon atoms and one aldehyde group, glucose is a simple sugar. The molecular formula for this monosaccharide is C₆H₁₂O₆. Dextrose is another name for it. It's called aldohexose because it has six carbon atoms and an aldehyde group.

Q 6.   What is blood sugar and why is it important?

Answer: When we talk about blood sugar levels, we're referring to glucose, the molecule that powers our cells and has a significant impact on our health. At the cellular level, glucose is the fundamental fuel that drives our bodies. We get glucose from the food we eat.

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