Glucozo là gì? Công thức, cấu tạo, tính chất và vai trò của glucozo

Glucose exists in most parts of humans, plants and animals. So what is glucose? Let's learn about the formula, structure, properties and roles of this important substance.

What is the definition of glucose?

Glucose (also known as dextrose) is the most common monosaccharide with the molecular formula C6H12O6. Glucose is mainly produced by plants and most algae during photosynthesis from water and CO2, using energy from sunlight. There it is used to make cellulose in cell walls and starch.

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In energy metabolism, glucose is the most important raw material source in all organisms to generate energy during cellular respiration. In plants it is stored mainly as cellulose and starch, and in animals it is stored in glycogen. (Source: Wikipedia)

• The molecular formula of glucose is: C6H12O6

• Molecular mass: 180

• Structural characteristics: The molecular structure of glucose is determined based on the results of the following experiments:

• Glucose participates in the silvering reaction and is oxidized by bromine water to form gluconic acid. From there, it shows that glucose has a CH=O group in the molecule.

• Glucose reacts with Cu(OH)2 to create a blue solution, this proves that the glucose molecule has many OH groups in adjacent positions.

• Glucose forms an ester containing 5 CH3COO acid residues. Thus, in the structure of glucose there are 5 OH groups.

• When glucose is completely reduced, hexane => 6 C is obtained, forming an unbranched chain.

From the above experiments, we have concluded: Glucose is a functional compound, in an acyclic molecular form with the structure of a monofunctional aldehyde and a 5-functional alcohol with the formula: CH2OH – CHOH – CHOH – CHOH – CHOH – CH=O

Abbreviated as: CH2OH(CHOH)4CHO

In which, people number the carbon starting from the CH=O group.

In fact, glucose exists mainly in two cyclic forms: α – glucose and β – glucose.

Natural state and physical properties of glucose

In nature, where does glucose appear? Let's learn about the natural state and physical properties of this substance.

Glucose exists in abundance in natural fruits, especially ripe grapes. (Photo: Internet Collection)

Natural state of glucose

• Glucose appears in most parts of plants, especially ripe fruits. In particular, glucose is abundant in ripe grapes, so it is also called grape sugar.

• Glucose accounts for 30% of the composition of honey.

• Humans and animals also contain glucose in their bodies.

Physical properties

Glucose is a colorless crystalline substance, easily soluble in water, and has a sweet taste but is milder than cane sugar.

Chemical properties of glucose

It has been proven that glucose has the typical chemical properties of polyfunctional alcohols and aldehydes through the experiments below.

Properties of polyfunctional alcohols

In solution, at normal temperature glucose dissolves Cu(OH)2 to give a blue copper-glucose complex solution:

2C6H12O6 + Cu(OH)2 → (C6H11O6)2Cu + 2H2O

C6H7O(OH)5 + 5(CH3CO)2O → C6H7O(OOCCH3)5 + 5CH3COOH

=> The reaction shows that glucose contains 5 -OH radicals

Properties of aldehydes

Glucose participates in silvering reactions, reduction reactions, alcoholic fermentation…

Glucose oxidation reaction

AgNO3 solution has the ability to oxidize Glucose in NH3 environment. The products formed are ammonium gluconate salt and silver. We can observe that they will stick to the walls of the test tube.

Equation:

CH2OH[CHOH]4CHO + 2AgNO3 + 3NH3 + H2O (condition: big) → CH2OH[CHOH]4COONH4 + 2Ag + 2NH4NO3

Glucose is oxidized by Cu(OH)2 in alkaline medium. The reaction results in sodium gluconate salt, copper (I) oxide and H2O.

Equation:

CH2OH[CHOH]4CHO + 2Cu(OH)2 + NaOH (condition: temperature)→ CH2OH[CHOH]4COONa + Cu2O ↓ (brick red) + 3H2O

Equation:

CH2OH[CHOH]4CHO + Br2 + 2H2O → CH2OH[CHOH]4COOH + 2HBr

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When hydrogen gas is introduced into a heated glucose solution with the addition of a Ni catalyst, we will obtain a polyancol also called sobitol.

Equation:

CH2OH[CHOH]4CHO + H2 (condition: to, Ni) → CH2OH[CHOH]4CH2OH

Alcohol fermentation reaction

When there is a catalytic enzyme, glucose will be fermented, creating the products ethyl alcohol and carbon dioxide.

Equation:

C6H12O6 (condition: enzyme, 30-35 degrees Celsius) → 2C2H5OH + 2CO2 ↑

See more:

How to prepare glucose

In industry and in nature, glucose preparation methods are different. Therefore, quality and price are two factors that we need to consider during use.

• In industry: Glucose is prepared by hydrolyzing starch using enzymes or dilute hydrochloric acid (HCl). Besides, people also hydrolyze cellulose (found in wood chips and sawdust) by catalyzing concentrated hydrochloric acid into glucose as a raw material for ethanol production.

Glucose preparation equation:

(C6H10O5)n + nH2O (temperature, H+)→ nC6H12O6

6CO2 + 12H20 (sunlight)→ C6H12O6 + 6O2 + 6H20

Roles and applications of glucose in life and production

Glucose was first isolated from raisins in 1747 by German chemist Andreas Marggraf. Glucose was discovered in grapes by Johann Tobias Lowitz in 1792 and was recognized as different from sucrose (according to Wikipedia). Since then, glucose has had particularly important applications in industry and medicine.

The role of glucose in industry

• Glucose is used to produce ethyl alcohol from starch or cellulose.

• In the food industry, glucose is used as a preservative.

• Glucose helps mixtures containing sugar avoid “sugar retention” – the phenomenon of small sugar particles emerging when left for a long time. At the same time, glu also helps candies dry out longer and retain their softness.

• Glucose is also used in the ice cream making process to keep the water and sugar mixture smooth.

• Glucose is used to coat mirrors and thermoses.

The role of glucose in medicine

• Glucose contains basic nutrients that help create energy for the body to function better, so it is used to make energy boosters for children, the elderly and even people with physical weakness.

• Glucose is used to mix serum (used in medical infusion).

• Glucose is used to produce vitamin C.

The role of glucose in humans

• Glucose is the body's main and direct source of energy, stored in the liver in the form of glycogen.

• Is a component participating in the structure of cells (RNA and DNA) and some other special substances (such as Mucopolysaccharide, heparin, hyaluronic acid, chondroitin…).

• Generates the energy necessary for life – a process that takes place in cells. The use of glucose by cells depends on the activity of cell membranes under the influence of insulin (except for brain cells, nerve cells, blood cells, kidney medulla and lens).

Glucose – Fructose isomers

After learning about glucose, let's learn about Fructose – the isomer of Glucose. In the general formula Cx(H2O)y, both of these compounds have x = 6, y = 6 and are both monosaccharides, but what is the difference between them?

Molecular formula: C6H12O6.

Fructose will have the following open-chain structural formula:

CH2OH – CHOH – CHOH – CHOH – CO – CH2OH

In solution, fructose exists mainly in the β, 5- or 6-membered ring form.

Unlike glucose, the typical physical properties of fructose are:

• Fructose is a colorless crystal, easily soluble in water, and tastes sweeter than cane sugar.

• They exist in abundance in sweet fruits and account for up to 40% of honey.

• Fructose is one and a half times sweeter than cane sugar and 2.5 times sweeter than glucose.

Chemical properties of Fructose:

The fructose molecule consists of 5 OH groups. There are 4 adjacent groups and 1 C = O functional group, so it has the chemical properties of polyfunctional alcohols and ketones. Fructose has properties similar to glucose.

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  Fructose dissolves Cu(OH)2 at room temperature.

• Reacts with acid anhydride to form 5-function ester.

• Properties of ketones: Reacts with H2 to create sobitol and participates in the HCN addition reaction

• In neutral or acidic environments, fructose does not show the reducing properties of aldehydes, but in alkaline environments, fructose has this property due to the conversion between glucose and fructose mediated by an endiol.

Note: In an alkaline environment, fructose is converted into glucose, so fructose has a mirror reaction and reacts with Cu(OH)2 in an alkaline environment. But fructose does not react to discolor Bromine solution. This is a sign to recognize fructose and glucose.

Exercises about glucose in Chemistry Textbook Grade 9 with solutions

From the knowledge about glucose above, you can apply that knowledge to solve some basic exercises in the following grade 9 chemistry textbook.

Solve Lesson 1, page 152, Chemistry Textbook Grade 9

Name some ripe fruits that contain glucose.

Suggested answer:

Glucose is found in some ripe fruits such as: ripe grapes, ripe bananas, ripe guava, ripe jackfruit, ripe custard apple (custard apple), ripe pineapple (pineapple).

Solve lesson 2 Chemistry 9 textbook page 152

Choose a reagent to chemically differentiate the following solutions. (Specify how to proceed).

a) Glucose solution and ethyl alcohol solution.

b) Glucose solution and acetic acid solution.

Suggested answer:

a) Extract test samples and number them:

Choose the reagent AgNO3 in NH3 solution (heat): Add a few drops of AgNO3 in NH3 solution into 2 test tubes one by one and place the test tubes in a cup of hot water:

The substance that participates in the reaction to create a product with a bright silvery color that sticks to the test tube wall is glucose

PTHH: C6H12O6 + Ag2O —> C6H12O7 + 2Ag (catalyst: NH3)

The remaining inactive substance is ethyl alcohol.

b) Extract test samples and number them:

Choose Na2CO3 as reagent: Add a few drops of Na2CO3 solution into 2 test tubes

Which test tube has the reaction that gives off gas called CH3COOH?

PTHH: 2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2

The remaining substance that does not react is glucose

(You can use red litmus as a reagent. The solution that changes the color of red litmus to red is CH3COOH. The remaining substance that does not change the color of red litmus is glucose).

Solve lesson 3 of Chemistry Textbook 9, page 152

Calculate the mass of glucose needed to prepare 500ml of 5% glucose solution with D = 1.0 g/cm3.

Suggested answer:

mdd glucose = 500. 1 = 500 (g)

mgglucose = (500.5) / 100 = 25 (g)

Solve Lesson 4, page 152, Chemistry Textbook Grade 9

When fermenting glucose, 11.2 liters of CO2 gas is released under standard conditions.

a) Calculate the mass of ethyl alcohol produced after fermentation.

b) Calculate the mass of glucose taken initially, knowing that the fermentation efficiency is 90%.

Suggested answer:

a) Volume of ethyl alcohol:

n(CO2) = 11.2 / 22.4 = 0.5 mol

Glucose fermentation equation:

C6H12O6 → 2C2H5OH + 2CO2.

According to the equation: n(ethyl alcohol) = nCO2 = 0.5 mol.

m(ethyl alcohol) = 0.5 × 46 = 23g.

b) Mass of glucose.

According to the equation glucose = 1/2. nCO2 = 1/2. 0.5 = 0.25 mol

Because the efficiency is 90%, the amount of glucose needed is:

0.25 x 180 x 100/90 = 50g

The above article has provided complete information about the formula, structure, properties, and role of glucose – a substance that is extremely commonly used around us. Share the article and visit the timhieulichsuquancaugiay.edu.vn website to gain more useful knowledge about other subjects such as math, physics, and chemistry in classes!

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