What organic substances do not undergo hydrolysis? Hydrolysis of salts and organic compounds

DEFINITION

Hydrolysis- the process of interaction of substances with water, as a result of which it decomposes into “component parts”.

Among all the diversity organic matter capable of hydrolyzing: halogen derivatives of alkanes, esters, alcoholates, carbohydrates, proteins, fats and nucleic acids.

High-molecular substances are decomposed by water into their constituent monomers; in simpler ones, the bonds of carbon with oxygen, halogens, nitrogen, sulfur and other substituents are broken.

Often, organic compounds are hydrolyzed in the presence of acids, alkalis or enzymes - acid, alkaline and enzymatic hydrolysis.

Hydrolysis of organic substances

Haloalkanes undergo hydrolysis in an alkaline environment, resulting in the formation of alcohols. Let's look at the example of chloropentane and chlorophenol:

C5H11Cl + H2O (NaOH) → C5H11OH;

C 6 H 5 Cl + H 2 O (NaOH) → C 6 H 5 OH.

Esters hydrolyze to the carboxylic acids and alcohols that form them. Let's look at the example of methyl ester of acetic acid (methyl acetate):

CH 3 COOCH 3 + H 2 O ↔ CH 3 COOH + CH 3 OH

Alcoholates- derivatives of alcohols, upon hydrolysis, decompose into the corresponding alcohol and alkali. Let's look at the example of sodium alkoxide:

C 2 H 5 ONa + H 2 O ↔ C 2 H 5 OH + NaOH

Carbohydrates hydrolyze starting from disaccharides. Let's look at the example of sucrose:

C 12 H 22 O 11 + H 2 O → C 6 H 12 O 6 (glucose) + C 6 H 12 O 6 (fructose)

Proteins and polypeptides partially undergo hydrolysis, during which amino acids are formed:

CH 2 (NH 2)-CO-NH-CH 2 -COOH + H 2 O ↔ 2CH 2 (NH 2)-COOH

During hydrolysis fat you can get a mixture of higher carboxylic acids and glycerol:

Nucleic acids hydrolyze in several stages. First, nucleotides are produced, then nucleosides, and then purine or pyrimidine bases, orthophosphoric acid and a monosaccharide (ribose or deoxyribose).

Examples of problem solving

EXAMPLE 1

Chemistry, like most exact sciences, which require a lot of attention and solid knowledge, has never been a favorite discipline for schoolchildren. But in vain, because with its help you can understand many processes occurring around and inside a person. Take, for example, the hydrolysis reaction: at first glance it seems that it is important only for chemist scientists, but in fact, without it, no organism could fully function. Let's learn about the features of this process, as well as its practical significance for humanity.

Hydrolysis reaction: what is it?

This phrase refers to a specific reaction of exchange decomposition between water and a substance dissolved in it with the formation of new compounds. Hydrolysis can also be called solvolysis in water.

This chemical term is derived from 2 Greek words: “water” and “decomposition”.

Hydrolysis products

The reaction under consideration can occur during the interaction of H 2 O with both organic and inorganic substances. Its result directly depends on what the water came into contact with, and also whether additional catalyst substances were used, or whether the temperature and pressure were changed.

For example, the hydrolysis reaction of a salt promotes the formation of acids and alkalis. And if we are talking about organic substances, other products are obtained. Aqueous solvolysis of fats promotes the formation of glycerol and higher fatty acids. If the process occurs with proteins, the result is the formation of various amino acids. Carbohydrates (polysaccharides) are broken down into monosaccharides.

In the human body, which is unable to fully assimilate proteins and carbohydrates, the hydrolysis reaction “simplify” them into substances that the body is able to digest. So solvolysis in water plays an important role in the normal functioning of each biological individual.

Hydrolysis of salts

Having learned about hydrolysis, it is worth familiarizing yourself with its occurrence in substances of inorganic origin, namely salts.

The peculiarity of this process is that when these compounds interact with water, the weak electrolyte ions in the salt are detached from it and form new substances with H 2 O. It could be either acid or both. As a result of all this, a shift in the equilibrium of water dissociation occurs.

Reversible and irreversible hydrolysis

In the example above, in the latter you can notice instead of one arrow there are two, both directed in different directions. What does it mean? This sign indicates that the hydrolysis reaction is reversible. In practice, this means that, interacting with water, the taken substance is simultaneously not only decomposed into components (which allow new compounds to arise), but also formed again.

However, not all hydrolysis is reversible, otherwise it would not make sense, since the new substances would be unstable.

There are a number of factors that can contribute to such a reaction becoming irreversible:

• Temperature. Whether it increases or decreases determines in which direction the equilibrium in the ongoing reaction shifts. If it becomes higher, there is a shift towards an endothermic reaction. If, on the contrary, the temperature decreases, the advantage is on the side of the exothermic reaction.
• Pressure. This is another thermodynamic quantity that actively influences ionic hydrolysis. If it increases, the chemical equilibrium is shifted towards the reaction, which is accompanied by a decrease in the total amount of gases. If it goes down, vice versa.
• High or low concentration of substances involved in the reaction, as well as the presence of additional catalysts.

Types of hydrolysis reactions in saline solutions

• By anion (ion with a negative charge). Solvolysis in water of salts of acids of weak and strong bases. Due to the properties of the interacting substances, such a reaction is reversible.

Degree of hydrolysis

When studying the features of hydrolysis in salts, it is worth paying attention to such a phenomenon as its degree. This word implies the ratio of salts (which have already entered into a decomposition reaction with H 2 O) to the total amount of this substance contained in the solution.

The weaker the acid or base involved in hydrolysis, the higher its degree. It is measured in the range of 0-100% and is determined by the formula presented below.

N is the number of molecules of a substance that have undergone hydrolysis, and N0 is their total number in the solution.

In most cases, the degree of aqueous solvolysis in salts is low. For example, in a 1% sodium acetate solution it is only 0.01% (at a temperature of 20 degrees).

Hydrolysis in substances of organic origin

The process under study can also occur in organic chemical compounds.

In almost all living organisms, hydrolysis occurs as part of energy metabolism (catabolism). With its help, proteins, fats and carbohydrates are broken down into easily digestible substances. At the same time, water itself is rarely able to start the process of solvolysis, so organisms have to use various enzymes as catalysts.

If we are talking about a chemical reaction with organic substances aimed at producing new substances in a laboratory or production environment, then strong acids or alkalis are added to the solution to speed up and improve it.

Hydrolysis in triglycerides (triacylglycerols)

This difficult-to-pronounce term refers to fatty acids, which most of us know as fats.

They come in both animal and plant origin. However, everyone knows that water is not capable of dissolving such substances, so how does fat hydrolysis occur?

The reaction in question is called saponification of fats. This is aqueous solvolysis of triacylglycerols under the influence of enzymes in an alkaline or acidic environment. Depending on it, alkaline and acid hydrolysis are distinguished.

In the first case, the reaction results in the formation of salts of higher fatty acids (better known to everyone as soaps). Thus, ordinary solid soap is obtained from NaOH, and liquid soap is obtained from KOH. So alkaline hydrolysis in triglycerides is the process of forming detergents. It is worth noting that it can be freely carried out in fats of both plant and animal origin.

The reaction in question is the reason that soap washes rather poorly in hard water and does not wash at all in salt water. The fact is that hard is called H 2 O, which contains an excess of calcium and magnesium ions. And soap, once in the water, again undergoes hydrolysis, breaking down into sodium ions and a hydrocarbon residue. As a result of the interaction of these substances, insoluble salts are formed in water, which look like white flakes. To prevent this from happening, sodium bicarbonate NaHCO 3, better known as baking soda. This substance increases the alkalinity of the solution and thereby helps the soap perform its functions. By the way, to avoid such troubles, in modern industry synthetic detergents are made from other substances, for example from salts of esters of higher alcohols and sulfuric acid. Their molecules contain from twelve to fourteen carbon atoms, due to which they do not lose their properties in salty or hard water.

If the environment in which the reaction occurs is acidic, the process is called acid hydrolysis of triacylglycerols. In this case, under the influence of a certain acid, the substances evolve to glycerol and carboxylic acids.

Hydrolysis of fats has another option - the hydrogenation of triacylglycerols. This process is used in some types of purification, such as removing traces of acetylene from ethylene or oxygen impurities from various systems.

Hydrolysis of carbohydrates

The substances in question are among the most important components of human and animal food. However, sucrose, lactose, maltose, starch and glycogen in pure form the body is unable to assimilate. Therefore, as in the case of fats, these carbohydrates are broken down into digestible elements using a hydrolysis reaction.

Aqueous solvolysis of carbons is also actively used in industry. From starch, as a result of the reaction in question with H 2 O, glucose and molasses are extracted, which are included in almost all sweets.

Another polysaccharide that is actively used in industry for the manufacture of many useful substances and products is cellulose. Technical glycerin, ethylene glycol, sorbitol and the well-known ethyl alcohol are extracted from it.

Hydrolysis of cellulose occurs with prolonged exposure high temperature and the presence of mineral acids. The end product of this reaction is, as in the case of starch, glucose. It should be taken into account that the hydrolysis of cellulose is more difficult than that of starch, since this polysaccharide is more resistant to mineral acids. However, since cellulose is the main component of the cell walls of all higher plants, the raw materials containing it are cheaper than for starch. At the same time, cellulose glucose is more used for technical needs, while the product of starch hydrolysis is considered better suited for nutrition.

Protein hydrolysis

Proteins are the main building material for the cells of all living organisms. They consist of numerous amino acids and are very important product for the normal functioning of the body. However, being high-molecular compounds, they can be poorly absorbed. To simplify this task, they are hydrolyzed.

As with other organic substances, this reaction breaks down proteins into low molecular weight products that are easily absorbed by the body.

Hydrolysis
called
reactions
exchange
interaction
substances with water that lead to their
decomposition.

Peculiarities

Hydrolysis of organic
substances
Living organisms carry out
hydrolysis of various organic
substances during reactions at
participation of ENZYMES.
For example, during hydrolysis at
participation of digestive
enzymes PROTEINS are broken down
on AMINO ACIDS,
FATS - for GLYCEROL and
FATTY ACID,
POLYSACCHARIDES (eg.
starch and cellulose) - on
MONOSACHARIDES (for example,
GLUCOSE), NUCLEIN
ACIDS - to free
NUCLEOTIDES.
During the hydrolysis of fats in
presence of alkalis
get soap; hydrolysis
fats in the presence
catalysts used
to obtain glycerol and
fatty acids. Hydrolysis
wood produces ethanol, and
peat hydrolysis products
find application in
feed production
yeast, wax, fertilizers and
etc.

Hydrolysis of organic compounds

fats are hydrolyzed to produce glycerol and
carboxylic acids (with NaOH – saponification).
starch and cellulose are hydrolyzed to
glucose:

Reversible and irreversible hydrolysis

Almost all hydrolysis reactions
organic matter
reversible. But there is also
irreversible hydrolysis.
General property of irreversible
hydrolysis - one (preferably both)
from hydrolysis products should
be removed from the sphere of reaction
as:
- DRAFT,
- GAS.
CaС₂ + 2Н₂О = Ca(OH)₂↓ + С₂Н₂
During hydrolysis of salts:
Al₄C₃ + 12 H₂O = 4 Al(OH)₃↓ + 3CH₄
Al₂S₃ + ​​6 H₂O = 2 Al(OH)₃↓ + 3 H₂S
CaH₂ + 2 H₂O = 2Ca(OH)₂↓ + H₂

G I D R O L I S S O L E Y

HYDROLYSIS OF SALT
Hydrolysis of salts -
type of reactions
hydrolysis due
the course of reactions
ion exchange in solutions
(aqueous) soluble
electrolyte salts.
Driving force of the process
is interaction
ions with water, leading to
education of the weak
electrolyte in ionic or
molecular form
(“ion binding”).
There are reversible and
irreversible hydrolysis of salts.
1. Hydrolysis of weak salt
acid and strong base
(hydrolysis by anion).
2. Hydrolysis of strong salt
acid and weak base
(hydrolysis by cation).
3. Hydrolysis of weak salt
acid and weak base
(irreversible).
Salt of a strong acid and
no strong reason
undergoes hydrolysis.

Reaction equations

Hydrolysis of a salt of a weak acid and a strong base
(hydrolysis by anion):
(the solution is alkaline, the reaction proceeds
reversible, hydrolysis in the second stage proceeds in
insignificant degree).
Hydrolysis of a salt of a strong acid and a weak base
(hydrolysis by cation):
(the solution is acidic, the reaction is reversible,
hydrolysis at the second stage proceeds in negligible
degrees).

10.

Hydrolysis of a salt of a weak acid and a weak base:
(equilibrium is shifted towards products, hydrolysis
leaks almost completely, since both products
reactions leave the reaction zone in the form of a precipitate or
gas).
The salt of a strong acid and a strong base is not
undergoes hydrolysis, and the solution is neutral.

11. SODIUM CARBONATE HYDROLYSIS SCHEME

Na₂CO₃
NaOH
strong foundation
H₂CO₃
weak acid
ALKALINE ENVIRONMENT
ACIDIC SALT, hydrolysis by
ANION

12. SCHEME FOR HYDROLYSIS OF COPPER (II) CHLORIDE

CuCl₂
Cu(OH)₂↓
weak foundation
HCl
strong acid
ACIDIC MEDIUM
BASIC SALT, hydrolysis according to
CATION

13. SCHEME FOR HYDROLYSIS OF ALUMINUM SULPHIDE

Al₂S₃
Al(OH)₃↓
weak foundation
H₂S
weak acid
NEUTRAL REACTION
ENVIRONMENTS
irreversible hydrolysis

14.

ROLE OF HYDROLYSIS IN NATURE
Transformation of the earth's crust
Providing a slightly alkaline marine environment
water
ROLE OF HYDROLYSIS IN LIFE
PERSON
Wash
Washing dishes
Washing with soap
Digestive processes

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Lesson type: a lesson in mastering new knowledge and consolidating the material being studied.

Lesson Objectives :

Educational: form a concept about the hydrolysis of organic substances, teach how to draw up equations for the reactions of hydrolysis of various organic substances. Deepen students' knowledge about reversible chemical reactions. Improve your skills in working with test tasks of various types.

Educational: develop in students the ability to compare and analyze theoretical information, apply it in practice, and draw conclusions; highlight the main thing in the process of demonstrating experience, develop logical thinking.

Educational: to form a natural scientific worldview; information culture.

During the classes

Hydrolysis….

What substances?

Lesson topic: “Hydrolysis of organic substances.”

Knowing the topic of the lesson, select from the list of words that correspond to this topic (underline them) and give them a definition.

, pyrolysis, polycondensation, water, wax, alkanes, decomposition, exchange, connection.

Find these words in the given text and underline them.

Hydrolysis of organic substances

Living organisms hydrolyze various organic substances during reactions starring . For example, during hydrolysis with the participation of digestive enzymes split into , - on And , (for example, and) - on (for example, on), - on free. When hydrolyzed in the presence of ; hydrolysis of fats in the presence is used to obtain and. By hydrolysis of wood it is obtained , and the products are used in the production of feed, , and etc.

Did you define the words correctly?

Homework:

From scientific text you have chosen words unknown to you, find their definition in information sources and compile a dictionary of unknown words.

Compose several tasks (for ratios) based on the text “Hydrolysis of esters”:

Historically, the first example of such a reaction was the alkaline cleavage of higher fatty acid esters to produce soap. This happened in 1811, when the French scientist E. Chevreul. By heating fats with water in an alkaline environment, he obtained glycerin and soaps - salts of higher carboxylic acids. Based on this experiment, the composition of fats was established; they turned out to be esters, but only “triple esters,” derivatives of the trihydric alcohol glycerol - triglycerides. And the process of hydrolysis of esters in an alkaline environment is still called “saponification.”

For example, saponification of an ester formed by glycerin, palmitic and stearic acids:

Sodium salts of higher carboxylic acids are the main components of solid soap, potassium salts are the main components of liquid soap.

The French chemist M. Berthelot in 1854 carried out the esterification reaction and synthesized fat for the first time. Consequently, the hydrolysis of fats (as well as other esters) is reversible. The reaction equation can be simplified as follows:

Enzymatic hydrolysis of fats occurs in living organisms. In the intestine, under the influence of the lipase enzyme, food fats are hydrated into glycerol and organic acids, which are absorbed by the intestinal walls, and new fats characteristic of the given organism are synthesized in the body. They travel through the lymphatic system into the blood and then into the adipose tissue. From here, fats enter other organs and tissues of the body, where, in the process of metabolism in cells, they are again hydrolyzed and then gradually oxidized to carbon monoxide and water, releasing the energy necessary for life.

In technology, hydrolysis of fats is used to obtain glycerin, higher carboxylic acids, and soap.

Used Books:

Textbook “Chemistry 11th grade. A basic level of",O.S. Gabrielyan, Moscow 2007, Bustard.

“Teacher's handbook. Chemistry 11th grade” Part 1,O.S. Gabrielyan, G.G. Lysova, A.G. Vvedenskaya , M.: 2003, Bustard.

“We are preparing for the unified state exam. Chemistry”,O.S. Gabrielyan, P.V. Reshetnikov, I.G. Ostroumova, A.M. Nikityuk , M.: 2004, Bustard.

Textbook “Chemistry 11th grade”,O.S. Gabrielyan, G.G. Lysova M. : 2002, Bustard.

“Educational and methodological manual in chemistry for specialized training in medical and biological classes”, Krasnodar 2008, compiled by professorT.N. Litvinova , manager Department of General Chemistry KSMU.