Chemistry, like most exact sciences, requiring a lot of attention and solid knowledge, has never been a favorite discipline of students. But in vain, because with its help you can understand the many processes taking place around and inside a person. Take, for example, the hydrolysis reaction: at first glance, it seems that it matters only to chemical scientists, but in fact, without it, no organism could fully function. Let's find out about the features of this process, as well as its practical significance for humanity.
Hydrolysis reaction: what is it?
This phrase is a specific reaction of the 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 in question can occur during the interaction of H 2 O with both organic and inorganic substances. Its result directly depends on what the water was in contact with, as well as whether additional catalyst substances were used, and whether the temperature and pressure changed.
For example, the salt hydrolysis reaction promotes the formation of acids and alkalis. And when it comes to organic substances, other products are obtained. Aqueous solvolysis of fats contributes to the occurrence of glycerol and higher fatty acids. If the process occurs with proteins, various amino acids are formed as a result. Carbohydrates (polysaccharides) are decomposed into monosaccharides.
In a human body that is unable to fully absorb proteins and carbohydrates, the hydrolysis reaction “simplifies” them to 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 what the hydrolysis reaction is , it is worth familiarizing yourself with its course in substances of inorganic origin, namely salts.
The peculiarity of this process is that during the interaction of these compounds with water, weak electrolyte ions in the composition of the salt detach from it and form new substances with 2 . It could be either acid, or a weak base, or both. As a result of all this, a shift in the equilibrium of dissociation of water occurs.
Reversible and irreversible hydrolysis
In the above example, in the last hydrolysis equation , two arrows can be seen instead of one arrow, both of which are 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 simultaneously not only decomposes into components (which allow new compounds to appear), but also forms again.
However, not every hydrolysis is reversible, otherwise it would not make sense, since new substances would be unstable.
There are a number of factors that can help make such a reaction irreversible:
- Temperature. From which it rises or falls, depends on which side the equilibrium shifts in the ongoing reaction. If it becomes higher, there is a shift to the 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 affects ion hydrolysis. If it rises, 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. Such a reaction is reversible due to the properties of the interacting substances.
- By cation (ion with a positive charge). Hydrolysis of a strong acid salt and a weak base. It is also reversible.
- The reaction of a salt of a weak acid and a weak base. Such a process can be considered practically irreversible, since all newly formed substances leave the so-called reaction zone, precipitating or turning into gas.
- If both the base and the acid salt are strong, aqueous solvolysis does not occur in such a solution.
Degree of hydrolysis
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 the decomposition reaction with H 2 O) to the total amount of this substance in 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 below.
N is the number of molecules of the substance that underwent hydrolysis, and N 0 is their total number in solution.
In most cases, the degree of aqueous solvolysis in the salts is small. For example, in a solution of sodium acetate 1% it is only 0.01% (at a temperature of 20 degrees).
Hydrolysis in substances of organic origin
The studied process can 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. Moreover, often the 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 obtaining new substances in a laboratory or production environment, then to accelerate and improve it, strong acids or alkalis are added to the solution.
Hydrolysis in triglycerides (triacylglycerols)
This hard-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 able to dissolve such substances, how does hydrolysis of fats occur?
The reaction in question is called saponification of fats. This is an aqueous solvolysis of triacylglycerols under the influence of enzymes in an alkaline or acidic environment. Depending on it, alkaline hydrolysis and acid are released.
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 a process of detergent formation. It is worth noting that it can be freely carried out in fats of both plant and animal origin.
The reaction under consideration is the reason that the soap does not wash well enough in hard water and generally does not lather 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 water, is again hydrolyzed, decomposing into sodium ions and a hydrocarbon residue. As a result of the interaction of these substances in water, insoluble salts are formed, which look like white flakes. To prevent this from happening, sodium bicarbonate NaHCO 3 , better known as baking soda, is added to the water. This substance increases the alkalinity of the solution and thereby helps the soap perform its functions. By the way, in order 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, so that they do not lose their properties in salt or hard water.
If the environment in which the reaction occurs is acidic, such a process is called acid hydrolysis of triacylglycerols. In this case, under the action of a certain acid, substances evolve to glycerol and carboxylic acids.
Fat hydrolysis has another option - this is the hydrogenation of triacylglycerols. This process is used in some types of purification, for example, when removing traces of acetylene from ethylene or oxygen impurities from various systems.
Hydrolysis of carbohydrates
The substances under consideration are one of the most important components of human and animal food. However, sucrose, lactose, maltose, starch and glycogen in its pure form, the body is not able to absorb. Therefore, as in the case of fats, these carbohydrates are broken down into digestible elements by the hydrolysis reaction.
Also, aqueous solvolysis of carbon is actively used in industry. From starch, due to the reaction with H 2 O, glucose and molasses are extracted, which are part of 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, fodder yeast, sorbitol and ethyl alcohol, well known to all, are extracted from it.
Cellulose hydrolysis occurs with prolonged exposure to high temperature and the presence of mineral acids. The end product of this reaction is, as is the case with starch, glucose. It should be borne in mind 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 starch hydrolysis product is considered to be better suitable for food.
Protein hydrolysis
Proteins are the main building material for the cells of all living organisms. They consist of numerous amino acids and are a very important product for the normal functioning of the body. However, being high molecular weight compounds, they can be poorly absorbed. To simplify this task, their hydrolysis occurs.
As in the case of other organic substances, this reaction destroys proteins to low molecular weight products that are easily absorbed by the body.