Organic acids in the life of each of us. Organic and inorganic acids Organic acids list from a to z

Carboxylic acids – these are organic compounds containing in the molecule a carboxyl group –COOH, which is a functional group.

Acids can be mono- and polybasic, saturated, unsaturated, aromatic, etc.

Homologous series of monobasic organic acids: formic HCOOH, acetic CH 3 COOH, butyric C 3 H 7 COOH, palmitic C 15 H 31 COOH, stearic C 17 H 35 COOH.

Homologous series of dibasic acids: oxalic COOH–COOH, malonic COOH–CH 2 –COOH, succinic COOH–(CH 2) 2 –COOH.

Unsaturated acids contain one or more multiple bonds in the radical: CH 2 =CH–COOH – acrylic; C 17 H 33 COOH – oleic; C 17 H 31 COOH - linoleic, etc.

Aromatic acids begin their homologous series with benzoic acid, and then there is an extension of the side chain or the addition of methyl radicals to the benzene ring.

Physical properties. Lower monocarboxylic acids (C 1 – C 9) are colorless liquids with a specific odor, soluble in water. Higher aliphatic and aromatic acids are solids and are insoluble in water.

Chemical properties. All organic acids have acidic properties, which are influenced by many factors, such as the structure of the radical (size and presence of substituents). Organic acids easily form salts:

2CH 3 COOH + Zn(CH 3 COO) 2 Zn+ H 2;

CH 3 COOH + NaOHCH 3 COONa + H 2 O;

2CH 3 COOH + CuO(CH 3 COO) 2 Cu+ H 2 O,

esters (esterification reaction):

benzoic acid methyl benzoate

acid anhydrides:

acetic anhydride

Anhydrides are used to produce artificial fibers and medicines.

Preparation of acid amides:

acetamide

Saturated hydrocarbon radicals of acids can undergo radical substitution reactions with halogens:

2-chloroethanoic acid (chloroacetic acid)

G The –COOH group, as an orienting agent of the second kind, has a meta-orienting effect:

m-bromobenzoic acid

m-sulfobenzoic acid

Dibasic organic acids.

Dicarboxylic acids – crystalline substances soluble in water. Representatives of acids: HOOS–COOH – oxalic acid, HOOS–(CH 2) 2 –COOH – succinic acid, C 6 H 4 (COOH) 2 – terephthalic acid.

Oxalic acid is found in the leaves of sorrel, sorrel, and rhubarb. Succinic acid is an intermediate product of the biological breakdown of proteins, carbohydrates and fats, found in amber, brown coal, in many plants, especially in unripe fruits, and is a useful component for the life of the body.

Chemical properties dicarboxylic acids are similar to monocarboxylic acids, but reactions can occur with the participation of one or two carboxyl groups at the same time:

HOOC–COOH + 2NaOHNaOOC–COONa+ 2H 2 O.

sodium oxalate

Esters of dibasic acids are thermally unstable. The decarboxylation reaction occurs when heated:

oxalic acid formic acid

Dibasic aromatic acids – phthalic and terephthalic are widely used in organic synthesis.

Phthalic acid V industry is obtained from o-xylene or naphthalene by oxidation:

Phthalic acid derivatives are used to produce plasticizers for polyvinyl chloride and as repellents; are the starting material for the technical synthesis of indigo dyes, phenolphthalein, fluorescein and other substances.

Terephthalic acid is obtained mainly by isomerization of the potassium salt of phthalic acid at 400°C. It can also be obtained by oxidation of p-xylene with atmospheric oxygen.

catalyst

Terephthalic acid is used in large quantities for the synthesis of lavsan by condensation with ethylene glycol.

remainder balance

terephthalic acid ethylene glycol

When phthalic anhydride condenses with phenol, phenolphthalein (an indicator and laxative) is formed.

phthalic anhydride phenolphthalein

Unsaturated carboxylic acids. Unsaturated acids are characterized by the general properties of carboxylic acids and the properties of unsaturated hydrocarbons - the formation of salts, esters, polymers and addition reactions, etc.

The simplest representative of unsaturated monobasic carboxylic acids is acrylic acid, which has the ability to easily polymerize:

Representatives of unsaturated carboxylic acids are found in fats, such as oleic, linoleic and linolenic acids.

Formic acid (HCOOH) is a colorless liquid with a pungent odor and pungent taste.

Formic (methane) acid is found in a free state in the body of ants, nettles and in small quantities in the urine and sweat of animals.

Alcohol solutions of acid (1.25%) are used in the treatment of rheumatism. The acid is used in the textile industry.

Formic acid is a good preservative for succulent and wet food.

Formic acid is produced industrially by the action of carbon monoxide (II) on a hot solution of sodium hydroxide under pressure.

Acetic (ethanoic) acid CH 3 COOH is obtained in various ways:

a) acetic acid fermentation of sugars,

b) dry distillation of wood,

c) from acetylene (according to Kucherov’s reaction).

Pure acetic acid is a colorless liquid with a pungent odor. Anhydrous acetic acid can exist in a solid state (mp. 16.6 ° C) - it is called glacial acetic acid.

Acetic acid is used in everyday life, food, chemical, leather, textile industries, and is used for the synthesis of a number of drugs and artificial fibers.

Salts of this acid are used for mordant dyeing in the textile industry. Some salts (copper and other metals) are used to control agricultural pests. Esters of acetic acid are used as solvents for varnishes and paints.

Basic copper acetate (CH 3 COO) 2 Cu-Cu(OH) 2 - Paris green - is poisonous and is used to control plant pests and as a dye.

Butyric acid C 3 H 7 COOH is part of cow butter as a complex triglyceride; in a free state it is found in rancid butter and in sweat, and has an unpleasant odor.

Palmitic Andstearic acid (C 15 H 31 COOH, C 17 H 35 COOH) – tasteless and odorless solids. Their mixture is called stearin. Palmitic acid is found in spermaceti and beeswax. Their glycerol esters are the main components of fats.

Benzoic acid C 6 H 5 COOH is obtained by the oxidation of toluene. This solid crystalline substance sublimes easily, is almost odorless, is used for the preparation of dyes, has antiseptic properties, therefore it is used in medicine and in food preservation, and is the starting material for the production of saccharin.

Acrylic acid – unsaturated acid CH 2 = CHCOOH is obtained synthetically. It is a liquid with a pungent odor and easily polymerizes. Esters of polyacrylic acid are used in the production of plastics; they are transparent. The best plexiglass is considered to be plexiglass–polymethacrylic acid methyl ester:

Oleic acid C 17 H 33 COOH is part of almost all natural fats (in olive oil up to 80%). Pure oleic acid is an oily liquid without taste or odor.

Found in pure form in plants, as well as taking the form of salts or esters - organic compounds

In a free state, such polybasic hydroxy acids are often found in fruits, while the compounds are characteristic primarily of other plant elements such as stems, leaves, and so on. If you look at organic acids, their list is constantly growing and, in general, is not closed, that is, it is regularly replenished. Such acids have already been discovered:

Adipic,

Benzoinaya,

Dichloroacetic,

Valerian,

Glycolic,

Glutarovaya,

Lemon,

Maleic,

Margarine,

Oily,

Dairy,

Monochloroacetic,

Ant,

Propionic,

Salicylic acid,

Trifluoroacetic,

Fumarovaya,

Vinegar,

Sorrel,

Apple,

Succinic and many other organic acids.

Often such substances can be found in fruit and berry plants. Fruit plants include apricots, quince, cherry plum, grapes, cherries, pears, citrus fruits and apples, while berry plants include lingonberries, cherries, blackberries, cranberries, gooseberries, raspberries, black currants. They basically contain tartaric, citric, salicylic, oxalic and organic acids. The berries also contain organic acids, including many

To date, many properties of acids have been studied directly in the field of pharmacology and biological effects on the human body. For example:

• firstly, organic acids are quite significant components of metabolism (metabolism, namely proteins, fats and carbohydrates);
• secondly, they cause secretory activity of the salivary glands; promote acid-base balance;
• thirdly, they take a significant part in increasing the secretion of bile, gastric and pancreatic juices;
• and finally, they are antiseptics.

Their acidity ranges from four point four to five point five.

In addition, organic acids play an important role in the food industry, acting as a direct detector of the quality or poor quality of products. For the latter, the method of ion chromatography is very often used, in which not only organic acids, but also inorganic ions can be detected at a time. With this method, conductometric detection with suppression of background electrical conductivity shows a result almost ten times more accurate than detection at low wavelengths of ultraviolet radiation.
Identifying the profile of organic acids in fruit juices is necessary not only to establish the quality of the drink and its acceptability for consumption, but also helps to identify counterfeits.
If we consider directly the properties of carboxylic acids, then they primarily include:

Giving red color to litmus paper;

Easy solubility in water;

Present sour taste.

They are also a fairly important electrical conductor. In terms of the strength of decay, absolutely all acids belong to the weak group of electrolytes, with the exception, of course, of formic acid, which in turn occupies an average value in intensity. The height of the molecular weight of the carboxylic acid affects the force of decomposition and has an inversely proportional relationship. With the help of specifically defined metals, it becomes possible to separate hydrogen and salt from acids, which occurs much more slowly than when interacting with something like sulfuric or hydrochloric acid. Salts also appear when exposed to basic oxides and bases.

DEFINITION

Acids– electrolytes, upon dissociation of which only H + ions are formed from positive ions:

HNO 3 ↔ H + + NO 3 —

CH 3 COOH↔ H + +CH 3 COO —

Classification of acids

Acids are primarily classified into inorganic and organic (carbonic). Organic compounds such as alcohols and phenols exhibit weak acidic properties. Inorganic and carboxylic acids, in turn, have their own classifications. Thus, all inorganic acids can be classified:

• by the number of hydrogen atoms capable of elimination in an aqueous solution (monobasic –HCl, HNO2, dibasic –H2SO4, H2SiO3, tribasic –H3PO4)
• by acid composition (oxygen-free - HI, HF, H 2 S and oxygen-containing - HNO 3, H 2 CO 3)

Carboxylic acids are classified:

• by the number of carboxyl groups (monobasic - HCOOH, CH 3 COOH and dibasic -H 2 C 2 O 4)

Physical properties of acids

At no. Most inorganic acids exist in a liquid state, some exist in a solid state (H 3 PO 4, H 3 BO 3).

Organic acids with up to 3 carbon atoms are highly mobile, colorless liquids with a characteristic pungent odor; acids with 4-9 carbon atoms are oily liquids with an unpleasant odor, and acids with a large number of carbon atoms are solids insoluble in water.

The structure of the carboxyl group

DEFINITION

Carboxyl group— -COOH consists of a carbonyl group -> C=O and a hydroxyl group –OH, which mutually influence each other. The lone pair of electrons of the oxygen atom in the hydroxide ion is shifted towards the carbon atom of the carbonyl group, which weakens the –OH bond and causes the presence of acidic properties (Figure 1).

Rice. 1 Structure of the carboxyl group

Obtaining acids

Inorganic and organic acids are obtained in different ways. Thus, inorganic acids can be obtained:

• by the reaction of acid oxides with water

  SO 3 + H 2 O = H 2 SO 4

• by the reaction of non-metals with hydrogen

  H 2 + S ↔ H 2 S

• by exchange reaction between salts and other acids

  K 2 SiO 3 + 2HCl → H 2 SiO 3 ↓ + 2KCl

Organic acids are obtained by:

• oxidation of aldehydes and primary alcohols (KMnO 4 and K 2 Cr 2 O 7 act as oxidizing agents)

  R – CH 2 –OH → R –C(O)H → R-COOH,

  where R is a hydrocarbon radical.

Chemical properties of acids

The general chemical properties of both organic and inorganic acids include:

— the ability to change the color of indicators, for example, when litmus gets into an acid solution, it becomes red (this is due to the dissociation of acids);

— interaction with active metals

2RCOOH + Mg = (RCOO)2 Mg + H2

Fe + H 2 SO 4 (p - p) = FeSO 4 + H 2

— interaction with basic and amphoteric oxides

2RCOOH + CaO = (RCOO)2Ca + H2O

6RCOOH + Al 2 O 3 = 2(RCOO) 3 Al + 3H 2 O

2HCl + FeO = FeCl 2 + H 2 O

6HNO 3 + Al 2 O 3 = 2Al(NO 3) 3 + 3H 2 O

- interaction with bases

RCOOH + NaOH = RCOONa + H 2 O

H 2 SO 4 + 2NaOH = Na 2 SO 4 + H 2 O

- interaction with salts of weak acids

RCOOH + NaHCO 3 = RCOONa + H 2 O + CO 2

CH 3 COONa + HCl = CH 3 COOH + NaCl

Specific properties of inorganic acids

The specific properties of inorganic acids include redox reactions associated with the properties of acid anions:

H 2 SO 3 + Cl 2 + H 2 O = H 2 SO 4 + 2HCl

Pb + 4HNO 3(conc) = Pb(NO 3) 2 + 2NO 2 + 2H 2 O

Specific properties of organic acids

The specific properties of organic acids include the formation of functional derivatives by substitution of the hydroxyl group (1, 2, 3, 4), as well as halogenation (5), reduction (6) and decarboxylation (7).

R –C(O)-OH + PCl 5 = R –C(O)-Cl (acid chloride) + POCl 3 + HCl (1)

R –C(O)-OH + H-O-C(O)-R = R – C(O) – O – C(O) – R (anhydride) (2)

CH 3 COOH + CH 3 -CH 2 -OH = CH 3 -C(O)-O-C 2 H 5 (ethyl acetate (ester)) + H 2 O (3)

CH 3 COOH + CH 3 –NH 2 = CH 3 -C(O)-NH-CH 3 (amide) + H 2 O (4)

CH 3 –CH 2 -COOH + Br 2 = CH 3 – CHBr –COOH + HBr (catalyst – Pcr) (5)

R-COOH + LiAlH 4 (aqueous solution, acidified with HCl) = R-CH 2 -OH + AlCl 3 + LiCl (6)

CH 2 =CH-CH 2 -COOH = CO 2 + CH 2 =CH-CH 3 (7)

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Organic acids are products of the decomposition of substances during metabolic reactions, the molecule of which includes a carboxyl group.

The compounds act as intermediate elements and main components of metabolic energy conversion based on the production of adenosine triphosphate, the Krebs cycle.

The concentration of organic acids in the human body reflects the level of mitochondrial functioning, fatty acid oxidation and metabolism. In addition, the compounds contribute to the spontaneous restoration of the acid-base balance of the blood. Defects in mitochondrial metabolism cause deviations in metabolic reactions, the development of neuromuscular pathologies and changes in concentration. Moreover, they can lead to cell death, which is associated with the aging process and the appearance of amyotrophic lateral sclerosis, Parkinson's and Alzheimer's diseases.

Classification

The highest content of organic acids is in products of plant origin, which is why they are often called “fruit”. They give the fruits a characteristic taste: sour, tart, astringent, therefore they are often used in the food industry as preservatives, moisture-retaining agents, acidity regulators, and antioxidants. Let's consider common organic acids, and under what food additive number they are recorded: formic (E236); apple (E296); wine (E335 – 337, E354); dairy (E326 – 327); sorrel; benzoin (E210); sorbic acid (E200); lemon (E331 – 333, E380); vinegar (E261 – 262); propionic (E280); fumaric (E297); ascorbic acid (E301, E304); amber (E363).
The human body “extracts” organic acids not only from food during the digestion of food, but also produces it independently. Such compounds are soluble in alcohol and water, and perform a disinfecting function, improving human well-being and health.

The role of organic acids

The main function of carbon compounds is to maintain the acid-base balance of the human body.
Organic substances increase the pH level of the environment, which improves the absorption of nutrients by internal organs and the removal of toxins. The fact is that the immune system, beneficial bacteria in the intestines, chemical reactions, cells work better in an alkaline environment. Acidification of the body, on the contrary, is ideal conditions for the flourishing of diseases, which are based on the following reasons: acid aggression, demineralization, enzymatic weakness. As a result, a person experiences malaise, constant fatigue, increased emotionality, acidic saliva, belching, spasms, gastritis, cracks in the enamel, hypotension, insomnia, and neuritis. As a result, the tissues try to neutralize excess acid using internal reserves. A person loses muscle mass and feels a lack of vitality. Organic acids are involved in the following digestive processes, alkalizing the body:

• activate intestinal motility;
• normalize daily bowel movements;
• slow down the growth of putrefactive bacteria and fermentation in the large intestine;
• stimulate the secretion of gastric juice.

Functions of some organic compounds:

Wine acid. It is used in analytical chemistry, medicine, and the food industry for the detection of sugars, aldehydes, and in the production of soft drinks and juices. Acts as an antioxidant. It is found in the greatest quantities in grapes.

Lactic acid. It has a bactericidal effect and is used in the food industry to acidify confectionery products and soft drinks. It is formed during lactic acid fermentation and accumulates in fermented milk products, pickled, salted, pickled fruits and vegetables.

Oxalic acid. Stimulates the functioning of muscles and nerves, improves calcium absorption. However, remember, if oxalic acid becomes inorganic during processing, its salts (oxalates) formed cause the formation of stones and destroy bone tissue. As a result, a person develops arthritis, arthrosis, and impotence. In addition, oxalic acid is used in the chemical industry (for the production of ink, plastics), metallurgy (for cleaning boilers from oxides, rust, scale), in agriculture (as an insecticide), and cosmetology (for skin whitening). Found naturally in beans, nuts, rhubarb, sorrel, spinach, beets, bananas, sweet potatoes, and asparagus.

Lemon acid. Activates the Krebs cycle, accelerates metabolism, exhibits detoxification properties. It is used in medicine to improve energy metabolism, in cosmetology - to regulate the pH of the product, exfoliate “dead” epidermal cells, smooth out wrinkles and preserve the product. In the food industry (baking, for the production of fizzy drinks, liquor, confectionery, jelly, ketchup, mayonnaise, jam, processed cheese, cold tonic tea, canned fish) it is used as an acidity regulator to protect against destructive processes, giving a characteristic sour taste products. Sources of the compound: Chinese lemongrass, unripe oranges, lemons, grapefruits, sweeties.

It has antiseptic properties, so it is used as an antifungal and antimicrobial agent for skin diseases. Benzoic acid salt (sodium) is an expectorant. In addition, the organic compound is used for food preservation, dye synthesis, and the creation of eau de parfum. To extend shelf life, E210 is included in chewing gum, jam, marmalade, candy, beer, liqueur, ice cream, fruit purees, margarine, and dairy products. Natural sources: cranberries, lingonberries, blueberries, yogurt, curdled milk, honey, clove oil.

Sorbic acid. It is a natural preservative and has an antimicrobial effect, therefore it is used in the food industry to disinfect products. In addition, it prevents darkening of condensed milk, molding of soft drinks, bakery and confectionery products, fruit juices, semi-smoked sausages, and granular caviar. Remember, sorbic acid exhibits its beneficial properties only in an acidic environment (at a pH below 6.5). The largest amount of organic compound was found in rowan fruits.

Acetic acid. Participates in metabolism, used for preparing marinade and preservation. It is found in salted/pickled vegetables, beer, wine, and juices.

Ursolic and oleic acids dilate the venous vessels of the heart, prevent skeletal muscle atrophy, and reduce the amount of glucose in the blood. Tartronic slows down the conversion of carbohydrates into triglycerides, preventing atherosclerosis and obesity, uronic acid removes radionuclides and heavy metal salts from the body, and gallic acid has an antiviral and antifungal effect. Organic acids are flavor components that, in a free state or in the form of salts, are part of food products, determining their taste. These substances improve the absorption and digestion of food. The energy value of organic acids is three kilocalories of energy per gram. Carbonic and sulfonic compounds can be formed during the production of processed products or be a natural part of raw materials. To improve taste and smell, organic acids are added to dishes during their preparation (baked goods, jams). In addition, they reduce the pH of the environment, inhibit the processes of putrefaction in the gastrointestinal tract, activate intestinal motility, stimulate juice secretion in the stomach, and have anti-inflammatory and antimicrobial effects.

Daily value, sources

To maintain the acid-base balance within normal limits (pH 7.36 - 7.42), it is important to consume foods containing organic acids daily.

For most vegetables (cucumbers, bell peppers, cabbage, onions), the amount of compound per 100 grams of edible part is 0.1 - 0.3 grams. Increased content of beneficial acids in rhubarb (1 gram), ground tomatoes (0.8 grams), sorrel (0.7 grams), fruit juices, kvass, curd whey, koumiss, sour varieties of wine (up to 0.6 grams). The leaders in the level of organic substances are berries and fruits:

• lemon – 5.7 grams per 100 grams of product;
• cranberries – 3.1 grams;
• red currant – 2.5 grams;
• black currant – 2.3 grams;
• garden rowan - 2.2 grams;
• cherry, pomegranate, tangerines, grapefruit, strawberries, chokeberry - up to 1.9 grams;
• pineapple, peaches, grapes, quince, cherry plum - up to 1.0 grams.

Fermented milk products contain up to 0.5 grams of organic acids. Their quantity depends on the freshness and type of product. During long-term storage, acidification of such products occurs, as a result of which they become unsuitable for consumption. Considering that each type of organic acid has a special effect, the body’s daily need for many of them varies from 0.3 to 70 grams. With chronic fatigue, decreased secretion of gastric juice, and vitamin deficiencies, the need increases. In case of diseases of the liver, kidneys, or increased acidity of gastric juice, on the contrary, it decreases. Indications for additional intake of natural organic acids: low endurance of the body, chronic malaise, decreased tone of skeletal muscles, headaches, fibromyalgia, muscle spasms.

Conclusion

Organic acids are a group of compounds that alkalize the body, participate in energy metabolism and are found in plant products (root vegetables, leafy greens, berries, fruits, vegetables). A lack of these substances in the body leads to serious diseases. Acidity increases, absorption of vital minerals (calcium, magnesium) decreases. Painful sensations arise in the muscles and joints, osteoporosis, diseases of the bladder, and cardiovascular system develop, immunity decreases, and metabolism is disrupted. With increased acidity (acidosis), lactic acid heats up in muscle tissue, increasing the risk of diabetes mellitus and the formation of a malignant tumor. An excess of fruit compounds leads to problems with joints, digestion, and disrupts kidney function. Remember, organic acids normalize the acid-base balance of the body, preserve human health and beauty, having a beneficial effect on the skin, hair, nails, and internal organs. Therefore, in their natural form, they should be present in your diet every day!

A huge number of compounds known to the modern world are organic acids. In nature, they are obtained mainly from sugars as a result of complex biochemical reactions. Their role in all life processes is invaluable. For example, in the biosynthesis of glycosides, amino acids, alkaloids and other biologically reactive substances; in carbohydrate, fat and protein metabolism... There are a great many vital processes involving organic acids.

What's special about them? Organic acids acquire unique chemical and biological properties due to their own elemental and functional composition of molecules. A certain sequence of connections of atoms of different nature and the specifics of their combination give the substance individual characteristics and features of interaction with others.

Qualitative composition of organic substances

The main building block, a kind of monometer of all living things, is carbon, or, as it is also called, carbon. All “skeletons” are built from it - basic structures, skeletons - of organic compounds and acids, among others. In second place in terms of prevalence is hydrogen; another name for the element is hydrogen. It fills the valences of carbon that are free from connection with other atoms, giving the molecules volume and density.

The third is oxygen, or oxygen, it combines with carbon as part of groups of atoms, giving a simple aliphatic or aromatic substance completely new characteristics, for example, oxidizing ability. Next in the series of prevalence is nitrogen; its contribution to the properties of organic acids is special; there is a separate class of amino-containing compounds. Organic compounds also contain sulfur, phosphorus, halogens and some other elements in much smaller quantities.

Other organic substances are also classified into a separate class. Nucleic acids are phosphorus- and nitrogen-containing biological polymers, built from monomers - nucleotides, forming the most complex structures of DNA and RNA.

Rationale for chemical individuality

The determining factor in distinguishing it from other substances is the presence in the compound of an association of atoms that has a strict sequence of their binding to each other and carries a kind of genetic code for the class, like a functional group of organic acids. It is called carboxyl, consists of one carbon atom, hydrogen and two oxygen, and, in fact, combines carbonyl (-C=O) and hydroxyl (-OH) groups.

The constituent parts interact at the electronic level, giving rise to the individual properties of acids. In particular, they are not characterized by carbonyl addition reactions, and the ability to donate a proton is several times higher than that of alcohols.

Structural features

What happens at the electronic level of mutual influence in the functional group of the organic acid class? The carbon atom has a partially positive charge due to the pull of bond density towards oxygen, which has a much higher ability to hold it. The oxygen from the hydroxyl part has an unshared pair of electrons, which now begins to be attracted to the carbon. This reduces the oxygen-hydrogen bond density, as a result of which hydrogen becomes more mobile. Acid-type dissociation becomes possible for the compound. A decrease in the positive charge of carbon causes the cessation of the addition processes, as mentioned above.

The role of specific fragments

Each functional group has individual properties and imparts them to the substance in which it is contained. The presence of several in one excludes the possibility of giving certain reactions that previously distinguished specific fragments separately. This is an important feature that characterizes organic chemistry. Acids can contain groups containing nitrogen, sulfur, phosphorus, halogens, etc.

Class of carboxylic acids

The most famous group of substances from the entire family. You should not assume that only compounds of this class are all organic acids. Carbon representatives are the largest group, but not the only one. There are, for example, sulfonic acids, they have a different functional fragment. Of these, aromatic derivatives, which are actively involved in the chemical production of phenols, have a special status.

There is another significant class that belongs to such a branch of chemistry as organic substances. Nucleic acids are separate compounds that require individual consideration and description. They have already been briefly mentioned above.

Carbonaceous representatives of organic substances contain a characteristic functional group. It is called carboxyl, the specifics of its electronic structure were described earlier. It is the functional group that determines the presence of strong acidic properties, thanks to the mobile hydrogen proton, which is easily split off during dissociation. Of this series, only acetate (vinegar) is weak.

Classification of carboxylic acids

Based on the type of structure of the hydrocarbon skeleton, aliphatic (straight) and cyclic are distinguished. For example, propionic, heptanoic, benzoic, trimethylbenzoic organic carboxylic acids. According to the presence or absence of multiple bonds - saturated and unsaturated - butyric, acetic, acrylic, hexene, etc. Depending on the length of the skeleton, there are lower and higher (fatty) carboxylic acids, the category of the latter begins with a chain of ten carbon atoms.

The quantitative content of a structural unit, such as a functional group of organic acids, is also a principle of classification. There are one-, two-, three- and polybasic ones. For example, formic carboxylic acid, oxalic acid, citric acid and others. Representatives containing, in addition to the main group, also specific groups are called heterofunctional.

Modern nomenclature

Today in chemical science two methods of naming compounds are used. Rational and systematic nomenclatures have largely the same rules, but differ in some details of the composition of names. Historically, there were trivial “names” of compounds that were given to substances based on their inherent chemical properties, occurrence in nature, and other factors. For example, butanoic acid is called butyric acid, propenoic acid - acrylic acid, diureidoacetic acid - allantoic acid, pentanic acid - valeric acid, etc. Some of them are now allowed to be used in rational and systematic nomenclatures.

Step-by-step algorithm

The way to construct the names of substances, including such as organic acids, is as follows. First you need to find the longest hydrocarbon chain and number it. The first number must be in close proximity to the branching end so that the hydrogen atom substituents in the skeleton receive the smallest locants—numbers indicating the numbers of the carbon atoms to which they are bonded.

Next, it is necessary to detect the main functional group, and then identify the others, if any. So, the name consists of: listed in alphabetical order and with the corresponding locating substituents, the main part speaks of the length of the carbon skeleton and its saturation with hydrogen atoms, the penultimate part is determined by the class of substances, indicating a special suffix and the prefix di- or tri- for polybasic , for example, for carboxylic acids it is “-ova” and the word acid is written at the end. Ethanoic, methanedioic, propenoic, butic acid, hydroxyacetic, pentanedioic, 3-hydroxy-4-methoxybenzoic, 4-methylpentanoic and so on.

Basic functions and their meaning

Many acids, organic and inorganic, are invaluable for people and their activities. Coming from the outside or being produced internally, they initiate many processes, participate in biochemical reactions, ensuring the proper functioning of the human body, and are also used by it in many other areas.

Hydrochloric (or hydrochloric) acid is the basis of gastric juice and neutralizes most unnecessary and dangerous bacteria that enter the gastrointestinal tract. An indispensable raw material in the chemical industry is sulfuric acid. The organic part of representatives of this class is even more significant - milk, ascorbic, vinegar and many others. Acids change the pH environment of the digestive system to the alkaline side, which is essential for maintaining normal microflora. In many other aspects they have an irreplaceable positive effect on human health. It is absolutely impossible to imagine industry without the use of organic acids. All this works only thanks to their functional groups.