Chemical properties of benzoic acid equation of reactions. Formula of benzoic acid. The need for benzoic acid decreases

Appearance.Benzoic acid is a colorless silky shiny scales or crystals and plates white color;

(or crystalline powder) for low-grade Chinese production acid.

Physical properties of benzoic acid.

Molar weight 122.12 g / mol

Physical properties.

Condition (st. Sl.) Solid

Thermal properties

Melting point 122.4 ° C

Boiling point 249.2 ° C

Defayment temperature 370 ° C

Specific heat of vaporization 527 J / kg

Specific heat melting 18 J / kg

Chemical properties

Water solubility 0.001 g / 100 ml

Description of benzoic acid and differences of different brands.

Benzoic acid is first isolated by sublimation in the 16th century from a benzoic resin, hence the coincidence, rare in science, when it turned out after in 1832, Yustus von Lubih (German chemist) determined the structural formula of benzoic acid. The name coincided with the real formula. Until now, its acquisition is the oxidation of methylbenzene (toluene.)

1 Recrystallization of the product and commodity packaging, all Chinese and former Russian manufacturers did this.

In this case, the product is prone to rapid and inevitable peeling. Bags with benzoic acid turn into a stone, which is difficult to smash even by the machine.

Purification of such an acid does not exceed 97%, on labels the Chinese write proudly 99.5%, but this is due to the presence of crystallohydrates. The actual content of dry matter is much less.

The second feature of direct crystallization is the presence of a large number of aldehydes, which causes a sharp threaded eye sickening chemical smell.

Currently, there are several unradical firms engaged in shuffling Chinese benzoic acid under the European DSM brand. These sublims can always be distinguished by the presence in benzoic acid bags in crystals and sharp odor.

Such benzoic acid has nothing to do with the manufacturer of DSM.

2 The production method provides for an additional stage, the melting of benzoic acid crystals and subsequent recrystallization from the melt.

This stage allows you to achieve several tasks:

1 The product is obtained by small scales, which are not dusty and not lifting.

2 Due to the high temperature, foreign impurities evaporate and the main substance content is 99.9% or 103% by crystalline hydrogen.

A distinctive feature of this acid is scales and not crystals and a much softer smell. Only such acid can be used for synthesis, inhibition. So for food and feed purposes as an E210 additive.

Specification for benzoic acid manufactured by DSM (Kalama).

A distinctive feature of this DSM brand (Kalama): melt crystallization allows you to get a product with a minimal coefficient of the track, and a much lower odor compared to other manufacturers.

Specifications for this brand of benzoic acid:
Flakes size 0.5-4.5 mm
Bulk density 540kg / m3

Security for man.

IN lately A lot of articles appear in which various data about the terrible harm of this product are given. This is strongly not true.

benzoic acid can be called a natural compound, since it is present in some berries (blueberries, lingonberries, cranberries), and also formed in fermented milk products, such as yogurts or sources. It allows berries to withstand fungal diseases and mold. So this is one of the few invented by the nature of preservatives, but nobody has canceled the right dosages. If they are exceeded, there may be unpleasant features of the behavior of any chemical ingredient.

Benzoic acid for animals.

Fans of cats should be remembered that for your pets, benzoic acid and its salts are extremely dangerous by themselves, even in meager quantities. Therefore, before offering your cat, any product from your table, make sure that there is no such preservative in its composition. In general, this is one of many reasons why do not feed domestic pets with "human" canning products. But for pigs, it has long been used in large quantities, but for some reason no one says the words of benzoic acid, and all the veterinarians know it as a Vovaital's additive (VEVOVITALLA) (not to be confused with a biovethel of different things, though consonant), which is in its composition Purest 99.9% benzoic acid.

Around the world, benzoic acid is actively used in fattening and growing pigs.

1 Effect on the use of benzoic acid high-purity 99.9%

When feeding piglets.

10% Improving Piglets Weight Set

5% Reduction of feed intake.

Reducing odor on the farm and beyond.

Adding benzoic acid high-purity (at least 99.9%) leads to urine acidification.

- After the absorption of the intestine, benzoic acid is converted into hippuric acid in the liver of an animal, this acid is easy to display with urine. And leads to its intensive acidification. At the same time, in its composition hypospuric acid contains amine. This leads to a significant reduction in the emissions of NH4 + NH3 ammonia.

This leads to a significant decrease in smell on the pig farm.

Following this, problems with UTI (sowers) are reduced

Benzoic acid is present in the intestinal tract, suppressing the development of anaerobic bacteria and reducing gas evolution. What significantly reduces the smell on the fam and external emissions.

Antimicrobial protection of young people with a benzoic acid high-purity (at least 99.9%) data of research "in Vitro"

1, / 2 inhibiting benzoic acid concentrations.

for inhibiting 50% of the growth of microorganisms.

E210 (benzoic acid) is a food additive used in the food industry as a preservative. The E210 conservative manifests an antimicrobial and anti-gribal action, has an oppressive impact on mold, yeast and some types of bacteria. In nature, benzoic acid is contained in products such as a lingonberry, cranberry, blueberry, honey. Naturally, it is formed in cheese, prostropro, yogurt, in apples, and also contained in the discharge of some animals.

From the point of view of chemistry, the E210 supplement is a carboxylic acid relating to the class of simplest monoxide acids of the aromatic series. Chemical formula of benzoic acid: C 7 H 6 O 2 (C 6 H 5 COOH).

From a physical point of view, benzoic acid is a crystalline white powder with a characteristic odor. The E210 additive is poorly soluble in water, because of which, instead of benzoic acid, sodium benzoate is most often used (Food additive E211). At the same time, the E210 additive is quite soluble in diethyl ether and ethanol.

For the first time, benzoic acid was obtained by sublimation in the 16th century from the Renovaya Ladan (benzoic resin). Hence the benzoic acid and got its name. In 1832, the structure of benzoic acid was determined by the German chemist, and its properties and contact with hypric acid was determined. In 1875, the anti-grab properties of benzoic acid were found and studied, as a result of which it was used for a long time when preserving fruits.

In industry, the E210 additive is obtained by the oxidation of toluene (methylbenzene) with the participation of catalysts. This process uses cheap raw materials and is considered environmentally friendly.

Benzoic acid is well absorbed by the human body and in the form of hypric acid (interacting with protein compounds) is excreted through the kidneys. There are reasonable concerns that food additives E210 and E211 can enter into non-alcoholic beverages in reactions with ascorbic acid (vitamin C, additive E300) to form free benzene, which is a strong carcinogen. Therefore, it is recommended to avoid drinking beverages, which contain these additives at the same time.

In the food industry, the E210 additive is used in the manufacture of products such as sauces, pastes, ketchups, soups, puree, pulp, jelly, marmalands, meat and fish products, soft and alcoholic beverages, canned vegetables and fruits.

In the Russian Federation, the E210 dietary supplement is allowed for use, but the clear values \u200b\u200bof the maximum permissible concentration in food products are established. According to the recommendations of WHO, the maximum permissible consumption of preservative E210 does not exceed 5 ml / kg. Excess this concentration values \u200b\u200bof E210 additives adversely affect primarily on the liver and kidneys.

In medicine, benzoic acid is used as antimicrobial and antifungal agents, for example, with sweating of the legs, for the treatment of fungal diseases of the skin, such as slouching and ringing deprived. But the largest share of benzoic acid is used in the chemical industry as the main reagent to obtain many organic substances.

Their manifold is associated with the unique carbon ability to create atomic chains with high stability. One of the representatives of organic compounds with a benzene ring is benzoic acid. Interesting story Opening, a wide range of applications, methods for obtaining, benefit and harm for a person will be described in this article.

Description, physical properties of the connection

At room temperature, benzoic acid looks like white powder. If you consider it under the microscope, you will see that the crystals have the form of needles or scales (tablets). The connection has a sharp specific smell. The chemical formula of this carbonic (organic) acid is C 6 H 5 COOH or C 7 H 6 O 2. When heated to 122.4 ⁰c, it begins to melt, and at 249 ⁰c - boil, a further increase in temperature to 370 ⁰C will lead to thermal decomposition. It is easy to calculate the molar mass of the compound, it is 122.12 grams / mol. The reagent is very poorly soluble in water, and in ethanol and ether - well. C 6 H 5 COOH reagent is weak acid, its dissociation constant is 4.202.

Sublimation

The reagent is easily accustomed to sublimation. At the same time, the crystals are sublimated from the vapor, bypassing the liquid phase. Such a transition is easy to trace with the help of the experience of "Winter in a glass" or "artificial snow". To do this, a small amount of reagent and a spruce are placed in heat-resistant chemical dishes. From above, there is a round bottom flask with water, it will serve as a refrigerator and a lid. The design is installed on a tripod and exposed to heating. At the same time, the reagent begins to apone. Couple reaching flasks with cold watercrystallized and turn into "snow". They settled on the fir branch and the walls of a glass in the form of thin needles. Stunning spectacle! It also has practical applications - sublimation is used to obtain and benzoic acid.

History opening

The benzoic acid obtained its name through a natural compound, from which was first allocated, - Rosnaya Ladan. This process is described by Nostradamus in 1556, and a little later, by the French alchemist de Vizhevin. The benzoic resin for a long time was considered the only source of carboxylic acid synthesis, for which it was nicknamed by RosNolandan. Huge contribution The study of the structure and composition of the compound was made by Y. Lubi and A. Kolbe. In 1875, the antiseptic and antimicotic properties of benzoic acid were studied. The discovery belongs to the German physiologist E. L. Salkovsky. This made it possible to apply a reagent in medicine.

Characteristic chemical reactions

Benzoic acid, chemical properties which directly depend on the presence of an aromatic ring, enters the reaction of electrophile substitution. Moreover, it is more susceptible to it the third carbon atom located in an equal distance from the carboxyl group. Much slowly proceeds in -COOH. For C 6 H 5 COOH, the same interactions are characterized as for carboxylic acids. With the esterification reaction (with alcohols), esters are formed having pleasant aroma. Like all organic compounds, benzoic acid burns with the release of CO 2 and water. The interactions with bases and metals occur in a carboxyl group to form salts - benzoatov. Dehydrification leads to cycloalkanes. A characteristic chemical reaction (high-quality) on C 6 H 5 COOH is the release of iron benzoate (III). It falls in the form of a yellowish pink precipitate due to benzoic acid interaction with FECL 3.

Getting and cleaning

As already described above, the first benzoic acid was allocated from the Raznaya Ladan. This natural compound is a resin of the styractive tree. For this, crushed raw materials were heated on a sandy bath and harvested sublimated crystals in a small drawer, sailed paper. The resulting product had a pleasant fragrance due to the presence of essential oils in the Renal Ladan - cinnamon and vanilla.

Also used method of interaction of hyprome acid with salt with strong heating. The first was obtained by evaporation of the urine of herbivores, then purified by crystallization until the characteristic odor disappears. But how does the modern synthesis of such a substance like benzoic acid flow? Getting it very cheap, simple and eco. It is carried out using industrial oxidation of methylbenzene KMNO 4, or by partial interaction of the initial reagent with O 2. Purification of raw materials is based on the physical properties of reagent - low solubility of benzoic acid in cold water and high - in hot, and is called recrystallization.

Indispensable conservative

Considering the labels of food products, you often encounter components encoded by the letter E. Under this labeling, various dyes, flavors, emulsifiers, preservatives and taste amplifiers. Benzoic acid can be found under the E210 code. This nutritional supplement is a natural preservative, which is produced in fermented dairy products. In nature, the compound can be found in various parts of plants, resins, beaver jet. Used E210 in the manufacture of food products - sauces, soups, jelly, preservation, beverages. Since the component is not soluble in water, more often taking a benzoic acid salt, for example, sodium benzoate with the E211 code.

Influence of the connection on the human body

Conservative E210, falling into the human body, reacts with proteins, forming hippuric acid, which is removed by the kidneys. This component is approved by the WHO Association, but only at a concentration of no more than 5 mg / kg of daily consumption. In large doses, benzoic acid may cause damage to the liver and kidneys. In addition, it is worthwhile to beware of products in which the preservative is present with vitamin C. The interaction of these components leads to the formation of free benzene, which is the strongest carcinogen.

Application

Benzoic acid has found applied not only in the food industry. It is used in medicine as a disinfecting and antifungal agent, added to expectorant preparations and ointments from skin diseases. The reagent is raw materials for chemical synthesis of phenol, plasticizers and dyes. Great importance For perfumes have benzoic acid esters. They are used as flavored clamps. In order not to get poisoning, the means of protecting the skin and lungs should be used, because the entry of reagent to the body leads to burns, irritation of mucous membranes, nausea.

Introduction

Physical properties and finding in nature

Chemical properties

Methods for obtaining single-axis carboxylic acids of aromatic row

Nitrobenzoic acids

Application

Conclusion

Bibliography

Introduction

Systematic Name Benzoic Acid

Traditional benzoic acid names

Chemical formula C6H5COOH

Molar weight 122.12 g / mol

Physical properties

Condition (st. Sl.) Solid

Thermal properties

Melting point 122.4 ° C

Boiling point 249.2 ° C

Defayment temperature 370 ° C

Specific heat of vaporization 527 J / kg

Specific heat melting 18 j / kg

Chemical properties

Water solubility 0.001 g / 100 ml

Aromatic carboxylic acids are called derivatives of benzene containing carboxyl groups directly related to carbon atoms of the benzene nucleus. Acids containing carboxyl groups in the side chain are treated as fat andaromatic.

Aromatic acids can be separated by the number of carboxyl groups on one-, two- and more basic. The names of the acids, in which the carboxyl group is directly related to the nucleus, are made from aromatic hydrocarbons. The names of acids with carboxyl in the side chain are usually produced from the names of the corresponding fatty acids. The greatest value These are the first type acids: for example, benzoic (benzenecarbonovaya) from 6 H 5 -Con, p- Tolulyova ( p -Tololcarbonovaya), phthalic (1,2-benzestidicarbonovaya), isophthalic (1,3-benzoldidicarbonovaya), terephthalic (1,4-benzestidicarbonovaya):

History

For the first time, it was allocated for the subrange in the 16th century from benzoic resin (Rosnaya Ladan), hence he received its name. This process was described by Nostradamus (1556), and then at Gydolamo Ruselly (1560, under the alexius Pedemontanus pseudonym) and Blaise de Vigenère (1596).

In 1832, the German chemist Yustus background Lubih determined the structure of benzoic acid. He also investigated how it was associated with hypric acid.

In 1875, the German physiologist Ernst Leopold Salkovsky investigated the antifungal properties of benzoic acid, which for a long time was used in the preservation of fruits.

Sulfosalicylic acid

2-oxy-5-sulfobenzoic acid

HO3S (HO) C6H3COOH · 2H2O M 254,22

Description

Sulfosalicylic acid is a colorless translucent crystal needle shape or white crystalline powder.

Sulfosalicylic acid is easily soluble in water, alcohol and ether, insoluble in benzene and chloroform, photosensitory. Aqueous solutions have a sour response.

Application

Sulfosalicylic acid is used in medicine for high-quality definition of protein in the urine, when conducting analytical work to determine the content of nitrates in water.

In industry, sulfosalicylic acid is used as additives to basic raw materials, during the synthesis of substances.

Physical properties and finding in nature

Monocarboxylic acids of a series of benzene are colorless crystalline substances with a melting point above 100 ° C. Acids S. couple- The position of the substituents melted at significantly higher temperatures than their isomers. Aromatic acids boil with somewhat higher and melted at significantly higher temperatures than fatty acid acids with the same number of carbon atoms. Monocarboxylic acids are quite poorly dissolved in cold water and is much better in hot. Lower acids flying with water vapor. In aqueous solutions, monocarboxylic acids detect a greater degree of dissociation than fatty acid acids: a benzoic acid dissociation constant 6.6 · 10 -5, acetic acid 1.8 · 10 -5. At 370s it decomposes to benzene and CO2 (phenol and CO) are formed in a small amount). When interacting with benzoyl chloride at elevated temperatures, benzoic acid turns into benzoic anhydride. Benzoic acid and its esters are contained in essential oils (for example, in the clove, Toluansky and Peruvian balsams, benzoic resin). A derivative of benzoic acid and glycine - hypuric acid - the product of animal vital activity. Crystallizes in the form of colorless plates or needles melting at 121 ° C, easily soluble in alcohol and ether, but difficult to soluble in water. Currently, benzoic acid is quite widely used in the dyes industry. Benzoic acid has antishentic properties and is therefore used to preserve food. Considerable application also find various benzoic acid derivatives.

Chemical properties

Benzole was opened by Faraday in 1825 and its gross formula-C 6 H 6 was established. In 1865, Kekule proposed its structural formula as cyclohexastrienne-1,3,5. This formula is also used at present, although it will be shown later, it is imperfect - does not respond to the fully properties of benzene.

Most characteristic feature Chemical behaviorBenzene is the amazing inertness of double carbon-carbon ties in its molecule: in contrast to the considered; Previously unshakable compounds, it is resistant to the action of oxidizers (for example, potassium permanganate in an acidic and alkaline medium, chromium anhydride in acetic acid) and does not enter into conventional reactions of electrophyl addition, characteristic of alkenes, alkadiennes and alkins.

Trying to explain the properties of benzene features of the structure, many scientists after Kekule advanced their hypotheses on this issue. Since the disappearance of benzene was clearly not manifested, believed that there were no double ties in the benzene molecule. Thus, Armstrong and Bayer, as well as Klaus, suggested that in the benzene molecule, the fourth valence of all six carbon atoms were sent to the center and saturate each other, Ladenburg - that the carbon skeleton of benzene is a prism, Chichibabin - that in benzene carbon trivalent.

Tile, improving the formula Kekule, argued that the double bonds are not fixed in the latter, and constantly moved- "oscillating", and Dewar and Hyukkel proposed the structural formulas of benzene with double bonds and small cycles.

Currently, on the basis of these numerous studies, it can be considered firmly established that six carbon and six hydrogen atoms in the benzene molecule are in the same plane and that the clouds of the π-electrons of carbon atoms are perpendicular to the plane of the molecule and, therefore, are parallel to each other and interact with each other. The cloud of each π-electrone is overlapped by clouds of π-electrons of neighboring carbon atoms. A real benzene molecule with a uniform distribution of π-electron density throughout the ring can be represented as a flat hexagon lying between two thorahs.

It follows that the benzene formula is logical to portray in the form of a proper hexagon with a ring inside, thereby emphasizing the complete delocalization of π-electrons in benzol Ring and the equivalence of all carbon-carbon ties in it. The justice of the latter is confirmed, in particular, the results of measuring the length of C-C-links in the benzene molecule; They are the same and equal to 0.139 nm (C-C-communication in the benzene ring in shorter of the ordinary (3,154 nm), but longer than double (0.132 nm)). Distribution of electron density in the benzene molecule; Length of ties, valence angles

A very important derivative of benzoic acid is its chlorohydride - benzoyl chloride. This is a liquid with a characteristic odor and a strong polycrimatte action. Used as a benzoylating agent.

Peroxide Benzoyl It is used as an initiator for polymerization reactions, as well as a whitening agent for food oils, fats, flour.

Tolusyl acids. Methylbenzoic acids are called tolusyl acids. They are formed with partial oxidation of O-, m- and p -xilolov. NN-diethyl m. -Toluelimide is effective repellent - drug by screking insects:

p-tert -Butylbenzoic acid is obtained on an industrial scale with liquid-phase oxidation tert -Butololool in the presence of a soluble cobalt salt as a catalyst. It is used in the production of polyester resins.

Phenyloxus acid It is prepared from the benzyl chloride through nitrile or through magnesium-organized compounds. This is a crystalline substance with t. Pl. 76 ° C. Due to the mobility of the residential atoms of the methyl group, it easily enters the condensation reaction. This acid and its esters are used in perfumery.

Aromatic acids enter into all those reactions that are peculiar and fatty acids. Reactions involving the carboxyl group are obtained by various derivatives. Salts are obtained by the effects of acids on carbonates or alkali. Esters - heating the mixture of acid and alcohol in the presence of mineral (usually sulfur) acid:

If deputies B. ortho- No position, then esterification of the carboxyl group occurs as easily as in the case of aliphatic acids. If one is ortho -The locations are substituted, the speed of esterification is greatly reduced, and if both ortho- Provisions are occupied, esterification usually does not go (spatial difficulties).

Esters. ortho -Telated benzoic acids can be obtained by the reaction of silver salts with haloalkyls (the esters of spatially difficult aromatic acids are easily and quantitatively washed in the presence of crown ether). Due to spatial difficulties, they hardly undergo hydrolysis. Groups are large than hydrogen, to such an extent fill the space around the carbon atom of the carboxyl group, which make it difficult for the formation and washing of ether.

Getting C6H5Cone:

Main ways:

1. By oxidizing a wide variety of benzene derivatives having one side chain, for example, toluene, ethylbenzene, benzyl alcohol, etc.: C6H5SH3 ® C6H5CO

2. From the benzonitrile, which for this is hydrolyzed with acid or alkali: 2N2 O C6H5SN ¾¾® C6H5CHON + NH3

Benzoic (or RosNolandanna), Acidum Benzoicum Sublimatum, Flores Benzoës - a very common substance of the composition of C7H6O2, or C6H5-coxy; It contains in some resins, balms, in grassy parts and in the roots of many plants (according to the previous, still not proven observations), as well as in the colors of Unona Odoratissima (in the essence of Alan-Zhilan, or Ylang-Ylang), in a beaver jet, And mostly in benzoic resin, or Rosna Ladan, from where its name. About the products of dry distillation of this resin there are instructions even in writings related to the XVI cent.; Blaise de Vigenère in his treatise (1608) "TRAITÉ DU FEU ET DU SEL" The first mentions the crystalline substance from the benzoic resin, which was subsequently studied closer and got the name Flores Benzoës. The composition is finally established by Lubikha in 1832, and Kolbe offered to consider it as phenylcarboxylic acid. B. Acid can be obtained from benzene synthetically and is formed with many reactions performed with the bodies of the aromatic series. For pharmaceutical necessary, they use exclusively acid produced by sublimation of benzoic resin. It is best for this purpose to take the Siamese dew incense, as there is no cinnamon acid, or Calcutt, cheaper and also containing a lot of B. acid. The crushed resin is slightly heated on the sand bath in the iron boilers, and the mass is first melted, and then highlights heavy pairs of B. acids that sit on the cold parts of the instrument in the form of crystals. To assemble the substance, the bowler is covered with a paper cone or a lid with a wide tube, along which the pairs are discharged into the wooden box, plated paper. At the end of the operation (and it is necessary to avoid severe heating) with a strong heating) of the acid in the receiver or on a paper cone in the form of snow-white crystals or flakes. The drug obtained by this by means has an obvious smell of vanilla, which depends on the content of a small amount of essential oil in the resin. The best outputs can be achieved by insisting for a long time finely divided resin with lime milk or soda. The mixture is then heated to the melting of the resin, and from the resulting benzo-acid salt, the substance is separated by hydrochloric acid. The acid obtained by this method has a weaker smell than that that is obtained by sublimation. For technical purposes, as the starting material take hypproves (see. This is synchd.), Contained in the urine of herbivores. The urine is quickly evaporated to ⅓ initial volume, filtered and treated with an excess of hydrochloric acid, with hippuric acid stands out in crystalline form. After a day, the crystals are separated from the uterine solution and purified by re-crystallization until the stubborn smell of urine disappears almost at all. Purified hippuric acid is boiled with hydrochloric acid, with a splitting on B. acid and glycocol:

HOOC-CH2 + H2O \u003d HOOC-CH2 (NH2) + C6H5-COOH.

In large quantities B. acid can be obtained from toluene C6H5-CH3, oxidizing it with nitric acid; But it is more profitable (as practiced at the factories), it is not toluene to take for this purpose, but benzenyl chloride C6H5CCl3; This latter is heated with water in hermetically closed vessels; The resulting acid stubbornly keeps halogen-substituted products. Further, B. acid is obtained by heating the lime salts of phthalic acid with lime eating; Finally, significant quantities remain in the form of a by-product when facing oil of bitter almonds due to the oxidation of the latter. Produced by one or another B. Acid is purified by recrystallization from hot water; The decolorization of solutions is carried out by treating animal coal or heating with weak nitric acid. Synthetically benzoic acid received a kecule, acting by coal acid on bromobenzene in the presence of metal sodium:

C6H5B + 2NA + CO2 \u003d C6H5CO2NA + NABR.

Frestere and Krafts prepared it directly from benzene and coalic acid in the presence of aluminum chloride. Pure B. Acid represents colorless one-riner needles or signs, dd. Weights 1,2 (at 21 °), which do not vary in light, whereas the resulting sublimation from the Razny Ladan turns yellow after a while due to the decomposition of the essential oil contained in it. The substance melts at 121, ° 4 C., boils at 249 °, 2 without decomposition and is denied below the boiling point; There is no smell. Couples act an irritant way to mucous membranes respiratory organs. With water vapor, the acid flies below 100 °, and therefore the aqueous solutions cannot be condensed by evaporation. 1000 hours of water dissolve at 0 ° 1.7 weight. h. and at 100 ° 58.75 h. B. Acids. It is also well soluble in alcohol, ether, chloroform, essential and oily oils. Some impurities, even in very small amounts, change its physical properties so sharply, which one time recognized the existence of isomeric B. acid and was called its salyl acid, but both substances turned out to be quite identical (Bailstein). When passing a vapor through a strongly heated pimem or, better, with a dry distillation with a caustic barite or hawed lime B. Acid disintegrates on benzene and carbon dioxide. When fusing with caustic potassium, all three oxybenzoic acids are obtained along with other products; Oxidifiers act quite difficult for it. The sodium amalgam is formed: benzoic aldehyde, benzyl alcohol and other products of complex composition. Chlorine and bromine, as well as iodine in the presence of jodded acid act a replacement manner; Smoking nitric acid gives nitrobenzoic, and smoking sulfur - sulfobenzoic acids. In general, the hydrogens of the phenyl group in B. acid one by one may be substituted by various residues, and a huge number of diverse compounds is formed, of which several isomeric forms are known for many. Of the derivatives of B. Acids formed through the substitution in the carboxyl group, the simplest will be the following:

Benzoyl chloride, B. Chloranhydride, C6H5-COCL was obtained for the first time with Lubikh and Vyler in 1832. When processing dry chlorine oil of bitter almonds; It is also formed under the action of a five chicrist or three-chloride phosphorus on benzoic acid or phosphoric chlorocycy onto a benzoomnonate salt. Colorless liquid with a sharp smell, dd. weights 1.324 (at 0 °), boiling at 198 °; Hardens in the cooling mixture to crystals (melting. at -1 °). Hot water is quickly decomposed on salt and B. acid; Easily enters double decomposition with a number of substances; Thus, under the action of ammonia, Lubih and Vyler received bezamide from it, or amide B. acid, C6H5-conH2, a crystalline substance, melting at 128 °, UD. Weights of 1.341 (at 4 °), soluble in hot water, alcohol and ether. Benzamide is also obtained when heated by B. Acid with rodania ammonium. Water-based substances easily translate it into nitrile B. acid, benzonitrile or phenyl cyanide - C6H5CN. This latter is also obtained from a potassium salt of sulfobenzoic acid and cyano potassium. The substance is a liquid with a bitcomintal smell, boiling at 190 °, ice. Weight 1.023 (at 0 °), frozen with strong cooling into a solid mass. It is difficult to soluble in boiling water and easily in alcohol and ether.

Methods for getting simonial carboxylic acids of aromatic row

Monostic carboxylic acids of the aromatic row can be obtained by all common methodsknown for fatty acids.

Oxidation of alkyl groups of benzene homologs. This is one of the most frequently used methods for producing aromatic acids:

Oxidation is carried out either by boiling hydrocarbon with an alkaline solution of potassium permanganate, or when heated in sealed tubes with dilute nitric acid. As a rule, this method gives good results. Complications are only in cases where a benzene ring is destroyed under the action of oxidants.

Oxidation of aromatic ketones . Aromatic ketones are easily obtained by Fredel's reaction - Krafts. Oxidation is usually carried out with hypochlorites according to the scheme:

However, other oxidizing agents can be used. Acetorates are oxidized easier than hydrocarbons.

Hydrolysis of trigogel production with halogens in one carbon atom. In the chlorination of toluene, three types of chlorine derivatives are formed: the benzyl chloride (comes to produce a benzyl alcohol), benzyl hydrogen chloride (for producing benzoic aldehyde), benzotrychloride (processed into benzoic acid and benzoyl chloride). Direct hydrolysis of benzotrychloride is bad. Therefore, benzotrichloride heating with benzoic acid is converted to a benzoyl chloride, which further in hydrolysis easily gives benzoic acid:

Hydrolysis of nitriles:

This method is widely used in a bold row. In the aromatic row, the initial nitriles are obtained from diazo compounds, from halogen production exchange with copper cyanide in pyridine or fusion of sulfonates with potassium cyanide. Nitrile acids with a nitrile group in the side chain receive an exchange reaction from halogen derivatives.

The reaction of aromatic hydrocarbons with halogen derivatives of coalic acid

The carboxyl group can be introduced into the core by means of a reaction similar to the synthesis of ketones along Friedel - Korfraft. The catalyst is the aluminum chloride:

The reactions of metallorganic compounds with CO 2:

Usually used lithium or magnesium-organic connections.

Chloranhydrides are obtained at acid chloride acid or phosphorus pentachloride:

Anhydrides are obtained by distillation of a mixture of acid with acetic anhydride in the presence of phosphoric acid or the action of chloranhydrides on the salts:

Under the action of the benzoyl chloride on sodium peroxide, a crystalline peroxide benzoyl is obtained:

Under the action of alcoholate on benzoyl peroxide, a subridic acid salt (benzoyl hydroperoxide) is obtained. This acid is used to obtain oxides from unsaturated compounds. (Priary Reaction) :

Benzol in the absence of a catalyst does not react with bromine and chlorine, thereby demonstrating the stability of three double bonds in its molecule to the action of electrophilic agents. At the same time, the presence of the latter is confirmed by the interaction of benzene with chlorine during irradiation, leading to the formation of hexachlorcyclohexane (hexachlororan):

An interesting reaction with the participation of double bonds is observed when the benzene is irradiated in the liquid phase with light with a wavelength of 253.7 nm. Under these conditions, the benzene molecule is rebuilt, turning into the so-called valence isomers.

Nitrobenzoic acids

When nitration of benzoic acid, it turns out 78% -Met-, 20% ortho- and 2% couple- nitrobenzoic acids. The last two isomes without impurities of other isomers are obtained by oxidation ortho- and couple- Nitrotoluols.

Nitrobenzoic acids have stronger acidic properties than benzoic acid (TO \u003d 6.6 · 10 -5): about- Isomer - 100 times, m- Isomer - 4.7 times and p-Iso measures - 5.6 times. Similar pattern is observed in the case of halogen-substituted acids.

Application

Benzoic acid and its salts have high bactericidal and bacteriostatic activity, sharply increasing with a decrease in the pH of the medium. Thanks to these properties, as well as non-substitution, benzoic acid apply:

preservative in the food industry (additive 0.1% acid to sauces, pickles, fruit juices, jamam, meat minced, etc.)

in medicine skin diseases As an external antiseptic (antimicrobial) and fungicidal (antifungal) agent, and its sodium salt is like an expectorant.

In addition, benzoic acid and its salts are used when preserving food products (nutritional supplements E210, E211, E212, E213). Benzoic acid esters (from methyl to amylovoy), which have a strong smell, are used in the perfume industry. Various benzoic acid derivatives, such as chlorine and nitrobenzoic acids, are widely used for the synthesis of dyes.

Benzoic acid is used in production

caprolactama

benzoyl chloride

supplement to alkyd varnishes, improving glitter, adhesion, hardness and chemical coating resistance

Great practical value have salts and benzoic acid esters (benzoate).

Sodium benzoate Food preservative, polymer stabilizer, corrosion inhibitor in heat exchangers, expectorant in medicine.

Ammonium benzoate - antiseptic, preservative in the food industry, corrosion inhibitor, stabilizer in the production of latex and adhesives.

Benzoates of transition metals are catalysts of liquid-phase oxidation of alkylaromatic hydrocarbons into benzoic acid.

Benzoic acid esters from methyl to isoamyl - fragrant substances. Methylbenzoate - cellulose ethers solvent.

Isoamilbenzoate - component of fruit essences.

Benzylbenzoate - a ficker of smell in perfumery, solvent of fragrant substances, an antiseptic, repellent from moth.

Precautions:

When entering the skin causes irritation.

Inhalation of aerosol causes a convulsive cough, runny nose, sometimes nausea and vomiting.

Conclusion

Latin name: Acidum Benzoicum

Benzoic acid C6H5Cone - the simplest monoxide carboxylic acid of aromatic row.

Benzoic acid is colorless crystals, poorly soluble in water, well - in ethanol and diethyl ether.

It is mainly used in the form of sodium (large solubility in water) - fuel station sodium, potassium and calcium salts.

Melting point - 122.4 ° C,

Boiling point - 249 ° C.

It is easily disposed (one of the ways to produce a dry distillation of benzoine resin); Runs with water vapor.

Benzoic acid (BK) is used in medicine under skin diseases as an outer antiseptic (antimicrobial) and a fungicidal (antifungal) agent, and its sodium salt is like an expectorant.

B. K. and its salts have high bactericidal and bacteriostatic activity, sharply increasing with a decrease in the pH of the medium.

Reaction with some forms possible ascorbic acid (vitamin C).

In the body, benzoic acid is combined with glycine, forming harmless hippuric acid, which is outlined with urine.

The permissible dose of benzoic acid and its salt for humans is 5 mg / kg body weight per day.

Concentration of recipes: 0.2-0.5% (per 50 g of cream - 0.2 g of sodium benzoate).

The activity of benzoic acid falls in the presence of non-ionic surfactants, proteins and glycerin.

Used together with other preservatives.

Being soluble in fats, it can be applied as preservative fats, lipsticks, etc. The maximum concentration in cosmetic products is 0.5%.

Benzoic acid salts - benzoates (for example, sodium benznot) are also used as preservatives.

Another use: Benzoic acid esters with a strong smell applied in the perfume industry.

Various benzoic acid derivatives, such as chlorine and nitrobenzoic acids, are widely used for the synthesis of dyes.

B. K. and its esters are contained in essential oils (for example, in cloves), Toluansky and Peruvian balsams, benzoic resin (up to 20% acid and up to 40% of its esters).

Additional Information:

In practice, the aqueous solutions of sodium benzoate with a concentration of 5 to 25% are used.

For the preparation of the solution, the desired amount of preservative is dissolved in approximately half the required volume drinking waterheated to 50 ... 80s. After complete dissolution of the salt into the resulting solution, the remaining water is added and stirred thoroughly. It is recommended to filter the solution through a layer of cotton fabric (bosy). If the preservative is dissolved in rigid water, then the solution can be slightly muddy, but this does not affect its preservative effect.

When developing a particular recipe for a preservative, a product must be considered as follows:

the acidity of the medium affects the effectiveness of preservatives - the more acidic reaction has a product, the less you need to add a preservative;

as a rule, low calorie products have a high water content and easily subjected to damage, so the amount of preservative added to them should be 30-40% more than recommended for conventional products;

alcohol additive, a large amount of sugar or other substance that exhibits preservative properties, reduces the required amount of preservative.

Literature

1 Zemtsova M.N. Methodical instructions for execution term paper for organic chemistry.

2. Chemical reagents and preparations of state publicism 1953, p. 241-242.

3. Karyakin Yu.V., Angels I.I. Clean chemical substances Ed. 4th, per. and add. M.: Chemistry 1974, p. 121-122.

4. "Brief Chemical Encyclopedia" ed. Soviet Encyclopedia, T.4 M. 1965 p. 817-826.

5. Petrov A.A., Balian Kh.V., Trochenko A.T. Organic Chemistry: Textbook for universities. - St. Petersburg: "Ivan Fedorov", 2002, p. 421-427.

6. Gityis S.S., Eye A.I., Ivanov A.V.Practikum on Organic Chemistry: -M.: High Sk., 1991. - 303.: Il.

7. Shabarov Yu.S. Organic Chemistry: Textbook for universities in 2-kN. - M.: Chemistry, 1996.str. 558-561, 626-629.

Benzoic acid is known to humanity for a long time. The first mention of this substance belongs to the sixteenth century. It was then that scientists first managed to highlight benzoic acid from the resin of the sublimation method. And in the nineteenth century, German chemists investigated this compound in more detail and compared the properties of benzoic acid with hypric acid properties. The antimicrobial and antifungal effect of benzoic acid was the reason that in the twentieth century it began to be used as a food preservative in the production of food.

Physical and chemical properties of benzoic acid

Own external species Benzoic acid resembles thin oblong leaves or white-colored needles with a characteristic gloss. It dissolves very well in almost any environment: in fats, alcohols and in ordinary water. In addition, at a temperature of over 122 degrees Celsius, benzoic acid is melted and passes into a gaseous state.

Any chemist will tell you that this compound belongs to the carbon monoxide acids of an aromatic row. But it is more interesting for us, what are the properties of benzoic acid, and does not cause harm to human health. On food labels, it is indicated by the E210 code. On an industrial scale, benzoic acid is made from toluene, the method of oxidation of the latter. Previously, it was obtained from phthalic acid or benzotrychloride, but now this method is not relevant for the high cost and complexity of the technological process.

As for safety and naturalness, the benzoic acid can be called a natural compound, since it is present as part of some berries (blueberries, lingers, cranberries), and also formed in fermented milk products, such as yogurts or sources. This does not mean that it is also a lot there as in some canned products of factory production. But, on the other hand, this suggests that benzoic acid is not toxic and is not dangerous for a person if it is used in reasonable quantities.

The use of benzoic acid

The E210 conservative is actively used by the brewing, confectionery and bakery industry. Here is an incomplete list of products manufactured using benzoic acid:

Fruit juices and puree;
Jam, jam and jam;
Milk products;
Canned vegetables;
Ice cream;
Liqueurs, beer, wines;
Candy and sugar substitutes;
Salt and pickled fish;
Margarine and oil;
Chewing gum.

The effect of benzoic acid on health

When benzoic acid falls into our body, it reacts with protein molecules and transformed into hippuric acid, and is already being outlined with urine. Of course, this process is an excessive load on excretory systemTherefore, Russian legislation establishes the maximum permissible rate of use of benzoic acid in the production of food. It should not be more than 5 milligrams per 1 kilogram of the finished product.

But the dangers of benzoic acid are usually reasoned not in the context of the burden on the kidneys. The fact is that under certain conditions from this chemical compound Clean benzene can be formed - a hazardous substance related to carcinogens, that is, provoking the development of oncological diseases. But so that such a reaction occurred, it is necessary very heat. In the human body, the release of benzene from benzoic acid is impossible. However, preserved products are not intended for this, and they are not recommended to use them in this form.

Some modern specialists in the field of food chemistry believe that in the interaction of benzoic acid E210 and ascorbic acid E300, unwanted chemical reactions with the separation of benzene may occur. But for this process also requires a special medium with increased temperature. In any case, you can learn from the label if there is a combination of substances in a particular product, and make a decision, buy it or not.