Benzoic acid is the simplest monobasic carboxylic acid of the aromatic series. It is registered as a food additive E210, belonging to the group of preservatives.
General characteristics of Benzoic acid
Benzoic acid is a white crystalline substance, practically insoluble in water, but highly soluble in chloroform and ethanol. It is considered a weak acid and has a specific odor (calorizator). Named after the name of dew incense (otherwise benzoin resin), from which it was obtained by sublimation in the 16th century. In the mid-19th century, Justus von Liebig discovered the structures of benzoic acid.
Benzoic acid has a pronounced property of inhibiting the growth and development of mold, some types of bacteria and yeast, and acts as an antimicrobial agent. It is found in nature and the industrial method for producing E210 is the oxidation of toluene using catalysts.
The food additive E210 has a negative effect on human health caused by its carcinogenic effect and can cause severe allergic reactions. Dangerous to health, can cause rash and provoke asthma attacks. The substance is well absorbed into the body and excreted through the kidneys with urine. When reacting with ( , ) it forms free benzene, a strong carcinogen. You should carefully study the composition of products (especially) in order to refuse to purchase those that contain both food additives.
Application of E210
The antimicrobial effect of E210 is used in the food industry in the production of sauces, ketchups, canned fruits and vegetables, fish products, marmalades, jellies, alcoholic and non-alcoholic drinks.
Medicine uses benzoic acid as an antifungal and antimicrobial agent; it is part of many drugs for the treatment of skin fungus and various types of lichen diseases. The substance has also found application in the chemical industry and is the main reagent for the production of organic substances by chemical means.
Use of E210 Benzoic acid in Russia
On the territory of the Russian Federation, the use of E210 as a food preservative is permitted, but strictly in the maximum permissible concentration. The maximum permissible amount of E210 allowed for use is 5 ml/kg.
Benzoic acid (benzene carboxylic acid, food additive E210)– an organic acid with high bactericidal and bacteriostatic activity, which increases sharply with decreasing pH of the environment. In nature, benzoic acid is found in lingonberries (Vaccinium vitus-idaea L), blueberries (Vaccinium murtillus L), in honey, sour milk, yogurt and cheese. The high shelf life of lingonberries and cranberries is explained by the high content of benzoic acid (500-2000 mg/kg). For industrial use, benzoic acid is obtained synthetically, but it is completely identical to natural one.
Physicochemical characteristics.
Gross formula C 7 H 6 O 2.
Structural formula:
Benzoic acid - white crystals (monoclinic leaves or needles). Density 1.2659 g/cm3. Melting point 122.4°C. Boiling point 249°C. Solubility in ethanol (15°C) 47.1 g/100 g; in diethyl ether (15°C) 40 g/100 g. Soluble in methanol, carbon tetrachloride. Solubility in 98.5% pure glycerol (20°C) 2.2 g/100 g. 1-2 g of benzoic acid dissolves in 100 g of fatty oils. Benzoic acid is, like most other organic acids, a weak acid. In preservative concentrations it may cause a slight change in taste in food products.
The action of benzoic acid is directed mainly against yeasts and molds, including aflatoxin-forming fungi. Bacteria are only partially inhibited. Benzoic acid is ineffective against lactic acid bacteria and clostridia.
Benzoic acid, by blocking enzymes, slows down metabolism in single-celled organisms. Since only undissociated acid can penetrate the cell wall, benzoic acid exhibits antimicrobial effects only in acidic foods at a pH of 2.5-5.0.
| Type of microorganisms | pH value | Minimum effective concentration of benzoic acid, g/kg |
| Bacteria: | ||
| Pseudomonas spec. | 6,0 | 2-4,8 |
| Micrococcus spec. | 5,5-5,6 | 0,5-1 |
| Lactobacillus spec. | 4,3-6,0 | 3-18 |
| Escherichia coli | 5,2-5,6 | 0,5-1,2 |
| Bacillus cereus | 6,3 | 5 |
| Yeast: | ||
| Sporogenic yeast | 2,6-4,5 | 0,2-2 |
| Asporogenic yeast | 4,0-5,0 | 0,7-1,5 |
| Rhodotorula spec. | 1-2 | |
| Pichia pastori | 3 | |
| Pichia membranaefaciens | 7 | |
| Hansenula subpelliculosa | 2-3 | |
| Candida krusei | 3-7 | |
| Torulopsis spec. | 2-5 | |
| Oospora lactis | 3 | |
| Molds: | ||
| Mucor racemosus | 5,0 | 0,3-1,2 |
| Penicillum spec. | 2,6-5,0 | 0,3-2,8 |
| Aspergillus spec. | 3,0-5,0 | 0,2-3 |
| Rhizopus nigricans. | 5,0 | 0,3-1,2 |
| Penicillum glaucum | 5,0 | 4-5 |
| Cladosporium herbarum | 5,1 | 1 |
Application.
Benzoic acid is used as a preservative in the food industry E210 (addition of 0.1% acid to sauces, brines, fruit juices, jams, minced meat, etc.), an antiseptic in medicine (dermatology), perfumery and for preserving cosmetics (no more than 0. 5% benzoic acid). In pharmaceuticals, it is used in the form of benzyl benzoate (up to 25%) in ointments against scabies and mites. Benzene carboxylic acid is used in the production of phenol, caprolactam, benzoyl chloride, as an additive to alkyd varnishes, improving gloss, adhesion, hardness and chemical resistance of the coating.
E210 is allowed in fat emulsions (except butter) with a fat content of more than 60%, olives and products made from them, jams, marmalades, jellies, low-sugar and sugar-free jam of paste-like consistency, emulsified sauces with a fat content of more than 60 %, jelly for jellied dishes in amounts up to 500 mg/kg; in fat emulsions (except butter) with a fat content of less than 60%, tomato products (except juices), emulsified sauces with a fat content of less than 60%, non-emulsified sauces, sugar-glazed (condied) fruits and vegetables, spices and seasonings in quantities of up to 1 g/kg; in boiled beets, pickled, salted or oiled vegetables (except olives), canned fish, including caviar, boiled shrimp, biologically active food additives, liquid in amounts up to 2 g/kg; in non-alcoholic flavored drinks in amounts up to 150 mg/kg; in non-alcoholic beer, alcoholic drinks with an alcohol content of less than 15 vol. %, salted fish, dried in amounts up to 200 mg/kg; in milk-based desserts not treated with heat in amounts up to 300 mg/kg; in chewing gum, ready-made salads, mustard, dietary therapeutic and prophylactic food products (excluding products for children), dietary mixtures for weight loss, sugary confectionery products, candies, chocolate with filling in amounts up to 1.5 g/kg; for surface processing of sausages, sausages, cheeses and casings, as well as in films and coatings, in dried meat products (surface processing).
Benzoic acid is used in rubber vulcanization technology. Benzoic acid is a scorch retardant. Scalding retarders - phthalemide derivatives, benzoic acid and anhydrides - prevent premature scorching of rubber compounds during their manufacture and processing, and also increase the time before vulcanization begins. They are introduced into rubber mixtures in an amount of 0.2-0.5% by weight of rubber.
Preservatives based on benzoic acid are allowed to be used in the production of meat, fish and seafood in varying maximum quantities, depending on the type of product.
Benzoic acid is used as a preservative when harvesting plants with high humidity for silage.
Benzoic acid application rates:
For non-silling plants (alfalfa, sainfoin, fodder beans and rank in the flowering phase): 4 kg/t of green mass;
For hard-to-hull plants (clover, perennial cereal grasses before the flowering phase, annual legume-cereal mixtures until the phase of waxy grain ripeness in the two lower tiers): 3 kg/t of green mass;
For easily silted plants (corn, sorghum, sunflower, Sudan grass, perennial cereal grasses in the flowering phase): 2 kg/t of green mass.
Benzoic acid inhibits the development of yeast, putrefactive microflora and mold, and has almost no effect on lactic acid bacteria.
Silage treated with benzoic acid is fed to dairy cows in an amount of no more than 20-25 kg per day, to pregnant cows - up to 10 kg, to calves from 6-12 months - 8-10 kg, to young animals 12-18 months of age - 12-15 kg, and for fattening livestock - ad libitum.
| Index | Silage without additives | Benzoic Acid Silage |
| Average daily milk yield, kg | 12 | 12,6 |
| Feed consumption per 1 kg of milk, feed units | 0,89 | 0,90 |
| Profitability level, % | 15,2 | 20,3 |
| Fat content in milk,% | 3,78 | 3,85 |
| Dry matter,% | 12,08 | 12,22 |
| Dry skimmed milk residue, % | 8,42 | 8,53 |
| Milk sugar, % | 4,48 | 4,49 |
| Total protein, % | 2,91 | 2,93 |
| Casein, % | 2,31 | 2,33 |
| Acidity, T | 17 | 17 |
| Density, g/cm 3 | 1,028 | 1,028 |
The positive effect of feed chemically preserved with benzoic acid on animal productivity is explained by its higher nutritional value compared to conventional silage. The increase in the cost of chemically preserved silage due to the cost of additives is fully paid for by improving the safety of feed and increasing animal productivity.
The health hazards of benzoic acid.
Inhalation: cough, irritation.
Skin: redness, irritation.
Eyes: redness, irritation, pain.
Ingestion: abdominal pain, nausea, vomiting.
An explosion is possible if it is mixed in powder form with air.
Receipt.
On an industrial scale, benzoic acid is produced by the oxidation of toluene with oxygen with the participation of a catalyst (manganese or cobalt naphthenate).
It is found in bound form in strawberries, lingonberries, blueberries and honey, in the form of a microbial decomposition product of hippuric acid in yogurt, yogurt and cheese, in the form of esters in essential oils such as clove oil.
Plan
Introduction
Physical properties and occurrence in nature
Chemical properties
Methods for producing monobasic aromatic carboxylic acids
Nitrobenzoic acids
Application
Conclusion
Bibliography
Introduction
Systematic name benzoic acid
Traditional names benzoic acid
Chemical formula C6H5COOH
Molar mass 122.12 g/mol
Physical properties
Condition (standard condition) solid
Thermal properties
Melting point 122.4 °C
Boiling point 249.2 °C
Decomposition temperature 370 °C
Specific heat of vaporization 527 J/kg
Specific heat of fusion 18 J/kg
Chemical properties
Solubility in water 0.001 g/100 ml
Aromatic carboxylic acids are benzene derivatives containing carboxyl groups directly bonded to the carbon atoms of the benzene ring. Acids containing carboxyl groups in the side chain are considered aromatic fatty acids.
Aromatic acids can be divided according to the number of carboxyl groups into one-, two-, or more basic ones. The names of acids in which the carboxyl group is directly bonded to the nucleus are derived from aromatic hydrocarbons. The names of acids with a carboxyl in the side chain are usually derived from the names of the corresponding fatty acids. The acids of the first type are of greatest importance: for example, benzoic (benzenecarbonic) C 6 H 5 -COOH, P- toluyl ( P-toluenecarbonate), phthalic (1,2-benzenedicarboxylic), isophthalic (1,3-benzenedicarboxylic), terephthalic (1,4-benzenedicarboxylic):
Story
It was first isolated by sublimation in the 16th century from benzoin resin (dewy incense), hence its name. This process was described by Nostradamus (1556), and then by Girolamo Ruschelli (1560, under the pseudonym Alexius Pedemontanus) and Blaise de Vigenère (1596).
In 1832, the German chemist Justus von Liebig determined the structure of benzoic acid. He also investigated how it relates to hippuric acid.
In 1875, German physiologist Ernst Leopold Zalkowski investigated the antifungal properties of benzoic acid, which had long been used in fruit canning.
Sulfosalicylic acid
2-Hydroxy-5-sulfobenzoic acid
HO3S(HO)C6H3COOH 2H3O M 254.22
Description
Sulfosalicylic acid is colorless, translucent, needle-shaped crystals or white crystalline powder.
Sulfosalicylic acid is easily soluble in water, alcohol and ether, insoluble in benzene and chloroform, and photosensitive. Aqueous solutions are acidic.
Application
Sulfosalicylic acid is used in medicine for the qualitative determination of protein in urine, and during analytical work to determine the content of nitrates in water.
In industry, sulfosalicylic acid is used as an additive to basic raw materials in the synthesis of substances.
Physical properties and occurrence in nature
Monocarboxylic acids of the benzene series are colorless crystalline substances with a melting point above 100 °C. Acids with pair- the position of the substituents melt at significantly higher temperatures than their isomers. Aromatic acids boil at slightly higher temperatures and melt at significantly higher temperatures than fatty acids with the same number of carbon atoms. Monocarboxylic acids dissolve rather poorly in cold water and much better in hot water. Lower acids are volatile with water vapor. In aqueous solutions, monocarboxylic acids exhibit a greater degree of dissociation than fatty acids: the dissociation constant of benzoic acid is 6.6·10 -5, acetic acid is 1.8·10 -5. At 370C it decomposes to benzene and CO2 (phenol and CO are formed in small quantities). When reacting with benzoyl chloride at elevated temperatures, benzoic acid is converted to benzoic anhydride. Benzoic acid and its esters are found in essential oils (for example, clove, tolu and Peruvian balsam, benzoin). A derivative of benzoic acid and glycine, hippuric acid, is a waste product of animals. It crystallizes in the form of colorless plates or needles, melting at 121 oC, easily soluble in alcohol and ether, but sparingly soluble in water. Currently, benzoic acid is widely used in the dye industry. Benzoic acid has antisentic properties and is therefore used for food preservation. Various derivatives of benzoic acid are also widely used.
Chemical properties
Benzene was discovered by Faraday in 1825 and its gross formula was established as C 6 H 6. In 1865, Kekule proposed its structural formula as cyclohexatriene-1,3,5. This formula is still used today, although it, as will be shown later, is imperfect - it does not fully correspond to the properties of benzene.
The most characteristic feature of chemical behavior benzene is the amazing inertness of the carbon-carbon double bonds in its molecule: in contrast to those considered; previously unsaturated compounds, it is resistant to the action of oxidizing agents (for example, potassium permanganate in acidic and alkaline environments, chromic anhydride in acetic acid) and does not enter into the usual electrophilic addition reactions characteristic of alkenes, alkadienes and alkynes.
Trying to explain the properties of benzene by structural features, many scientists, following Kekule, put forward their own hypotheses on this matter. Since the unsaturation of benzene did not clearly manifest itself, it was believed that there were no double bonds in the benzene molecule. Thus, Armstrong and Bayer, as well as Klaus, suggested that in the benzene molecule the fourth valences of all six carbon atoms are directed towards the center and saturate each other, Ladenburg - that the carbon skeleton of benzene is a prism, Chichibabin - that in benzene the carbon is trivalent.
Thiele, improving Kekule's formula, argued that the double bonds in the latter are not fixed, but constantly move - “oscillate”, and Dewar and Hückel proposed structural formulas of benzene with double bonds and small rings.
Currently, based on numerous studies, it can be considered firmly established that the six carbon and six hydrogen atoms in the benzene molecule are in the same plane and that the clouds of π-electrons of the carbon atoms are perpendicular to the plane of the molecule and, therefore, parallel to each other and interact with each other. The cloud of each π-electron is overlapped by the 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 tori.
It follows that it is logical to depict the formula of benzene in the form of a regular hexagon with a ring inside, thereby emphasizing the complete delocalization of π-electrons in the benzene ring and the equivalence of all carbon-carbon bonds in it. The validity of the latter conclusion is confirmed, in particular, by the results of measuring the lengths of C-C bonds in the benzene molecule; they are identical and equal to 0.139 nm (C-C bonds in the benzene ring are shorter than single ones (3.154 nm), but longer than double ones (0.132 nm)). Electron density distribution in a benzene molecule; bond lengths, bond angles
A very important derivative of benzoic acid is its acid chloride - benzoyl chloride. It is a liquid with a characteristic odor and a strong lachrymatory effect. Used as a benzoylating agent.
Benzoyl peroxide used as an initiator for polymerization reactions, and also as a bleaching agent for edible oils, fats, and flour.
Toluic acids. Methylbenzoic acids are called toluic acids. They are formed during the partial oxidation of o-, m- And P-xylenes. NN -Diethyl- m-toluilmide is effective repellent- insect repellent:
n-tert-Butylbenzoic acid is produced on an industrial scale by liquid-phase oxidation rubs-butyltoluene in the presence of a soluble cobalt salt as a catalyst. Used in the production of polyester resins.
Phenylacetic acid obtained from benzyl chloride through nitrile or through organomagnesium compounds. This is a crystalline substance with m.p. 76 °C. Due to the mobility of similar atoms of the methyl group, it easily enters into condensation reactions. This acid and its esters are used in perfumery.
Aromatic acids undergo all the reactions that are characteristic of fatty acids. Reactions involving the carboxyl group produce various acid derivatives. Salts are obtained by the action of acids on carbonates or alkalis. Esters - by heating a mixture of acid and alcohol in the presence of mineral (usually sulfuric) acid:
If the substituents in ortho- If this is not the case, then esterification of the carboxyl group occurs as easily as in the case of aliphatic acids. If one of ortho-positions are substituted, the rate of esterification is greatly reduced, and if both ortho- the positions are occupied, esterification usually does not occur (spatial difficulties).
Ethers ortho-substituted benzoic acids can be obtained by the reaction of silver salts with haloalkyl (esters of sterically hindered aromatic acids are easily and quantitatively saponified in the presence of crown ethers). Due to spatial constraints, they are difficult to hydrolyze. Groups larger than hydrogen fill the space around the carbon atom of the carboxyl group to such an extent that they make the formation and saponification of the ester difficult.
Preparation of C6H5COOH:
Main methods:
1. By oxidation of a wide variety of benzene derivatives having one side chain, for example, toluene, ethylbenzene, benzyl alcohol, etc.: C6H5CH3 ® C6H5COOH
2. From benzonitrile, which is hydrolyzed with an acid or alkali for this purpose: 2H2 O C6H5CN ¾¾® C6H5COOH + NH3
Benzoic acid (or rosemary), Acidum benzoicum sublimatum, Flores Benzoës - a very common substance in nature with the composition C7H6O2, or C6H5-COOH; found in some resins, balms, in herbaceous parts and in the roots of many plants (according to previous, still untested observations), as well as in the flowers of Unona odoratissima (in the essence of Alan-Gilan, or ylang-ylang), in beaver stream, but mainly in benzoin resin, or dew incense, hence its name. There are indications about the products of dry distillation of this resin in works dating back to the 16th century; Blaise de Vigenère, in his treatise (1608) "Traité du feu et du sel", was the first to mention a crystalline substance of benzoin gum, which was subsequently examined more closely and received the name Flores benzoës. Its composition was finally established by Liebig in 1832, and Kolbe proposed to consider it as phenylcarboxylic acid. B. acid can be obtained synthetically from benzene and is formed in many reactions occurring with aromatic bodies. For pharmaceutical needs, they use exclusively acid obtained by sublimation of benzoin resin. It is best to take Siamese dew incense for this purpose, since it does not contain cinnamic acid, or Calcutta, which is cheaper and also contains a lot of B. acid. The crushed resin is slightly heated in a sand bath in iron pots, during which the mass first melts and then releases heavy acid vapors, which settle on the cold parts of the device in the form of crystals. To collect the substance, the pot is covered with a paper cone or a lid with a wide tube through which the vapors are discharged into a wooden box covered with paper. At the end of the operation (and strong heating should be avoided if possible), the acid remains in the receiver or on the paper cone in the form of snow-white crystals or flakes. The preparation obtained in this way has a distinct smell of vanilla, which depends on the content of a small amount of essential oil in the resin. Better yields can be achieved by infusing finely ground resin with milk of lime or soda for a long time. The mixture is then heated until the resin melts, and the substance is separated from the resulting benzoic acid salt with hydrochloric acid. The acid obtained in this way has a weaker odor than that obtained by sublimation. For technical purposes, hippuric acid (see this next) contained in the urine of herbivores is taken as a starting material. The urine is quickly evaporated to ⅓ of the original volume, filtered and treated with excess hydrochloric acid, and hippuric acid is released in crystalline form. After 24 hours, the crystals are separated from the mother liquor and purified by repeated crystallization until the persistent smell of urine has almost completely disappeared. Purified hippuric acid is boiled with hydrochloric acid, which splits into B. acid and glycol:
HOOC-CH3 + H3O = HOOC-CH3(NH3) + 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 is practiced in factories) to take for this purpose not toluene, but benzenyl chloride C6H5CCl3; this latter is heated with water in hermetically sealed vessels; the acid formed in this way stubbornly retains halogenated products. Further, B. acid is obtained by heating the lime salt of phthalic acid with caustic lime; finally, significant quantities of it remain as a by-product during the fabrication of bitter almond oil due to the oxidation of the latter. The acid obtained in one way or another is purified by recrystallization from hot water; solutions are decolorized by treatment with animal charcoal or heating with weak nitric acid. Kekule obtained benzoic acid synthetically by reacting carbonic acid on bromobenzene in the presence of sodium metal:
C6H5Br + 2Na + CO2 = C6H5CO2Na + NaBr.
Friedel and Crafts prepared it directly from benzene and carbonic acid in the presence of aluminum chloride. Pure B. acid presents as colorless single-clinomer needles or tablets, ud. weight 1.2 (at 21°), not changing in the light, while the one obtained by sublimation from dewy incense turns yellow after some time 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 sublimes below the boiling point; has no smell. Its vapors act as an irritant on the mucous membranes of the respiratory organs. With water vapor, the acid flies below 100°, and therefore its aqueous solutions cannot be concentrated by evaporation. 1000 parts of water are dissolved at 0° 1.7 wt. hours, and at 100° 58.75 hours B. acid. It is also highly soluble in alcohol, ether, chloroform, essential and fatty oils. Some impurities, even in very small quantities, change its physical properties so dramatically that at one time the existence of an isomeric B. acid was recognized and called salic acid, but both substances turned out to be completely identical (Beilstein). When vapor is passed through highly heated pumice or, better yet, dry distillation with caustic barite or slaked lime, the acid breaks down into benzene and carbon dioxide. When fused with caustic potash, all three hydroxybenzoic acids are obtained along with other products; oxidizing agents have a rather difficult effect on it. With sodium amalgam the following are formed: benzoaldehyde, benzyl alcohol and other products of complex composition. Chlorine and bromine, as well as iodine, act substitutively in the presence of iodic acid; fuming nitric acid produces nitrobenzoic acids, and fuming sulfuric acid produces sulfobenzoic acids. In general, the hydrogens of the phenyl group in the acid can be replaced one after another by various residues, and a huge number of diverse compounds are formed, of which several isomeric forms are known for many. Of the derivatives of B. acid formed through substitution in the carboxyl group, the simplest will be the following:
Benzoyl chloride, the acid chloride of B. acid, C6H5-COCl, was first obtained by Liebig and Wöhler in 1832 by treating bitter almond oil with dry chlorine; it is also formed by the action of phosphorus pentachloride or trichloride on benzoic acid or phosphorus oxychloride on benzoinonate salt. Colorless liquid with a pungent odor, st. weight 1.324 (at 0°), boiling at 198°; hardens in the cooling mixture into crystals (melting at -1°). Hot water quickly decomposes into hydrochloric and fermented acids; easily enters into double decompositions with a number of substances; Thus, under the action of ammonia, Liebig and Wöhler obtained from it benzamide, or B. acid amide, C6H5-CONH3, a crystalline substance that melts at 128°, sp. weight 1.341 (at 4°), soluble in hot water, alcohol and ether. Benzamide is also obtained by heating B. acid with ammonium thiocyanate. Water-removing substances easily convert it into B. acid nitrile, benzonitrile or phenyl cyanide - C6H5CN. This latter is also obtained from the potassium salt of sulfobenzoic acid and potassium cyanide. The substance is a liquid with a bitter almond odor, boiling at 190°, bpm. weight 1.023 (at 0°), solidifying upon strong cooling into a solid mass. Difficult to dissolve in boiling water and easily in alcohol and ether.
Methods of obtainingmonobasic carboxylic acids of the aromatic series
Monobasic aromatic carboxylic acids can be prepared by all general methods known for fatty acids.
Oxidation of alkyl groups of benzene homologues. This is one of the most commonly used methods for producing aromatic acids:
Oxidation is carried out either by boiling the hydrocarbon with an alkaline solution of potassium permanganate, or by heating it in sealed tubes with dilute nitric acid. Typically this method gives good results. Complications occur only in cases where the benzene ring is destroyed by the action of oxidizing agents.
Oxidation of aromatic ketones. Aromatic ketones are easily prepared by the Friedel-Crafts reaction. Oxidation is usually carried out using hypochlorites according to the following scheme:
However, other oxidizing agents can be used. Aceto derivatives oxidize more easily than hydrocarbons.
Hydrolysis of trihalogen derivatives with halogens at one carbon atom. When toluene is chlorinated, three types of chlorine derivatives are formed: benzyl chloride (used to obtain benzyl alcohol), benzylidene chloride (to obtain benzoaldehyde), benzotrichloride (processed into benzoic acid and benzoyl chloride). Direct hydrolysis of benzotrichloride does not proceed well. Therefore, benzotrichloride is converted by heating with benzoic acid into benzoyl chloride, which then, upon hydrolysis, easily gives benzoic acid:
Hydrolysis of nitriles:
This method is widely used in the fat row. In the aromatic series, the starting nitriles are obtained from diazo compounds, from halogen derivatives by exchange with copper cyanide in pyridine or by fusion of sulfonates with potassium cyanide. Acid nitriles with a nitrile group in the side chain are obtained by an exchange reaction from halogen derivatives.
Reaction of aromatic hydrocarbons with halogen derivatives of carbonic acid
The carboxyl group can be introduced into the nucleus through a reaction similar to the Friedel-Crafts synthesis of ketones. The catalyst is aluminum chloride:
Reactions of organometallic compounds with CO 2 :
Lithium or organomagnesium compounds are usually used.
Acid chlorides are prepared by reacting with thionyl chloride or phosphorus pentachloride acids:
Anhydrides are obtained by distillation of a mixture of acid and acetic anhydride in the presence of phosphoric acid or by the action of acid chlorides on salts:
When benzoyl chloride reacts with sodium peroxide, crystalline benzoyl peroxide is obtained:
When an alcoholate reacts with benzoyl peroxide, a salt of perbenzoic acid (benzoyl hydroperoxide) is obtained. This acid is used to obtain oxides from unsaturated compounds (Prilezhaev reaction):
Benzene, in the absence of a catalyst, does not react with bromine and chlorine, thereby demonstrating the stability of the 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 hexachlorocyclohexane (hexachlorane):
An interesting reaction involving double bonds is observed when benzene in the liquid phase is irradiated with light with a wavelength of 253.7 nm. Under these conditions, the benzene molecule is rearranged, turning into so-called valence isomers.
Nitrobenzoic acids
The nitration of benzoic acid produces 78%-meta-, 20% ortho- and 2% pair- nitrobenzoic acids. The last two isomers without impurities of other isomers are obtained by oxidation ortho- And pair- nitrotoluenes.
Nitrobenzoic acids have stronger acidic properties than benzoic acid (TO= 6.6·10 -5): O- isomer - 100 times, m- isomer - 4.7 times and n-iso measures - 5.6 times. A similar pattern is observed in the case of halogen-substituted acids.
Application
Benzoic acid and its salts have high bactericidal and bacteriostatic activity, which increases sharply with decreasing pH. Due to these properties, as well as non-toxicity, benzoic acid is used:
preservative in the food industry (addition of 0.1% acid to sauces, brines, fruit juices, jams, minced meat, etc.)
in medicine for skin diseases as an external antiseptic (antimicrobial) and fungicidal (antifungal) agent, and its sodium salt as an expectorant.
In addition, benzoic acid and its salts are used in food preservation (food additives E210, E211, E212, E213). Esters of benzoic acid (from methyl to amyl), which have a strong odor, are used in the perfume industry. Various benzoic acid derivatives, such as chloro- and nitrobenzoic acids, are widely used for the synthesis of dyes.
Benzoic acid is used in the production
caprolactam
benzoyl chloride
additive to alkyd varnishes that improves gloss, adhesion, hardness and chemical resistance of the coating
Salts and esters of benzoic acid (benzoates) are of great practical importance.
Sodium benzoate is a food preservative, polymer stabilizer, corrosion inhibitor in heat exchangers, expectorant in medicine.
Ammonium benzoate is an antiseptic, preservative in the food industry, corrosion inhibitor, stabilizer in the production of latexes and adhesives.
Transition metal benzoates are catalysts for the liquid-phase oxidation of alkyl aromatic hydrocarbons to benzoic acid.
Esters of benzoic acid from methyl to isoamyl are fragrant substances. Methyl benzoate is a solvent for cellulose ethers.
Isoamyl benzoate is a component of fruit essences.
Benzyl benzoate is an odor fixer in perfumery, a solvent for fragrant substances, an antiseptic, and a moth repellent.
Precautionary measures:
Causes irritation upon contact with skin.
Inhalation of the aerosol causes a convulsive cough, runny nose, and sometimes nausea and vomiting.
Conclusion
Latin name: Acidum benzoicum
Benzoic acid C6H5COOH is the simplest monobasic carboxylic acid of the aromatic series.
Benzoic acid is colorless crystals, poorly soluble in water, well soluble in ethanol and diethyl ether.
It is used mainly in the form of sodium (high solubility in water) - sodium benzonate, potassium and calcium salts.
Melting point - 122.4°C,
Boiling point - 249°C.
Easily sublimes (one of the methods of production is dry distillation of benzoin resin); distilled with steam.
Benzoic acid (BA) is used in medicine for skin diseases as an external antiseptic (antimicrobial) and fungicidal (antifungal) agent, and its sodium salt is used as an expectorant.
B. and its salts have high bactericidal and bacteriostatic activity, which increases sharply with decreasing pH of the environment.
A reaction with some forms of ascorbic acid (vitamin C) is possible.
In the body, benzoic acid combines with glycine to form harmless hippuric acid, which is excreted in the urine.
The permissible dose of benzoic acid and its salt for humans is 5 mg/kg of body weight per day.
Concentration in recipes: 0.2-0.5% (per 50 g of cream - 0.2 g of sodium benzoate).
The activity of benzoic acid decreases in the presence of nonionic surfactants, proteins and glycerol.
Used in conjunction with other preservatives.
Being fat soluble, it can be used as a preservative for fats, lipsticks, etc. The maximum concentration in cosmetic products is 0.5%.
Salts of benzoic acid - benzoates (for example, sodium benzoate) are also used as preservatives.
Other uses: Benzoic acid esters, which have a strong odor, are used in the perfume industry.
Various benzoic acid derivatives, such as chloro- and nitrobenzoic acids, are widely used for the synthesis of dyes.
B. and its esters are contained in essential oils (for example, clove oil), Tolu and Peruvian balsams, and benzoic resin (up to 20% acid and up to 40% its esters).
Additional Information:
In practice, aqueous solutions of sodium benzoate with a concentration of 5 to 25% are most often used.
To prepare the solution, the required amount of preservative is dissolved in approximately half the required volume of drinking water, heated to 50...80C. After the salt has completely dissolved, add the remaining water to the resulting solution and mix thoroughly. It is recommended to filter the solution through a layer of cotton fabric (calico). If a preservative is dissolved in hard water, the solution may be slightly cloudy, but this does not affect its preservative effect.
When developing a specific recipe for adding a preservative to a product, the following must be taken into account:
the acidity of the environment affects the effectiveness of preservatives - the more acidic the product is, the less preservative needs to be added to it;
as a rule, low-calorie products have a high water content and are easily spoiled, so the amount of preservative added to them should be 30-40% more than recommended for regular products;
the addition of alcohol, a large amount of sugar or other substance exhibiting preservative properties reduces the required amount of preservative.
Literature
1 Zemtsova M.N. Guidelines for completing coursework in organic chemistry.
2. Chemical reagents and preparations Goskhimizdat 1953, Pp. 241-242.
3. Karyakin Yu.V., Angelov I.I. Pure chemicals Ed. 4th, lane and additional M.: Chemistry 1974, pp. 121-122.
4. “Concise chemical encyclopedia” Ed. Soviet Encyclopedia, T.4 M. 1965 Page. 817-826.
5. Petrov A.A., Balyan H.V., Troshchenko A.T. Organic chemistry: Textbook for universities. – St. Petersburg: “Ivan Fedorov”, 2002, Page. 421-427.
6. Gitis S.S., Glaz A.I., Ivanov A.V. Workshop on organic chemistry: -M.: Higher school, 1991. - 303.: ill.
7. Shabarov Yu.S. Organic chemistry: Textbook for universities in 2 books. – M.: Chemistry, 1996.Pp. 558-561, 626-629.
- acids are very common... the reaction is used to detect benzoin acids on chromatograms. Oxybenzoic acids according to the number OH...
Selecting an amidation catalyst and studying the conversion of m-toluyl in its presence acids in N,N-diethyl-m-toluamide
Thesis >> ChemistryContains ortho- and para-isomers, as well as benzoin acid, to identify the reactivity of all... 3.3. Table 3.3 Relative rates of amidation of derivatives benzoin acids diethylamine (molar ratio of reagents 1:5, t° = 300°C...
Synthesis of malonic diethyl ether acids. Properties and basic methods for obtaining esters
Coursework >> ChemistryWith increased content of this acids. Sorrel acid– one of the most... even without mineral additives acids-catalyst, and aromatic acids, especially those ... results of esterification work benzoin acids methanol containing a heavy isotope...
Benzoic acid is a monobasic carboxylic substance isolated in the 16th century by sublimation of benzoic resin.
It is a natural compound. Contained in cranberries, blueberries, lingonberries, raspberries, and cherry tree bark. Found bound in honey. Interestingly, benzoic acid is formed during the microbial decomposition of N - benzoylglycine in fermented dairy products (kefir, fermented baked milk, yogurt, yogurt).
The structural formula of the aromatic compound is C6H5COOH.
Benzoic acid exhibits antimicrobial and antifungal effects: it prevents the proliferation of butyric acid fermentation bacteria, yeast, and inhibits the activity of enzymes of pathogenic cells. Due to its antiseptic properties, it is used in the food industry as a natural preservative (E210) in the manufacture of food and beverages.
Application
In appearance, benzoic acid is elongated white crystals that have a characteristic shine. At a temperature of 122 degrees Celsius it turns into a gaseous state. Benzoic acid is soluble in alcohols. It is produced on an industrial scale by the oxidation of toluene. In addition, the substance is obtained from benzotrichloride, phthalic acid.
The preservative is used in the baking, confectionery, and brewing industries for the production of the following products:
- fruit and vegetable purees;
- soft drinks;
- berry juices;
- fish products;
- canned fruits, olives;
- ice cream;
- preserves, jam, marmalade;
- canned vegetables;
- margarine;
- chewing gum;
- sweets and sweeteners;
- delicacy caviar;
- dairy products
- liquor, beer, wine.
The antiseptic and antibacterial properties of benzoic acid are used in the pharmaceutical industry for the production of antifungal medications and ointments for scabies. And special foot baths using an organic compound relieve excessive sweating and foot fungus. In addition, benzoic acid is added to cough syrups because it has expectorant properties and thins mucus.
It is used as a preservative in cosmetics to preserve beneficial properties and extend the shelf life of creams, lotions, and balms. Due to its strong whitening properties, the compound is included in masks, the action of which is aimed at ridding the face of freckles, uneven skin, and age spots.
Health effects
When it enters the body, benzoic acid reacts with protein molecules, turning into N - benzoylglycine (hippuric acid). After transformation, the compound is excreted in the urine. This process “loads” the human excretory system, therefore, in order to avoid harm to health, the legislation of each state establishes the permissible norm for the use of acid in the manufacture of food products. Today it is allowed to use up to five milligrams of the substance per kilogram of finished products. Exceeding the permissible value is punishable by law and imposes a ban on the sale of such products.
The harm of benzoic acid lies not only in increasing the load on the kidneys. It is the “progenitor” of a dangerous carcinogenic substance: it can produce benzene in its pure form, which provokes the growth of malignant tumors. It takes very high temperatures to turn acid into poison.
The isolation of benzene in the human body from the benzoin compound is impossible. However, it is not recommended to heat canned foods that are not intended for this purpose and then eat them, as this can lead to food poisoning.
Remember, the preservative E210, even in minute quantities (up to 0.01 milligrams), has a detrimental effect on pets: it undermines health and worsens well-being. Therefore, before feeding your pet, make sure that the product does not contain benzoic acid, otherwise the consequences can be extremely tragic.
The activity of the compound decreases in the presence of glycerol, proteins, and nonionic surfactants. If it comes into contact with the surface of the skin, it causes redness and irritation; inhalation of the aerosol causes nausea, vomiting, convulsive cough, and runny nose. Therefore, when working with the substance and its salts, use personal protective equipment (rubber gloves, overalls, dust respirators), and observe personal hygiene measures.
Simultaneous intake of foods rich in ascorbic and benzoic acids leads to the formation of toxic free benzene. Therefore, the minimum break between taking such products (soft drinks and citrus fruits) is two hours.
Excess and deficiency
The permissible daily intake of benzoic acid for an adult without harm to health is determined based on the calculation: 5 milligrams of organic matter per kilogram of body weight.
An overdose of benzoic acid worsens the functioning of the liver, kidneys, lungs, and causes mental problems. A person exhibits signs of asthma, an allergic reaction (swelling, rashes), and the functioning of the thyroid gland is disrupted.
Acid deficiency in the body causes digestive disorders, headaches, and depression. A person's metabolism is disrupted, weakness, irritability occurs, and hair becomes brittle. As a result of a long-term lack of “natural preservative”, anemia occurs.
The body's need for the compound decreases with a low level of blood clotting, at rest, with pathologies of the thyroid gland and increases with allergies, blood thickening, and infectious diseases.
Interestingly, benzoic acid (within normal limits) improves milk production in lactating women.
Benzoic acid salts
Let's look at what benzoates are, their properties and uses:
- Ammonium benzoate. It is an inorganic compound of benzoic acid and ammonium salt. It is colorless and soluble in ethanol and water. Structural formula – NH4(C6H5COO). It is used as an antiseptic (prevents decomposition processes on the surface of open wounds), a preservative in the food industry to increase the shelf life of products, a stabilizer in the manufacture of adhesives, latexes and a corrosion inhibitor.
- Lithium benzoate. It is a white crystalline salt of lithium and benzoic acid. The chemical formula of the compound is C6H5 – COOLi. It has a sweetish taste, odorless, and dissolves in water. It is used in pharmacology as a mood stabilizer to normalize the mental state. Has antimanic, sedative, antidepressant effects. This effect is due to the fact that lithium ions displace sodium ions from cells, reducing the bioelectrical activity of brain neurons. As a result, the level of serotonin in tissues and the concentration of norepinephrine decreases, and the sensitivity of hippocampal neurons to the action of dopamine increases. At therapeutic concentrations, it reduces the concentration of neuronal inositol and blocks the activity of inosyl-1-phosphatase.
- Sodium benzoate. It acts as a food additive, registered under code E211, and belongs to the group of preservatives. Structural formula – C6H5COONa. The sodium salt of benzoic acid has a characteristic faint odor of benzaldehyde and a white color. The preservative inhibits the growth of mold fungi, including aflatoxin-forming fungi, yeast and reduces the activity of enzymes that break down starch and triglycerides.
In natural products, sodium benzoate is found in apples, mustard, raisins, cranberries, and cinnamon. It is used for canning fruits and berries, fish, meat products, and sweet carbonated drinks. Included in expectorants and cosmetic products.
Remember, sodium benzoate can disrupt the DNA region in mitochondria and cause neurodegenerative diseases, Parkinson's disease, cirrhosis of the liver. Therefore, the use of the E211 additive, due to its unsafety for human health, has been rapidly declining in recent years.
Thus, benzoic acid and its salts are organic additives used in the food, pharmaceutical, aviation and cosmetology industries as a preservative. To maintain health, you need to consume foods containing E210 in moderation. The safe dose is 5 milligrams of the substance per kilogram of weight. Otherwise, oversaturation of the body with benzoic acid can cause allergic reactions and damage to the nervous system.
Appearance. Benzoic acid is colorless, silky, shiny flakes or white crystals and plates;
(or crystalline powder) for low grade acid made in China.
Physical properties of benzoic acid.
Molar mass 122.12 g/mol
Physical properties.
Condition (standard condition) solid
Thermal properties
Melting point 122.4 °C
Boiling point 249.2 °C
Decomposition temperature 370 °C
Specific heat of vaporization 527 J/kg
Specific heat of fusion 18 J/kg
Chemical properties
Solubility in water 0.001 g/100 ml
Description of benzoic acid and differences between different brands.
Benzoic acid was first isolated by sublimation in the 16th century from benzoic resin, hence its name, a rare coincidence in science, when it turned out after Justus von Liebig (a German chemist) determined the structural formula of benzoic acid in 1832, the name coincided with the real formula. Until now, the main way to obtain it is the oxidation of methylbenzene (toluene.)
1 recrystallization of the product and commercial packaging, all Chinese and former Russian manufacturers did exactly this.
In this case, the product is prone to rapid and inevitable caking. Bags of benzoic acid turn into stone, which is difficult to break even by machine.
The purity of such an acid does not exceed 97%; on the labels the Chinese proudly write 99.5%, but this is due to the presence of crystalline hydrates. The actual dry matter content is significantly less.
The second feature of direct crystallization is the presence of a large amount of aldehydes, which causes a sharp, nauseous chemical odor that stings the eyes.
Currently, there are several careless companies engaged in shuffling Chinese benzoic acid under the European DSM BRAND. These fakes can always be distinguished by the presence of benzoic acid in crystals in the bags and their pungent odor.
This benzoic acid has nothing to do with the manufacturer of DSM.
2 production method involves an additional stage, melting benzoic acid crystals and subsequent recrystallization from the melt.
This stage allows you to achieve several goals:
1 The product is obtained in small scales that do not generate dust or cake.
2, due to the high temperature, foreign impurities evaporate and the content of the main substance is 99.9% or 103% of the crystalline hydrate.
A distinctive feature of this acid is that it has flakes rather than crystals and a much milder odor. Only such an acid can be used for synthesis and inhibition. and for food and feed purposes as an additive E210.
Specification for benzoic acid produced by DSM (KALAMA).
A distinctive feature of this DSM (KALAMA) brand: crystallization from the melt, which allows you to obtain a product with a minimum caking coefficient and a significantly lower odor compared to other manufacturers.
Technical characteristics for this brand of benzoic acid:
Flake size 0.5-4.5 mm
Bulk density 540kg/m3
Safety for humans.
Recently, many articles have appeared that provide various data on the terrible dangers of this product. This is greatly untrue.
benzoic acid can be called a natural compound, since it is present in some berries (blueberries, lingonberries, cranberries), and is also formed in fermented milk products such as yogurt or yogurt. It allows the berries to resist fungal diseases and mold. So this is one of the few preservatives invented by nature, but of course the correct dosages have not been canceled. If they are exceeded, unpleasant behavior of any chemical ingredient may occur.
Benzoic acid for animals.
Cat lovers should remember that benzoic acid and its salts are extremely dangerous for your pets on their own, even in minute quantities. Therefore, before offering your cat any product from your table, make sure that it does not contain such a preservative. In general, this is one of the many reasons why you should not feed your pets “human” canned food. But for pigs it has long been used in large quantities, but for some reason no one says the word benzoic acid, and all veterinarians know it as the additive VIOVITAL (VevoVitall) (not to be confused with biovetal, different things are similar, although they are similar), which is what it is in its composition pure 99.9% benzoic acid.
All over the world, benzoic acid is actively used in fattening and raising pigs.
1 Effect of using high-purity benzoic acid 99.9%
When feeding piglets.
10% improvement in piglet weight gain
5% reduction in feed intake.
Reduce odor on and off the farm.
The addition of high-purity benzoic acid (at least 99.9%) leads to acidification of urine.
– After absorption from the intestine, benzoic acid is converted into hippuric acid in the animal’s liver, this acid is easily excreted in the urine. And leads to its intense acidification. At the same time, hippuric acid contains an amine. This leads to a significant reduction in NH4+ NH3 ammonia emissions.
This results in a significant reduction in odor on the pig farm.
In addition, problems with UTI (sows) are reduced
Benzoic acid is also present in the intestinal tract, inhibiting the development of anaerobic bacteria and reducing gas production. Which significantly reduces odor on the surface and external emissions.
Antimicrobial protection of young pigs using high-purity benzoic acid (not less than 99.9%) data from in vitro studies
1./2 inhibitory concentration of benzoic acid was used.
to inhibit 50% of microbial growth.
