Benzoic acid ba oh 2. Acetylsalicylic (2-(acetyloxy)-benzoic) acid

Benzoic acid

Chemical properties

This substance is a monobasic carboxylic acid of the aromatic series. Racemic Formula of Benzoic Acid: C7H6O2. Structural formula: C6H5COOH. It was first synthesized back in the 16th century from dew incense and benzoin resin, which is where it got its name. These are white small crystals that are poorly soluble in water, highly soluble in chloroform , ethanol And diethyl ether . Molecular mass of the substance = 122.1 grams per mole.

Chemical properties of Benzoic Acid. The substance exhibits weak acidic properties and is quite easily sublimated and distilled using steam. It participates in all reactions characteristic of the carboxyl group. Nitration reaction ( HNO3) is more complicated than electrophilic aromatic addition at the 3rd position. When introducing a substituent, for example, alkyl , substitution occurs more easily in the second position. The chemical compound forms ethers , amides , benzoic anhydride , acid halides , orthoesters , salt.

Qualitative reaction to Benzoic Acid. To establish the identity of the substance, a reaction is carried out with ferric chloride 3, FeCl3, as a result, a complex basic compound is poorly soluble in water. Iron benzoate 3 , with a characteristic yellow-pink color.

Receiving from toluene . To obtain Benzoic Acid from toluene, it is necessary to expose the product to a strong oxidizing agent, for example, MnO2 in the presence of a catalyst – sulfur to-you . As a result, water and ions are formed Mn2+. Toluene can also be oxidized. In order to carry out the reaction to obtain Benzoic Acid from benzene first you need to get toluene : benzene + CH3Cl, in the presence aluminum chloride = toluene + . Also, when obtaining a substance, hydrolysis reactions are used benzamide And benzonitrile ; Cannizzaro reaction or Grignard reaction (carboxylation phenylmagnesium bromide ).

Application of the substance:

• for calibration of calorimeters, used as a thermal standard;
• raw materials for obtaining benzoyl chloride , benzoate plasticizers;
• as a preservative, in pure form or in the form of sodium, calcium and potassium salts, code E210, E212, E211, E213;
• for some skin diseases and as an expectorant (sodium salt);
• acid esters are used in the perfume industry;
• nitro And chlorobenzoic acid used in the synthesis of dyes.

pharmachologic effect

Antiseptic, antifungal.

Pharmacodynamics and pharmacokinetics

Benzoic Acid has the ability to block enzymes and slow down metabolic processes in fungal cells and in some single-celled microorganisms. Prevents the growth of yeast, mold and harmful bacteria. Undissociated acid penetrates the microbial cell; in acidic conditions pH.

The safe dosage of the substance for humans is 5 mg per kg of body weight per day. The drug is present in the urine of mammals as a component hippuric acid .

Indications for use

Used as part of various drugs from, trichophytosis ; for complex treatment of burns and non-healing wounds; during treatment trophic ulcers And bedsores , .

Contraindications

Individual intolerance.

Side effects

Benzoic Acid rarely causes adverse reactions; burning and itching may be felt at the site of application. The symptoms go away on their own over time. Allergic reactions are rarely observed.

Instructions for use (Method and dosage)

Preparations with the addition of Benzoic Acid are used externally. The frequency of use depends on the disease and the concentration of the substance. The drugs are applied to the affected areas of the skin, to wound surfaces, if indicated - under a gauze bandage. Treatment is usually continued until complete healing.

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 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, 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 applications:

1. 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.
2. 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.
3. 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.

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-CH2 + H2O = 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 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 amide of B. acid, C6H5-CONH2, 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 readily soluble in alcohol and ether.

Methods of obtaining monobasic 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.