Chemical properties of phenol reaction equations. Phenol (hydroxybenzene, carbolic acid)

Phenols- derivatives of aromatic hydrocarbons, which may contain one or more hydroxyl groups connected to a benzene ring.

What are phenols called?

According to IUPAC rules, the name " phenol" The numbering of atoms comes from the atom that is directly bonded to the hydroxy group (if it is the senior one) and is numbered so that the substituents receive the lowest number.

Representative - phenol - C 6 H 5 OH:

The structure of phenol.

The oxygen atom has a lone electron pair at its outer level, which is “pulled” into the ring system (+M effect HE-groups). As a result, 2 effects can occur:

1) increasing the electron density of the benzene ring to the ortho- and para- positions. Basically, this effect manifests itself in electrophilic substitution reactions.

2) the density on the oxygen atom decreases, as a result of which the bond HE weakens and may tear. The effect is associated with the increased acidity of phenol compared to saturated alcohols.

Mono-substituted derivatives phenol(cresol) can be in 3 structural isomers:

Physical properties of phenols.

Phenols are crystalline substances at room temperature. Poorly soluble in cold water, but well soluble in hot water and in aqueous solutions of alkalis. They have a characteristic odor. Due to the formation of hydrogen bonds, they have a high boiling and melting point.

Preparation of phenols.

1. From halobenzenes. When chlorobenzene and sodium hydroxide are heated under pressure, sodium phenolate is obtained, which, after reacting with acid, turns into phenol:

2. Industrial method: the catalytic oxidation of cumene in air produces phenol and acetone:

3. From aromatic sulfonic acids by fusion with alkalis. The reaction most often carried out to produce polyhydric phenols is:

Chemical properties of phenols.

R The -orbital of the oxygen atom forms a single system with the aromatic ring. Therefore, the electron density on the oxygen atom decreases, and on the benzene ring it increases. Communication polarity HE increases, and the hydrogen of the hydroxyl group becomes more reactive and can easily be replaced by a metal atom even under the action of alkalis.

The acidity of phenols is higher than that of alcohols, so the following reactions can be carried out:

But phenol is a weak acid. If carbon dioxide or sulfur dioxide is passed through its salts, phenol is released, which proves that carbonic and sulfurous acids are stronger acids:

The acidic properties of phenols are weakened by the introduction of type I substituents into the ring and enhanced by the introduction of type II.

2) Formation of esters. The process occurs under the influence of acid chlorides:

3) Electrophilic substitution reaction. Because HE-group is a substituent of the first kind, then the reactivity of the benzene ring in the ortho- and para-positions increases. When phenol is exposed to bromine water, a precipitate is observed - this is a qualitative reaction to phenol:

4) Nitration of phenols. The reaction is carried out with a nitrating mixture, resulting in the formation of picric acid:

5) Polycondensation of phenols. The reaction occurs under the influence of catalysts:

6) Oxidation of phenols. Phenols are easily oxidized by atmospheric oxygen:

7) A qualitative reaction to phenol is the effect of a solution of ferric chloride and the formation of a violet complex.

Application of phenols.

Phenols are used in the production of phenol-formaldehyde resins, synthetic fibers, dyes and medicines, and disinfectants. Picric acid is used as explosives.

Formed on the basis of benzene. Under normal conditions, they are solid toxic substances with a specific aroma. In modern industry, these chemical compounds play an important role. In terms of volume of use, phenol and its derivatives are among the twenty most popular chemical compounds in the world. They are widely used in the chemical and light industries, pharmaceuticals and energy. Therefore, the production of phenol on an industrial scale is one of the main tasks of the chemical industry.

Phenol designations

The original name of phenol is carbolic acid. Later, this compound was given the name “phenol”. The formula of this substance is shown in the figure:

The phenol atoms are numbered from the carbon atom that is connected to the OH hydroxo group. The sequence continues in such an order that the other substituted atoms receive the lowest numbers. Phenol derivatives exist in the form of three elements, the characteristics of which are explained by the differences in their structural isomers. Various ortho-, meta-, para-cresols are only a modification of the basic structure of the compound of the benzene ring and hydroxyl group, the basic combination of which is phenol. The formula of this substance in chemical notation looks like C 6 H 5 OH.

Physical properties of phenol

Visually, phenol appears as solid, colorless crystals. In open air they oxidize, giving the substance a characteristic pink tint. Under normal conditions, phenol is quite poorly soluble in water, but with an increase in temperature to 70 o this figure increases sharply. In alkaline solutions this substance is soluble in any quantity and at any temperature.

These properties are also preserved in other compounds, the main components of which are phenols.

Chemical properties

The unique properties of phenol are explained by its internal structure. In the molecule of this chemical substance, the p-orbital of oxygen forms a single p-system with the benzene ring. This tight interaction increases the electron density of the aromatic ring and decreases this indicator for the oxygen atom. In this case, the polarity of the bonds of the hydroxo group increases significantly, and the hydrogen included in its composition is easily replaced by any alkali metal. This is how various phenolates are formed. These compounds do not decompose with water like alcoholates, but their solutions are very similar to salts of strong bases and weak acids, so they have a fairly pronounced alkaline reaction. Phenolates react with various acids; as a result of the reaction, phenols are reduced. The chemical properties of this compound allow it to react with acids, forming esters. For example, the reaction of phenol and acetic acid leads to the formation of phenyl ester (phenyacetate).

The nitration reaction is widely known, in which, under the influence of 20% nitric acid, phenol forms a mixture of para- and orthonitrophenols. When phenol is treated with concentrated nitric acid, it produces 2,4,6-trinitrophenol, which is sometimes called picric acid.

Phenol in nature

As an independent substance, phenol is found in nature in coal tar and in certain types of oil. But for industrial needs this quantity does not play any role. Therefore, obtaining phenol artificially has become a priority for many generations of scientists. Fortunately, this problem was resolved and artificial phenol was eventually obtained.

Properties, receiving

The use of various halogens makes it possible to obtain phenolates, from which benzene is formed upon further processing. For example, heating sodium hydroxide and chlorobenzene produces sodium phenolate, which, when exposed to acid, breaks down into salt, water and phenol. The formula for such a reaction is given here:

C 6 H 5 -CI + 2NaOH -> C 6 H 5 -ONa + NaCl + H 2 O

Aromatic sulfonic acids are also a source for the production of benzene. The chemical reaction is carried out by simultaneous melting of alkali and sulfonic acid. As can be seen from the reaction, phenoxides are formed first. When treated with strong acids, they are reduced to polyhydric phenols.

Phenol in industry

In theory, the simplest and most promising way to obtain phenol looks like this: with the help of a catalyst, benzene is oxidized with oxygen. But until now, a catalyst for this reaction has not been selected. Therefore, other methods are currently used in industry.

A continuous industrial method for producing phenol consists of the interaction of chlorobenzene and a 7% sodium hydroxide solution. The resulting mixture is passed through a one and a half kilometer system of pipes heated to a temperature of 300 C. Under the influence of temperature and maintained high pressure, the starting substances react, resulting in 2,4-dinitrophenol and other products.

Not long ago, an industrial method for producing phenol-containing substances using the cumene method was developed. This process consists of two stages. First, isopropylbenzene (cumene) is obtained from benzene. To do this, benzene is alkalated with propylene. The reaction looks like this:

After this, cumene is oxidized with oxygen. The output of the second reaction is phenol and another important product, acetone.

Phenol can be produced on an industrial scale from toluene. To do this, toluene is oxidized on oxygen contained in the air. The reaction occurs in the presence of a catalyst.

Examples of phenols

The closest homologues of phenols are called cresols.

There are three types of cresols. Meta-cresol under normal conditions is a liquid, para-cresol and ortho-cresol are solids. All cresols are poorly soluble in water, and their chemical properties are almost similar to phenol. In their natural form, cresols are found in coal tar; in industry they are used in the production of dyes and some types of plastics.

Examples of diatomic phenols include para-, ortho-, and meta-hydrobenzenes. All of them are solids, easily soluble in water.

The only representative of trihydric phenol is pyrogallol (1,2,3-trihydroxybenzene). Its formula is presented below.

Pyrogallol is a fairly strong reducing agent. It oxidizes easily, so it is used to produce oxygen-free gases. This substance is well known to photographers; it is used as a developer.

DEFINITION

Phenols- derivatives of aromatic hydrocarbons, in the molecules of which hydroxyl groups are directly bonded to the carbon atoms of the benzene ring. The functional group, like that of alcohols, is OH.

Phenol is a solid, colorless, crystalline substance, low-melting, very hygroscopic, with a characteristic odor. In air, phenol oxidizes, so its crystals initially acquire a pinkish tint (Fig. 1), and during long-term storage they darken and become more red. It is slightly soluble in water at room temperature, but dissolves quickly and well at 60 - 70 o C. Phenol is low-melting, its melting point is 43 o C. It is toxic.

Rice. 1. Phenol. Appearance.

Preparation of phenol

On an industrial scale, phenol is obtained from coal tar. Among the laboratory methods I most often use the following:

- hydrolysis of chlorobenzene

C 6 H 5 Cl + NaOH→C 6 H 5 OH + NaCl (kat = Cu, t 0).

- alkaline melting of salts of arenesulfonic acids

C 6 H 5 SO 3 Na + 2NaOH → C 6 H 5 OH + Na 2 SO 3 + H 2 O (t 0).

— cumene method (oxidation of isopropylbenzene)

C 6 H 5 -C(CH 3)H-CH 3 + O 2 →C 6 H 5 OH + CH 3 -C(O)-CH 3 (H +, t 0).

Chemical properties of phenol

Chemical transformations of phenol occur mainly with splitting:

1) O-H connections

— interaction with metals

2C 6 H 5 OH + 2Na → 2C 6 H 5 ONa + H 2 .

- interaction with alkalis

C 6 H 5 OH + NaOH → C 6 H 5 ONa + H 2 O.

— interaction with carboxylic acid anhydrides

C 6 H 5 -OH + Cl-C(O)-O-C(O)-CH 3 → C 6 H 5 -O-C(O)-CH 3 + CH 3 COOH (t 0).

— interaction with carboxylic acid halides

C 6 H 5 -OH + Cl-C(O)-CH 3 → C 6 H 5 -O-C(O)-CH 3 + HCl (t 0).

- interaction with FeCl 3 (qualitative reaction to phenol - the appearance of a purple color, which disappears when acid is added)

6C 6 H 5 OH + FeCl 3 → (C 6 H 5 OH) 3 + 3Cl - .

2) connections C sp 2 -H predominantly in O- And n- provisions

- bromination

C 6 H 5 -OH + 3Br 2 (aq) →Br 3 -C 6 H 2 -OH↓ + 3HBr.

- nitration (formation of picric acid)

C 6 H 5 -OH + 3HONO 2 (conc) → (NO 2) 3 -C 6 H 2 -OH + 3H 2 O (H +).

3) a single 6π-electron cloud of the benzene ring

- hydrogenation

C 6 H 5 OH + 3H 2 → C 6 H 11 -OH (kat = Ni, t 0 = 130 - 150, p = 5 - 20 atm).

Application of phenol

Phenol is used in large quantities for the production of dyes, phenol-formaldehyde plastics, and medicinal substances.

Of the diatomic phenols, resorcinol is used in medicine as an antiseptic and a substance for some clinical tests, and hydroquinone and other diatomic phenols are used as developers in the processing of photographic materials.

In medicine, Lysol, which contains various phenols, is used to disinfect rooms and furniture.

Some phenols are used as antioxidants - substances that prevent food spoilage during long-term storage (fats, oils, food concentrates).

Examples of problem solving

EXAMPLE 1

EXAMPLE 2

Why is phenol dangerous?

Phenols are organic substances that contain one or more hydroxyl groups attached to the carbon of the benzene ring. The simplest phenol, also called carbolic acid, has the formula C6H5OH. The melting point of phenol is low - 40.9 ° C, therefore, under normal conditions, phenol is colorless crystals, which, after lying in air for a while, acquire a pinkish tint.

Phenol is a volatile substance with a characteristic pungent odor. Its vapors are poisonous. If phenol comes into contact with skin, it causes painful burns.

In the chemical industry, phenols are used to make dyes, pesticides, pharmaceuticals, phenol-formaldehyde resins and synthetic fibers. Previously, phenol in the form of a diluted solution was used as an antiseptic (the so-called “carbolic acid”) to disinfect linen and premises. And today, many cleaning and disinfecting solutions also contain various phenols, which act as bactericidal agents. Phenols are added to pesticides and fungicides, and they are also used as preservatives for glue and wood.

The scope of application of these substances is quite wide, but most residents of our country learned about them because of the scandal that erupted in the late 1990s. around the notorious “phenolic houses” - panel high-rise buildings of the P-49/P series, built in the late 1970s - early 1980s.

These houses were considered experimental at one time. Phenol-formaldehyde was added to the concrete used in their construction. This was supposed to speed up its hardening and thereby bring the houses closer to completion. And to reduce the cost of the process, it was decided to use glass wool impregnated with phenol-formaldehyde resins as insulation for the panels. The joints between the tiles were filled with it. Almost immediately after the “phenolic houses” were built, cracks began to spread along their walls, the tightness of the seams was broken, and toxic phenolic fumes crawled inside the apartments. The reason for this was both design errors and imperfect technology for the production and installation of prefabricated structures. But it is unlikely that these explanations will somehow reassure the people who received apartments in such buildings.

In total, in the 70-80s, 5.7 million square meters were built in Moscow. meters of standard housing series II-49/P. It is difficult to say exactly how many of them became objects of the “experiment.” According to city authorities, there are about 260 “phenolic houses” in the city today. Some of them are located in the east of Moscow - on the Open Highway and Nikolai Khimushin Street.

The new residents, who at first were delighted with the spacious apartments, soon realized that along with their new housing they received a whole bunch of health problems - allergies, diseases of the eyes, kidneys, respiratory tract, and even malignant neoplasms.

The fact is that phenol and its derivatives easily penetrate the human body through the skin and gastrointestinal tract, and phenol vapors through the lungs. In the body, phenol easily forms compounds with other substances present in the body. The higher the concentration of phenol in the blood, the stronger its adverse effect on human health. The products of the interaction of phenol with other substances, as well as part of the unbound phenol, are excreted in the urine.

The presence of phenol in the body can be determined by urine analysis. It also helps to determine that a given person has been poisoned by phenol or substances that have turned into phenol in his body. But a urine test alone will not allow us to state that the patient has become a victim of phenol poisoning, since many chemical substances, when entering the body, enter into chemical reactions to form this substance.

Therefore, if there are suspicions that phenol or its vapors are present in drinking water or in the air of a living or working room, it is better to order an appropriate laboratory test, because phenol poisoning - both acute and chronic - poses a real threat not only to human health, but also to human life .

Symptoms of phenol poisoning

In case of acute poisoning that accompanies contact of phenol on the skin or inhalation of its vapors, a severe burning sensation is observed in the areas directly exposed to it. Burns of mucous tissues appear; severe pain occurs in the mouth, throat, and abdomen; nausea, vomiting, diarrhea; severe pallor, weakness, pulmonary edema; acute allergic manifestations are possible; blood pressure is reduced; cardiopulmonary failure develops, convulsions are possible; urine is brown, quickly darkens in air.

First aid is to remove clothes (preferably immediately under the shower), rinse the affected area with plenty of water. Cover the phenol burns with a clean white cloth. If phenol splashes into your eyes, rinse them with plenty of water for at least 15 minutes. Rinse the stomach with water and give activated charcoal inside. Alcohol and petroleum jelly are contraindicated. During inpatient treatment, the patient is given enveloping agents and analgesics, O2 is supplied to ensure adequate ventilation of the lungs, and the water-electrolyte balance is corrected.

Chronic phenol poisoning leads to anorexia - progressive weight loss; causes diarrhea, dizziness, difficulty swallowing, and excessive salivation. In case of chronic poisoning with phenols, dark coloration of urine is noted. Scientists who have studied the consequences of phenol poisoning indicate that as a result of prolonged exposure to phenol, a person may feel muscle pain and weakness. The liver of such people is enlarged. Chronic phenol poisoning causes damage to the central nervous system, nervous disorders accompanied by headaches and loss of consciousness, as well as damage to the kidneys, liver, respiratory system and cardiovascular system.

According to the US Environmental Protection Agency (EPA), the maximum dose of phenol, which is conditionally safe when ingested by the human body, is 0.6 mg/1 kg of live weight for 1 day. This dose is calculated without taking into account the possible carcinogenic effect of phenols, which can manifest itself after a fairly long period of time. It should be noted that this value serves only as a reference point: it shows that at phenol concentrations above this, the likelihood of adverse effects on human health increases sharply. Similarly, the EPA sets the permissible phenol content in the air - it is 0.006 mg/m3.

In our country, the maximum permissible concentration of phenol in a residential area is 0.03 mg/m3 (SanPin 2.1.2.1002-00), and in the air of a working area - 0.3 mg/m3.

The smell of phenol - strong and sweetish - begins to be felt if the concentration of phenol in the air exceeds 0.04 ppm (0.000004%)

Chronic phenol poisoning threatens not only residents of “phenol houses”. Unscrupulous manufacturers of furniture, construction and finishing materials, paints and varnishes, decorative cosmetics and even children's toys may neglect safety requirements and produce products with unacceptably high contents of toxic substances such as phenols and derivatives.

Remember, if you are alarmed by the unpleasant smell of a recently purchased item, if it seems to you that your health has deteriorated after purchasing furniture or recent renovations, it will be better to call an environmental specialist who will conduct all the necessary research and give the necessary recommendations than to remain in anxiety and doubt, fearing for their health and the health of their loved ones.

Irina Karpenko,
environmental engineer LLC Ecosystem

This lesson is taught according to the textbook edited by G. E. Rudzitis “Organic Chemistry” in the 10th grade in the section: “Alcohols and phenols.” The lesson is conducted using traditional teaching methods, demonstration experiments, as well as modern multimedia forms of teaching. This allows you to present the material more clearly and intelligibly; Conduct a quick assessment of students’ assimilation of what they have learned in the lesson (test). The use of modern audio/video teaching methods expands the possibilities for students to more firmly and consciously master educational material.

Educational objectives:

1. study the composition, structure, properties of phenol and its compounds
2. using phenol as an example, to concretize students’ knowledge about the structural features of substances belonging to the class of phenols, to consider the dependence of the mutual influence of atoms in the phenol molecule on its properties
3. introduce students to the physical and chemical properties of phenol and some of its compounds, study qualitative reactions to phenols
4. consider the presence in nature, the use of phenol and its compounds, their biological role

Developmental tasks:

1. improve students’ ability to predict the properties of a substance based on its structure
2. continue to develop the ability to observe, analyze, and draw conclusions when performing a chemical experiment

Educational tasks:

1. continue the formation of the chemical picture of the world through the chemical picture of nature (cognition, control of chemical processes)
2. expand students’ understanding of the impact of phenol-containing industrial waste and construction materials on the environment and human health
3. consider the biological role of phenol and its compounds on the human body (positive and negative)

Lesson type: lesson - learning new knowledge.

Teaching methods: verbal, visual, practical (chemical experiment - student and demonstration)

Means of education: Computer, projector, school chemical experiment (demonstration and student), reference notes, videos.

Equipment and reagents: Demonstration experiment: solutions of C 6 H 5 OH, NaOH, FeCl 3, bromine water, Na, test tubes, rubber stoppers.

Lesson Plan

1. Organizational moment

2. Updating knowledge

3. Learning new knowledge

• Determination of phenols Compounds in which the aromatic radical phenyl C6H5- is directly bonded to the hydroxyl group differ in properties from aromatic alcohols, so much so that they are classified into a separate class of organic compounds called phenols.

• classification and isomerism of phenols Depending on the number of OH groups, they distinguish monatomic phenols (such as the above phenol and cresols) and polyatomic. Among polyhydric phenols, the most common are diatomic:

As can be seen from the above examples, phenols are characterized by structural isomerism(isomerism of the position of the hydroxy group).

• Physical properties of phenol ( Appendix No. 2 )

A consequence of the polarity of the O–H bond and the presence of lone pairs of electrons on the oxygen atom is the ability of hydroxy compounds to form hydrogen bonds

This explains why phenol has quite high melting points (+43) and boiling points (+182). The formation of hydrogen bonds with water molecules contributes to the solubility of hydroxy compounds in water:

The ability to dissolve in water decreases with increasing hydrocarbon radical and from polyatomic hydroxy compounds to monoatomic ones. Methanol, ethanol, propanol, isopropanol, ethylene glycol and glycerin are mixed with water in any ratio. The solubility of phenol in water is limited.

• The structure of the phenol molecule

• Chemical properties of phenol (demonstration experiment underway)
• a) Consider the reactions of phenol at the OH group:

The acidic properties of phenol are more pronounced than those of alcohol C 2 H 5 OH. Phenol is a weak acid (carbolic acid).

• b) Reactions of phenol on the benzene ring:

What conclusion can be drawn about the mutual influence of atoms in a phenol molecule?
The phenyl group C6H5 – and hydroxyl –OH mutually influence each other.

• c) Qualitative reaction to phenols (video)

C 6 H 5 OH + FeCl 3 -> purple color

• Preparation of phenol(Appendix No. 1)

• Physiological effect of phenol and its use

Phenol is poisonous!!! If it comes into contact with the skin, it causes burns, while it is absorbed through the skin and causes poisoning. A phenol solution is used as a disinfectant (carbolic acid). Diatomic phenols - pyrocatechol, resorcinol, and hydroquinone ( pair- dihydroxybenzene) are used as antiseptics (antibacterial disinfectants), added to tanning agents for leather and fur, as stabilizers for lubricating oils and rubber, as well as for processing photographic materials and as reagents in analytical chemistry.

Phenols are used to a limited extent in the form of individual compounds, but their various derivatives are widely used. Phenols serve as starting compounds for the production of various polymer products - phenolic resins, polyamides, polyepoxides. Numerous drugs are obtained from phenols, for example, aspirin, salol, phenolphthalein, in addition, dyes, perfumes, plasticizers for polymers and plant protection products.

Biological role of phenol compounds: