According to the number of hydroxyl groups:

Monatomic; For example:

Diatomic; For example:

Triatomic; For example:

There are phenols of higher atomicity.

The simplest monohydric phenols

C 6 H 5 OH - phenol (hydroxybenzene), the trivial name is carbolic acid.

The simplest diatomic phenols

Electronic structure of the phenol molecule. Mutual influence of atoms in a molecule

The hydroxyl group -OH (like alkyl radicals) is a substituent of the 1st kind, i.e., an electron donor. This is due to the fact that one of the lone electron pairs of the hydroxyl oxygen atom enters into p, π-conjugation with the π-system of the benzene ring.

The result of this is:

An increase in electron density on carbon atoms in the ortho- and para-positions of the benzene ring, which facilitates the replacement of hydrogen atoms in these positions;

An increase in the polarity of the O-H bond, leading to an increase in the acidic properties of phenols compared to alcohols.

Unlike alcohols, phenols partially dissociate in aqueous solutions into ions:

i.e., they exhibit weakly acidic properties.

Physical properties

The simplest phenols under normal conditions are low-melting, colorless crystalline substances with a characteristic odor. Phenols are slightly soluble in water, but dissolve well in organic solvents. They are toxic substances and cause skin burns.

Chemical properties

I. Reactions involving the hydroxyl group (acidic properties)

(neutralization reaction, unlike alcohols)

Phenol is a very weak acid, so phenolates are decomposed not only by strong acids, but even by such a weak acid as carbonic acid:

II. Reactions involving the hydroxyl group (formation of esters and ethers)

Like alcohols, phenols can form ethers and esters.

Esters are formed by the reaction of phenol with anhydrides or acid chlorides of carboxylic acids (direct esterification with carboxylic acids is more difficult):

Ethers (alkylaryl ethers) are formed by the interaction of phenolates with alkyl halides:

III. Substitution reactions involving the benzene ring

The formation of a white precipitate of tribromophenol is sometimes considered a qualitative reaction to phenol.

IV. Addition reactions (hydrogenation)

V. Qualitative reaction with iron (III) chloride

Monohydric phenols + FeCl 3 (solution) → Blue-violet color, disappearing upon acidification.

The names of phenols are compiled taking into account the fact that for the parent structure, according to IUPAC rules, the trivial name “phenol” is retained. The numbering of the carbon atoms of the benzene ring starts from the atom directly bonded to the hydroxyl group (if it is the highest function), and continues in such a sequence that the available substituents receive the lowest numbers.

Mono-substituted phenol derivatives, for example methylphenol (cresol), can exist in the form of three structural isomers - ortho-, meta- and para-cresols.

Physical properties.

Phenols are mostly crystalline substances (-cresol - liquid) at room temperature. They have a characteristic odor, are rather poorly soluble in water, but dissolve well in aqueous solutions of alkalis (see below). Phenols form strong hydrogen bonds and have fairly high boiling points.

Methods of obtaining.

1. Preparation from halobenzenes. When chlorobenzene and sodium hydroxide are heated under pressure, sodium phenolate is obtained, upon further processing of which with acid, phenol is formed:

2. Preparation from aromatic sulfonic acids (see reaction 3 in the section “Chemical properties of benzene”, § 21). The reaction is carried out by fusing sulfonic acids with alkalis. The initially formed phenoxides are treated with strong acids to obtain free phenols. The method is usually used to obtain polyhydric phenols:

Chemical properties.

In phenols, the p-orbital of the oxygen atom forms a single -system with the aromatic ring. As a result of this interaction, the electron density of the oxygen atom decreases and that of the benzene ring increases. The polarity of the O-H bond increases, and the hydrogen of the OH group becomes more reactive and is easily replaced by a metal even under the action of alkalis (unlike saturated monohydric alcohols).

In addition, as a result of such mutual influence in the phenol molecule, the reactivity of the benzene ring in the ortho and cara positions in electrophilic substitution reactions (halogenation, nitration, polycondensation, etc.) increases:

1. The acidic properties of phenol manifest themselves in reactions with alkalis (the old name “carbolic acid” has been preserved):

Phenol, however, is a very weak acid. When carbon dioxide or sulfur dioxide gases are passed through a solution of phenolates, phenol is released - this reaction proves that phenol is a weaker acid than carbonic and sulfur dioxide:

The acidic properties of phenols are weakened by the introduction of substituents of the first kind into the ring and enhanced by the introduction of substituents of the second kind.

2. Formation of esters. Unlike alcohols, phenols do not form esters when exposed to carboxylic acids; For this purpose, acid chlorides are used:

3. Halogenation. When phenol is exposed to bromine water (compare with the conditions for the bromination of benzene - § 21), a precipitate of 2,4,6-tribromophenol is formed:

This is a qualitative reaction for the detection of phenol.

4. Nitration. Under the influence of 20% nitric acid, phenol is easily converted into a mixture of ortho- and para-nitrophenols. If phenol is nitrated with concentrated nitric acid, 2,4,6-trinitrophenol is formed - a strong acid (picric acid).

5. Oxidation. Phenols are easily oxidized even under the influence of atmospheric oxygen.

Thus, when standing in air, phenol gradually turns pinkish-red. During the vigorous oxidation of phenol with a chromium mixture, the main oxidation product is quinone. Diatomic phenols are oxidized even more easily. The oxidation of hydroquinone produces quinone:

Monohydric phenols are clear liquids or crystalline substances, often colored pink-red due to their oxidation. These are poisons and cause burns if they come into contact with the skin. They kill many microorganisms, that is, they have disinfectant and antiseptic properties. The solubility of phenols in water is low, their boiling points are relatively high due to the existence of intermolecular hydrogen bonds.

Physical properties

Phenols are slightly soluble in water, but dissolve well in alcohol, ether, benzene, form crystalline hydrates with water, and are distilled with steam. In air, phenol itself easily oxidizes and darkens. The introduction of substituents such as halogens, nitro groups, etc. into the para position of the phenol molecule significantly increases the boiling point and melting point of the compounds:

Picture 1.

Phenols are polar substances with a dipole moment $\mu$ = 1.5-1.6 $D$. The $EI$ value of 8.5-8.6 eV indicates the greater donor properties of phenols compared to arenes such as benzene (9.25 eV), toluene (8.82 eV), and ethylbenzene (8.76 eV). This is due to the interaction of the hydroxyl group with the $\pi$ bonds of the benzene ring due to the positive $M$ effect of the $OH$ group; its negative $I$ effect predominates.

Spectral characteristics of phenols

The absorption maximum in the UV part of the spectrum for phenol is shifted towards longer wavelengths by approximately 15 nm compared to benzene (bathochromic shift) due to the participation of $\pi$-electrons of oxygen in conjugation with the benzene ring and appears at 275 nm with a fine structure.

The IR spectra of phenols, as well as alcohols, are characterized by intense $v_(OH)$ bands in the region of 3200-3600 cm$^(-1)$ and 3600-3615 cm$^(-1)$ for highly diluted solutions , but for $v_(c\_D)$ phenols there is a band around 1230 cm$^(-1)$, in contrast to 1220-1125 cm$^(-1)$ for alcohols.

In the NMR spectra, the signal of the proton of the $OH$ group of phenols appears in a wide range (4.0-12.0 ppm) compared to alcohols, depending on the nature and concentration of the solvent, temperature, and the presence of inter- or intramolecular hydrogen bonds . Often the signal of the proton of the $OH$ group is recorded at 8.5-9.5 ppm. in dimethyl sulfoxide or at 4.0-7.5 ppm, in $CCl_4$.

In the mass spectrum of phenol, the main direction of fragmentation is the elimination of $HCO$ and $CO$ particles:

Figure 2.

If alkyl radicals are present in a phenol molecule, the primary process will be benzyl cleavage.

Chemical properties of phenols

In contrast to alcohols, which are characterized by reactions involving the cleavage of both the $O-H$ bond (acid-base properties, formation of esters, oxidation, etc.) and the $C-O$ bond (reactions of nucleophilic substitution, dehydration, rearrangement) , phenols are more characterized by reactions of the first type. In addition, they are characterized by electrophilic substitution reactions in the benzene ring activated by the electron-donating hydroxyl group.

The chemical properties of phenols are determined by the mutual influence of the hydroxyl group and the benzene ring.

The hydroxyl group has a $-I-$ and + $M$ effect. The latter significantly exceeds the $-I$ effect, which determines the $n-\pi$-conjugation of free electrons of oxygen with the $\pi$-orbital of the benzene nucleus. Due to $n-\pi$-conjugation, the length of the $C - O$ bond, the magnitude of the dipole moment and the position of the absorption bands of bonds in the IR spectra decrease compared to ethyl alcohol:

Some characteristics of phenol and ethanol:

Figure 3.

$n-\pi$-Conjugation leads to a decrease in the electron density on the oxygen atom, therefore the polarity of the $O - H$ bond in phenols increases. In this regard, the acidic properties of phenols are more pronounced than those of alcohols. The greater acidity of phenols compared to alcohols is also explained by the possibility of charge delocalization into the phenolate anion, which entails stabilization of the system:

Figure 4.

The difference in acidity between phenol and alcohols is indicated by the dissociation constant. For comparison: Kd = $1.3 \cdot 10^(-10)$ for phenol and Kd = $10^(-18)$ for ethyl alcohol.

Therefore, phenols, unlike alcohols, form phenolates not only with alkali metals, but also through interaction with alkalis:

Figure 5.

The reaction of phenol with alkali metals is quite violent and can be accompanied by an explosion.

But phenol is a weak acid, weaker even than carbonic acid ($K = 4.7 \cdot 10^(-7)$). Therefore, carbonic acid displaces phenol from the phenolate solution. These reactions are used to separate phenols, alcohols or carboxylic acids. Electron-withdrawing groups in the phenol molecule significantly enhance, and donor groups weaken, the acidic properties of phenolic hydroxyl.

In addition, phenol is characterized by a number of reactions of different directions:

1. formation of ethers and esters;
2. alkylation and acylation reactions;
3. oxidation reactions

4. electrophilic substitution reactions in the aromatic ring, including reactions:

   • halogenation,
   • sulfonation,
   • nitrosation,
   • formylation,
   • condensation with aldehydes and ketones,
   • carboxylation.

Phenol is an organic chemical substance, a hydrocarbon. Other names: carbolic acid, hydroxybenzene. It comes in natural and industrial origin. What is phenol and what is its significance in human life?

Origin of the substance, chemical and physical properties

The chemical formula of phenol is c6h5oh. In appearance, the substance resembles crystals in the form of needles, transparent, with a white tint. In the open air, when exposed to oxygen, the color becomes light pink. The substance has a specific odor. Phenol smells like gouache paint.

Natural phenols are antioxidants that are present in varying amounts in all plants. They determine color, aroma, and protect plants from harmful insects. Natural phenol is beneficial for the human body. It is found in olive oil, cocoa beans, fruits, and nuts. But there are also toxic compounds, such as tannin.

The chemical industry produces these substances through synthesis. They are poisonous and very toxic. Phenol is dangerous for humans, and the industrial scale of its production significantly pollutes the environment.

Physical properties:

• Phenol dissolves normally in water, alcohol, alkali;
• has a low melting point, at 40°C it turns into gas;
• its properties are in many ways similar to alcohol;
• has high acidity and solubility;
• at room temperature they are in a solid state;
• The smell of phenol is pungent.

How are phenols used?

More than 40% of the substances are used in the chemical industry to produce other organic compounds, mainly resins. It is also made from artificial fibers - nylon, nylon. The substance is used in the oil refining industry to purify oils that are used in drilling rigs and other technological facilities.

Phenol is used in the production of paints and varnishes, plastics, and in chemicals and pesticides. In veterinary medicine, farm animals are treated with the substance to prevent infections.

The use of phenol in the pharmaceutical industry is significant. It is included in many medications:

• antiseptics;
• painkillers;
• antiplatelet agents (thin the blood);
• as a preservative for vaccine production;
• in cosmetology as part of preparations for chemical peeling.

In genetic engineering, phenol is used to purify DNA and extract it from cells.

Toxic effect of phenol

Phenol is poison. In terms of its toxicity, the compound belongs to hazard class 2. This means that it is highly hazardous to the environment. The degree of impact on living organisms is high. The substance can cause serious damage to the ecological system. The minimum recovery period after the action of phenol is at least 30 years, provided that the source of pollution is completely eliminated.

Synthetic phenol has a negative effect on the human body. Toxic effect of the compound on organs and systems:

1. If vapors are inhaled or swallowed, the mucous membranes of the digestive tract, upper respiratory tract, and eyes are affected.
2. If it comes into contact with the skin, a phenol burn will form.
3. With deep penetration it causes tissue necrosis.
4. Has a pronounced toxic effect on internal organs. When the kidneys are damaged, it causes pyelonephritis, destroys the structure of red blood cells, which leads to oxygen starvation. Can cause allergic dermatitis.
5. When phenol is inhaled in high concentrations, brain activity is disrupted and can lead to respiratory arrest.

The mechanism of the toxic effect of phenols is a change in the structure of the cell and, as a consequence, its functioning. Neurons (nerve cells) are the most susceptible to toxic substances.

Maximum permissible concentration (MPC of phenol):

• the maximum single dose in the atmosphere for populated areas is 0.01 mg/m³, which remains in the air for half an hour;
• the average daily dose in the atmosphere for populated areas is 0.003 mg/m³;
• the lethal dose when ingested is for adults from 1 to 10 g, for children from 0.05 to 0.5 g.

Symptoms of phenol poisoning

The harm of phenol to living organisms has long been proven. When it comes into contact with the skin or mucous membranes, the compound is quickly absorbed, overcomes the hematogenous barrier and spreads through the blood throughout the body.

The brain is the first to respond to the effects of poison. Signs of poisoning in humans:

• Psyche. Initially, the patient experiences mild excitement, which does not last long and is replaced by irritation. Then comes apathy, indifference to what is happening around, the person is in a depressed state.
• Nervous system. General weakness, lethargy, loss of strength increases. Tactile sensitivity is blurred, but the reaction to light and sounds is exacerbated. The victim feels nausea, which is not related to the functioning of the digestive system. Dizziness appears and the headache becomes more intense. Severe poisoning can lead to convulsions and unconsciousness.
• Skin. The skin becomes pale and cold to the touch, and in severe cases acquires a blue tint.
• Respiratory system. If even small doses enter the body, a person may experience shortness of breath and rapid breathing. Due to irritation of the nasal mucosa, the victim is continuously sneezing. In case of moderate poisoning, a cough and spastic contractions of the larynx develop. In severe cases, the threat of spasm of the trachea and bronchi increases and, as a result, suffocation, leading to death.

Circumstances under which poisoning can occur are violation of safety rules when working with particularly dangerous substances, overdose of medications, household poisoning with detergents and cleaning products, as a result of an accident.

If the house contains low-quality furniture, children's toys that do not meet international safety standards, or the walls are painted with paint that is not intended for these purposes, then the person constantly inhales the emanating phenol vapors. In this case, chronic poisoning develops. Its main symptom is chronic fatigue syndrome.

Principles of first aid

The first thing to do is to interrupt human contact with the poisonous source.

Take the victim out of the room into fresh air, unfasten buttons, locks, and zippers to better ensure access to oxygen.

If the phenol solution gets on your clothing, remove it immediately. Rinse the affected skin and mucous membranes of the eyes thoroughly and repeatedly with running water.

If phenol gets into your mouth, do not swallow anything, but immediately rinse your mouth for 10 minutes. If the substance has managed to enter the stomach, you can drink the sorbent with a glass of water:

• activated or white carbon;
• enterosorb;
• enterosgel;
• sorbex;
• carbolene;
• polysorb;
• lactofiltrum.

You should not rinse the stomach, as this procedure will increase the severity of the burn and increase the area of ​​damage to the mucous membrane.

Phenol antidote is a solution of calcium gluconate for intravenous administration. In case of poisoning of any severity, the victim is taken to the hospital for observation and treatment.

In case of severe poisoning, phenol can be removed from the body in a hospital setting using the following methods:

1. Hemosorption is the purification of blood with a special sorbent that binds molecules of a toxic substance. The blood is purified by passing through a special apparatus.
2. Detoxification therapy is the intravenous infusion of solutions that dilute the concentration of a substance in the blood and promote its natural elimination from the body (through the kidneys).
3. Hemodialysis is indicated in severe cases where there is a potential threat to life. The procedure is carried out using an “artificial kidney” apparatus, in which the blood passes through special membranes and leaves molecules of a toxic substance. Blood returns to the body clean and saturated with useful microelements.

Phenol is a synthetic toxic substance that is dangerous to humans. Even a naturally occurring compound can be harmful to health. To avoid poisoning, it is necessary to responsibly work in production where there is a risk of contact with poison. When shopping, be interested in the composition of the products. The unpleasant smell of plastic products should alert you. When using medications containing phenol, follow the prescribed dosage.

Molecular formula: C 6 H 5 – OH.

Molecule structure: in a phenol molecule, the hydroxyl group of atoms is connected to the benzene ring (nucleus).

The aromatic radical phenyl (C 6 H 5 –) or the benzene ring, in contrast to the radicals of saturated hydrocarbons, has the property of attracting electrons of the oxygen atom of the hydroxyl group, therefore in the phenol molecule the chemical bond between the oxygen and hydrogen atoms becomes more polar, and the hydrogen atom - more mobile than in alcohol molecules, and phenol exhibits the properties of a weak acid (it is called carbolic acid).

On the other hand, the hydroxyl group affects the benzene ring (core) so that a redistribution of electron density occurs in it and the hydrogen atoms in positions 2,4,6 become more mobile than in the benzene molecule. Therefore, in substitution reactions, phenol is characterized by the replacement of three hydrogen atoms in positions 2,4,6 (in benzene only one hydrogen atom is replaced). Thus, in the phenol molecule there is a mutual influence of the hydroxyl group and the benzene ring on each other.

Physical properties: phenol is a colorless crystalline substance with a characteristic odor; in air it is pink in color, because oxidizes. Melting point – 42 ºC.

Phenol is a toxic substance! Causes burns upon contact with skin!

Chemical properties: chem. properties are due to the hydroxyl group and the benzene ring (core).

· Reactions occurring at the hydroxyl group:

The hydrogen atom in the hydroxyl group of phenol is more mobile than in alcohols, therefore phenol exhibits the properties of a weak acid (another name is carbolic acid) and interacts not only with active metals, like alcohols, but also with alkalis (alcohols do not react with alkalis! ).

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

phenol sodium hydroxide sodium phenolate

· Reactions occurring on the benzene ring (nucleus):

Phenol reacts vigorously (without heating or catalysts) with bromine and nitric acid, and three hydrogen atoms are replaced in the 2,4,6 positions in the benzene ring.

phenol bromine 2,4,6 – tribromophenol hydrogen bromide

phenol nitric acid 2,4,6-trinitrophenol

Application: Phenol is used for the production of medicinal substances, dyes, disinfectants (antiseptics), plastics (phenoplasts), explosives

Receipt: from coal tar and from benzene.

Aldehydes, their structure and properties. Preparation and use of formic and acetaldehydes.

Aldehydes are organic substances containing a functional aldehyde group

Associated with a hydrocarbon radical or hydrogen atom.

General formula of aldehydes: or R – COH

The structure of molecules. In an aldehyde molecule, there are σ bonds between the carbon and hydrogen atoms, and one σ bond and one π bond between the carbon and oxygen atoms. The electron density is shifted from the carbon atom to a more electronegative atom, the oxygen atom. That. the carbon atom of the aldehyde group acquires a partial positive charge (δ+), and the oxygen atom acquires a partial negative charge (δ–).

Nomenclature. The names of aldehydes are given: 1) from the historical names of the corresponding organic acids into which they are converted during oxidation - formic aldehyde, acetaldehyde, etc. 2) according to the international nomenclature - from the names of the corresponding hydrocarbons + suffix - al. For example,

H – C or H – CHO formic aldehyde, or methanal

CH 3 – C or CH 3 – CHO acetaldehyde, or ethanal

Physical properties. Methanal is a colorless gas with a pungent odor, ethanal and the following aldehydes are liquids, and higher aldehydes are solids.

Chemical properties.

Oxidation reactions. Qualitative reactions to aldehydes:

1) “silver mirror” reaction – oxidation of aldehydes with an ammonia solution of silver oxide when heated:

CH 3 – C HO + Ag 2 O → CH 3 – COOH + 2Ag ↓

Acetaldehyde acetic acid

the oxidizing agent silver oxide is reduced to silver, which settles on the walls of the test tube, and the aldehyde is oxidized into the corresponding acid

2) Oxidation of aldehydes with copper (II) hydroxide when heated.

H – C HO + 2 Cu(OH) 2 → H – COOH + 2CuOH + H 2 O

blue yellow

formic acid formic acid

2CuOH → Cu 2 O + H 2 O

yellow Red

The oxidizing agent is copper with oxidation state +2, which is reduced to copper with oxidation state +1.

Addition reactions.

3) Aldehydes, when heated and in the presence of a catalyst, add hydrogen due to the cleavage of the double bond in the aldehyde group. In this case, the aldehyde is reduced - converted into the corresponding alcohol. For example, methanal is converted to methanol:

H– C HO + H 2 → CH 3 – OH

methanal methyl alcohol (methanol)

Receipt.

Aldehydes can be obtained:

1. Oxidation of primary alcohols, for example,

2CH 3 OH + O 2 → 2H – C HO + 2H 2 O

methyl alcohol formic aldehyde (methanal).

2. methanal can also be obtained by direct oxidation of methane:

CH 4 + O 2 → H – CHO + H 2 O

3. Acetaldehyde can be obtained by hydration of ethylene in the presence of a catalyst (mercury salts) - reaction M.G. Kucherova:

H – C ≡ C – H + H 2 O → CH 3 – CHO

Application. Methanal and ethanal are the most widely used.

· Methanal is used to produce phenol-formaldehyde resin, from which plastics - phenolics - are made.

· When this resin is dissolved in acetone or alcohol, various varnishes are obtained.

· Methanal is used to produce some medicinal substances and dyes.

· A 40% aqueous solution of methanal – formaldehyde – is widely used. It is used for tanning leather (coagulates protein - the leather hardens and does not rot), for preserving biological preparations, for disinfecting and treating seeds.

· Ethanal is mainly used to produce acetic acid.