Phenols.

1. Definition. Classification.

2. Nomenclature and isomerism. Main representatives

3. Receipt

4. Physical properties

5. Chemical properties

6. Application. Impact on human health.

Phenols are benzene derivatives with one or more hydroxyl groups.

Classification.

Depending on the number of hydroxy groups phenols are divided according to their atomicity into: one-, two- and triatomic.

By degree of volatility of substances They are usually divided into two groups - phenols that are volatile with steam (phenol, cresols, xylenols, guaiacol, thymol) and non-volatile phenols (resorcinol, pyrocatechol, hydroquinone, pyrogallol and other polyhydric phenols). We will consider the structure and nomenclature of individual representatives below.

Nomenclature and isomerism. Main representatives.

The first representative, as a rule, is called by a trivial nomenclature, phenol (hydroxybenzene, obsolete carbolic acid).

https://pandia.ru/text/78/359/images/image005_11.gif" width="409" height="104">

3,5-dimethylphenol 4-ethylphenol

Often for phenols to varying degrees substitutions use trivial names.

Receipt

1) Isolation from dry coal tar products, as well as from the pyrolysis products of brown coal and wood (tar).

2) Through benzenesulfonic acid. First, benzene is treated by heating with concentrated sulfuric acid

C6H6 + H2SO4 = C6H5SO3H + H2O

The resulting benzenesulfonic acid is fused with alkali

C6H5SO3H + 3NaOH = C6H5ONa + 2H2O + Na2SO3

After treating the phenolate with a strong acid, phenol is obtained.

3) Cumene method (based on oxidation aromatic hydrocarbon cumene (isopropylbenzene) with atmospheric oxygen followed by decomposition of the resulting hydroperoxide diluted with H2SO4). The reaction proceeds with high yield and is attractive in that it allows one to obtain two technically valuable products at once - phenol and acetone (you need to consider it yourself).

Physical properties

Phenol are colorless needle-shaped crystals that turn pink in air due to oxidation, resulting in colored products. They have a specific gouache smell. Soluble in water (6 g per 100 g of water), in alkali solutions, in alcohol, in benzene, in acetone.

When working with phenol, you must follow safety precautions: work under a hood, use personal protective equipment, as it causes burns if it comes into contact with the skin.

Chemical properties of phenols

The structure of the phenol molecule

The benzene ring and the OH group combined in a phenol molecule influence each other, mutually increasing each other's reactivity. The phenyl group absorbs a lone pair of electrons from the oxygen atom in the OH group.

https://pandia.ru/text/78/359/images/image007_10.gif" width="348" height="62">

Catalytic interaction with alcohols leads to ethers, and as a result of reaction with anhydrides or acid chlorides carboxylic acids are formed esters. These are reactions similar to the reactions of alcohols that were studied in the last lecture (they are also called o-alkylation and o-acylation).

2. Reactions involving abstraction of an OH group

When interacting with ammonia (at elevated temperature and pressure), the OH group is replaced by NH2, and aniline is formed.

3. Reactions of substitution of hydrogen atoms in the benzene ring

(electrophilic substitution reactions) .

The OH group is a type I activating orientation agent. Therefore, during halogenation, nitration, sulfonation and alkylation of phenol, centers with increased electron density are attacked, i.e., substitution occurs predominantly in ortho- And pair- provisions. Such reactions were studied in detail in the lecture on the rules of orientation in the benzene ring.

Reactions of phenols with halogens proceed quickly, without catalysts.

o-chloro- and p-chlorophenol

Phenol in action conc.HNO3 converted to 2,4,6-trinitrophenol (picric acid). Nitration is accompanied by oxidation, so the product yield is low.

Mononitrophenols are formed by nitration of phenol with dilute nitric acid (at room temperature).

o-nitro- and p-nitrophenol

Phenol is easily sulfonated concentratedH2 SO 4, while at a temperature of 15-20°C the o-isomer is predominantly obtained, and at 100°C - the p-isomer.

o-phenol- and p-phenolsulfonic acids

Phenols are also easily subjected to alkylation and acylation to the core.

One of the most striking reactions is the heating of phenols with phthalic anhydride in the presence of sulfuric acid, which leads to the production of triarylmethylene dyes called phenolphthaleins.

Aspirin" href="/text/category/aspirin/" rel="bookmark">aspirin. Sodium and potassium phenolates react with CO2. At a temperature of 125°C, the o - isomer of phenolcarboxylic acid is obtained, which is acylated at the OH group, forming aspirin.

It is important to note two more qualitative reactions of phenols:

1) Reaction of phenols with bromine: it proceeds very quickly and it is very difficult to stop it at the monobromination stage. As a result, 2.4.6-tribromophenol is formed - a white precipitate.

The reaction is used to detect phenol in water: turbidity is noticeable even with an extremely low phenol content in water (1:100,000).

2) Reaction with Fe(III) salts. The reaction is based on the formation of complexes of iron phenolates, which have a purple color.

https://pandia.ru/text/78/359/images/image023_0.gif" width="204" height="49">

Hydrogenation with hydrogen in the presence of a nickel catalyst affects the aromatic ring, reducing it.

4. Oxidation of phenols

Phenols are sensitive to the action of oxidizing agents. Under the influence of chromic acid, phenol and hydroquinone are oxidized to p-benzoquinone, and pyrocatechol to o-benzoquinone. Phenol metaderivatives are quite difficult to oxidize.

Finishing materials and work" href="/text/category/otdelochnie_materiali_i_raboti/" rel="bookmark">finishing materials, paint and varnish products, decorative cosmetics and even children's toys can neglect safety requirements and produce products with unacceptably high contents of toxic substances such as phenols and their derivatives.

Therefore, it is necessary to be vigilant and take action at the first symptoms of poisoning. Remember if you are concerned bad smell recently purchased item, if it seems to you that your health has deteriorated after purchasing furniture or recent renovations, it would be better to call an environmental specialist who will carry out everything necessary research and will give the necessary recommendations than to remain in anxiety and doubt, fearing for your health and the health of your loved ones.

In the Second world war phenol was used in concentration camps The Third Reich for killing.

Phenol also seriously affects environment: in unpolluted or slightly polluted river waters, the content of phenols usually does not exceed 20 μg/dm3. Exceeding the natural background may indicate pollution of water bodies. In contaminated with phenols natural waters their content can reach tens and even hundreds of micrograms per liter. The maximum permissible concentration of phenols in water for Russia is 0.001 mg/dm3

Water analysis for phenol is important for natural and Wastewater. It is necessary to test water for phenol content if there is a suspicion of contamination of watercourses with industrial effluents.

Phenols are unstable compounds and are subject to biochemical and chemical oxidation . Polyhydric phenols are destroyed mainly by chemical oxidation.

However, when treating water containing phenol impurities with chlorine, very dangerous organic compounds can form. toxicants - dioxins.

Phenol concentration in surface waters susceptible seasonal changes. IN summer period the phenol content decreases (with increasing temperature the rate of decomposition increases). The release of phenolic waters into reservoirs and watercourses sharply worsens their general sanitary condition, affecting living organisms not only with its toxicity, but also significant change regime of nutrients and dissolved gases (oxygen, carbon dioxide). As a result of chlorination of water containing phenols, stable compounds of chlorophenols are formed, the slightest traces of which (0.1 μg/dm3) give the water a characteristic taste.

Formed on the basis of benzene. At normal conditions 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, obtaining phenol in industrial scale- 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 difference in their structural isomers. Various ortho-, meta-, para-cresols are only modifications of the basic structure of the compound benzene ring and a 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 its 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 unified p-system with a 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, the production of 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. Chemical reaction 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.

Continuous industrial method obtaining phenol consists of the interaction of chlorobenzene and a 7% solution caustic soda. 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 to produce 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 other 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 natural form Cresols are found in coal tar and are used industrially 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.

Phenols - organic substances whose molecules contain a phenyl radical linked to one or more hydroxo groups. Just like alcohols, phenols are classified by atomicity, i.e. by the number of hydroxyl groups.

Monohydric phenols contain one hydroxyl group in the molecule:

Polyhydric phenols contain more than one hydroxyl group in molecules:

There are also polyhydric phenols containing three or more hydroxyl groups in the benzene ring.

Let's take a closer look at the structure and properties of the simplest representative of this class - phenol C 6 H 5 OH. The name of this substance formed the basis for the name of the entire cass - phenols.

Physical properties of phenol

Phenol is a solid, colorless crystalline substance, melting point = 43°C, boiling point = 181°C, with a sharp characteristic odor. Toxic. Phenol is slightly soluble in water at room temperature. An aqueous solution of phenol is called carbolic acid. On contact with skin it causes burns, Therefore, phenol must be handled very carefully!

Chemical properties of phenol

In most reactions, phenols are more active at the O–H bond, since this bond is more polar due to the shift of electron density from the oxygen atom towards the benzene ring (participation of the lone electron pair of the oxygen atom in the p-conjugation system). The acidity of phenols is much higher than that of alcohols. For phenols, rupture reactions S-O connections are not characteristic, since the oxygen atom is firmly bonded to the carbon atom of the benzene ring due to the participation of its lone electron pair in the conjugation system. The mutual influence of atoms in the phenol molecule is manifested not only in the behavior of the hydroxy group, but also in the greater reactivity benzene nucleus. The hydroxyl group increases the electron density in the benzene ring, especially at the ortho and para positions (OH groups)

Acid properties of phenol

The hydrogen atom of the hydroxyl group is acidic in nature. Because The acidic properties of phenol are more pronounced than those of water and alcohols, then phenol reacts not only with alkali metals, but also with alkalis with the formation of phenolates:

The acidity of phenols depends on the nature of the substituents (electron density donor or acceptor), position relative to the OH group and the number of substituents. The greatest influence on the OH-acidity of phenols is exerted by groups located in the ortho- and para-positions. Donors increase strength O-N connections(thereby reducing hydrogen mobility and acidic properties), acceptors reduce the strength of the O-H bond, while acidity increases:

However, the acidic properties of phenol are less pronounced than those of inorganic and carboxylic acids. For example, the acidic properties of phenol are approximately 3000 times less than those of carbonic acid. Therefore, passing sodium phenolate through an aqueous solution carbon dioxide, free phenol can be isolated.

Adding hydrochloric or sulfuric acid to an aqueous solution of sodium phenolate also leads to the formation of phenol:

Qualitative reaction to phenol

Phenol reacts with ferric chloride (3) to form an intensely colored purple complex compound. This reaction allows it to be detected even in very limited quantities. Other phenols containing one or more hydroxyl groups on the benzene ring also give a bright blue-violet color when reacted with ferric chloride (3).

Reactions of the benzene ring of phenol

The presence of a hydroxyl substituent greatly facilitates the occurrence of electrophilic substitution reactions in the benzene ring.

1. Bromination of phenol. Unlike benzene, the bromination of phenol does not require the addition of a catalyst (iron(3) bromide). In addition, the interaction with phenol occurs selectively: bromine atoms are directed to ortho- And pair- positions, replacing the hydrogen atoms located there. The selectivity of substitution is explained by the features discussed above electronic structure phenol molecules.

Thus, when phenol interacts with bromine water a white precipitate of 2,4,6-tribromophenol is formed:

This reaction, like the reaction with iron(3) chloride, serves to qualitative detection of phenol.

2.Nitration of phenol also occurs more easily than benzene nitration. The reaction with dilute nitric acid occurs at room temperature. As a result, a mixture is formed ortho- And paro isomers of nitrophenol:

When concentrated nitric acid is used, 2,4,6, trinitritephenol-picric acid, an explosive, is formed:

3. Hydrogenation of the aromatic ring of phenol in the presence of a catalyst passes easily:

4.Polycondensation of phenol with aldehydes, in particular, with formaldehyde it occurs with the formation of reaction products - phenol-formaldehyde resins and solid polymers.

The interaction of phenol with formaldehyde can be described by the following scheme:

The dimer molecule retains “mobile” hydrogen atoms, which means that further continuation of the reaction is possible with a sufficient number of reagents:

Reaction polycondensation, those. the polymer production reaction, which occurs with the release of a low-molecular-weight by-product (water), can continue further (until one of the reagents is completely consumed) with the formation of huge macromolecules. The process can be described by the summary equation:

The formation of linear molecules occurs at ordinary temperatures. Carrying out the same reaction when heated leads to the fact that the resulting product has a branched structure, it is solid and insoluble in water. As a result of heating a phenol-formaldehyde resin with a linear structure with an excess of aldehyde, solid plastic masses are obtained with unique properties. Polymers based on phenol-formaldehyde resins are used for the manufacture of varnishes and paints, plastic products that are resistant to heating, cooling, water, alkalis, and acids. They have high dielectric properties. The most responsible and important details electrical appliances, power unit housings and machine parts, polymer base of printed circuit boards for radio devices. Adhesives based on phenol-formaldehyde resins are capable of reliably connecting parts of a wide variety of natures, maintaining the highest joint strength over a very wide temperature range. This adhesive is used to attach the metal base of lighting lamps to a glass bulb. Thus, phenol and products based on it are widely used.

Application of phenols

Phenol - solid, with a characteristic odor, causes burns upon contact with skin. Poisonous. It dissolves in water, its solution is called carbolic acid (antiseptic). She was the first antiseptic introduced into surgery. Widely used in plastic production, medicines(salicylic acid and its derivatives), dyes, explosives.

Monohydric phenols are transparent 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 causing $n-\pi$-conjugation free electrons oxygen with the $\pi$-orbital of the benzene ring. 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 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.

1. Phenols- derivatives of aromatic hydrocarbons, in the molecules of which the hydroxyl group (-OH) is directly bonded to the carbon atoms in the benzene ring.

2. Classification of phenols

One-, two-, and trihydric phenols are distinguished depending on the number of OH groups in the molecule:

In accordance with the number of condensed aromatic rings in the molecule, phenols themselves are distinguished (one aromatic ring - benzene derivatives), naphthols (2 condensed rings - naphthalene derivatives), anthranols (3 condensed rings - anthracene derivatives) and phenanthroles:

3. Isomerism and nomenclature of phenols

There are 2 types of isomerism possible:

• isomerism of the position of substituents in the benzene ring

• side chain isomerism (structure of the alkyl radical and number of radicals)

For phenols, trivial names that have developed historically are widely used. The names of substituted mononuclear phenols also use prefixes ortho-,meta- And pair -, used in the nomenclature of aromatic compounds. For more complex compounds, the atoms that make up the aromatic rings are numbered and the position of the substituents is indicated using digital indices

4. Molecule structure

The phenyl group C 6 H 5 – and hydroxyl –OH mutually influence each other

• unshared electron pair oxygen atom is attracted by the 6-electron cloud of the benzene ring, due to which the O–H bond is even more polarized. Phenol is a stronger acid than water and alcohols.

• In the benzene ring, the symmetry of the electron cloud is disrupted, the electron density increases in positions 2, 4, 6. This makes them more reactive S-N connections in positions 2, 4, 6. and – bonds of the benzene ring.

5. Physical properties

Most monohydric phenols under normal conditions are colorless crystalline substances with a low melting point and a characteristic odor. Phenols are slightly soluble in water, readily soluble in organic solvents, toxic, and when stored in air they gradually darken as a result of oxidation.

Phenol C6H5OH (carbolic acid ) - a colorless crystalline substance oxidizes in air and becomes pink; at ordinary temperatures it is sparingly soluble in water; above 66 °C it is miscible with water in any proportions. Phenol - toxic substance, causes skin burns, is an antiseptic

6. Toxic properties

Phenol is poisonous. Causes dysfunction of the nervous system. Dust, vapors and phenol solution irritate the mucous membranes of the eyes, respiratory tract, and skin. Once in the body, Phenol is very quickly absorbed even through intact areas of the skin and within a few minutes begins to affect brain tissue. First, short-term excitement occurs, and then paralysis of the respiratory center. Even when exposed to minimal doses of phenol, sneezing, coughing, headache, dizziness, pallor, nausea, and loss of strength are observed. Severe cases of poisoning are characterized by unconsciousness, cyanosis, difficulty breathing, insensitivity of the cornea, rapid, barely perceptible pulse, cold sweat, and often convulsions. Phenol is often the cause of cancer.

7. Application of phenols

1. Production of synthetic resins, plastics, polyamides

2. Medicines

3. Dyes

4. Surfactants

5. Antioxidants

6. Antiseptics

7. Explosives

8. Preparation of phenol V industry

1). Cumene method for producing phenol (USSR, Sergeev P.G., Udris R.Yu., Kruzhalov B.D., 1949). Advantages of the method: waste-free technology (yield of useful products > 99%) and cost-effectiveness. Currently, the cumene method is used as the main method in the global production of phenol.

2). Made from coal tar (as a by-product - the yield is small):

C 6 H 5 ONa+ H 2 SO 4 (diluted) → C 6 H 5 – OH + NaHSO 4

sodium phenolate

(product ofresin bootscaustic soda)

3). From halobenzenes :

C 6 H 5 -Cl + NaOH t , p→ C 6 H 5 – OH + NaCl

4). Fusion of salts of aromatic sulfonic acids with solid alkalis :

C 6 H 5 -SO 3 Na+ NaOH t → Na 2 SO 3 + C 6 H 5 – OH

sodium salt

benzenesulfonic acids

9. Chemical properties of phenol (carbolic acid)

I . Properties of the hydroxyl group

Acid properties– expressed more clearly than in saturated alcohols (the color of the indicators does not change):

• With active metals-

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

sodium phenolate

• With alkalis-

C6H5-OH + NaOH (water solution)↔ C 6 H 5 -ONa + H 2 O

! Phenolates are salts of weak carbolic acid, decomposed by carbonic acid -

C6H5-ONa+H2O+WITHO 2 → C 6 H 5 -OH + NaHCO 3

In terms of acidic properties, phenol is 10 6 times superior to ethanol. At the same time, it is inferior by the same amount acetic acid. Unlike carboxylic acids, phenol cannot displace carbonic acid from its salts

C 6 H 5 - OH + NaHCO 3 = the reaction does not occur - it dissolves perfectly in aqueous solutions alkalis, it is virtually insoluble in an aqueous solution of sodium bicarbonate.

The acidic properties of phenol are enhanced under the influence of electron-withdrawing groups associated with the benzene ring ( NO 2 - , Br - )

2,4,6-trinitrophenol or picric acid is stronger than carbonic acid

II . Properties of the benzene ring

1). The mutual influence of atoms in the phenol molecule is manifested not only in the behavior of the hydroxy group (see above), but also in the greater reactivity of the benzene ring. The hydroxyl group increases the electron density in the benzene ring, especially in ortho- And pair- positions (+ M-OH group effect):

Therefore, phenol is much more active than benzene in electrophilic substitution reactions in the aromatic ring.

• Nitration. Under the influence of 20% nitric acid HNO 3, phenol is easily converted into a mixture ortho- And pair- nitrophenols:

When concentrated HNO 3 is used, 2,4,6-trinitrophenol ( picric acid):

• Halogenation. Phenol easily reacts with bromine water at room temperature to form a white precipitate of 2,4,6-tribromophenol ( qualitative reaction for phenol):

• Condensation with aldehydes. For example:

2). Hydrogenation of phenol

C6H5-OH + 3H2 Ni, 170ºC→ C 6 H 11 – OH cyclohexyl alcohol (cyclohexanol)