Hydroxybenzene
Chemical properties
What is Phenol? Hydroxybenzene, what is it? According to Wikipedia, this is one of the simplest representatives of its class of aromatic compounds. Phenols are organic aromatic compounds in the molecules of which carbon atoms from the aromatic ring are attached to the hydroxyl group. The general formula of Phenols: C6H6n(OH)n. According to the standard nomenclature, organic substances of this series are distinguished by the number of aromatic nuclei and HE- groups. There are monohydric arenols and homologues, dihydric arendiols, terchatomic arentriols and polyhydric formulas. Phenols also tend to have a number of spatial isomers. For instance, 1,2-dihydroxybenzene (pyrocatechin ), 1,4-dihydroxybenzene (hydroquinone ) are isomers.
Alcohols and phenols differ from each other by the presence of an aromatic ring. ethanol is a homologue of methanol. Unlike phenol, methanol interacts with aldehydes and enters into esterification reactions. The statement that methanol and Phenol are homologues is incorrect.
Consider it in detail structural formula Phenol, it can be noted that the molecule is a dipole. In this case, the benzene ring is the negative end, and the group HE- positive. The presence of a hydroxyl group causes an increase in the electron density in the ring. The lone pair of oxygen electrons enters into conjugation with the pi system of the ring, and the oxygen atom is characterized by sp2 hybridization. Atoms and atomic groups in a molecule have a strong mutual influence on each other, and this is reflected in the physical and chemical properties of substances.
physical properties. The chemical compound has the form of colorless needle-shaped crystals that turn pink in air, as they are subject to oxidation. The substance has a specific chemical smell, it is moderately soluble in water, alcohols, alkali, acetone and benzene. Molar mass = 94.1 grams per mole. Density = 1.07 g per liter. Crystals melt at 40-41 degrees Celsius.
What does Phenol interact with? Chemical properties of Phenol. Due to the fact that the compound molecule contains both an aromatic ring and a hydroxyl group, it exhibits some properties of alcohols and aromatic hydrocarbons.
How does the group react? HE? The substance does not exhibit strong acidic properties. But it is a more active oxidizing agent than alcohols, unlike ethanol, it interacts with alkalis forming phenolate salts. Reaction with sodium hydroxide :C6H5OH + NaOH → C6H5ONa + H2O. The substance reacts with sodium (metal): 2C6H5OH + 2Na → 2C6H5ONa + H2.
Phenol does not react with carboxylic acids. Esters are obtained by reacting salts of phenolates with acid halides or anhydrides. For a chemical compound, ether formation reactions are not characteristic. Esters form phenolates under the action of haloalkanes or halogen derivatives of arenes. Hydroxybenzene reacts with zinc dust, while the hydroxyl group is replaced by H, the reaction equation looks like this: C6H5OH + Zn → C6H6 + ZnO.
Chemical interaction along the aromatic ring. The substance is characterized by reactions of electrophilic substitution, alkylation, halogenation, acylation, nitration and sulfonation. Of particular importance is the reactions of the synthesis of salicylic acid: C6H5OH + CO2 → C6H4OH(COONa), proceeds in the presence of a catalyst sodium hydroxide . Then, upon exposure, it is formed.
Interaction reaction with bromine water is a qualitative reaction to Phenol. C6H5OH + 3Br2 → C6H2Br2OH + 3HBr. Bromination produces a white solid 2,4,6-tribromophenol . Another qualitative response ferric chloride 3 . The reaction equation looks like this: 6C6H5OH + FeCl3 → (Fe(C6H5OH)6)Cl3.
Phenol nitration reaction: C6H5OH + 3HNO3 → C6H2(NO2)3OH + 3H2O. The substance is also characterized by an addition reaction (hydrogenation) in the presence of metal catalysts, platinum, alumina, chromium, and so on. As a result, cyclohexanol and cyclohexanone .
The chemical compound undergoes oxidation. The stability of the substance is much lower than that of benzene. Depending on the reaction conditions and the nature of the oxidizing agent, different reaction products are formed. Under the action of hydrogen peroxide in the presence of iron, diatomic Phenol is formed; under action manganese dioxide , chromium mixture in an acidified medium - para-quinone.
Phenol reacts with oxygen, combustion reaction: С6Н5ОН + 7О2 → 6СО2 + 3Н2О. Also of particular importance for industry is the reaction of polycondensation with formaldehyde (For example, metanalem ). The substance enters into a polycondensation reaction until one of the reactants is completely consumed and huge macromolecules are formed. As a result, solid polymers are formed, phenol-formaldehyde or formaldehyde resins . Phenol does not interact with methane.
Receipt. At the moment, there are several methods for the synthesis of hydroxybenzene that are actively used. The cumene method for obtaining Phenol is the most common of them. About 95% of the total production of the substance is synthesized in this way. In this case, non-catalytic oxidation by air undergoes cumene and formed cumene hydroperoxide . The resulting compound is decomposed by sulfuric acid on the acetone and Phenol. An additional by-product of the reaction is alpha-methylstyrene .
Also, the compound can be obtained by oxidation toluene , the reaction intermediate will be benzoic acid . Thus, about 5% of the substance is synthesized. All other raw materials for various needs are isolated from coal tar.
How to get from benzene? Phenol can be obtained using the direct oxidation reaction of benzene NO2() with further acid decomposition sec-butylbenzene hydroperoxide . How to get phenol from chlorobenzene? There are two options for getting chlorobenzene this chemical compound. The first is the reaction of interaction with alkali, for example, with sodium hydroxide . As a result, phenol and table salt are formed. The second is the reaction with water vapor. The reaction equation looks like this: C6H5-Cl + H2O → C6H5-OH + HCl.
Receipt benzene from Phenol. To do this, you first need to treat benzene with chlorine (in the presence of a catalyst), and then add an alkali to the resulting compound (for example, NaOH). As a result, Phenol is formed and.
transformation methane - acetylene - benzene - chlorobenzene can be done as follows. First, the methane decomposition reaction is carried out at a high temperature of 1500 degrees Celsius to acetylene (C2H2) and hydrogen. Then acetylene, under special conditions and high temperature, is converted into benzene . Chlorine is added to benzene in the presence of a catalyst FeCl3, get chlorobenzene and hydrochloric acid: C6H6 + Cl2 → C6H5Cl + HCl.
One of the structural derivatives of Phenol is an amino acid that is of great biological importance. This amino acid can be considered as para-substituted Phenol or alpha-substituted para-cresol . Cresols - quite common in nature along with polyphenols. Also, the free form of a substance can be found in some microorganisms in an equilibrium state with tyrosine .
Hydroxybenzene is used:
- in production bisphenol A , epoxy resin and polycarbonate ;
- for the synthesis of phenol-formaldehyde resins, capron, nylon;
- in the oil refining industry, in the selective purification of oils from aromatic sulfur compounds and resins;
- in the production of antioxidants, surfactants, cresols , lek. drugs, pesticides and antiseptics;
- in medicine as an antiseptic and anesthetic for topical use;
- as a preservative in the manufacture of vaccines and smoked foods, in cosmetology during deep peeling;
- for disinfection of animals in cattle breeding.
Hazard Class. Phenol is an extremely toxic, poisonous, caustic substance. When a volatile compound is inhaled, the work of the central nervous system, vapors irritate the mucous membranes of the eyes, skin, respiratory tract and cause severe chemical burns. Upon contact with the skin, the substance is rapidly absorbed into the bloodstream and reaches the brain tissue, causing paralysis of the respiratory center. The lethal dose by ingestion for an adult is 1 to 10 grams.
pharmachologic effect
Antiseptic, cauterizing.
Pharmacodynamics and pharmacokinetics
The agent exhibits bactericidal activity against aerobic bacteria, their vegetative forms and fungi. Virtually no effect on fungal spores. The substance interacts with protein molecules of microbes and leads to their denaturation. Thus, the colloidal state of the cell is disturbed, its permeability is significantly increased, redox reactions are disturbed.
In an aqueous solution, it is an excellent disinfectant. When using a 1.25% solution, almost microorganisms die within 5-10 minutes. Phenol, in a certain concentration, has a cauterizing and irritating effect on the mucous membrane. The bactericidal effect of the use of the product increases with increasing temperature and acidity.
Upon contact with the surface of the skin, even if it is not damaged, the drug is rapidly absorbed, penetrates into the systemic circulation. With systemic absorption of a substance, its toxic effect is observed, mainly on the central nervous system and the respiratory center in the brain. About 20% of the dose taken undergoes oxidation, the substance and its metabolic products are excreted by the kidneys.
Indications for use
Application of Phenol:
- for disinfection of tools and linen and disinfestation;
- as a preservative in some lek. products, vaccines, suppositories and serums;
- with superficial pyoderma , folliculitis , conflict , osteofolliculitis , sykose , streptococcal impetigo ;
- for the treatment of inflammatory diseases of the middle ear, oral cavity and pharynx, periodontitis , genital spiky warts .
Contraindications
The substance is not used:
- with widespread lesions of the mucous membrane or skin;
- for the treatment of children;
- during breastfeeding and;
- when on Phenol.
Side effects
Sometimes the drug can provoke the development of allergic reactions, itching, irritation at the site of application and a burning sensation.
Instructions for use (Method and dosage)
Preservation of drugs, sera and vaccines is carried out using 0.5% solutions of Phenol.
For external use, the drug is used in the form of an ointment. The drug is applied in a thin layer to the affected areas of the skin several times a day.
In the treatment, the substance is used in the form of a 5% solution in. The drug is heated and instilled 10 drops into the affected ear for 10 minutes. Then you need to remove the remnants of the medicine with cotton wool. The procedure is repeated 2 times a day for 4 days.
Phenol preparations for the treatment of ENT diseases are used in accordance with the recommendations in the instructions. Duration of therapy - no more than 5 days.
To eliminate spiky warts they are treated with a 60% Phenol solution or a 40% solution tricresol . The procedure is carried out once every 7 days.
When disinfecting linen, 1-2% soap-based solutions are used. With the help of a soap-phenolic solution, the room is treated. When disinsection, phenol-turpentine and kerosene mixtures are used.
Overdose
When the substance gets on the skin, burning, redness of the skin, anesthesia of the affected area occur. The surface is treated with vegetable oil or polyethylene glycol . Carry out symptomatic therapy.
Symptoms of Phenol poisoning if ingested. There are severe pains in the abdomen, pharynx, in the oral cavity, the victim vomits with a brown mass, pale skin, general weakness and dizziness
The product should not treat large areas of the skin.
Before using the substance to disinfect household items, they must be mechanically cleaned, as the product is absorbed by organic compounds. After processing, things may still long time keep a specific smell.
The chemical compound must not be used to treat premises for the storage and preparation of food products. It does not affect the color and structure of the fabric. Damages varnished surfaces.
children
The tool can not be used in pediatric practice.
During pregnancy and lactation
Phenol is not prescribed during breastfeeding and during pregnancy .
Preparations containing (Analogues)
Coincidence in the ATX code of the 4th level:
Phenol is part of the following drugs: Feresol , Phenol solution in glycerin , Pharmaseptic . As a preservative, it is contained in preparations: Belladonna extract , Skin Diagnosis Kit for Drug Allergy , etc.
There are one-, two-, three-atomic phenols depending on the number of OH groups in the molecule (Fig. 1)
Rice. one. SINGLE-, TWO- AND TRI-ATOMIC PHENOLS
In accordance with the number of fused aromatic cycles in the molecule, there are (Fig. 2) phenols themselves (one aromatic ring - benzene derivatives), naphthols (2 fused rings - naphthalene derivatives), anthranols (3 fused rings - anthracene derivatives) and phenantrols (Fig. 2).
Rice. 2. MONO- AND POLYNUCLEAR PHENOLS
Nomenclature of alcohols.
For phenols, trivial names that have developed historically are widely used. Prefixes are also used in the names of substituted mononuclear phenols ortho-,meta- and pair -, used in the nomenclature of aromatic compounds. For more complex compounds, the atoms that are part of the aromatic cycles are numbered and the position of the substituents is indicated using digital indices (Fig. 3).
Rice. 3. NOMENCLATURE OF PHENOLS. Substituent groups and corresponding numerical indices are highlighted in different colors for clarity.
Chemical properties of phenols.
The benzene nucleus and the OH group combined in the phenol molecule affect each other, significantly increasing the reactivity of each other. The phenyl group pulls the lone electron pair away from the oxygen atom in the OH group (Fig. 4). As a result, the partial positive charge on the H atom of this group increases (indicated by d+), the polarity of the O–H bond increases, which manifests itself in an increase in the acidic properties of this group. Thus, compared to alcohols, phenols are stronger acids. The partial negative charge (denoted by d–), passing to the phenyl group, is concentrated in the positions ortho- and pair-(with respect to the OH group). These reaction sites can be attacked by reagents that tend to electronegative centers, the so-called electrophilic ("electron loving") reagents.
Rice. 4. ELECTRON DENSITY DISTRIBUTION IN PHENOL
As a result, two types of transformations are possible for phenols: the substitution of a hydrogen atom in the OH group and the substitution of the H-atomobenzene nucleus. A pair of electrons of the O atom, drawn to the benzene ring, increases the strength of the C–O bond, so reactions that occur with the breaking of this bond, which are characteristic of alcohols, are not typical for phenols.
1. Substitution reactions of the hydrogen atom in the OH group. When phenols are treated with alkalis, phenolates are formed (Fig. 5A), the catalytic reaction with alcohols leads to ethers (Fig. 5B), and as a result of the reaction with anhydrides or acid chlorides of carboxylic acids, esters are formed (Fig. 5C). When interacting with ammonia ( fever and pressure), the OH group is replaced by NH 2 , aniline is formed (Fig. 5D), reducing reagents convert phenol to benzene (Fig. 5E)
2. Substitution reactions of hydrogen atoms in the benzene ring.
During halogenation, nitration, sulfonation and alkylation of phenol, centers with increased electron density are attacked (Fig. 4), i.e. substitution takes place mainly in ortho- and pair- positions (fig.6).
With a deeper reaction, two and three hydrogen atoms are replaced in the benzene ring.
Of particular importance are the condensation reactions of phenols with aldehydes and ketones, in essence, this is alkylation, which takes place easily and under mild conditions (at 40–50 ° C, an aqueous medium in the presence of catalysts), while the carbon atom is in the form of a methylene group CH 2 or substituted methylene group (CHR or CR 2) is inserted between two phenol molecules. Such condensation often leads to the formation of polymeric products (Fig. 7).
Diatomic phenol (trade name bisphenol A, Fig. 7), is used as a component in the preparation epoxy resins. The condensation of phenol with formaldehyde underlies the production of widely used phenol-formaldehyde resins (phenolic plastics).
Methods for obtaining phenols.
Phenols are isolated from coal tar, as well as from pyrolysis products of brown coal and wood (tar). industrial way The production of C 6 H 5 OH phenol itself is based on the oxidation of the aromatic hydrocarbon cumene (isopropylbenzene) with atmospheric oxygen, followed by decomposition of the resulting hydroperoxide diluted with H 2 SO 4 (Fig. 8A). The reaction proceeds with a high yield and is attractive in that it allows one to obtain two technically valuable products at once - phenol and acetone. Another method is the catalytic hydrolysis of halogenated benzenes (Fig. 8B).
Rice. eight. METHODS FOR OBTAINING PHENOL
The use of phenols.
A solution of phenol is used as a disinfectant (carbolic acid). Diatomic phenols - pyrocatechol, resorcinol (Fig. 3), as well as hydroquinone ( pair- dihydroxybenzene) is used as antiseptics (antibacterial disinfectants), introduced into 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.
In the form of individual compounds, phenols are used to a limited extent, but their various derivatives are widely used. Phenols serve as starting compounds for the production of various polymeric products, such as phenol-aldehyde resins (Fig. 7), polyamides, and polyepoxides. Based on phenols, numerous drugs are obtained, for example, aspirin, salol, phenolphthalein, in addition, dyes, perfumes, plasticizers for polymers and plant protection products.
Mikhail Levitsky
Profile chemical and biological class
Lesson type: lesson learning new material.
Lesson methods:
- verbal (conversation, explanation, story);
- visual (computer presentation);
- practical (demonstration experiments, laboratory experiments).
Lesson Objectives:Learning Objectives: on the example of phenol, 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; to acquaint students with the physical and chemical properties of phenol and some of its compounds, to study qualitative reactions to phenols; consider the presence in nature, the use of phenol and its compounds, their biological role
Educational Goals: Create conditions for independent work students, strengthen students' skills in working with text, highlight the main thing in the text, perform tests.
Development goals: To create dialogue interaction in the lesson, to promote the development of students' skills to express their opinion, listen to a friend, ask each other questions and supplement each other's speeches.
Equipment: chalk, board, screen, projector, computer, electronic media, textbook "Chemistry", grade 10, O.S. Gabrielyan, F.N. Maskaev, textbook "Chemistry: in tests, tasks and exercises", 10th grade, O.S. Gabrielyan, I.G. Ostroumov.
Demonstration: D. 1. Displacement of phenol from sodium phenolate by carbonic acid.
D 2. Interaction of phenol and benzene with bromine water (video clip).
D. 3. The reaction of phenol with formaldehyde.
Lab Experience:1. Solubility of phenol in water at ordinary and elevated temperatures.
2. Interaction of phenol and ethanol with alkali solution.
3. Reaction of phenol with FeCl 3 .
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MUNICIPAL EDUCATIONAL INSTITUTION
"GRAMMAR SCHOOL № 5"
TYRNYAUZA KBR
Open lesson-study in chemistry
Chemistry teacher: Gramoteeva S.V.
I qualification category
Class: 10 "A", chemical and biological
Date: 14.02.2012
Phenol: structure, physical and Chemical properties pheno la.
The use of phenol.
Profile chemical and biological class
Lesson type: lesson learning new material.
Lesson methods:
- verbal (conversation, explanation, story);
- visual (computer presentation);
- practical (demonstration experiments, laboratory experiments).
Lesson Objectives: Teaching Objectives: on the example of phenol, 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; to acquaint students with the physical and chemical properties of phenol and some of its compounds, to study qualitative reactions to phenols; consider the presence in nature, the use of phenol and its compounds, their biological role
Educational Goals:Create conditions for independent work of students, strengthen students' skills in working with text, highlight the main thing in the text, and perform tests.
Development goals:To create dialogue interaction in the lesson, to promote the development of students' skills to express their opinion, listen to a friend, ask each other questions and supplement each other's speeches.
Equipment: chalk, board, screen, projector, computer, electronic media, textbook "Chemistry", grade 10, O.S. Gabrielyan, F.N. Maskaev, textbook "Chemistry: in tests, tasks and exercises", 10th grade, O.S. Gabrielyan, I.G. Ostroumov.
Demonstration: D. 1.Displacement of phenol from sodium phenolate by carbonic acid.
D 2. Interaction of phenol and benzene with bromine water (video clip).
D. 3. The reaction of phenol with formaldehyde.
Lab Experience: 1. Solubility of phenol in water at ordinary and elevated temperatures.
3. Reaction of phenol with FeCl 3 .
DURING THE CLASSES
- Organizing time.
- Preparing to study new material.
- Front poll:
- What alcohols are called polyhydric? Give examples.
- What are the physical properties of polyhydric alcohols?
- What reactions are typical for polyhydric alcohols?
- Write qualitative reactions characteristic of polyhydric alcohols.
- Give examples of the esterification reaction of ethylene glycol and glycerol with organic and inorganic acids. What are the names of the reaction products?
- Write the reactions of intramolecular and intermolecular dehydration. Name the reaction products.
- Write reactions of interaction of polyhydric alcohols with hydrogen halides. Name the reaction products.
- What are the ways to get ethylene glycol?
- What are the ways to get glycerin?
- What are the applications of polyhydric alcohols?
- Checking the house. tasks: p. 158, ex. 4-6 (optional at the board).
- Learning new material in the form of a conversation.
The slide shows the structural formulas of organic compounds. You need to name these substances and determine which class they belong to.
Phenols - These are substances in which the hydroxo group is connected directly to the benzene ring.
What is the molecular formula of the phenyl radical: C 6H5 - phenyl. If one or more hydroxyl groups are attached to this radical, then we get phenols. Note that the hydroxyl groups must be directly attached to the benzene ring, otherwise we get aromatic alcohols.
Classification
As well as alcohols, phenolsclassified by atomicity, i.e. by the number of hydroxyl groups.
- Monatomic phenols contain one hydroxyl group in the molecule:
- Polyhydric phenols contain more than one hydroxyl group in their molecules:
The most important representative of this class is phenol. The name of this substance formed the basis for the name of the entire class - phenols.
Many of you will become doctors in the near future, so they should know as much as possible about phenol. Currently, there are several main areas of use of phenol. One of them is production medicines. Most of these drugs are derivatives of salicylic acid derived from phenol: o-HOC 6 H 4 COOH. The most common antipyretic - aspirin is nothing more than acetylsalicylic acid. The ester of salicylic acid and phenol itself is also well known under the name salol. In the treatment of tuberculosis, para-aminosalicylic acid (PASA) is used. And, finally, when phenol is condensed with phthalic anhydride, phenolphthalein, aka purgen, is obtained.
Phenols - organic substances, the molecules of which contain a phenyl radical associated with one or more hydroxyl groups.
Why do you think phenols were singled out in a separate class, although they contain the same hydroxyl group as alcohols?
Their properties are very different from those of alcohols. Why?
The atoms in a molecule mutually influence each other. (Butlerov's theory).
Consider the properties of phenols on the example of the simplest phenol.
Discovery history
In 1834 German organic chemist Friedlieb Runge discovered a white crystalline substance with a characteristic odor in the products of the distillation of coal tar. He failed to determine the composition of the substance, he did it in 1842. August Laurent. The substance had pronounced acidic properties and was a derivative of benzene discovered shortly before. Laurent called it benzene, so the new acid was called phenylic. Charles Gerard considered the resulting substance to be alcohol and suggested calling it phenol.
Physical Properties
Lab Experience: 1. Study of physical properties phenol.
instruction card
1. Consider the substance given to you and write its physical properties.
2. Dissolve the substance in cold water.
3. Slightly heat the test tube. Note the observations.
Phenol C 6 H 5 OH (carbolic acid)- colorless crystalline substance, t pl = 43 0 C, t bp = 182 0 C, oxidizes and turns pink in air, sparingly soluble in water at ordinary temperatures, miscible with water above 66 °C in any proportion. Phenol is a toxic substance, causes skin burns, is an antiseptic, thereforephenol must be handled with care!
Phenol itself and its vapors are poisonous. But there are phenols of plant origin, contained, for example, in tea. They have a beneficial effect on the human body.
A consequence of the polarity of the О–Н 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 temperatures melting (+43) and boiling (+182). The formation of hydrogen bonds with water molecules promotes 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 miscible with water in any ratio. The solubility of phenol in water is limited.
Isomerism and nomenclature
2 types possible isomerism:
- isomerism of the position of substituents in the benzene ring;
- side chain isomerism (structures of the alkyl radical and numberradicals).
Chemical properties
Look closely at the structural formula of phenol and answer the question: “What is so special about phenol that it was singled out in a separate class?”
Those. phenol contains both a hydroxyl group and a benzene ring, which, according to the third position of A.M. Butlerov, influence each other.
What properties of compounds should phenol formally have? That's right, alcohols and benzene.
The chemical properties of phenols are due precisely to the presence of a functional hydroxyl group and a benzene ring in the molecules. Therefore, the chemical properties of phenol can be considered both by analogy with alcohols and by analogy with benzene.
Think about what alcohols react with. Let's watch a video of the interaction of phenol with sodium.
- Reactions involving the hydroxyl group.
- Interaction of mo with alkali metals(similar to alcohols).
2C 6 H 5 OH + 2Na → 2C 6 H 5 ONa + H 2 (sodium phenolate)
Do you remember whether alcohols react with alkalis? No, what about phenol? Let's do a lab experiment.
Lab Experience: 2. Interaction of phenol and ethanol with alkali solution.
1. Pour NaOH solution and 2-3 drops of phenolphthalein into the first tube, then add 1/3 of the phenol solution.
2. Add NaOH solution and 2-3 drops of phenolphthalein to the second test tube, then add 1/3 part of ethanol.
Make observations and write reaction equations.
- The hydrogen atom of the hydroxyl group of phenol is acidic. The acidic properties of phenol are more pronounced than those of water and alcohols.Unlike alcohols. and water phenol reacts not only with alkali metals, but with alkalis to form phenolates:
C 6 H 5 OH + NaOH → C 6 H 5 ONa + H 2 O
However, the acidic properties of phenols are less pronounced than those of inorganic and carboxylic acids. So, for example, the acidic properties of phenol are about 3000 times less than those of carbonic acid, therefore, passing carbon dioxide through a solution of sodium phenolate, free phenol can be isolated ( demo ):
C 6 H 5 ONa + H 2 O + CO 2 → C 6 H 5 OH + NaHCO 3
Adding hydrochloric or sulfuric acid to an aqueous solution of sodium phenolate also leads to the formation of phenol:
C 6 H 5 ONa + HCl → C 6 H 5 OH + NaCl
Phenolates are used as starting materials for the production of ethers and esters:
C 6 H 5 ONa + C 2 H 5 Br → C 6 H 5 OC 2 H 5 + NaBr (ethyphenyl ether)
C 6 H 5 ONa + CH 3 COCl → CH 3 - COOC 6 H 5 + NaCl
Acetyl chloride phenyl acetate, acetic acid phenyl ester
How can one explain the fact that alcohols do not react with alkali solutions, but phenol does?
Phenols are polar compounds (dipoles). The benzene ring is the negative end of the dipole, the group - OH - is positive. The dipole moment is directed towards the benzene ring.
The benzene ring pulls electrons from the lone pair of oxygen electrons. The displacement of the lone pair of electrons of the oxygen atom towards the benzene ring leads to an increase in polarity O-H bonds. An increase in the polarity of the O-H bond under the action of the benzene nucleus and the appearance of a sufficiently large positive charge on the hydrogen atom leads to the fact that the phenol moleculedissociates in water solutionsacid type:
C 6 H 5 OH ↔ C 6 H 5 O - + H + (phenolate ion)
Phenol is weak acid. This is the main difference between phenols andalcohols, which arenon-electrolytes.
- Reactions involving the benzene ring
The benzene ring changed the properties of the hydroxo group!
Is there a reverse effect - have the properties of the benzene ring changed?
Let's do one more experiment.
Demo: 2. Interaction of phenol with bromine water (video clip).
Substitution reactions. Electrophilic substitution reactions in the benzene ring of phenols proceed much more easily than in benzene, and under milder conditions due to the presence of a hydroxyl substituent.
- Halogenation
Bromination occurs especially easily in aqueous solutions. Unlike benzene, phenol bromination does not require the addition of a catalyst (FeBr 3 ). When phenol reacts with bromine water, a white precipitate of 2,4,6-tribromophenol is formed:
- Nitration also occurs more easily than the nitration of benzene. The reaction with dilute nitric acid proceeds at room temperature. As a result, a mixture of ortho- and para-isomers of nitrophenol is formed:
O-nitrophenol p-nitrophenol
When using concentrated nitric acid, 2,4,6-trinitrophenol is formed - picric acid, an explosive:
As you can see, phenol reacts with bromine water to form a white precipitate, but benzene does not. Phenol, like benzene, reacts with nitric acid, but not with one molecule, but with three at once. What explains this?
Having acquired an excess of electron density, the benzene ring destabilized. The negative charge is concentrated in the ortho and para positions, so these positions are the most active. The substitution of hydrogen atoms occurs here.
Phenol, like benzene, reacts with sulfuric acid, but with three molecules.
- Sulfonation
The ratio of ortho- and para-measurements is determined by the reaction temperature: at room temperature, mainly o-phenolsulfoxylate is formed, at a temperature of 100 0 С is a para-isomer.
- The polycondensation of phenol with aldehydes, in particular with formaldehyde, occurs with the formation of reaction products - phenol-formaldehyde resins and solid polymers ( demo ):
Reaction polycondensation,i.e., a polymer production reaction proceeding with the release of a low molecular weight product (for example, water, ammonia, etc.),can continue further (until the complete consumption of one of the reagents) with the formation of huge macromolecules. The process can be described by the overall equation:
The formation of linear molecules occurs at ordinary temperature. Carrying out this reaction when heated leads to the fact that the generatrix has a branched structure, it is solid and insoluble in water. As a result of heating a linear phenol-formaldehyde resin with an excess of aldehyde, solid plastic masses with unique properties are obtained.
Polymers based on phenol-formaldehyde resins are used for the manufacture of varnishes and paints. Plastic products made on the basis of these resins are resistant to heating, cooling, alkalis and acids, they also have high electrical properties. Polymers based on phenol-formaldehyde resins are used to make the most important parts of electrical appliances, power unit cases and machine parts, the polymer base of printed circuit boards for radio devices.
Adhesives based on phenol-formaldehyde resins are able to reliably connect parts of various nature, maintaining the highest bond strength over a very wide temperature range. Such glue is used to fasten the metal base of lighting lamps in a glass bulb.
All plastics containing phenol are hazardous to humans and nature. It is necessary to find a new type of polymer that is safe for nature and easily decomposed into harmless waste. This is your future. Create, invent, do not let dangerous substances destroy nature!”
Qualitative reaction to phenols
In aqueous solutions, monatomic phenols interact with FeCl 3 with the formation of complex phenolates, which have a purple color; the color disappears after the addition of a strong acid
Lab Experience: 3. Reaction of phenol with FeCl 3 .
Add 1/3 of the phenol solution to the test tube and drop by drop the FeCl solution 3 .
Make observations.
How to get
- cumene method.
Benzene and propylene are used as feedstock, from which isopropylbenzene (cumene) is obtained, which undergoes further transformations.
Cumene method for the production of phenol (USSR, Sergeev P.G., Udris R.Yu., Kruzhalov B.D., 1949). Advantages of the method: waste-free technology (yield useful products> 99%) and economy. Currently, the cumene method is used as the main one in the world production of phenol.
- From coal tar.
Coal tar containing phenol as one of the components is treated first with an alkali solution (phenolates are formed), and then with an acid:
C 6 H 5 OH + NaOH → C 6 H 5 ONa + H 2 O (sodium phenolate, intermediate)
C 6 H 5 ONa + H 2 SO 4 → C 6 H 5 OH + NaHSO 4
- Fusion of salts of arenesulfonic acids with alkali:
3000C
C 6 H 5 SO 3 Na + NaOH → C 6 H 5 OH + Na 2 SO 3
- Interaction of halogen derivatives of aromatic hydrocarbons with alkalis:
300 0 C, P, Cu
C 6 H 5 Cl + NaOH (8-10% solution) → C 6 H 5 OH + NaCl
or with steam:
450-500 0 C, Al 2 O 3
C 6 H 5 Cl + H 2 O → C 6 H 5 OH + HCl
The biological role of phenol compounds
Positive | Negative (toxic effect) |
|
Accordingly, actually phenol, as a substance, is the simplest representative of the phenol group and has one aromatic nucleus and one hydroxyl group HE.
Isopropylbenzene is obtained by treating benzene with pure propylene or propane-propylene fraction of oil cracking, purified from other unsaturated compounds, moisture, mercaptans and hydrogen sulfide poisoning the catalyst. Aluminum trichloride dissolved in polyalkylbenzene is used as a catalyst, for example. in diisopropylbenzene. Alkylation is carried out at 85 ° C and excess pressure 0.5 MPa, which ensures the flow of the process in the liquid phase. Isopropylbenzene is oxidized to hydroperoxide with atmospheric oxygen or technical oxygen at 110-130°C in the presence of salts of metals of variable valency (iron, nickel, cobalt, manganese) Decompose hydroperoxide with dilute acids (sulphuric or phosphoric) or small amounts of concentrated sulfuric acid at 30-60 °С. After distillation, phenol, acetone and a certain amount of α-methylstyrene. The industrial cumene method developed in the USSR is the most economically advantageous in comparison with other methods for the production of phenol. The production of phenol through benzenesulfonic acid is associated with the consumption of large amounts of chlorine and alkali. Oxidative chlorination of benzene is associated with a large 
Benzoylsalicylic acid decomposes with water vapor into salicylic and benzoic acids. Phenol is formed as a result of the rapid decarboxylation of salicylic acid.
