Organic substances are phenols. Phenol (hydroxybenzene, carbolic acid)
Phenols are derivatives of arenes in which one or more hydrogen atoms of the aromatic ring are replaced by an OH group.
Classification.
1. Monohydric phenols:
2. Polyhydric phenols:
Physical properties:
Phenol and its lower homologues are colorless, low-melting crystalline substances or liquids with a characteristic odor.
Phenol is moderately soluble in water. Phenol is capable of forming hydrogen bonds, which underlies its antiseptic properties. Aqueous solutions of phenol cause tissue burns. A dilute aqueous solution of phenol is called carbolic acid. Phenol is toxic, the toxicity of phenol homologues decreases, bactericidal activity increases as the alkyl radical becomes more complex.
Methods for obtaining phenols
1. Made from coal tar.
2. Cumene method
3. Fusion of salts of aromatic sulfonic acids with alkali:
4. Decomposition of diazonium salts:
5. Hydrolysis of halogen derivatives
§11. Chemical properties of phenols.
1. Acid properties: phenols form salts:
Phenol is a weaker acid than carbonic H 2 CO 3:
2. Reactions involving the OH group.
a) alkylation (formation of ethers)
b) acylation (formation of esters):
3. Reactions of substitution of OH group:
Phenol does not interact with NH 3 and R – NH 2.
4. Electrophilic substitution reactions characteristic of arenes.
The substitution proceeds faster than that of benzene. The OH group directs the new substituent to the ortho and para positions.
a) halogenation (discoloration of bromine water - qualitative reaction to phenol):
b) nitration
c) sulfonation:
5. Condensation reactions
a) with formaldehyde
b) with phthalic anhydride
6. Oxidation
a) white phenol crystals turn pink in air;
b) phenol with a solution of FeCl 3 gives a red-violet color;
cresol – blue color;
c) oxidation by strong oxidizing agents
7. Recovery
8. Carboxylation (Kolbe-Schmitt reaction):
Application
1. Phenol is used in the production of phenol-formaldehyde resins, caprolactam, picric acid, dyes, insecticides, medicines.
2. Pyrocatechol and its derivatives are used in the production of medicines (the synthetic hormone adrenaline is obtained) and aromatic substances.
3. Resorcinol is used in the synthesis of dyes; in medicine as a disinfectant.
Experimental part
Experience 1. The influence of the radical and the number of hydroxyl groups on the solubility of alcohols.
Add 4-5 drops of ethyl, isoamyl alcohol and glycerin into three test tubes. Add 5-6 drops of water to each test tube and shake. What did you observe?
Experience 2. Detection of water in ethyl alcohol and its dehydration.
Add 10 drops of ethyl alcohol to a dry test tube, add a little anhydrous copper sulfate, mix thoroughly, and let it settle. If the alcohol contains water, the copper sulfate precipitate will turn blue due to the formation of copper sulfate CuSO 4 · 5H 2 O. Save the anhydrous alcohol for later experiment.
Experience 3. Formation of sodium ethoxide.
Place a small piece of sodium in a dry test tube, add 3 drops of anhydrous ethyl alcohol (from the previous experiment) and close the hole of the test tube with your finger. The evolution of hydrogen immediately begins.
At the end of the reaction, without lifting your finger from the hole of the test tube, bring it to the burner flame. When the test tube is opened, hydrogen ignites with a characteristic sound, forming a bluish ring. A whitish precipitate of sodium ethoxide or its solution remains at the bottom of the test tube.
When 1 drop of an alcohol solution of phenolphthalein is added to a test tube, a red color appears.
Write the equations for the reactions that occur.
Experience 4. Oxidation of ethyl alcohol with a chromium mixture.
Add 3-4 drops of ethyl alcohol into the test tube. Add 1 drop of 2N sulfuric acid solution and 2 drops of 0.5N potassium dichromate solution. Heat the resulting orange solution over a burner flame until the color begins to change. Usually within a few seconds the color of the solution turns bluish-green. At the same time, a characteristic smell of acetaldehyde is felt, reminiscent of the smell of apples. The method can be used to distinguish primary and secondary alcohols.
Write the reaction equations.
Experience 5. Preparation of ethyl acetate.
Place a little anhydrous sodium acetate powder (layer height about 2 mm) and 3 drops of ethyl alcohol into a dry test tube. Add 2 drops of concentrated sulfuric acid and heat gently over a burner flame. After a few seconds, the characteristic pleasant refreshing smell of ethyl acetate appears.
Reaction equations:
CH 3 C(O)ONa + HOSO 3 H NaHSO 4 + CH 3 C(O)OH
C 2 H 5 OH + HOSO 3 H H 2 O + C 2 H 5 OSO 3 H
CH 3 C(O)OH + HOSO 3 HH 2 SO 4 + CH 3 C(O)O C 2 H 5
Experience 6. Reaction of glycerol with copper (II) hydroxide in an alkaline medium .
Place 3 drops of 0.2 N CuSO 4 solution and 2 drops of 2 N NaOH solution into a test tube and mix. A gelatinous precipitate of copper (II) hydroxide appears:
When heated in an alkaline medium to boiling, the resulting hydroxide
copper(II) decomposes. This is detected by the release of a black precipitate of copper (II) oxide:
Repeat the experiment, but before boiling copper (II) hydroxide, add 1 drop of glycerol to the test tube. Shake. Heat the resulting solution to a boil and make sure that the copper glycerate solution does not decompose when boiled. Here a chelate compound is formed
Experience 7. Formation of acrolein from glycerol.
Place 3-4 potassium bisulfate crystals and 1 drop of glycerin in a test tube. Heat on a burner flame. A sign of the beginning of the decomposition of glycerin is the browning of the liquid in the test tube and the appearance of heavy vapors of the resulting acrolein, which has a very pungent odor.
Experience 8. Solubility of phenol in water.
Place 1 drop of liquid phenol in a test tube, add 1 drop of water and
shake it up. The result is a cloudy liquid - a phenol emulsion. When standing
such an emulsion stratifies, and at the bottom there will be a solution of water in phenol,
or liquid phenol, and at the top - a solution of phenol in water, or carbolic water.
Add water drop by drop, shaking the test tube each time until
you will get a clear solution of phenol in water. Save the received
phenolic water for subsequent experiments.
Experience 9.Color reactions to phenolic water.
Place 3 drops of clear phenolic water in a test tube and add 1 drop of 0.1 N FeCl 3 solution - a violet color appears.
A more sensitive reaction to phenol is the colored indophenol
Place 1 drop of clear carbolic water in a test tube. Add to it 3 drops of a 2N solution of NH 4 OH and then 3 drops of a saturated solution of bromine water. After a few seconds, a blue color can be seen on the white background of the paper, gradually increasing due to the formation of a coloring substance - indophenol.
Experience 10. Formation of tribromophenol.
Place 3 drops of bromine water in a test tube and add 1 drop of clear carbolic water. Phenols with free ortho- and para-positions discolor bromine water and form substitution products, which usually precipitate.
Experience 11. Evidence of the acidic nature of phenol.
Add 1 more drop of phenol to the remaining phenol water and shake. Add 1 drop of 2N NaOH solution to the newly obtained emulsion. A clear solution of sodium phenolate is instantly formed, since it dissolves well in water.
§10. Problems to solve independently.
1. Write the structural formulas of the following compounds:
3-methyl-2-pentanol; 2-methyl-3-butyn-2-ol; 1-phenylpropanol-1.
2. Use the Grignard reaction to obtain the following alcohols:
1) 2-methyl-3-pentanol;
2) 2,3-dimethyl-3-pentanol;
3) 2,2-dimethyl-1-propanol.
3. Obtain by hydration of the corresponding ethylene hydrocarbons
the following alcohols:
a) 2-methylpentanol-2; b) 3,3-dimethylbutanol-2.
4. Write the oxidation reactions of secondary butyl alcohol;
2-methylbutanol-1.
5. Subject 2-pentanol to dehydration, then oxidize the reaction product with an aqueous solution of potassium permanganate. Treat the resulting compound with acetic acid. Write the reaction equations and name all the products.
6. Obtain phenol from benzene and 1-butene through the stage of formation of sec.butyl hydroperoxide.
7. Describe the scheme of the following transformations:
8. Position following connections in descending order of acid properties:
One-, two-, and three-atomic phenols are distinguished depending on the number of OH groups in the molecule (Fig. 1)
Rice. 1. ONE-, BI- AND TRICHATIC PHENOLS
In accordance with the number of condensed aromatic rings in the molecule, they are distinguished (Fig. 2) into phenols themselves (one aromatic ring - benzene derivatives), naphthols (2 condensed rings - naphthalene derivatives), anthranols (3 condensed rings - anthracene derivatives) and phenanthroles (Fig. 2).
Rice. 2. MONO- AND POLYNUCLEAR PHENOLS
Nomenclature of alcohols.
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 are part of the aromatic rings are numbered and the position of the substituents is indicated using digital indices (Fig. 3).
Rice. 3. NOMENCLATURE OF PHENOLS. Substituting groups and corresponding digital indices are highlighted in different colors for clarity.
Chemical properties of phenols.
The benzene ring and the OH group, combined in a phenol molecule, influence each other, significantly increasing reactivity each other. The phenyl group absorbs a lone pair of electrons 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 the d+ symbol), 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. A partial negative charge (denoted by d–), transferring to the phenyl group, is concentrated in positions ortho- And pair-(relative to the OH group). These reaction points can be attacked by reagents that gravitate toward electronegative centers, so-called electrophilic (“electron-loving”) reagents.
Rice. 4. ELECTRON DENSITY DISTRIBUTION IN PHENOL
As a result, two types of transformations are possible for phenols: substitution of a hydrogen atom in the OH group and substitution of the H-atomobenzene ring. A pair of electrons of the O atom, drawn to the benzene ring, increases the strength of the C–O bond, therefore reactions that occur with the rupture of this bond, characteristic of alcohols, are not typical for phenols.
1. Reactions of substitution of a hydrogen atom in the OH group. When phenols are exposed to alkalis, phenolates are formed (Fig. 5A), catalytic interaction with alcohols leads to ethers (Fig. 5B), and as a result of reaction with anhydrides or acid chlorides carboxylic acids esters are formed (Fig. 5B). When interacting with ammonia ( elevated temperature and pressure) the OH group is replaced by NH 2, aniline is formed (Fig. 5D), reducing reagents convert phenol into benzene (Fig. 5E)
2. Reactions of substitution 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. replacement 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; essentially, this is alkylation, which occurs easily and under mild conditions (at 40–50 ° C, aquatic environment in the presence of catalysts), while a carbon atom in the form of a methylene group CH 2 or a substituted methylene group (CHR or CR 2) is inserted between two phenol molecules. Often such condensation leads to the formation of polymer products (Fig. 7).
Diatomic phenol ( trade name bisphenol A, Fig. 7), is used as a component in the production of epoxy resins. The condensation of phenol with formaldehyde underlies the production of widely used phenol-formaldehyde resins (phenoplasts).
Methods for obtaining phenols.
Phenols are isolated from coal tar, as well as from the pyrolysis products of brown coal and wood (tar). Industrial method obtaining phenol itself C 6 H 5 OH is based on oxidation aromatic hydrocarbon cumene (isopropylbenzene) with atmospheric oxygen, followed by decomposition of the resulting hydroperoxide, diluted with H 2 SO 4 (Fig. 8A). The reaction occurs in 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. 8. METHODS FOR OBTAINING PHENOL
Application of phenols.
A phenol solution is used as a disinfectant (carbolic acid). Diatomic phenols - pyrocatechol, resorcinol (Fig. 3), as well as hydroquinone ( pair- dihydroxybenzene) are used as antiseptics (antibacterial disinfectants), added to tanning agents for leather and fur, as stabilizers for lubricating oils and rubber, as well as for processing photographic materials and as reagents in analytical chemistry.
Phenols are used to a limited extent in the form of individual compounds, but their various derivatives are widely used. Phenols serve starting compounds for the production of a variety of polymer products - phenol-aldehyde resins (Fig. 7), polyamides, polyepoxides. Based on phenols, numerous medicines eg aspirin, salol, phenolphthalein, also dyes, perfumes, plasticizers for polymers and plant protection products.
Mikhail Levitsky
Profile chemical and biological class
Lesson type: lesson of learning new material.
Lesson teaching methods:
- verbal (conversation, explanation, story);
- visual (computer presentation);
- practical (demonstration experiments, laboratory experiments).
Lesson objectives:Learning Objectives: using 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; introduce students to the physical and chemical properties of phenol and some of its compounds, 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 points in the text, and perform tests.
Developmental goals: Create dialogue interaction in the lesson, promote the development of students’ skills to express their opinions, listen to a friend, ask each other questions and complement each other’s speeches.
Equipment: chalk, board, screen, projector, computer, electronic media, textbook “Chemistry”, 10th grade, O.S. Gabrielyan, F.N. Maskaev, textbook “Chemistry: in tests, problems and exercises”, 10th grade, O.S. Gabrielyan, I.G. Ostroumov.
Demonstration: D. 1. Displacement of phenol from sodium phenolate with carbonic acid.
D. 2. Interaction of phenol and benzene with bromine water (video).
D. 3. Reaction of phenol with formaldehyde.
Laboratory experience:1. Solubility of phenol in water at normal 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
"GYMNASIUM No. 5"
TYRNYAUZA KBR
Open lesson-research in chemistry
Chemistry teacher: Gramoteeva S.V.
I qualification category
Class: 10 "A", chemical and biological
Date: 02/14/2012
Phenol: structure, physical and chemical properties pheno la.
Application of phenol.
Profile chemical and biological class
Lesson type: lesson of learning new material.
Lesson teaching methods:
- verbal (conversation, explanation, story);
- visual (computer presentation);
- practical (demonstration experiments, laboratory experiments).
Lesson Objectives: Learning Objectives: using 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; introduce students to the physical and chemical properties of phenol and some of its compounds, 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 students to work independently, strengthen students’ skills in working with text, highlight the main points in the text, and perform tests.
Developmental goals:Create dialogue interaction in the lesson, promote the development of students’ skills to express their opinions, listen to a friend, ask each other questions and complement each other’s speeches.
Equipment: chalk, board, screen, projector, computer, electronic media, textbook “Chemistry”, 10th grade, O.S. Gabrielyan, F.N. Maskaev, textbook “Chemistry: in tests, problems and exercises”, 10th grade, O.S. Gabrielyan, I.G. Ostroumov.
Demonstration: D. 1.Displacement of phenol from sodium phenolate with carbonic acid.
D. 2. Interaction of phenol and benzene with bromine water (video).
D. 3. Reaction of phenol with formaldehyde.
Laboratory experience: 1. Solubility of phenol in water at normal and elevated temperatures.
3. Reaction of phenol with FeCl 3 .
PROGRESS OF THE LESSON
- Organizational moment.
- Preparing to study new material.
- Frontal survey:
- 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 reaction products called?
- Write the reactions of intramolecular and intermolecular dehydration. Name the reaction products.
- Write the reactions of polyhydric alcohols with hydrogen halides. Name the reaction products.
- What are the methods for producing ethylene glycol?
- What are the methods for producing glycerin?
- What are the applications of polyhydric alcohols?
- Checking the house. assignments: page 158, ex. 4-6 (selectively at the board).
- Learning new material in the form of a conversation.
The slide shows the structural formulas 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 6 H 5 – phenyl. If one or more hydroxyl groups are added to this radical, we obtain phenols. Note that the hydroxyl groups must be directly attached to the benzene ring, otherwise we will get aromatic alcohols.
Classification
Same as alcohols, phenolsclassified 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 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 the production of medicines. Most of these drugs are derivatives of phenol-derived salicylic acid: 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. Para-aminosalicylic acid (PAS for short) is used in the treatment of tuberculosis. And finally, the condensation of phenol with phthalic anhydride produces phenolphthalein, also known as purgen.
Phenols – organic matter, the molecules of which contain a phenyl radical associated with one or more hydroxy groups.
Why do you think phenols are classified as a separate class, even though 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).
Let's look at the properties of phenols using the simplest phenol as an example.
History of discovery
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 was unable to determine the composition of the substance; he did this in 1842. Auguste Laurent. The substance had pronounced acidic properties and was a derivative of benzene, discovered shortly before. Laurent called it benzene phenone, so the new acid was called phenyl acid. Charles Gerard considered the resulting substance to be alcohol and proposed calling it phenol.
Physical properties
Laboratory experience: 1. Studying physical properties phenol.
Instruction card
1.Look at the substance given to you and write down its physical properties.
2.Dissolve the substance in cold water.
3. Warm the test tube slightly. Note the observations.
Phenol C6H5 OH (carbolic acid)- colorless crystalline substance, t pl = 43 0 C, t boil = 182 0 C, oxidizes in air and turns 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, thereforePhenol must be handled with care!
Phenol itself and its vapors are poisonous. But phenols exist plant origin, contained, for example, in tea. They have a beneficial effect on the human body.
A consequence of the polarity of the O–H bond and the presence of lone pairs of electrons on the oxygen atom is the ability of hydroxy compounds to form hydrogen bonds
This explains why phenol has quite high 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 mixed 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 (structure of the alkyl radical and numberradicals).
Chemical properties
Look carefully at the structural formula of phenol and answer the question: “What is so special about phenol that it was placed in a separate class?”
Those. phenol contains both a hydroxyl group and a benzene ring, which, according to the third position of the theory of A.M. Butlerov, influence each other.
What properties 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.
Remember what substances alcohols react with. Let's watch a video of the interaction of phenol with sodium.
- Reactions involving the hydroxyl group.
- Interaction mo alkali metals (similarity 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 conduct a laboratory experiment.
Laboratory experience: 2. Interaction of phenol and ethanol with alkali solution.
1. Pour NaOH solution and 2-3 drops of phenolphthalein into the first test 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 in nature. 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. For example, the acidic properties of phenol are approximately 3000 times less than those of carbonic acid, therefore, passing sodium phenolate through a solution carbon dioxide, free phenol can be isolated ( demonstration):
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 preparation 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 phenylacetate, acetic acid phenyl ester
How can you 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 OH group is the positive end. The dipole moment is directed towards the benzene ring.
The benzene ring draws 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 connections. An increase in the polarity of the O-H bond under the influence of the benzene ring 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 andalcoholswhich 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.
Demonstration: 2. Interaction of phenol with bromine water (video).
Substitution reactions. Electrophilic substitution reactions in the benzene ring of phenols occur 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, the bromination of phenol 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 benzene nitration. Reaction with dilute nitric acid goes with room temperature. As a result, a mixture of ortho- and para-isomers of nitrophenol is formed:
O-nitrophenol p-nitrophenol
When concentrated nitric acid is used, 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 react. Phenol, like benzene, reacts with nitric acid, but not with one molecule, but with three at once. What explains this?
Having acquired excess electron density, the benzene ring became destabilized. The negative charge is concentrated in the ortho and para positions, so these positions are the most active. The replacement of hydrogen atoms occurs here.
Phenol, like benzene, reacts with sulfuric acid, but with three molecules.
- Sulfonation
The ratio of ortho- and para-dimensions is determined by the reaction temperature: at room temperature, o-phenolsulfoxylate is mainly formed, at a temperature of 100 0 C – para-isomer.
- Polycondensation of phenol with aldehydes, in particular with formaldehyde, occurs with the formation of reaction products - phenol-formaldehyde resins and solid polymers ( demonstration):
Reaction polycondensation,i.e., a polymer production reaction that occurs with the release of a low molecular weight product (for example, water, ammonia, etc.),can continue further (until one of the reagents is completely consumed) with the formation of huge macromolecules. The process can be described by the overall equation:
The formation of linear molecules occurs at ordinary temperatures. Carrying out this reaction when heated leads to the fact that the constituents have 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, hard 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, and they also have high electrical properties. The most important parts of electrical appliances, power unit housings and machine parts, and the polymer base of printed circuit boards for radio devices are made from polymers based on phenol-formaldehyde resins.
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 glue is used to attach the metal base of lighting lamps to a glass bulb.
All plastics containing phenol are dangerous to humans and nature. Need to find new look polymers, safe for nature and easily decomposed into safe waste. This is your future. Create, invent, don’t let dangerous substances destroy nature!”
Qualitative reaction to phenols
In aqueous solutions, monohydric phenols react with FeCl 3 with the formation of complex phenolates, which have a purple color; color disappears after adding strong acid
Laboratory 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 .
Record your observations.
Methods of obtaining
- Cumene method.
Benzene and propylene are used as feedstock, from which isopropylbenzene (cumene) is obtained, which undergoes further transformations.
Cumene method for producing phenol (USSR, Sergeev P.G., Udris R.Yu., Kruzhalov B.D., 1949). Advantages of the method: waste-free technology(exit healthy products> 99%) and cost-effectiveness. Currently, the cumene method is used as the main method in the global production of phenol.
- Made from coal tar.
Coal tar, containing phenol as one of the components, is first treated 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:
300 0 C
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
C6H5 Cl + NaOH (8-10% solution) → C 6 H 5 OH + NaCl
or with water vapor:
450-500 0 C, Al 2 O 3
C 6 H 5 Cl + H 2 O → C 6 H 5 OH + HCl
Biological role of phenol compounds
Positive | Negative (toxic effect) |
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