Lecture No. 3.

Polyhydric alcohols, their structure and properties.

Representatives of polyhydric alcohols are ethylene glycol and glycerin. Dihydric alcohols containing two hydroxyl groups - OH are called glycols, or diols, trihydric alcohols containing three hydroxyl groups - glycerols, or triols.

The position of hydroxyl groups is indicated by numbers at the end of the name.

Physical properties

Polyhydric alcohols are colorless, syrupy liquids with a sweetish taste, highly soluble in water, poorly soluble in organic solvents; have high boiling points. For example, the boiling point of ethylene glycol is 198°C, density () 1.11 g/cm3; tboil (glycerin) = 290°C, glycerin = 1.26 g/cm3.

Receipt

Di- and trihydric alcohols are obtained by the same methods as monohydric ones. Alkenes, halogen derivatives and other compounds can be used as starting compounds.

1. Ethylene glycol (ethanediol-1,2) is synthesized from ethylene in various ways:

3CH 2 =CH 2 + 2KMnO 4 + 4H 2 O ® 3HO–CH 2 –CH 2 –OH + 2MnO 2 + 2KOH

2. Glycerin (propanetriol -1,2,3) is obtained from fats, as well as synthetically from petroleum cracking gases (propylene), i.e. from non-food raw materials.

Chemical properties

Polyhydric alcohols have chemical properties similar to monohydric alcohols. However, the chemical properties of polyhydric alcohols have features due to the presence of two or more hydroxyl groups in the molecule.

The acidity of polyhydric alcohols is higher than that of monohydric alcohols, which is explained by the presence in the molecule of additional hydroxyl groups that have a negative inductive effect. Therefore, polyhydric alcohols, unlike monohydric alcohols, react with alkalis, forming salts. For example, ethylene glycol reacts not only with alkali metals, but also with heavy metal hydroxides.

By analogy with alcoholates, salts of dihydric alcohols are called glycolates, and trihydric alcohols are called glycerates.

When ethylene glycol reacts with hydrogen halides (HCl, HBr), one hydroxyl group is replaced by a halogen:

The second hydroxo group is more difficult to replace under the action of PCl5.

When copper (II) hydroxide reacts with glycerin and other polyhydric alcohols, the hydroxide dissolves and a bright blue complex compound is formed.

This reaction is used to detect polyhydric alcohols having hydroxyl groups at adjacent carbon atoms -CH(OH)-CH(OH)-:

In the absence of alkali, polyhydric alcohols do not react with copper (II) hydroxide - their acidity is insufficient for this.

Polyhydric alcohols react with acids to form esters (see §7). When glycerin reacts with nitric acid in the presence of concentrated sulfuric acid, nitroglycerin (glycerol trinitrate) is formed:

Alcohols are characterized by reactions that result in the formation of cyclic structures:

Application

Ethylene glycol is used mainly for the production of lavsan and for the preparation of antifreeze - aqueous solutions that freeze well below 0 ° C (using them to cool engines allows cars to operate in winter).

Glycerin is widely used in the leather and textile industries for finishing leather and fabrics and in other areas of the national economy. The most important use of glycerin is in the production of glycerol trinitrate (incorrectly called nitroglycerin), a powerful explosive that explodes on impact, and also a medicine (vasodilator). Sorbitol (hexahydric alcohol) is used as a sugar substitute for diabetics.

Test No. 4.

Properties of polyhydric alcohols

1. Which of the following substances will glycerin react with?

1) HBr 2) HNO 3 3) H 2 4) H 2 O 5) Cu(OH) 2 6) Ag 2 O/NH 3

2. Glycerol does not react with 1)HNO 3 2)NaOH 3)CH 3 COOH 4)Cu(OH) 2

3. Ethylene glycol does not react with 1)HNO 3 2)NaOH 3)CH 3 COOH 4)Cu(OH) 2

4. The following will not interact with freshly precipitated copper (II) hydroxide: 1) glycerol;

2) butanone 3) propanal 4) propanediol-1,2

5. A freshly prepared precipitate of Cu(OH) 2 will dissolve if added to it

1) propanediol-1,2 2) propanol-1 3) propene 4) propanol-2

6. Glycerol in an aqueous solution can be detected using

1) bleach 2) iron (III) chloride 3) copper (II) hydroxide 4) sodium hydroxide

7. Which alcohol reacts with copper (II) hydroxide?

1) CH 3 OH 2) CH 3 CH 2 OH 3) C 6 H 5 OH 4) HO-CH 2 CH 2 -OH

8. A characteristic reaction for polyhydric alcohols is interaction with

1) H 2 2) Cu 3) Ag 2 O (NH 3 solution) 4) Cu(OH) 2

9. A substance that reacts with Na and Cu(OH) 2 is:

1) phenol; 2) monohydric alcohol; 3) polyhydric alcohol 4) alkene

10. Ethanediol-1,2 can react with

1) copper (II) hydroxide

2) iron (II) oxide

3) hydrogen chloride

4)hydrogen

6) phosphorus

Lecture No. 4.

Phenols, their structure. Properties of phenol, mutual influence of atoms in the phenol molecule. Ortho-, vapor-orienting effect of the hydroxyl group. Preparation and use of phenol

PHENOLS – class of organic compounds. They contain one or more C–OH groups, with the carbon atom being part of an aromatic (for example, benzene) ring.

Classification of phenols. One-, two-, and three-atomic phenols are distinguished depending on the number of OH groups in the molecule (Fig. 1)

Rice. 1. ONE-, DUAL 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 phenols

For phenols, trivial names that have developed historically are widely used. The names of substituted mononuclear phenols also use the prefixes ortho-, meta- and para-, 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 (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 each other's reactivity. 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. The partial negative charge (denoted by d–), transferring to the phenyl group, is concentrated in the ortho- and para-positions (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. It has weak acidic properties; when exposed to alkalis, it forms salts - phenolates (for example, sodium phenolate - C6H6ONa):

C 6 H 5 OH + NaOH = C 6 H 5 ONa + H 2 O

It undergoes electrophilic substitution reactions on the aromatic ring. The hydroxy group, being one of the strongest donor groups, increases the reactivity of the ring to these reactions and directs substitution to the ortho and para positions. Phenol is easily alkylated, acylated, halogenated, nitrated and sulfonated.

Kolbe-Schmidt reaction.

2. Interaction with sodium metal:

C 6 H 5 OH + Na = C 6 H 5 ONa + H 2

3. Interaction with bromine water (qualitative reaction to phenol):

C 6 H 5 OH + 3Br 2 (aq) → C 6 H 2 (Br) 3 OH + 3HBr produces 2,4,6 tribromophenol

4. Interaction with concentrated nitric acid:

C 6 H 5 OH + 3HNO 3 conc → C 6 H 2 (NO 2) 3 OH + 3H 2 O 2,4,6 trinitrophenol is formed

5. Interaction with iron (III) chloride (qualitative reaction to phenol):

C 6 H 5 OH + FeCl 3 → 2 + (Cl)2- + HCl iron (III) dichloride phenolate is formed (violet color )

Methods for obtaining phenols.

Phenols are isolated from coal tar, as well as from the pyrolysis products of brown coal and wood (tar). The industrial method for producing phenol C6H5OH itself is based on the oxidation of the aromatic hydrocarbon cumene (isopropylbenzene) with atmospheric oxygen, followed by the decomposition of the resulting hydroperoxide diluted with H3SO4 (Fig. 8A). 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. 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 (para-dihydroxybenzene) are used as antiseptics (antibacterial disinfectants), added to tanning agents for leather and fur, as stabilizers for lubricating oils and rubber, and also for processing photographic materials and as reagents in analytical chemistry.

Phenols are used to a limited extent in the form of individual compounds, but their various derivatives are widely used. Phenols serve as starting compounds for the production of various polymer products - phenolic resins (Fig. 7), polyamides, polyepoxides. Numerous drugs are obtained from phenols, for example, aspirin, salol, phenolphthalein, in addition, dyes, perfumes, plasticizers for polymers and plant protection products.

Test No. 5 Phenols

1. How many phenols of the composition C 7 H 8 O are there? 1) One 2) Four 3) Three 4) two

2. The oxygen atom in the phenol molecule forms

1) one σ-bond 2) two σ-bonds 3) one σ-and one π-bond 4) two π-bonds

3. Phenols are stronger acids than aliphatic alcohols because...

1) a strong hydrogen bond is formed between alcohol molecules

2) the phenol molecule contains a larger mass fraction of hydrogen ions

3) in phenols, the electronic system is shifted towards the oxygen atom, which leads to greater mobility of the hydrogen atoms of the benzene ring

4) in phenols, the electron density of the O-H bond decreases due to the interaction of the lone electron pair of the oxygen atom with the benzene ring

4. Choose the correct statement:

1) phenols dissociate to a greater extent than alcohols;

2) phenols exhibit basic properties;

3) phenols and their derivatives do not have a toxic effect;

4) the hydrogen atom in the hydroxyl group of phenol cannot be replaced by a metal cation under the action of bases.

Properties

5. Phenol in aqueous solution is

1) strong acid 2) weak acid 3) weak base 4) strong base

1. A substance that reacts with Na and NaOH, giving a violet color with FeCl 3 is:

1) phenol; 2) alcohol 3) ether; 4) alkane

6. The effect of the benzene ring on the hydroxyl group in the phenol molecule is proven by the reaction of phenol with

1) sodium hydroxide 2) formaldehyde 3) bromine water 4) nitric acid

7. Chemical interaction is possible between substances whose formulas are:

1) C 6 H 5 OH and NaCl 2) C 6 H 5 OH and HCl 3) C 6 H 5 OH and NaOH 4) C 6 H 5 ONa and NaOH.

8. Phenol does not interact with

1) methanal 2) methane 3) nitric acid 4) bromine water

9. Phenol interacts with

1) hydrochloric acid 2) ethylene 3) sodium hydroxide 4) methane

10. Phenol does not interact with a substance whose formula is

1)HBr 2)Br 2 3)HNO 3 4)NaOH

11. Phenol does not react with 1) HNO 3 2) KOH 3) Br 2 4) Cu(OH) 2

12. Acid properties are most pronounced in 1) phenol 2) methanol 3) ethanol 4) glycerol

13. When phenol reacts with sodium,

1) sodium phenolate and water 2) sodium phenolate and hydrogen

3) benzene and sodium hydroxide 4) sodium benzoate and hydrogen

14. Establish a correspondence between the starting substances and the products that are predominantly formed during their interaction.

STARTING SUBSTANCES INTERACTION PRODUCTS

A) C 6 H 5 OH + K 1) 2,4,6-tribromophenol + HBr

B) C 6 H 5 OH + KOH 2) 3,5-dibromophenol + HBr

B) C 6 H 5 OH + HNO3 3) potassium phenolate + H 2

D) C 6 H 5 OH + Br 2 (solution) 4) 2,4,6-trinitrophenol + H 2 O

5) 3,5-dinitrophenol + HNO 3

6) potassium phenolate + H 2 O

15. Establish a correspondence between the starting materials and the reaction products.

STARTING SUBSTANCES REACTION PRODUCTS

A) C 6 H 5 OH + H 2 1) C 6 H 6 + H 2 O

B) C 6 H 5 OH + K 2) C 6 H 5 OK + H 2 O

B) C 6 H 5 OH + KOH 3) C 6 H 5 OH + KHCO 3

D) C 6 H 5 OK + H 2 O + CO 2 4) C 6 H 11 OH

5) C 6 H 5 OK + H 2

6) C 6 H 5 COOH + KOH

16. Phenol interacts with solutions

3) [Аg(NH 3) 2 ]OH

17. Phenol reacts with

1) oxygen

2) benzene

3) sodium hydroxide

4) hydrogen chloride

5) sodium

6) silicon oxide (IV)

Receipt

18. When hydrogen in the aromatic ring is replaced by a hydroxyl group, the following is formed:

1) ester; 2) ether; 3) limiting alcohol; 4) phenol.

19. Phenol can be obtained in the reaction

1) dehydration of benzoic acid 2) hydrogenation of benzaldehyde

3) hydration of styrene 4) chlorobenzene with potassium hydroxide

Interconnection, qualitative reactions.

20. Methanol. ethylene glycol and glycerin are:

1) homologues; 2) primary, secondary and tertiary alcohols;

32) isomers; 4) monohydric, dihydric, trihydric alcohols

21. A substance that does not react with either Na or NaOH, obtained by intermolecular dehydration of alcohols is: 1) phenol 2) alcohol 3) ether; 4) alkene

22.Interact with each other

1) ethanol and hydrogen 2) acetic acid and chlorine

3) phenol and copper (II) oxide 4) ethylene glycol and sodium chloride

23. Substance X can react with phenol, but does not react with ethanol. This substance:

1) Na 2) O 2 3) HNO 3 4) bromine water

24. A bright blue solution is formed when copper (II) hydroxide reacts with

1) ethanol 2) glycerin 3) ethanal 4) toluene

25. Copper(II) hydroxide can be used to detect

1) Al 3+ ions 2) ethanol 3) NO 3 ions - 4) ethylene glycol

26. In the transformation scheme C 6 H 12 O 6 à X à C 2 H 5 -O- C 2 H 5 substance “X” is

1) C 2 H 5 OH 2) C 2 H 5 COOH 3) CH 3 COOH 4) C 6 H 11 OH

27.In the transformation scheme ethanolà Xà butane substance X is

1) butanol-1 2) bromoethane 3) ethane 4) ethylene

28. In the transformation scheme propanol-1à Xà propanol-2 substance X is

1) 2-chloropropane 2) propanoic acid 3) propine 4) propene

29.Aqueous solutions of ethanol and glycerol can be distinguished using:

1) bromine water 2) ammonia solution of silver oxide

4) metallic sodium 3) freshly prepared precipitate of copper (II) hydroxide;

30. You can distinguish ethanol from ethylene glycol using:

31. You can distinguish phenol from methanol using:

1) sodium; 2) NaOH; 3) Cu(OH) 2 4) FeCl 3

32. You can distinguish phenol from ether using:

1) Cl 2 2) NaOH 3) Cu(OH) 2 4) FeCl 3

33. You can distinguish glycerin from 1-propanol using:

1) sodium 2) NaOH 3) Cu(OH) 2 4) FeCl 3

34. What substance should be used in order to distinguish ethanol and ethylene glycol from each other in the laboratory?

1) Sodium 2) Hydrochloric acid 3) Copper (II) hydroxide 4) Sodium hydroxide

Alcohols are a large group of organic chemicals. It includes subclasses of monohydric and polyhydric alcohols, as well as all substances of a combined structure: aldehyde alcohols, phenol derivatives, biological molecules. These substances undergo many types of reactions, both at the hydroxyl group and at the carbon atom bearing it. These chemical properties of alcohols should be studied in detail.

Types of alcohols

Alcohols contain a hydroxyl group attached to a supporting carbon atom. Depending on the number of carbon atoms to which the carrier C is connected, alcohols are divided into:

• primary (connected to the terminal carbon);
• secondary (connected to one hydroxyl group, one hydrogen and two carbon atoms);
• tertiary (connected to three carbon atoms and one hydroxyl group);
• mixed (polyhydric alcohols in which there are hydroxyl groups at secondary, primary or tertiary carbon atoms).

Alcohols are also divided depending on the number of hydroxyl radicals into monohydric and polyatomic. The former contain only one hydroxyl group at the supporting carbon atom, for example, ethanol. Polyhydric alcohols contain two or more hydroxyl groups at different supporting carbon atoms.

Chemical properties of alcohols: table

It is most convenient to present the material of interest to us using a table that reflects the general principles of the reactivity of alcohols.

Reaction connection, type of reaction	Reagent	Product
O-H bond, substitution	Active metal, active metal hydride, alkali or active metal amides	Alcoholates
C-O and O-H bond, intermolecular dehydration	Alcohol when heated in an acidic environment	Ether
C-O and O-H bond, intramolecular dehydration	Alcohol when heated over concentrated sulfuric acid	Unsaturated hydrocarbon
C-O bond, substitution	Hydrogen halide, thionyl chloride, quasiphosphonium salt, phosphorus halides	Haloalkanes
C-O bond - oxidation	Oxygen donors (potassium permanganate) with primary alcohol	Aldehyde
C-O bond - oxidation	Oxygen donors (potassium permanganate) with secondary alcohol
Alcohol molecule	Oxygen (combustion)	Carbon dioxide and water.

Reactivity of alcohols

Due to the presence of a hydrocarbon radical in the monohydric alcohol molecule - the C-O bond and the O-H bond - this class of compounds enters into numerous chemical reactions. They determine the chemical properties of alcohols and depend on the reactivity of the substance. The latter, in turn, depends on the length of the hydrocarbon radical attached to the supporting carbon atom. The larger it is, the lower the polarity of the O-H bond, which is why reactions involving the abstraction of hydrogen from alcohol will proceed more slowly. This also reduces the dissociation constant of the mentioned substance.

The chemical properties of alcohols also depend on the number of hydroxyl groups. One shifts the electron density towards itself along sigma bonds, which increases the reactivity at the O-H group. Since this polarizes the C-O bond, reactions involving its cleavage are more active in alcohols that have two or more O-H groups. Therefore, polyhydric alcohols, whose chemical properties are more numerous, react more readily. They also contain several alcohol groups, which is why they can freely enter into reactions with each of them.

Typical reactions of monohydric and polyhydric alcohols

The typical chemical properties of alcohols appear only in reactions with active metals, their bases and hydrides, and Lewis acids. Also typical are reactions with hydrogen halides, phosphorus halides and other components to produce haloalkanes. Alcohols are also weak bases, so they react with acids, forming hydrogen halides and esters of inorganic acids.

Ethers are formed from alcohols by intermolecular dehydration. These same substances undergo dehydrogenation reactions to form aldehydes from primary alcohol and ketones from secondary alcohol. Tertiary alcohols do not undergo such reactions. Also, the chemical properties of ethyl alcohol (and other alcohols) leave the possibility of their complete oxidation with oxygen. This is a simple combustion reaction, accompanied by the release of water with carbon dioxide and some heat.

Reactions at the hydrogen atom of the O-H bond

The chemical properties of monohydric alcohols allow the cleavage of the O-H bond and the elimination of hydrogen. These reactions occur upon interaction with active metals and their bases (alkalis), with hydrides of active metals, as well as with Lewis acids.

Alcohols also actively react with standard organic and inorganic acids. In this case, the reaction product is an ester or halocarbon.

Reactions of synthesis of haloalkanes (via the C-O bond)

Haloalkanes are typical compounds that can be produced from alcohols through several types of chemical reactions. In particular, the chemical properties of monohydric alcohols allow them to interact with hydrogen halides, trivalent and pentavalent phosphorus halides, quasiphosphonium salts, and thionyl chloride. Also, haloalkanes from alcohols can be obtained by an intermediate route, that is, by the synthesis of an alkyl sulfonate, which will later undergo a substitution reaction.

An example of the first reaction with a hydrogen halide is shown in the graphical appendix above. Here, butyl alcohol reacts with hydrogen chloride to form chlorobutane. In general, a class of compounds containing chlorine and a hydrocarbon saturated radical is called an alkyl chloride. The by-product of the chemical reaction is water.

Reactions producing alkyl chloride (iodide, bromide or fluoride) are quite numerous. A typical example is interaction with phosphorus tribromide, phosphorus pentachloride and other compounds of this element and its halides, perchlorides and perfluorides. They proceed through the mechanism of nucleophilic substitution. Alcohols also react with thionyl chloride to form a chloroalkane and release SO 2 .

The chemical properties of monohydric saturated alcohols containing a saturated hydrocarbon radical are clearly presented in the form of reactions in the illustrations below.

Alcohols react easily with the quasiphosphonium salt. However, this reaction is most favorable when occurring in monohydric secondary and tertiary alcohols. They are regioselective and allow the halogen group to be “implanted” in a strictly defined location. The products of such reactions are obtained with a high mass fraction of yield. And polyhydric alcohols, the chemical properties of which are somewhat different from those of monohydric alcohols, can isomerize during the reaction. Therefore, obtaining the target product is difficult. An example of a reaction in the image.

Intramolecular and intermolecular dehydration of alcohols

The hydroxyl group located at the supporting carbon atom can be cleaved with the help of strong acceptors. This is how intermolecular dehydration reactions occur. When one alcohol molecule interacts with another in a solution of concentrated sulfuric acid, a water molecule is split off from both hydroxyl groups, the radicals of which combine to form an ether molecule. During the intermolecular dehydration of ethanal, dioxane can be obtained, a dehydration product at four hydroxyl groups.

In intramolecular dehydration the product is an alkene.

The most important of the polyhydric alcohols are ethylene glycol and glycerin:

Ethylene glycol glycerin

These are viscous liquids, sweet in taste, highly soluble in water and poorly soluble in organic solvents.

Receipt. />

1. Hydrolysis of alkyl halides (similar to monohydric alcohols):

ClCH 2 - CH 2 Cl + 2 NaOH → HOCH 2 -CH 2 OH + 2 NaCl.

2. Ethylene glycol is formed by the oxidation of ethylene with an aqueous solution of potassium permanganate:

CH 2 = CH 2 + [O] + H 2 O → H O CH 2 -CH 2 OH.

3. Glycerin is obtained by hydrolysis of fats.

Chemical properties./>Di- and trihydric alcohols are characterized by the basic reactions of monohydric alcohols. One or two hydroxyl groups may participate in the reactions. The mutual influence of hydroxyl groups is manifested in the fact that polyhydric alcohols are stronger acids than monohydric alcohols. Therefore, polyhydric alcohols, unlike monohydric alcohols, react with alkalis, forming salts. By analogy with alcoholates, salts of dihydric alcohols are called glycolates, and trihydric alcohols are called glycerates.

The qualitative reaction to polyhydric alcohols containing OH groups at adjacent carbon atoms is a bright blue color when exposed to freshly precipitated copper hydroxide ( II ). The color of the solution is due to the formation of complex copper glycolate:

Polyhydric alcohols are characterized by the formation of esters. In particular, when glycerol reacts with nitric acid in the presence of catalytic amounts of sulfuric acid, glycerol trinitrate is formed, known as nitroglycerin (the latter name is incorrect from a chemical point of view, since in nitro compounds the group is NO 2 directly bonded to the carbon atom):

Application.Ethylene glycol is used for the synthesis of polymer materials and as an antifreeze. It is also used in large quantities to produce dioxane, an important (though toxic) laboratory solvent. Dioxane is obtained by intermolecular dehydration of ethylene glycol:

dioxane

Glycerin is widely used in cosmetics, the food industry, pharmacology, and the production of explosives. Pure nitroglycerin explodes even with a slight impact; it serves as a raw material for the production of smokeless gunpowder and dynamite -an explosive that, unlike nitroglycerin, can be safely thrown. Dynamite was invented by Nobel, who founded the world-famous Nobel Prize for outstanding scientific achievements in the fields of physics, chemistry, medicine and economics. Nitroglycerin is toxic, but in small quantities it serves as a medicine, as it dilates the heart vessels and thereby improves blood supply to the heart muscle.

4. Production of ethanol by alcoholic fermentation of sugary substances:

C 6 H 12 O 6 2CH 3 –CH 2 –OH + 2CO 2.

(glucose)

5. Production of methanol from synthesis gas (mixture of CO and H 2):

CO + 2H 2 CH 3 –OH.

Polyhydric saturated alcohols

Polyhydric alcohols contain several hydroxyl groups attached to different carbon atoms. The addition of several hydroxyl groups to one carbon atom is impossible, since in this case a dehydration process occurs and the corresponding aldehyde or carboxylic acid is formed:

Examples of polyhydric alcohols:

Polyhydric alcohols contain asymmetric carbon atoms and exhibit optical isomerism.

As an example of cyclic alcohols, we can cite hexahydric cyclic alcohols C 6 H 6 (OH) 6 - inositol, one of the isomers of which (mesoinositol) is part of phospholipids:

Chemical properties of polyhydric alcohols

1. Acid properties

Polyhydric alcohols have greater acidic properties compared to monohydric alcohols, which is explained by the mutual influence of functional groups:

sodium glycolate

2. Qualitative reaction to polyhydric alcohols – interaction with freshly precipitated copper(II) hydroxide:

3. Formation of complete and partial esters with inorganic and organic acids:

;

(nitroglycerine);

.

4.Dehydration of polyhydric alcohols

Preparation of polyhydric alcohols

1. Hydrolysis of dihaloalkanes:

Br–CH 2 –CH 2 –Br + 2KOH HO–CH 2 –CH 2 –OH + 2KBr.

2. Oxidation of alkenes with an aqueous solution of potassium permanganate (Wagner reaction):

3CH 2 =CH 2 +2KMnO 4 +4H 2 O®3HO–CH 2 –CH 2 –OH+2MnO 2 ¯+2KOH.

3. Obtaining glycerin:

(fat hydrolysis)

PHENOLS

Phenols- organic compounds of the aromatic series, in the molecules of which hydroxyl groups are bonded to the carbon atoms of the aromatic ring. Based on the number of OH groups, they are distinguished:

· monohydric phenols (arenols): phenol (C 6 H 5 OH) and its homologues:

phenol	ortho-cresol	meta-cresol	pair-cresol
Another isomer of the composition C 7 H 7 OH, benzyl alcohol, does not belong to phenols, since the functional group is not attached directly to the aromatic system. The hydroxyl group can also be attached to more complex aromatic systems, for example,
benzyl alcohol	a-naphthol	b-naphthol

• diatomic phenols (arenediols):

• triatomic phenols (arenetriols):

For phenol and its homologues, two types of isomerism are possible: isomerism of the position of substituents in the benzene ring and isomerism of the side chain (the structure of the alkyl radical and the number of radicals).

Physical properties.

Phenol is a colorless crystalline substance that turns pink in air. Has a characteristic odor. It is highly soluble in water, ethanol, acetone and other organic solvents. A solution of phenol in water is carbolic acid. Other phenols are colorless crystalline substances or liquids whose boiling points are higher than the boiling points of saturated alcohols with the same molar masses. Phenols are slightly soluble in water, soluble in organic solvents, and toxic.

Chemical properties.

The structure of phenol is characterized by the interaction of the lone pair of electrons of the oxygen atom and the p-electrons of the aromatic ring. The result of this is a shift in electron density from the hydroxyl group to the ring, while the O–H bond becomes more polar, and therefore less strong (phenols exhibit the properties of weak acids).

The hydroxyl group in relation to the benzene ring is a substituent of the first kind, orienting substitution reactions to the ortho and para positions.

Phenol reactions can be divided into two groups: reactions involving a functional group and reactions involving an aromatic ring.

Reactions by hydroxyl group

1. Acid properties:

2C 6 H 5 OH + 2Na ® H 2 + 2C 6 H 5 ONa (sodium phenolate);

C 6 H 5 OH + NaOH ® C 6 H 5 ONa + H 2 O;

C 6 H 5 ONa + H 2 O + CO 2 ® C 6 H 5 OH + NaHCO 3

(the acidic properties of phenol are weaker than carbonic acid);

The violet coloration of solutions in the presence of iron(III) chloride is a qualitative reaction to phenols.

In the case when the hydroxyl group is not directly connected to the aromatic ring, but is part of a substituent, the influence of the benzene ring on the functional group is weakened and acidic properties do not appear (class of aromatic alcohols). For example, benzyl alcohol reacts with sodium but does not react with NaOH.

2. Formation of esters and ethers (unlike alcohols, phenols do not react with carboxylic acids; esters are obtained indirectly from acid chlorides and phenolates): C 6 H 5 OH + CH 3 COOH ¹

C 6 H 5 ONa + R–Br ® C 6 H 5 OR + NaBr

3. Oxidation (phenols are easily oxidized even under the influence of atmospheric oxygen, therefore, when standing, they gradually turn pink):

benzoquinone

Reactions on the benzene ring.

1. Halogenation:

(unlike benzene and its homologues, phenol decolorizes bromine water).

2. Nitration:

Trinitrophenol (picric acid) is a yellow crystalline substance, similar in strength to inorganic acids).

3. Polycondensation (interaction with formaldehyde and formation of phenol-formaldehyde resins):

Preparation of phenol

3. Distillation of coal tar.

4. Preparation of phenol from halobenzenes:

C 6 H 5 Cl + 2NaOH C 6 H 5 ONa + NaCl + H 2 O;

C 6 H 5 ONa + HCl ® C 6 H 5 OH + NaCl.

5. Catalytic oxidation of isopropylbenzene (cumene) - cumene method:

ALDEHYDES AND KETONES

Aldehydes and ketones belong to carbonyl compounds and contain a carbonyl group. In aldehydes, the carbonyl group is necessarily bonded to a hydrogen atom (located in position 1 of the carbon chain); in ketones, it is located in the middle of the chain and is bonded to two carbon atoms. The general formula of aldehydes and ketones is C 2 H 2 n O (interclass isomers). For aldehydes there is only isomerism of the carbon skeleton, for ketones there is isomerism of the carbon skeleton and isomerism of the position of the functional group.

Nomenclature of aldehydes and ketones:

methanal (formaldehyde or formic aldehyde)	ethanal (acetaldehyde or acetaldehyde)	propanal (propionaldehyde)
butanal (butyraldehyde)	methylpropanal (isobutyraldehyde)	propenal (acrolein)
propanone (dimethylketone or acetone)	butanone (methyl ethyl ketone)	pentanone-1 (methylpropyl ketone)
pentanone-2 (diethyl ketone)	methylbutanone (methylisopropyl ketone)	methylphenylketone (acetophenone)
benzoaldehyde	diphenylketone (benzophenone)

Physical properties

Formaldehyde at room temperature is a gas, the boiling point of acetaldehyde is +20°C. The boiling points of aldehydes are lower than the boiling points of the corresponding alcohols (there are no hydrogen bonds between molecules). Acetone and its closest homologues are liquids lighter than water. Aldehydes and ketones are highly volatile and have a pungent odor. A solution of formaldehyde in water is formalin.

Chemical properties

The carbon atom of the carbonyl group is in the state sp 2-hybridization (flat fragment). The electrons of the double bond are strongly shifted towards the more electronegative oxygen atom (the C=O bond is polar). The redistribution of charges in the carbonyl group affects the polarity of the C–H bonds of the carbon atom adjacent to the carbonyl group (a-position):

Aldehydes and ketones are characterized by addition reactions at the double bond of a carbonyl group and reactions of substitution of a hydrogen atom at the a-carbon atom with a halogen. In addition, aldehydes are capable of oxidation at the hydrogen atom at the carbonyl group.

Addition reactions at the double bond of the C=O group (nucleophilic addition S N)

Due to the fact that the C=O bond of aldehydes and ketones is polar in nature, it is easily broken under the influence of polar molecules of the H–X type. In general, the reaction can be represented as:

1. Addition of hydrogen (reduction of aldehydes and ketones to primary and secondary alcohols):

2. Addition of water (hydration) is a reversible process (hydrates are stable only in aqueous solutions):

Methanal in aqueous solutions is 100% hydrated, ethanal is 50% hydrated, acetone is practically not hydrated.

3. Addition of alcohols:

(hemiacetal); (acetal).

4. Addition of sodium hydrosulfite (the reaction serves to separate aldehydes and ketones from mixtures with other organic substances):

.

5. Addition of ammonia (H–NH 2) and amines (H–NHR):

Ammonia combines with acetaldehyde and formic aldehyde in a special way:

(hexamethylenetetramine - methenamine, a disinfectant in urology for inflammation of the urinary tract)

5. Addition of hydrazine (H 2 N–NH 2) and phenylhydrazine (H 2 N–NH–C 6 H 5).

Organic hydrocarbons, in the molecular structure of which there are two or more -OH groups, are called polyhydric alcohols. The compounds are otherwise called polyalcohols or polyols.

Representatives

Depending on the structure, diatomic, triatomic, tetraatomic, etc. are distinguished. alcohols. They differ by one hydroxyl group -OH. The general formula of polyhydric alcohols can be written as C n H 2 n+2 (OH) n. However, the number of carbon atoms does not always correspond to the number of hydroxyl groups. This discrepancy is explained by the different structure of the carbon skeleton. For example, pentaerythritol contains five carbon atoms and four -OH groups (one carbon in the middle), while sorbitol contains six carbon atoms and -OH groups.

Rice. 1. Structural formulas of pentaerythritol and sorbitol.

The table describes the most well-known representatives of polyols.

Type of alcohol	Name	Formula	Physical properties
Diatomic (diols)	Ethylene glycol	HO-CH 2 -CH 2 -OH	Transparent, oily, highly toxic, odorless liquid with a sweet aftertaste
Triatomic (triols)	Glycerol		Viscous transparent liquid. Mixes with water in any proportions. Tastes sweet
Quadriatomic	Pentaerythritol		Crystalline white powder with a sweet taste. Soluble in water and organic solvents
Pentaatomic		CH 2 OH(CHOH) 3 CH 2 OH	The crystalline, colorless substance has a sweet taste. Soluble in water, alcohols, organic acids
Hexatom	Sorbitol (glucite)		Sweet crystalline substance, highly soluble in water, but poorly soluble in ethanol

Some crystalline polyhydric alcohols, for example, xylitol, sorbitol, are used as a sweetener and food additive.

Rice. 2. Xylitol.

Receipt

Polyols are obtained in laboratory and industrial ways:

• hydration of ethylene oxide (production of ethylene glycol):

  C 2 H 4 O + H 2 O → HO-CH 2 -CH 2 -OH;

• interaction of haloalkanes with alkali solutions:

  R-CHCl-CH 2 Cl + 2NaOH → R-CHOH-CH 2 OH + 2NaCl;

• oxidation of alkenes:

  R-CH=CH 2 + H 2 O + KMnO 4 → R-CHOH-CH 2 OH + MnO 2 + KOH;

• Saponification of fats (production of glycerin):

  C 3 H 5 (COO) 3 -R + 3NaOH → C 3 H 5 (OH) 3 + 3R-COONa

Rice. 3. Glycerol molecule.

Properties

The chemical properties of polyhydric alcohols are due to the presence of several hydroxyl groups in the molecule. Their close position facilitates easier breaking of hydrogen bonds than in monohydric alcohols. Polyhydric alcohols exhibit acidic and basic properties.

The main chemical properties are described in the table.

Reaction	Description	The equation
With alkali metals	By replacing the hydrogen atom in the -OH group with a metal atom, they form salts with active metals and their alkalis	HO-CH 2 -CH 2 -OH + 2Na → NaO-CH 2 -CH 2 -ONa + H 2 ; HO-CH 2 -CH 2 -OH + 2NaOH → NaO-CH 2 -CH 2 -ONa + 2H 2 O
With hydrogen halides	One of the -OH groups is replaced by a halogen	HO-CH 2 -CH 2 -OH + HCl → Cl-CH 2 -CH 2 -OH (ethylene chlorohydrin) + H 2 O
Esterification	React with organic and mineral acids to form fats - esters	C 3 H 8 O 3 + 3HNO 3 → C 3 H 5 O 3 (NO 2) 3 (nitroglycerin) + 3H 2 O
Qualitative reaction	When interacting with copper (II) hydroxide in an alkaline medium, a dark blue solution is formed	HO-CH 2 -CH 2 -OH + Cu(OH) 2 → C 4 H 10 O 4 + 2H 2 O

Salts of dihydric alcohols are called glycolates, and trihydric alcohols are called glycerates.

What have we learned?

From the chemistry lesson we learned what polyhydric alcohols or polyols are. These are hydrocarbons containing several hydroxyl groups. Depending on the amount of -OH, diatomic, triatomic, tetraatomic, pentaatomic, etc. are distinguished. alcohols. The simplest dihydric alcohol is ethylene glycol. Polyols have a sweet taste and are highly soluble in water. Diols and triols are viscous liquids. Higher alcohols are crystalline substances.

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