Alcohols are soluble in most organic solvents; the first three simplest representatives - methanol, ethanol and propanol, as well as tertiary butanol (H 3 C) 3 SON - are mixed with water in any ratio. With an increase in the number of C atoms in the organic group, a hydrophobic (water-repellent) effect begins to take effect, solubility in water becomes limited, and when R contains more than 9 carbon atoms, it practically disappears.

Due to the presence of OH groups, hydrogen bonds arise between alcohol molecules.

Rice. 5.

As a result, all alcohols have a higher boiling point than the corresponding hydrocarbons, for example, bp. ethanol +78° C, and T. boil. ethane -88.63° C; T. kip. butanol and butane, respectively, +117.4° C and -0.5° C.

Chemical properties of alcohols

Alcohols have a variety of transformations. The reactions of alcohols have some general principles: the reactivity of primary monohydric alcohols is higher than secondary ones, in turn, secondary alcohols are chemically more active than tertiary ones. For dihydric alcohols, in the case when OH groups are located at neighboring carbon atoms, increased (compared to monohydric alcohols) reactivity is observed due to mutual influence these groups. For alcohols, reactions are possible that involve the breaking of both C-O and O-H bonds.

1). Reactions occurring through O-N connections.

When interacting with active metals (Na, K, Mg, Al), alcohols exhibit the properties of weak acids and form salts called alcoholates or alkoxides:

2CH 3 OH + 2Na ® 2CH 3 OK + H 2

Alcoholates are chemically unstable and, when exposed to water, hydrolyze to form alcohol and metal hydroxide:

C 2 H 5 OK + H 2 O ® C 2 H 5 OH + KOH

This reaction shows that alcohols are weaker acids compared to water (a strong acid displaces a weak one); moreover, when interacting with alkali solutions, alcohols do not form alcoholates. However, in polyhydric alcohols (in the case when OH groups are attached to neighboring C atoms), the acidity of the alcohol groups is much higher, and they can form alcoholates not only when interacting with metals, but also with alkalis:

HO-CH 2 -CH 2 -OH + 2NaOH ® NaO-CH 2 -CH 2 -ONa + 2H 2 O

When HO groups in polyhydric alcohols are attached to non-adjacent C atoms, the properties of alcohols are close to monohydric ones, since the mutual influence of HO groups does not appear.

When interacting with mineral or organic acids, alcohols form esters - compounds containing the R-O-A fragment (A is the acid residue). The formation of esters also occurs during the interaction of alcohols with anhydrides and acid chlorides of carboxylic acids (Fig. 6).

1. Combustion with heat release:

C 2 H 5 OH + 3O 2 2C 2 + 3H 2 O + a

• 2. Interaction with active metals:
• 2C 2 H 5 OH+ Na 2C 2 H 5 O Na +H 2 - alcoholates
• 3. Interaction with hydrogens.

Ce CH 3 -Ce + H 2 O

H 2 SO 4 - chloromethane

4. When the temperature rises in the presence of water purifying substances, the maximum operating conditions are not

C 2 H 5 OH t>140 0 C C 2 H 4 +H 2 O - ethylene

The reaction in which water is eliminated is called a detration reaction.

5. Interaction with each other to form ethers.

CH 3 -O - CH 3 - dimethyl ether

Reacts with acids to form esters.

Rice. 6.

Under the action of oxidizing agents (K 2 Cr 2 O 7, KMnO 4), primary alcohols form aldehydes, and secondary alcohols form ketones (Fig. 7)

Rice. 7.

The reduction of alcohols leads to the formation of hydrocarbons containing the same number of C atoms as the molecule of the original alcohol (Fig. 8).

Rice. 8.

2) Reactions occurring through the C-O bond

In the presence of catalysts or strong mineral acids, dehydration of alcohols (elimination of water) occurs, and the reaction can proceed in two directions:

• a) intermolecular dehydration involving two alcohol molecules, in which the C-O bonds of one of the molecules are broken, resulting in the formation of ethers - compounds containing fragment R-O-R(Fig. 9A).
• b) during intramolecular dehydration, alkenes are formed - hydrocarbons with a double bond. Often both processes - the formation of an ether and an alkene - occur in parallel (Fig. 9B).

In the case of secondary alcohols, during the formation of an alkene, two reaction directions are possible, the predominant direction is one in which, during the condensation process, hydrogen is split off from the least hydrogenated carbon atom (marked by number 3), i.e. surrounded fewer hydrogen atoms (compared to atom 1).

Structure

Alcohols (or alkanols) are organic substances whose molecules contain one or more hydroxyl groups (-OH groups) connected to a hydrocarbon radical.

Based on the number of hydroxyl groups (atomicity), alcohols are divided into:

Monatomic
dihydric (glycols)
triatomic.

The following alcohols are distinguished by their nature:

Saturated, containing only saturated hydrocarbon radicals in the molecule
unsaturated, containing multiple (double and triple) bonds between carbon atoms in the molecule
aromatic, i.e. alcohols containing a benzene ring and a hydroxyl group in the molecule, connected to each other not directly, but through carbon atoms.

Organic substances containing hydroxyl groups in the molecule, bonded directly to the carbon atom of the benzene ring, differ significantly in chemical properties from alcohols and therefore are classified as an independent class of organic compounds - phenols. For example, hydroxybenzene phenol. We will learn more about the structure, properties and use of phenols later.

There are also polyatomic (polyatomic) ones containing more than three hydroxyl groups in the molecule. For example, the simplest hexahydric alcohol is hexaol (sorbitol).

It should be noted that alcohols containing two hydroxyl groups on one carbon atom are unstable and spontaneously decompose (subject to rearrangement of atoms) to form aldehydes and ketones:

Unsaturated alcohols containing a hydroxyl group at the carbon atom connected by a double bond are called ecols. It is not difficult to guess that the name of this class of compounds is formed from the suffixes -en and -ol, indicating the presence of a double bond and a hydroxyl group in the molecules. Enols, as a rule, are unstable and spontaneously transform (isomerize) into carbonyl compounds - aldehydes and ketones. This reaction is reversible, the process itself is called keto-enol tautomerism. Thus, the simplest enol, vinyl alcohol, isomerizes extremely quickly into acetaldehyde.

Based on the nature of the carbon atom to which the hydroxyl group is bonded, alcohols are divided into:

Primary, in the molecules of which the hydroxyl group is bonded to the primary carbon atom
secondary, in the molecules of which the hydroxyl group is bonded to a secondary carbon atom
tertiary, in the molecules of which the hydroxyl group is bonded to a tertiary carbon atom, for example:

Nomenclature and isomerism

When naming alcohols, the (generic) suffix -ol is added to the name of the hydrocarbon corresponding to the alcohol. The numbers after the suffix indicate the position of the hydroxyl group in the main chain, and the prefixes di-, tri-, tetra-, etc. indicate their number:

Starting from the third member of the homologous series, alcohols exhibit isomerism of the position of the functional group (propanol-1 and propanol-2), and from the fourth, isomerism of the carbon skeleton (butanol-1; 2-methylpropanol-1). They are also characterized by interclass isomerism - alcohols are isomeric to ethers.

Roda, which is part of the hydroxyl group of alcohol molecules, differs sharply from hydrogen and carbon atoms in its ability to attract and hold electron pairs. Due to this, alcohol molecules contain polar C-O and O-H bonds.

Physical properties of alcohols

Considering the polarity of the O-H bond and the significant partial positive charge, localized (focused) on a hydrogen atom, the hydrogen of the hydroxyl group is said to have an “acidic” character. In this way, it differs sharply from the hydrogen atoms included in the hydrocarbon radical.

It should be noted that the oxygen atom of the hydroxyl group has a partial negative charge and two lone electron pairs, which allows alcohols to form special, so-called hydrogen bonds between molecules. Hydrogen bonds occur when a partially positively charged hydrogen atom of one alcohol molecule interacts with a partially negatively charged oxygen atom of another molecule. It is thanks to hydrogen bonds between molecules that alcohols have boiling points that are abnormally high for their molecular weight. Thus, propane with a relative molecular weight of 44 under normal conditions is a gas, and the simplest of alcohols is methanol, having a relative molecular weight of 32, under normal conditions a liquid.

The lower and middle members of a series of saturated monohydric alcohols, containing from one to eleven carbon atoms, are liquids. Higher alcohols (starting from C 12 H 25 OH) are solids at room temperature. Lower alcohols have a characteristic alcoholic odor and pungent taste; they are highly soluble in water. As the hydrocarbon radical increases, the solubility of alcohols in water decreases, and octanol no longer mixes with water.

Chemical properties

The properties of organic substances are determined by their composition and structure. Alcohols confirm general rule. Their molecules include hydrocarbon and hydroxyl radicals, therefore chemical properties alcohols are determined by the interaction and influence of these groups on each other. The properties characteristic of this class of compounds are due to the presence of a hydroxyl group.

1. Interaction of alcohols with alkali and alkaline earth metals. To identify the effect of a hydrocarbon radical on a hydroxyl group, it is necessary to compare the properties of a substance containing a hydroxyl group and a hydrocarbon radical, on the one hand, and a substance containing a hydroxyl group and not containing a hydrocarbon radical, on the other. Such substances can be, for example, ethanol (or other alcohol) and water. The hydrogen of the hydroxyl group of alcohol molecules and water molecules is capable of being reduced by alkali and alkaline earth metals (replaced by them).

With water this interaction is much more active than with alcohol, is accompanied by a large release of heat, and can lead to an explosion. This difference is explained by the electron-donating properties of the radical closest to the hydroxyl group. Possessing the properties of an electron donor (+I-effect), the radical slightly increases the electron density on the oxygen atom, “saturates” it at its own expense, thereby reducing the polarity of the O-H bond and the “acidic” nature of the hydrogen atom of the hydroxyl group in alcohol molecules by compared to water molecules.

2. Interaction of alcohols with hydrogen halides. Substitution of a hydroxyl group with a halogen leads to the formation of haloalkanes.

For example:

C2H5OH + HBr<->C2H5Br + H2O

This reaction is reversible.

3. Intermolecular dehydration of alcohols - the splitting of a water molecule from two alcohol molecules when heated in the presence of water-removing agents.

As a result of intermolecular dehydration of alcohols, ethers are formed. Thus, when ethyl alcohol is heated with sulfuric acid to a temperature of 100 to 140 ° C, diethyl (sulfur) ether is formed.

4. The interaction of alcohols with organic and inorganic acids to form esters (esterification reaction):

The esterification reaction is catalyzed by strong inorganic acids.

For example, the interaction of ethyl alcohol and acetic acid produces ethyl acetate - ethyl acetate:

5. Intramolecular dehydration of alcohols occurs when alcohols are heated in the presence of water-removing agents to a higher temperature than the temperature of intermolecular dehydration. As a result, alkenes are formed. This reaction is due to the presence of a hydrogen atom and a hydroxyl group at adjacent carbon atoms. An example is the reaction of producing ethene (ethylene) by heating ethanol above 140 °C in the presence of concentrated sulfuric acid.

6. Oxidation of alcohols is usually carried out with strong oxidizing agents, such as potassium dichromate or potassium permanganate in an acidic environment. In this case, the action of the oxidizing agent is directed to the carbon atom that is already bonded to the hydroxyl group. Depending on the nature of the alcohol and the reaction conditions, various products can be formed. Thus, primary alcohols are oxidized first to aldehydes and then to carboxylic acids:

Tertiary alcohols are quite resistant to oxidation. However, under harsh conditions (strong oxidizing agent, high temperature), oxidation of tertiary alcohols is possible, which occurs with the rupture of carbon-carbon bonds closest to the hydroxyl group.

7. Dehydrogenation of alcohols. When alcohol vapor is passed at 200-300 °C over a metal catalyst, such as copper, silver or platinum, primary alcohols are converted into aldehydes, and secondary alcohols into ketones:

The presence of several hydroxyl groups in the alcohol molecule at the same time determines the specific properties of polyhydric alcohols, which are capable of forming bright blue complex compounds soluble in water when interacting with a freshly obtained precipitate of copper(II) hydroxide.

Monohydric alcohols are not able to enter into this reaction. Therefore, it is a qualitative reaction to polyhydric alcohols.

Alcoholates of alkali and alkaline earth metals undergo hydrolysis when interacting with water. For example, when sodium ethoxide is dissolved in water, a reversible reaction occurs

C2H5ONa + HON<->C2H5OH + NaOH

the balance of which is almost completely shifted to the right. This also confirms that water is superior to alcohols in its acidic properties (the “acidic” nature of the hydrogen in the hydroxyl group). Thus, the interaction of alcoholates with water can be considered as the interaction of a salt of a very weak acid (in this case, the alcohol that formed the alcoholate acts as this) with a stronger acid (water plays this role here).

Alcohols can exhibit basic properties when reacting with strong acids, forming alkyloxonium salts due to the presence of a lone electron pair on the oxygen atom of the hydroxyl group:

The esterification reaction is reversible (the reverse reaction is ester hydrolysis), the equilibrium shifts to the right in the presence of water-removing agents.

Intramolecular dehydration of alcohols proceeds in accordance with Zaitsev's rule: when water is removed from a secondary or tertiary alcohol, a hydrogen atom is detached from the least hydrogenated carbon atom. Thus, dehydration of 2-butanol results in 2-butene rather than 1-butene.

The presence of hydrocarbon radicals in the molecules of alcohols cannot but affect the chemical properties of alcohols.

The chemical properties of alcohols caused by the hydrocarbon radical are different and depend on its nature. So, all alcohols burn; unsaturated alcohols containing a double C=C bond in the molecule enter into addition reactions, undergo hydrogenation, add hydrogen, react with halogens, for example, decolorize bromine water, etc.

Methods of obtaining

1. Hydrolysis of haloalkanes. You already know that the formation of haloalkanes when alcohols interact with hydrogen halogens is a reversible reaction. Therefore, it is clear that alcohols can be obtained by hydrolysis of haloalkanes - the reaction of these compounds with water.

Polyhydric alcohols can be obtained by hydrolysis of haloalkanes containing more than one halogen atom per molecule.

2. Hydration of alkenes - the addition of water at the t-bond of an alkene molecule - is already familiar to you. Hydration of propene leads, in accordance with Markovnikov’s rule, to the formation of a secondary alcohol - propanol-2

HE
l
CH2=CH-CH3 + H20 -> CH3-CH-CH3
propene propanol-2

3. Hydrogenation of aldehydes and ketones. You already know that the oxidation of alcohols under mild conditions leads to the formation of aldehydes or ketones. It is obvious that alcohols can be obtained by hydrogenation (reduction with hydrogen, addition of hydrogen) of aldehydes and ketones.

4. Oxidation of alkenes. Glycols, as already noted, can be obtained by oxidation of alkenes with an aqueous solution of potassium permanganate. For example, ethylene glycol (ethanediol-1,2) is formed by the oxidation of ethylene (ethene).

5. Specific methods for producing alcohols. Some alcohols are obtained using methods that are unique to them. Thus, methanol is produced industrially by the interaction of hydrogen with carbon monoxide (II) (carbon monoxide) at elevated pressure and high temperature on the surface of a catalyst (zinc oxide).

The mixture of carbon monoxide and hydrogen required for this reaction, also called (think about why!) “synthesis gas,” is obtained by passing water vapor over hot coal.

6. Fermentation of glucose. This method of producing ethyl (wine) alcohol has been known to man since ancient times.

Let's consider the reaction of producing alcohols from haloalkanes - the hydrolysis reaction of halogenated hydrocarbons. It is usually carried out in an alkaline environment. The released hydrobromic acid is neutralized, and the reaction proceeds almost to completion.

This reaction, like many others, proceeds through the mechanism of nucleophilic substitution.

These are reactions the main stage of which is substitution, which occurs under the influence of a nucleophilic particle.

Let us recall that a nucleophilic particle is a molecule or ion that has a lone electron pair and is capable of being attracted to a “positive charge” - parts of the molecule with a reduced electron density.

The most common nucleophilic species are ammonia, water, alcohol, or anions (hydroxyl, halide, alkoxide ion).

The particle (atom or group of atoms) that is replaced by a reaction with a nucleophile is called a leaving group.

The replacement of the hydroxyl group of an alcohol with a halide ion also occurs through the mechanism of nucleophilic substitution:

CH3CH2OH + HBr -> CH3CH2Br + H20

Interestingly, this reaction begins with the addition of a hydrogen cation to the oxygen atom contained in the hydroxyl group:

CH3CH2-OH + H+ -> CH3CH2- OH

Under the influence of an attached positively charged ion S-O connection shifts further towards oxygen, the effective positive charge on the carbon atom increases.

This leads to the fact that nucleophilic substitution with a halide ion occurs much more easily, and a water molecule is split off under the action of a nucleophile.

CH3CH2-OH+ + Br -> CH3CH2Br + H2O

Preparation of ethers

When sodium alkoxide reacts with bromoethane, the bromine atom is replaced by an alkoxide ion and an ether is formed.

Nucleophilic substitution reaction in general view can be written as follows:

R - X +HNu -> R - Nu +HX,

if the nucleophilic particle is a molecule (HBr, H20, CH3CH2OH, NH3, CH3CH2NH2),

R-X + Nu - -> R-Nu + X - ,

if the nucleophile is an anion (OH, Br-, CH3CH2O -), where X is a halogen, Nu is a nucleophilic particle.

Individual representatives of alcohols and their significance

Methanol ( methyl alcohol CH3OH) is a colorless liquid with a characteristic odor and a boiling point of 64.7 °C. Burns with a slightly bluish flame. The historical name of methanol - wood alcohol - is explained by one of the methods of its production - distillation of hard wood (Greek - wine, to get drunk; substance, wood).

Methanol is very poisonous! It requires careful handling when working with it. Under the action of the enzyme alcohol dehydrogenase, it is converted in the body into formaldehyde and formic acid, which damage the retina, cause death of the optic nerve and complete loss of vision. Ingestion of more than 50 ml of methanol causes death.

Ethanol (ethyl alcohol C2H5OH) is a colorless liquid with a characteristic odor and a boiling point of 78.3 °C. Flammable Mixes with water in any ratio. The concentration (strength) of alcohol is usually expressed as a percentage by volume. “Pure” (medicinal) alcohol is a product obtained from food raw materials and containing 96% (by volume) ethanol and 4% (by volume) water. To obtain anhydrous ethanol - “absolute alcohol”, this product is treated with substances that chemically bind water (calcium oxide, anhydrous copper(II) sulfate, etc.).

In order to make alcohol used for technical purposes unsuitable for drinking, small amounts of difficult-to-separate toxic, bad-smelling and disgusting-tasting substances are added to it and tinted. Alcohol containing such additives is called denatured or denatured alcohol.

Ethanol is widely used in industry for the production of synthetic rubber, medicines, used as a solvent, included in varnishes and paints, perfumes. In medicine, ethyl alcohol is the most important disinfectant. Used for cooking alcoholic drinks.

When small amounts of ethyl alcohol enter the human body, they reduce pain sensitivity and block inhibition processes in the cerebral cortex, causing a state of intoxication. At this stage of the action of ethanol, water separation in the cells increases and, consequently, urine formation accelerates, resulting in dehydration of the body.

In addition, ethanol causes dilation of blood vessels. Increased blood flow in the skin capillaries leads to redness of the skin and a feeling of warmth.

In large quantities, ethanol inhibits brain activity (inhibition stage) and causes impaired coordination of movements. An intermediate product of ethanol oxidation in the body, acetaldehyde, is extremely toxic and causes severe poisoning.

Systematic consumption of ethyl alcohol and drinks containing it leads to a persistent decrease in brain productivity, death of liver cells and their replacement with connective tissue - liver cirrhosis.

Ethanediol-1,2 (ethylene glycol) is a colorless viscous liquid. Poisonous. Unlimitedly soluble in water. Aqueous solutions do not crystallize at temperatures significantly below 0 °C, which makes it possible to use it as a component of non-freezing coolants - antifreeze for internal combustion engines.

Propanetriol-1,2,3 (glycerol) is a viscous, syrupy liquid with a sweet taste. Unlimitedly soluble in water. Non-volatile. As a component of esters, it is found in fats and oils. Widely used in cosmetics, pharmaceutical and food industries. In cosmetics, glycerin plays the role of an emollient and soothing agent. It is added to toothpaste to prevent it from drying out. Glycerin is added to confectionery products to prevent their crystallization. It is sprayed onto tobacco, in which case it acts as a humectant that prevents the tobacco leaves from drying out and crumbling before processing. It is added to adhesives to prevent them from drying out too quickly, and to plastics, especially cellophane. In the latter case, glycerin acts as a plasticizer, acting like a lubricant between polymer molecules and thus giving plastics the necessary flexibility and elasticity.

1. What substances are called alcohols? By what criteria are alcohols classified? What alcohols should be classified as butanol-2? butene-Z-ol-1? penten-4-diol-1,2?

2. Write down the structural formulas of the alcohols listed in Exercise 1.

3. Are there quaternary alcohols? Explain your answer.

4. How many alcohols have the molecular formula C5H120? Make up the structural formulas of these substances and name them. Can this formula only correspond to alcohols? Make up the structural formulas of two substances that have the formula C5H120 and are not alcohols.

5. Name the substances whose structural formulas are given below:

6. Write the structural and empirical formulas of a substance whose name is 5-methyl-4-hexen-1-inol-3. Compare the number of hydrogen atoms in the molecule of this alcohol with the number of hydrogen atoms in the molecule of an alkane with the same number of carbon atoms. What explains this difference?

7. Comparing the electronegativity of carbon and hydrogen, explain why the O-H covalent bond is more polar than the C-O bond.

8. Which alcohol do you think - methanol or 2-methylpropanol-2 - will react more actively with sodium? Explain your answer. Write down equations for the corresponding reactions.

9. Write down reaction equations for the interaction of 2-propanol (isopropyl alcohol) with sodium and hydrogen bromide. Name the reaction products and indicate the conditions for their implementation.

10. A mixture of propanol-1 and propanol-2 vapors was passed over heated copper(P) oxide. What reactions could occur in this case? Write down equations for these reactions. What classes of organic compounds do their products belong to?

11. What products can be formed during the hydrolysis of 1,2-dichloropropanol? Write down equations for the corresponding reactions. Name the products of these reactions.

12. Write down equations for the reactions of hydrogenation, hydration, halogenation and hydrohalogenation of 2-propenol-1. Name the products of all reactions.

13. Write down equations for the interaction of glycerol with one, two and three moles of acetic acid. Write the equation for the hydrolysis of an ester - the product of the esterification of one mole of glycerol and three moles of acetic acid.

14*. When the primary saturated monohydric alcohol reacted with sodium, 8.96 liters of gas (n.e.) were released. When the same mass of alcohol is dehydrated, an alkene weighing 56 g is formed. Determine all possible structural formulas of the alcohol.

15*. Volume carbon dioxide, released during the combustion of saturated monohydric alcohol, is 8 times greater than the volume of hydrogen released during the action of excess sodium on the same amount of alcohol. Establish the structure of an alcohol if it is known that its oxidation produces a ketone.

Use of alcohols

Since alcohols have various properties, their area of ​​application is quite wide. Let's try to figure out where alcohols are used.

Alcohols in the food industry

Alcohol such as ethanol is the basis of all alcoholic beverages. And it is obtained from raw materials that contain sugar and starch. Such raw materials can be sugar beets, potatoes, grapes, as well as various cereals. Thanks to modern technologies When producing alcohol, it is purified from fusel oils.

Natural vinegar also contains ethanol-based raw materials. This product is obtained through oxidation by acetic acid bacteria and aeration.

But in the food industry they use not only ethanol, but also glycerin. This food additive promotes the connection of immiscible liquids. Glycerin, which is part of liqueurs, can give them viscosity and a sweet taste.

Also, glycerin is used in the manufacture of bakery, pasta and confectionery products.

Medicine

In medicine, ethanol is simply irreplaceable. In this industry, it is widely used as an antiseptic, as it has properties that can destroy microbes, delay painful changes in the blood and prevent decomposition in open wounds.

Ethanol is used by medical workers before performing various procedures. This alcohol has disinfecting and drying properties. During artificial ventilation of the lungs, ethanol acts as an antifoam. Ethanol can also be one of the components of anesthesia.

When you have a cold, ethanol can be used as a warming compress, and when cooling, as a rubbing agent, since its substances help restore the body during heat and chills.

In case of poisoning with ethylene glycol or methanol, the use of ethanol helps reduce the concentration of toxic substances and acts as an antidote.

Alcohols also play a huge role in pharmacology, as they are used to prepare healing tinctures and all kinds of extracts.

Alcohols in cosmetics and perfumes

In perfumery, it is also impossible to do without alcohol, since the basis of almost all perfume products is water, alcohol and perfume concentrate. Ethanol in this case acts as a solvent for fragrant substances. But 2-phenylethanol has a floral scent and can replace natural rose oil in perfumery. It is used in the manufacture of lotions, creams, etc.

Glycerin is also the base for many cosmetics, as it has the ability to attract moisture and actively moisturize the skin. And the presence of ethanol in shampoos and conditioners helps moisturize the skin and makes it easier to comb hair after washing your hair.

Fuel

Well, alcohol-containing substances such as methanol, ethanol and butanol-1 are widely used as fuel.

Thanks to the processing of plant materials such as sugar cane and corn, it was possible to obtain bioethanol, which is an environmentally friendly biofuel.

Recently, the production of bioethanol has become popular in the world. With its help, the prospect of renewing fuel resources appeared.

Solvents, surfactants

In addition to the applications of alcohols already listed, it can be noted that they are also good solvents. The most popular in this area are isopropanol, ethanol, and methanol. They are also used in the production of bit chemicals. Without them, proper care of a car, clothing, household utensils, etc. is not possible.

The use of alcohols in various areas of our activities has a positive effect on our economy and brings comfort to our lives.

Contents of the article

ALCOHOLS(alcohols) - a class of organic compounds containing one or more C–OH groups, with the hydroxyl group OH bonded to an aliphatic carbon atom (compounds in which the carbon atom in the C–OH group is part of the aromatic ring are called phenols)

The classification of alcohols is varied and depends on which structural feature is taken as a basis.

1. Depending on the number of hydroxyl groups in the molecule, alcohols are divided into:

a) monoatomic (contain one hydroxyl OH group), for example, methanol CH 3 OH, ethanol C 2 H 5 OH, propanol C 3 H 7 OH

b) polyatomic (two or more hydroxyl groups), for example, ethylene glycol

HO–CH 2 –CH 2 –OH, glycerol HO–CH 2 –CH(OH)–CH 2 –OH, pentaerythritol C(CH 2 OH) 4.

Compounds in which one carbon atom has two hydroxyl groups are in most cases unstable and easily turn into aldehydes, eliminating water: RCH(OH) 2 ® RCH=O + H 2 O

2. Based on the type of carbon atom to which the OH group is bonded, alcohols are divided into:

a) primary, in which the OH group is bonded to the primary carbon atom. A carbon atom (highlighted in red) that is bonded to just one carbon atom is called primary. Examples of primary alcohols - ethanol CH 3 - C H 2 –OH, propanol CH 3 –CH 2 – C H2–OH.

b) secondary, in which the OH group is bonded to a secondary carbon atom. A secondary carbon atom (highlighted in blue) is bonded to two carbon atoms at the same time, for example, secondary propanol, secondary butanol (Fig. 1).

Rice. 1. STRUCTURE OF SECONDARY ALCOHOLS

c) tertiary, in which the OH group is bonded to the tertiary carbon atom. The tertiary carbon atom (highlighted in green) is bonded to three neighboring carbon atoms simultaneously, for example, tertiary butanol and pentanol (Figure 2).

Rice. 2. STRUCTURE OF TERTIARY ALCOHOLS

According to the type of carbon atom, the alcohol group attached to it is also called primary, secondary or tertiary.

In polyhydric alcohols containing two or more OH groups, both primary and secondary HO groups may be present simultaneously, for example, in glycerol or xylitol (Fig. 3).

Rice. 3. COMBINATION OF PRIMARY AND SECONDARY OH-GROUPS IN THE STRUCTURE OF POLYATOMIC ALCOHOLS.

3. According to the structure of organic groups connected by an OH group, alcohols are divided into saturated (methanol, ethanol, propanol), unsaturated, for example, allyl alcohol CH 2 =CH–CH 2 –OH, aromatic (for example, benzyl alcohol C 6 H 5 CH 2 OH) containing an aromatic group in the R group.

Unsaturated alcohols in which the OH group is “adjacent” to the double bond, i.e. bonded to a carbon atom simultaneously involved in the formation of a double bond (for example, vinyl alcohol CH 2 =CH–OH), are extremely unstable and immediately isomerize ( cm ISOMERIZATION) to aldehydes or ketones:

CH 2 =CH–OH ® CH 3 –CH=O

Nomenclature of alcohols.

For common alcohols with a simple structure, a simplified nomenclature is used: the name of the organic group is converted into an adjective (using the suffix and ending “ new") and add the word "alcohol":

In the case when the structure of the organic group is more complex, they use common ones for the whole organic chemistry rules. Names compiled according to such rules are called systematic. In accordance with these rules, the hydrocarbon chain is numbered from the end to which the OH group is located closest. This number is then used to indicate the position various substituents along the main chain, at the end of the name the suffix “ol” and a number indicating the position of the OH group are added (Fig. 4):

Rice. 4. SYSTEMATIC NAMES OF ALCOHOLS. Functional (OH) and substituent (CH 3) groups, as well as their corresponding digital indices, are highlighted in different colors.

The systematic names of the simplest alcohols follow the same rules: methanol, ethanol, butanol. For some alcohols, trivial (simplified) names that have developed historically have been preserved: propargyl alcohol HCє C–CH 2 –OH, glycerin HO–CH 2 –CH(OH)–CH 2 –OH, pentaerythritol C(CH 2 OH) 4, phenethyl alcohol C 6 H 5 –CH 2 –CH 2 –OH.

Physical properties of alcohols.

Alcohols are soluble in most organic solvents; the first three simplest representatives - methanol, ethanol and propanol, as well as tertiary butanol (H 3 C) 3 СОН - are mixed with water in any ratio. With an increase in the number of C atoms in the organic group, a hydrophobic (water-repellent) effect begins to take effect, solubility in water becomes limited, and when R contains more than 9 carbon atoms, it practically disappears.

Due to the presence of OH groups, hydrogen bonds arise between alcohol molecules.

Rice. 5. HYDROGEN BONDS IN ALCOHOLS(shown in dotted line)

As a result, all alcohols have a higher boiling point than the corresponding hydrocarbons, for example, bp. ethanol +78° C, and T. boil. ethane –88.63° C; T. kip. butanol and butane, respectively, +117.4° C and –0.5° C.

Chemical properties of alcohols.

Alcohols have a variety of transformations. The reactions of alcohols have some general principles: the reactivity of primary monohydric alcohols is higher than secondary ones, in turn, secondary alcohols are chemically more active than tertiary ones. For dihydric alcohols, in the case when OH groups are located at neighboring carbon atoms, increased (compared to monohydric alcohols) reactivity is observed due to the mutual influence of these groups. For alcohols, reactions are possible that involve the breaking of both C–O and O–H bonds.

1. Reactions occurring at the O–H bond.

When interacting with active metals (Na, K, Mg, Al), alcohols exhibit the properties of weak acids and form salts called alcoholates or alkoxides:

2CH 3 OH + 2Na ® 2CH 3 OK + H 2

Alcoholates are chemically unstable and, when exposed to water, hydrolyze to form alcohol and metal hydroxide:

C 2 H 5 OK + H 2 O ® C 2 H 5 OH + KOH

This reaction shows that alcohols are weaker acids compared to water (a strong acid displaces a weak one); moreover, when interacting with alkali solutions, alcohols do not form alcoholates. However, in polyhydric alcohols (in the case when OH groups are attached to neighboring C atoms), the acidity of the alcohol groups is much higher, and they can form alcoholates not only when interacting with metals, but also with alkalis:

HO–CH 2 –CH 2 –OH + 2NaOH ® NaO–CH 2 –CH 2 –ONa + 2H 2 O

When HO groups in polyhydric alcohols are attached to non-adjacent C atoms, the properties of alcohols are close to monohydric ones, since the mutual influence of HO groups does not appear.

When interacting with mineral or organic acids, alcohols form esters - compounds containing the R-O-A fragment (A is the acid residue). The formation of esters also occurs during the interaction of alcohols with anhydrides and acid chlorides of carboxylic acids (Fig. 6).

Under the action of oxidizing agents (K 2 Cr 2 O 7, KMnO 4), primary alcohols form aldehydes, and secondary alcohols form ketones (Fig. 7)

Rice. 7. FORMATION OF ALDEHYDES AND KETONES DURING THE OXIDATION OF ALCOHOLS

The reduction of alcohols leads to the formation of hydrocarbons containing the same number of C atoms as the molecule of the original alcohol (Fig. 8).

Rice. 8. BUTANOL RESTORATION

2. Reactions occurring at the C–O bond.

In the presence of catalysts or strong mineral acids, dehydration of alcohols (elimination of water) occurs, and the reaction can proceed in two directions:

a) intermolecular dehydration involving two alcohol molecules, in which the C–O bonds of one of the molecules are broken, resulting in the formation of ethers—compounds containing the R–O–R fragment (Fig. 9A).

b) during intramolecular dehydration, alkenes are formed - hydrocarbons with a double bond. Often both processes—the formation of an ether and an alkene—occur in parallel (Fig. 9B).

In the case of secondary alcohols, during the formation of an alkene, two reaction directions are possible (Fig. 9B), the predominant direction is one in which, during the condensation process, hydrogen is split off from the least hydrogenated carbon atom (marked by number 3), i.e. surrounded by fewer hydrogen atoms (compared to atom 1). Shown in Fig. 10 reactions are used to produce alkenes and ethers.

The cleavage of the C–O bond in alcohols also occurs when the OH group is replaced by a halogen or amino group (Fig. 10).

Rice. 10. REPLACEMENT OF OH-GROUP IN ALCOHOLS WITH HALOGEN OR AMINO GROUP

The reactions shown in Fig. 10 is used for the production of halocarbons and amines.

Preparation of alcohols.

Some of the reactions shown above (Fig. 6,9,10) are reversible and, when conditions change, can proceed in the opposite direction, leading to the production of alcohols, for example, during the hydrolysis of esters and halocarbons (Fig. 11A and B, respectively), as well as by hydration alkenes - by adding water (Fig. 11B).

Rice. 11. OBTAINING ALCOHOLS BY HYDROLYSIS AND HYDRATION OF ORGANIC COMPOUNDS

The hydrolysis reaction of alkenes (Fig. 11, Scheme B) underlies the industrial production of lower alcohols containing up to 4 C atoms.

Ethanol is also formed during the so-called alcoholic fermentation of sugars, for example, glucose C 6 H 12 O 6. The process occurs in the presence of yeast and leads to the formation of ethanol and CO 2:

C 6 H 12 O 6 ® 2C 2 H 5 OH + 2CO 2

Fermentation can produce no more than a 15% aqueous solution of alcohol, since at a higher concentration of alcohol the yeast fungi die. Higher concentration alcohol solutions are obtained by distillation.

Methanol is produced industrially by the reduction of carbon monoxide at 400° C under a pressure of 20–30 MPa in the presence of a catalyst consisting of copper, chromium, and aluminum oxides:

CO + 2 H 2 ® H 3 COH

If instead of hydrolysis of alkenes (Fig. 11) oxidation is carried out, then dihydric alcohols are formed (Fig. 12)

Rice. 12. PREPARATION OF DIOHOMIC ALCOHOLS

Use of alcohols.

The ability of alcohols to participate in various chemical reactions allows them to be used for the production of all kinds of organic compounds: aldehydes, ketones, carboxylic acids, ethers and esters used as organic solvents in the production of polymers, dyes and drugs.

Methanol CH 3 OH is used as a solvent, as well as in the production of formaldehyde, used to produce phenol-formaldehyde resins; methanol has recently been considered as a promising motor fuel. Large volumes of methanol are used in production and transportation natural gas. Methanol is the most toxic compound among all alcohols, the lethal dose when ingested is 100 ml.

Ethanol C 2 H 5 OH is the starting compound for the production of acetaldehyde, acetic acid, as well as for the production of carboxylic acid esters used as solvents. In addition, ethanol is the main component of all alcoholic beverages; it is widely used in medicine as a disinfectant.

Butanol is used as a solvent for fats and resins; in addition, it serves as a raw material for the production of fragrant substances (butyl acetate, butyl salicylate, etc.). In shampoos it is used as a component that increases the transparency of solutions.

Benzyl alcohol C 6 H 5 –CH 2 –OH in the free state (and in the form of esters) is found in the essential oils of jasmine and hyacinth. It has antiseptic (disinfecting) properties; in cosmetics it is used as a preservative for creams, lotions, dental elixirs, and in perfumery as a fragrant substance.

Phenethyl alcohol C 6 H 5 –CH 2 –CH 2 –OH has a rose scent, is found in rose oil, and is used in perfumery.

Ethylene glycol HOCH 2 –CH 2 OH is used in the production of plastics and as an antifreeze (an additive that reduces the freezing point of aqueous solutions), in addition, in the manufacture of textile and printing inks.

Diethylene glycol HOCH 2 –CH 2 OCH 2 –CH 2 OH is used to fill hydraulic brake devices, as well as in textile industry when finishing and dyeing fabrics.

Glycerol HOCH 2 –CH(OH)–CH 2 OH is used to produce polyester glyphthalic resins; in addition, it is a component of many cosmetic preparations. Nitroglycerin (Fig. 6) is the main component of dynamite, used in mining and railway construction as an explosive.

Pentaerythritol (HOCH 2) 4 C is used to produce polyesters (pentaphthalic resins), as a hardener for synthetic resins, as a plasticizer for polyvinyl chloride, and also in the production of the explosive tetranitropentaerythritol.

Polyhydric alcohols xylitol СОН2–(СНН)3–CH2ОН and sorbitol СОН2– (СНН)4–СН2ОН have a sweet taste; they are used instead of sugar in the production of confectionery products for patients with diabetes and people suffering from obesity. Sorbitol is found in rowan and cherry berries.

Mikhail Levitsky

Goals:

Educational: familiarize students with the classification of alcohols, their nomenclature and isomerism. Consider the influence of the structure of alcohols on their properties. Developmental: Strengthen skills of working in groups, develop skills for finding relationships between new and studied material. Educational: developing teamwork skills Student - student, Student - teacher. Be able to analyze the information received.

Lesson type: Combined

Organizational form: frontal survey, laboratory work, independent work, conversation on problematic issues, analysis of the information received.

Equipment:

1. Set of slides ( Appendix 1) tables, individual sheets with tasks for independent work, assignment for laboratory work.
2. On student tables: bottles with alcohols (ethyl, isopropyl, glycerin), sodium, copper oxide (2), acetic acid, phenolphthalein, potassium permanganate, sand, sodium hydroxide, hydrochloric acid, tap water, chemical glassware, safety regulations .

Lesson plan:

1. 1.Definition of the class of alcohols, the structure of the molecule of monohydric saturated alcohols.
2. Classification of alcohols according to three criteria.
3. Nomenclature of alcohols.
4. Types of isomerism of monohydric saturated alcohols.
5. Physical properties of alcohols. The influence of hydrogen bonding on physical properties alcohols

2. 6.Chemical properties.
7. Consolidation of new material.

PROGRESS OF THE LESSON

I. Organizational moment

Teacher: We have completed the study of a large class of organic compounds consisting of only two chemical elements - carbon and hydrogen. What other chemical elements are most often found in organic compounds?

Student: Oxygen, nitrogen, phosphorus, sulfur and others.

II. Learning new material

Teacher: We are beginning to study a new class of organic compounds, which, in addition to carbon and hydrogen, include oxygen. They are called oxygen-containing. (Slide No. 1).
As we see, there are several classes of organic compounds consisting of carbon, hydrogen and oxygen. Today we are starting to study a class called “Alcohols”. Alcohol molecules contain a hydroxyl group, which is the functional group (FG) for this class. What do we call FG? (Slide No. 1).

Student: A group of atoms (or an atom) that determines whether a compound belongs to a certain class and determines its most important chemical properties is called a FG.

Teacher: Alcohols are a large class of organic compounds in terms of diversity and properties that are widely used in various areas of the national economy. (Slides No. 2-8)
As we see, this is pharmaceuticals, cosmetics production, food industry, and also as a solvent in the production of plastics, varnishes, paints, etc. Let's look at the table.

Table 1.

SOME IMPORTANT REPRESENTATIVES OF THE CLASS OF ALCOHOLS

Teacher: If we talk about the effect on the human body, then all alcohols are poisons. Alcohol molecules have a detrimental effect on living cells. (Slide No. 9) Spit - alkanes have an outdated name for alcohol. Alcohols are derivatives of hydrocarbons in which one or more hydrogen atoms are replaced by hydroxyl groups - OH.
In the simplest case, the structure of alcohol can be expressed by the following formula:

R–OH,

where R is a hydrocarbon radical.

Alcohols can be classified according to three criteria:

1. The number of hydroxyl groups (monoatomic, diatomic, polyatomic).

Table 2.

CLASSIFICATION OF ALCOHOLS ACCORDING TO THE NUMBER OF HYDROXYL GROUPS (–OH)

2. The nature of the hydrocarbon radical (saturated, unsaturated, aromatic).

Table 3.

CLASSIFICATION OF ALCOHOLS BY NATURE OF RADICAL

3. The nature of the carbon atom to which the hydroxyl group is connected (primary, secondary, tertiary)

Table 4.

CLASSIFICATION OF ALCOHOLS BY THE CHARACTER OF THE CARBON ATOM ASSOCIATED WITH THE FUNCTIONAL GROUP –OH

There are no quaternary alcohols because the quaternary C atom is bonded to 4 other C atoms, so there are no more valences to bind to the hydroxyl group.

Let's consider the basic principles of constructing the names of alcohols according to the substitutive nomenclature, using the scheme:

Name of alcohol = name HC + (prefix) + - OL +(n1, n2 ..., nn), where prefix denotes the number of –OH groups in the molecule: 2 – “di”, 3 – “three”, 4 – “tetra”, etc.
n indicates the position of hydroxyl groups in the carbon chain, for example:

Name construction order:

1. The carbon chain is numbered from the end closest to the –OH group.
2. The main chain contains 7 C atoms, which means the corresponding hydrocarbon is heptane.
3. The number of –OH groups is 2, the prefix is ​​“di”.
4. Hydroxyl groups are located at 2 and 3 carbon atoms, n = 2 and 4.

Alcohol name heptanediol-2,4

In our school course we will study in detail monohydric saturated alcohols with the general formula: CnH2n+1OH

Let's consider models of molecules of individual representatives of these alcohols (methyl, ethyl, glycerol). (Slides No. 10-13)

Homologous series of these alcohols starts with methyl alcohol:

CH3 – OH – methyl alcohol
CH3 – CH2 – OH – ethyl alcohol
CH3 – CH2 – CH2 – OH – propyl alcohol
CH3 – CH2 – CH2 – CH2 – OH – butyl alcohol
CH3 – CH2 – CH2 – CH2 – CH2 – OH – amyl alcohol or pentanol

Isomerism

The following are characteristic of saturated monohydric alcohols: types of isomerism:

1) positions of functional groups

2) carbon skeleton.

Please note– numbering of carbon atoms begins from the end close to the –OH group.

3) interclass isomerism (with ethers R – O – R)

Physical properties of alcohols

The first ten members of the homologous series of representatives of monohydric alcohols are liquids, higher alcohols are solids. (Slides 14, 15)
The hydrogen bond formed between alcohol molecules has a strong influence on the physical properties of alcohols. You are familiar with hydrogen bonding from the 9th grade program, topic “Ammonia”. Now your classmate, who received an individual assignment in the last lesson, will remind us what a hydrogen bond is.

Student answer

A hydrogen bond is a bond between the hydrogen atoms of one molecule and the highly electronegative atoms of another molecule. (F, O, N, CL). On the letter it is indicated by three dots. (Slides 16,17). A hydrogen bond is a special type of intermolecular bond that is weaker than a regular one. covalent bond 10-20 times, but it has a great influence on the physical properties of the compounds.
Two consequences of hydrogen bonding: 1) good solubility of substances in water; 2) increase in melting and boiling points. For example: the dependence of the boiling point of some compounds on the presence of a hydrogen bond.

Teacher: What conclusions can we draw about the effect of hydrogen bonding on the physical properties of alcohols?

Students: 1) In the presence of a hydrogen bond, the boiling point increases greatly.
2) The higher the atomicity of the alcohol, the more hydrogen bonds are formed.

This also helps to increase the boiling point.

CHEMICAL PROPERTIES OF ALCOHOLS

(Repeat PTB)

Burning of alcohols.

2. Interaction of alcohols with alkali metals.

3. Oxidation of alcohols (qualitative reaction) - production of aldehydes.

4. The interaction of alcohols with acids to form esters (esterification reaction).

5. Intramolecular dehydration of alcohols with the formation of unsaturated hydrocarbons.

6. Intermolecular dehydration of alcohols to form ethers.

7. Dehydrogenation of alcohols - obtaining aldehydes.

Teacher: write a five-line poem (Cinquain)

1st keyword

2nd two adjectives

3rd three verbs

4th sentence

5th word associated with the keyword.

Student. Alcohols.

Poisonous, liquid

They strike, they destroy, they destroy

They have a narcotic effect on the human body.

Drugs.

IV. Homework: paragraph No. 9, pp. 66-70 ex. No. 13 b.

Individual tasks. Using additional literature: 1) talk about the areas of application of glycerin and ethylene glycol; 2) talk about the production of alcohols from cellulose and fats; 3) how do these alcohols act on the human body?

V. Lesson summary Let's sum it up in the form of doing independent work in two options

Literature:

1. Chemistry 10th grade. Textbook for general education institutions. Bustard Moscow 2008. Basic level.4th ed. stereotypical.
2. Chemistry 100 class workbook for the textbook. Basic level. Bustard, 2007.
3. Lesson developments in chemistry. To the textbooks of O. S. Gabrielyan, . 10th grade
4. . . Chemistry 9th grade Smolensk Association XXI century 2006
5. . CHEMISTRY. New school aid for applicants to universities. Ed. 4th, corrected and supplemented. Rostov-on-Don. Phoenix 2007.

DEFINITION

Alcohols– compounds containing one or more hydroxyl groups –OH associated with a hydrocarbon radical.

The general formula of the homologous series of saturated monohydric alcohols is C n H 2 n +1 OH. The names of alcohols contain the suffix – ol.

Depending on the number of hydroxyl groups, alcohols are divided into one- (CH 3 OH - methanol, C 2 H 5 OH - ethanol), two- (CH 2 (OH)-CH 2 -OH - ethylene glycol) and triatomic (CH 2 (OH )-CH(OH)-CH 2 -OH - glycerol). Depending on which carbon atom the hydroxyl group is located at, primary (R-CH 2 -OH), secondary (R 2 CH-OH) and tertiary alcohols (R 3 C-OH) are distinguished.

Saturated monohydric alcohols are characterized by isomerism of the carbon skeleton (starting from butanol), as well as isomerism of the position of the hydroxyl group (starting from propanol) and interclass isomerism with ethers.

CH 3 -CH 2 -CH 2 -CH 2 -OH (butanol – 1)

CH 3 -CH (CH 3) - CH 2 -OH (2-methylpropanol - 1)

CH 3 -CH (OH) -CH 2 -CH 3 (butanol - 2)

CH 3 -CH 2 -O-CH 2 -CH 3 (diethyl ether)

Chemical properties of alcohols

1. Reactions that occur with the rupture of the O-H bond:

— the acidic properties of alcohols are very weakly expressed. Alcohols react with alkali metals

2C 2 H 5 OH + 2K → 2C 2 H 5 OK + H 2

but do not react with alkalis. In the presence of water, alcoholates are completely hydrolyzed:

C 2 H 5 OK + H 2 O → C 2 H 5 OH + KOH

This means that alcohols are weaker acids than water.

- formation of esters under the influence of mineral and organic acids:

CH 3 -CO-OH + H-OCH 3 ↔ CH 3 COOCH 3 + H 2 O

- oxidation of alcohols under the action of potassium dichromate or permanganate to carbonyl compounds. Primary alcohols are oxidized to aldehydes, which in turn can be oxidized to carboxylic acids.

R-CH 2 -OH + [O] → R-CH = O + [O] → R-COOH

Secondary alcohols are oxidized to ketones:

R-CH(OH)-R’ + [O] → R-C(R’) = O

Tertiary alcohols are more resistant to oxidation.

2. Reaction with breaking of the C-O bond.

— intramolecular dehydration with the formation of alkenes (occurs when alcohols with water-removing substances (concentrated sulfuric acid) are strongly heated):

CH 3 -CH 2 -CH 2 -OH → CH 3 -CH = CH 2 + H 2 O

— intermolecular dehydration of alcohols with the formation of ethers (occurs when alcohols are slightly heated with water-removing substances (concentrated sulfuric acid)):

2C 2 H 5 OH → C 2 H 5 -O-C 2 H 5 + H 2 O

— weak basic properties of alcohols manifest themselves in reversible reactions with hydrogen halides:

C 2 H 5 OH + HBr → C 2 H 5 Br + H 2 O

Physical properties of alcohols

Lower alcohols (up to C 15) are liquids, higher alcohols are solids. Methanol and ethanol are mixed with water in any ratio. As the molecular weight increases, the solubility of alcohols in alcohol decreases. Alcohols have high boiling and melting points due to the formation of hydrogen bonds.

Preparation of alcohols

The production of alcohols is possible using a biotechnological (fermentation) method from wood or sugar.

Laboratory methods for producing alcohols include:

- hydration of alkenes (the reaction occurs when heated and in the presence of concentrated sulfuric acid)

CH 2 = CH 2 + H 2 O → CH 3 OH

— hydrolysis of alkyl halides under the influence of aqueous solutions of alkalis

CH 3 Br + NaOH → CH 3 OH + NaBr

CH 3 Br + H 2 O → CH 3 OH + HBr

— reduction of carbonyl compounds

CH 3 -CH-O + 2[H] → CH 3 – CH 2 -OH

Examples of problem solving

EXAMPLE 1

Exercise	The mass fractions of carbon, hydrogen and oxygen in the molecule of saturated monohydric alcohol are 51.18, 13.04 and 31.18%, respectively. Derive the formula of alcohol.
Solution	Let us denote the number of elements included in the alcohol molecule by the indices x, y, z. Then, the formula of alcohol in general will look like C x H y O z. Let's write down the ratio: x:y:z = ω(С)/Ar(C): ω(Н)/Ar(Н) : ω(О)/Ar(О); x:y:z = 51.18/12: 13.04/1: 31.18/16; x:y:z = 4.208: 13.04: 1.949. Let's divide the resulting values ​​by the smallest, i.e. at 1.949. We get: x:y:z = 2:6:1. Therefore, the formula of alcohol is C 2 H 6 O 1. Or C 2 H 5 OH is ethanol.
Answer	The formula of saturated monohydric alcohol is C 2 H 5 OH.