Definition and classification of alcohols.

Alcohols are organic oxygen-containing compounds whose molecules contain one or more hydroxyl groups (–OH) associated with a hydrocarbon radical.

R – OH CH 3 – CH 2 – CH 2 – CH 2 – OH

butane ol -1 (1-butyl alcohol)

HO – R – OH HO – CH 2 – CH 2 – OH

ethane diol -1,2

Alcohols – these are organic compounds, derivatives of hydrocarbons, in the molecules of which one or more hydrogen atoms are replaced by a hydroxyl group (–OH).

Classifications of alcohols (parallel):

I. for the hydrocarbon radical (R–):

· limiting (saturated) (CH 3 –CH 2 –)

· unsaturated (unsaturated) (CH 2 =CH–, CH≡C–, etc.)

· aromatic (C 6 H 5 –CH 2 −).

II. by atomicity, i.e. by the number of hydroxyl groups ( hydroxyl groups are never attached to the same carbon atom ):

· monatomic

polyatomic:

Diatomic (glycols)

Triatomic, etc.

III. There are primary, secondary and tertiary alcohols:

primary alcohols (the hydroxyl group is located on a carbon atom connected to only one other carbon atom),

secondary alcohols (the hydroxyl group is located on a carbon atom connected to only two adjacent carbon atoms),

· tertiary alcohols (the hydroxyl group is located on a carbon atom connected to only three neighboring carbon atoms).

Compounds in which one carbon atom has two hydroxyl groups are in most cases unstable and easily turn into aldehydes, eliminating water in the process:

RCH → RC + H2O

Unsaturated alcohols in which the OH group is “adjacent” to the double bond, i.e. connected 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:

a) primary - into aldehydes

CH 3 −CH=CH–OH → CH 3 –CH 2 −CH=O

b) secondary – into ketones

CH 2 =C–OH → CH 3 –C=O

Nomenclature of alcohols.

According to international nomenclature in accordance with IUPAC nomenclature names alcohols produced by the name of the corresponding hydrocarbon with the addition of a suffix -ol to the name of the hydrocarbon of the longest carbon chain, including the hydroxyl group, from which the chain numbering begins. This numbering is then used to indicate the position of the various substituents along the main chain, followed by “ol” and a number indicating the position of the OH group. The number of hydroxyl groups is indicated by number di-, tri- etc. (each of them is numbered at the end). Or produced by the name of the hydrocarbon radical with the addition "-ovy" and words alcohol(for example, ethyl fresh alcohol ). If the alcohol is unsaturated, then indicate after –en or –in multiple connection location digit (minimum digit). As in other homologous series, each member of the alcohol series differs in composition from the previous and subsequent members by a homologous difference (-CH 2 -).

ormula	Name
systematic (according to IUPAC)	by radicals to which the hydroxyl group is connected
CH3−OH	methanol	methyl alcohol
CH 3 CH 2 -OH	ethanol	ethanol
CH 3 CH 2 CH 2 -OH	propanol-1	propyl-1 alcohol
CH 3 CH 2 CH 2 CH 2 −OH	butanol-1 (primary butanol)	butyl 1 alcohol
CH 3 −CH 2 −CH(OH)–CH 3	butanol-1 (secondary butanol)	butyl 2 alcohol
(CH 3) 2 CHCH 2 −OH	2-methylpropanol-1	2-methylpropyl-1alcohol
CH 3 −(CH 3)C(OH) –CH 3	2-methylpropanol-2 (tertiary butanol)	2-methylpropyl-2alcohol
CH 3 CH 2 CH 2 CH 2 CH 2 −OH	pentanol-1	pentyl-1 alcohol
CH 2 =CH−OH	ethenol	vinyl alcohol
C 6 H 5 –CH 2 –OH	phenylmethanol	benzyl alcohol
HO−CH2–CH2−OH	ethanediol-1,2	ethylene glycol
HO−CH 2 −CH(OH)–CH 2 −OH	propanetriol-1,2,3	glycerol

Isomerism of alcohols.

1. Isomerism of the carbon skeleton, starting with C 3

CH 3 –CH 2 –CH 2 –OH CH 3 –CH–OH

propanol 2-methylethanol

1. Position isomerism

A. multiple bond positions (for unsaturated alcohols)

CH 2 =CH–CH 2 –CH 2 −OH CH 3 –CH=CH–CH 2 −OH

butene-3ol-1 butene-2ol-1

b. positions of deputies

CH 2 –CH 2 –CH 2 –OH CH 3 –CH–CH 2 –OH

3-chloropropanol-1 2-chloropropanol-1

V. position of the functional (hydroxyl) group

CH 2 –CH 2 –CH 2 –OH CH 3 –CH–CH 3

propanol-1 (primary propanol) propanol-2 (secondary propanol)

The isomerism of di- and trihydric alcohols is determined by the mutual arrangement of hydroxyl groups.

1. Spatial isomerism (for unsaturated alcohols)

CH 3 –CH=CH–CH 2 –OH

H 3 C CH 2 −OH H CHO

cis-butene-2ol-1 trans-butene-2ol-1

1. Interclass isomerism:

a) with ethers, starting with C 2

CH 3 –CH 2 –CH 2 –OH CH 3 –O–CH 2 –CH 3

propanol-1 methyl ethyl ether

4. Physical properties of alcohols.

Monohydric saturated primary alcohols with a short chain of carbon atoms are liquids, and higher ones (starting from C 12 H 25 OH) are solids. Alcohols are soluble in most organic solvents. With an increase in the number of C atoms in the organic group, the influence of the hydroxyl group on the properties of alcohols decreases, the hydrophobic (water-repellent) effect begins to affect, solubility in water becomes limited (and when R contains more than 9 carbon atoms, it practically disappears), and their solubility in hydrocarbons increases . The physical properties of monohydric alcohols with high molecular weight are already very similar to the properties of the corresponding hydrocarbons.

Methanol, ethanol, propanol, and tertiary butanol are colorless liquids, soluble in water in any ratio, and have an alcoholic odor. Methanol is a strong poison. All alcohols are poisonous and have a narcotic effect.

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

H─O - - - H─O - - - H─O - - -

As a result, all alcohols have a higher boiling point than the corresponding hydrocarbons, for example, bp. ethanol +78° C, and boiling point. ethane –88.63° C; t kip. butanol and butane are +117.4° C and –0.5° C, respectively. And they are much less volatile, have higher melting points and are better soluble in water than the corresponding hydrocarbons; however, the difference decreases with increasing molecular weight.

Thus, the higher boiling points of alcohols compared to the boiling points of the corresponding hydrocarbons are due to the need to break hydrogen bonds when molecules pass into the gas phase, which requires additional energy. On the other hand, this type of association leads to an increase in molecular weight, which naturally causes a decrease in volatility.

Dihydric alcohols also called glycols, since they have a sweet taste - this is typical for all polyhydric alcohols. Polyhydric alcohols with a small number of carbon atoms - these are viscous liquids, higher alcohols− solids. Some of the polyhydric alcohols are poisonous.

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 are therefore 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

Given the polarity of the O-H bond and the significant partial positive charge localized (focused) on the hydrogen atom, the hydrogen of the hydroxyl group is said to be “acidic” in nature. 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 the general rule. Their molecules include hydrocarbon and hydroxyl radicals, so the chemical properties of 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 according to 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 tg 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, the C-O bond shifts even more towards oxygen, and 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 the 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.

The nucleophilic substitution reaction in general 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, is used as a solvent, is part of varnishes and paints, and perfumes. In medicine, ethyl alcohol is the most important disinfectant. Used for preparing 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*. The volume of carbon dioxide released during the combustion of saturated monohydric alcohol is 8 times greater than the volume of hydrogen released by 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, during the production of 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.

The general formula of the homologous series of saturated monohydric alcohols is C n H 2n+1 OH. Depending on which carbon atom the hydroxyl group is located at, primary (RCH 2 -OH), secondary (R 2 CH-OH) and tertiary (R 3 C-OH) alcohols are distinguished. The simplest alcohols:

Primary:

CH 3 -OH CH 3 -CH 2 -OH CH 3 -CH 2 -CH 2 -OH

methanol ethanol propanol-1

Secondary Tertiary

propanol-2 buganol-2 2-methylpropanol-2

Isomerism monohydric alcohols is related to the structure of the carbon skeleton (for example, butanol-2 and 2-methylpropanol-2) and to the position of the OH group (propanol-1 and propanol-2).

Nomenclature.

Alcohols are named by adding the ending -ol to the name of the hydrocarbon with the longest carbon chain containing a hydroxyl group. Chain numbering begins from the edge closest to which the hydroxyl group is located. In addition, the substitutive nomenclature is widespread, according to which the name of the alcohol is derived from the corresponding hydrocarbon radical with the addition of the word “alcohol”, for example: C 2 H 5 OH - ethyl alcohol.

Structure:

Alcohol molecules have an angular structure. The R-O-H angle in a methanol molecule is 108.5 0. The oxygen atom of the hydroxyl group is in sp 3 hybridization.

Receipt. Properties

Receipt.

1. The most common method of producing alcohols, which is of industrial importance, is the hydration of alkenes. The reaction occurs by passing an alkene with water vapor over a phosphate catalyst:

CH 2 = CH 2 + H 2 O → CH 3 -CH 2 -OH.

Ethyl alcohol is produced from ethylene, and isopropyl alcohol is obtained from propene. The addition of water follows Markovnikov’s rule, therefore, only ethyl alcohol can be obtained from primary alcohols using this reaction.

2. Another common method for producing alcohols is the hydrolysis of alkyl halides under the action of aqueous solutions of alkalis:

R-Br + NaOH → R-OH + NaBr.

This reaction can produce primary, secondary and tertiary alcohols.

3. Reduction of carbonyl compounds. When aldehydes are reduced, primary alcohols are formed, and when ketones are reduced, secondary alcohols are formed:

R-CH=O + H 2 → R-CH 2 -OH, (1)

R-CO-R" + H 2 → R-CH(OH) -R". (2)

The reaction is carried out by passing a mixture of aldehyde or ketone vapor and hydrogen over a nickel catalyst.

4. Effect of Grignard reagents on carbonyl compounds.

5. Ethanol is obtained from the alcoholic fermentation of glucose:

C 6 H 12 O 6 → 2C 2 H 5 OH + 2CO 2.

Chemical properties alcohols are determined by the presence of the hydroxyl group OH in their molecules. C-O and O-H bonds are highly polar and susceptible to breaking. There are two main types of reactions of alcohols involving the -OH functional group:

1) Reactions with breaking the O-H bond: a) interaction of alcohols with alkali and alkaline earth metals with the formation of alcoholates; b) reactions of alcohols with organic and mineral acids to form esters; c) oxidation of alcohols under the action of potassium dichromate or permanganate to carbonyl compounds. The rate of reactions in which the O-H bond is broken decreases in the order: primary alcohols > secondary > tertiary.

2) Reactions accompanied by the cleavage of the C-O bond: a) catalytic dehydration with the formation of alkenes (intramolecular dehydration) or ethers (intermolecular dehydration): b) replacement of the -OH group with a halogen, for example, by the action of hydrogen halides with the formation of alkyl halides. The rate of reactions in which the C-O bond is broken decreases in the order: tertiary alcohols > secondary > primary. Alcohols are amphoteric compounds.

Reactions that involve breaking the O-H bond.

1. The acidic properties of alcohols are very weakly expressed. Lower alcohols react violently with alkali metals:

2C 2 H 5 -OH + 2K→ 2C 2 H 5 -OK + H 2, (3)

but do not react with alkalis. As the length of the hydrocarbon radical increases, the rate of this reaction slows down.

In the presence of traces of moisture, alcohol salts (alcoholates) decompose to the original alcohols:

C 2 H 5 OK + H 2 O → C 2 H 5 OH + KOH.

This proves that alcohols are weaker acids than water.

2. When mineral and organic acids act on alcohols, esters are formed. The formation of esters proceeds by the nucleophilic addition-elimination mechanism:

C 2 H 5 OH + CH 3 COOH CH 3 SOOS 2 H 5 + H 2 O

Ethyl acetate

C 2 H 5 OH + HONO 2 C 2 H 5 ONO 2 + H 2 O

Ethyl nitrate

A distinctive feature of the first of these reactions is that the hydrogen atom is removed from the alcohol, and the OH group is removed from the acid. (Established experimentally using the “tagged atoms” method).

3. Alcohols are oxidized by 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 → R-CH=O → R-COOH.

Secondary alcohols are oxidized to ketones:

Tertiary alcohols can only be oxidized by breaking the C-C bonds.

Reactions involving the cleavage of the C-O bond.

1) Dehydration reactions occur when alcohols are heated with water-removing substances. With strong heating, intramolecular dehydration occurs with the formation of alkenes:

H 2 SO 4 ,t >150°С

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

With weaker heating, intermolecular dehydration occurs with the formation of ethers:

H2SO4,t< 150°С

2CH 3 -CH 2 -OH → C 2 H 5 -O-C 2 H 5 + H 2 O.

2) Alcohols react reversibly with hydrohalic acids (the weak basic properties of alcohols appear here):

ROH + HCl RCl + H 2 O

Tertiary alcohols react quickly, secondary and primary alcohols react slowly.

Application. Alcohols are mainly used in the organic synthesis industry. Ethanol is an important raw material for the food industry. Used as a solvent in medicine.

Methanol is used to produce formaldehyde, acrylic acid-based plastics, and as a solvent for varnishes and paints.

Alcohols- organic compounds whose molecules include one or more hydroxyl groups connected to a hydrocarbon radical.

Based on the number of hydroxyl groups in the molecule, alcohols are divided into monohydric, diatomic, triatomic, etc.

Monohydric alcohols

The general formula of monohydric alcohols is R—OH.

Based on the type of hydrocarbon radical, alcohols are divided into saturated, unsaturated and aromatic.

The general formula of saturated monohydric alcohols is C n N 2 n+1 -OH.

Organic substances containing hydroxyl groups in the molecule directly bonded to the carbon atoms of the benzene ring are called phenols. For example, C 6 H 5 -OH - hydroxobenzene (phenol).

Based on the type of carbon atom to which the hydroxyl group is bonded, primary (R-CH 2 -OH), secondary (R-CHOH-R") and tertiary (RR"R""C-OH) alcohols are distinguished.

C n N 2n+2 O is the general formula of both saturated monohydric alcohols and ethers.

Saturated monohydric alcohols are isomeric to ethers - compounds with the general formula R-O-R."

Isomers and homologues

G	CH3OH methanol
	CH3CH2OH ethanol				CH 3 OCH 3 dimethyl ether
	CH 3 CH 2 CH 2 OH propanol-1	propanol-2			CH 3 OCH 2 CH 3 methyl ethyl ether
	CH3(CH2)3OH butanol-1	butanol-2	2-methyl-propanol-2	2-methyl-propanol-1	CH 3 OCH 2 CH 2 CH 3 methylpropyl ether	CH 3 CH 2 OCH 2 CH 3 diethyl ether
	isomers

Alcohols are characterized by structural isomerism (isomerism of the carbon skeleton, isomerism of the position of the substituent or hydroxyl group), as well as interclass isomerism.

Algorithm for composing the names of monohydric alcohols

1. Find the carbon backbone - this is the longest chain of carbon atoms that has a functional group attached to one of them.
2. Number the carbon atoms in the main chain, starting with the end closest to the functional group.
3. Name the compound using the algorithm for hydrocarbons.
4. At the end of the name, add the suffix -ol and indicate the number of the carbon atom to which the functional group is associated.

The physical properties of alcohols are largely determined by the presence of hydrogen bonds between the molecules of these substances:

This is also related to the good solubility of lower alcohols in water.

The simplest alcohols are liquids with characteristic odors. As the number of carbon atoms increases, the boiling point increases and solubility in water decreases. The boiling point of primary alcohols is higher than that of secondary alcohols, and that of secondary alcohols is higher than that of tertiary alcohols. Methanol is extremely poisonous.

Chemical properties of alcohols

Preparation of alcohols

Polyhydric alcohols

Examples of polyhydric alcohols are the dihydric alcohol ethanediol (ethylene glycol) HO—CH 2 —CH 2 —OH and the trihydric alcohol propanetriol-1,2,3 (glycerol) HO—CH 2 —CH(OH)—CH 2 —OH.

These are colorless, syrupy liquids, sweet in taste, and highly soluble in water. Ethylene glycol is poisonous.

The chemical properties of polyhydric alcohols are for the most part similar to the chemical properties of monohydric alcohols, but the acidic properties are more pronounced due to the influence of hydroxyl groups on each other.

A qualitative reaction to polyhydric alcohols is their reaction with copper(II) hydroxide in an alkaline medium, which results in the formation of bright blue solutions of substances with complex structures. For example, for glycerol, the composition of this compound is expressed by the formula Na 2.

Phenols

The most important representative of phenols is phenol (hydroxobenzene, old names - hydroxybenzene, oxybenzene) C 6 H 5 -OH.

Physical properties of phenol: solid colorless substance with a pungent odor; poisonous; At room temperature it is noticeably soluble in water; an aqueous solution of phenol is called carbolic acid.

Chemical properties

Tasks and tests on the topic "Topic 4. "Alcohols. Phenols"."

• Alcohols - Organic substances grade 8–9

  Lessons: 3 Assignments: 9 Tests: 1

• Classification of substances - Classes of inorganic substances grade 8–9

  Lessons: 2 Assignments: 9 Tests: 1

• Crystal lattices - Structure of matter grade 8–9
  Check whether you can perform calculations using reaction equations taking into account the product yield.

  Example. Determine the volume of ethylene that can be obtained by dehydrating 92 g of ethyl alcohol if the product yield is 50%.

  Answer: 22.4 l

  After making sure that everything you need has been learned, proceed to completing the tasks. We wish you success.

  
  Recommended reading:
  • O. S. Gabrielyan and others. Chemistry 10th grade. M., Bustard, 2002;
  • G. E. Rudzitis, F. G. Feldman. Chemistry 10th grade. M., Education, 2001.
  • G. G. Lysova. Basic notes and tests in organic chemistry. M., Glik Plus LLC, 1999.

Alcohols are compounds containing one or more hydroxyl groups directly bonded to a hydrocarbon radical.

Classification of alcohols

Alcohols are classified according to various structural characteristics.

1. Based on the number of hydroxyl groups, alcohols are divided into

o monatomic(one group -OH)

For example, CH 3 – OH methanol,CH 3 – CH 2 – OH ethanol

o polyatomic(two or more -OH groups).

The modern name for polyhydric alcohols is polyols(diols, triols, etc.). Examples:

dihydric alcohol -ethylene glycol(ethanediol)

HO–CH 2 –CH 2 –OH

trihydric alcohol -glycerol(propanetriol-1,2,3)

HO–CH 2 –CH(OH)–CH 2 –OH

Diatomic alcohols with two OH groups at the same carbon atom R–CH(OH) 2 are unstable and, eliminating water, immediately turn into aldehydes R–CH=O. Alcohols R–C(OH) 3 do not exist.

2. Depending on which carbon atom (primary, secondary or tertiary) the hydroxy group is connected to, alcohols are distinguished

o primary R–CH 2 –OH,

o secondary R 2 CH–OH,

o tertiary R 3 C–OH.

For example:

In polyhydric alcohols, primary, secondary and tertiary alcohol groups are distinguished. For example, a molecule of the trihydric alcohol glycerol contains two primary alcohols (HO–CH2 –) and one secondary alcohol (–CH(OH)–) group.

3. According to the structure of radicals associated with the oxygen atom, alcohols are divided into

o limit(for example, CH 3 – CH 2 –OH)

o unlimited(CH 2 =CH–CH 2 –OH)

o aromatic(C 6 H 5 CH 2 –OH)

Unsaturated alcohols with an OH group at a carbon atom connected to another atom by a double bond are very unstable and immediately isomerize into aldehydes or ketones.

For example,vinyl alcohol CH 2 =CH–OH turns into acetaldehydeCH 3 –CH=O

Saturated monohydric alcohols

1. Definition

LIMITED MONO-ACHOLOGICAL ALCOHOLS – oxygen-containing organic substances, derivatives of saturated hydrocarbons, in which one hydrogen atom is replaced by a functional group (- OH)

2. Homologous series

3. Nomenclature of alcohols

Systematic names are given by the name of the hydrocarbon with the addition of a suffix -ol and a number indicating the position of the hydroxy group (if necessary). For example:

Numbering is based on the end of the chain closest to the OH group.

The number reflecting the location of the OH group is usually placed after the suffix “ol” in Russian.

According to another method (radical-functional nomenclature), the names of alcohols are derived from the names of radicals with the addition of the word " alcohol". In accordance with this method, the above compounds are called: methyl alcohol, ethyl alcohol, n-propyl alcohol CH 3 -CH 2 -CH 2 -OH, isopropyl alcohol CH 3 -CH(OH)-CH 3.

4. Isomerism of alcohols

Characteristic of alcohols structural isomerism:

· isomerism of OH group position(starting from C 3);
For example:

· carbon skeleton(starting from C 4);
For example, carbon skeleton isomers forC4H9OH:

· interclass isomerism with ethers
For example,

ethanol CH 3 CH 2 –OH and dimethyl ether CH 3 –O–CH 3

It is also possible spatial isomerism– optical.

For example, butanol-2 CH 3 C H(OH)CH 2 CH 3, in the molecule of which the second carbon atom (highlighted) is bonded to four different substituents, exists in the form of two optical isomers.

5. Structure of alcohols

The structure of the simplest alcohol - methyl (methanol) - can be represented by the formulas:

From the electronic formula it is clear that the oxygen in the alcohol molecule has two lone electron pairs.

The properties of alcohols and phenols are determined by the structure of the hydroxyl group, the nature of its chemical bonds, the structure of hydrocarbon radicals and their mutual influence.

O–H and C–O bonds are polar covalent. This follows from the differences in electronegativity of oxygen (3.5), hydrogen (2.1) and carbon (2.4). The electron density of both bonds is shifted towards the more electronegative oxygen atom:

Oxygen atom in alcohols characterized by sp 3 hybridization. Two 2sp 3 -atomic orbitals participate in the formation of its bonds with the C and H atoms; the C–O–H bond angle is close to tetrahedral (about 108°). Each of the other two 2 sp 3 orbitals of oxygen is occupied by a lone pair of electrons.

The mobility of the hydrogen atom in the hydroxyl group of alcohol is slightly less than in water. Methyl alcohol (methanol) will be more “acidic” in the series of monohydric saturated alcohols.
Radicals in the alcohol molecule also play a role in the manifestation of acidic properties. Typically, hydrocarbon radicals reduce acidic properties. But if they contain electron-withdrawing groups, then the acidity of alcohols increases noticeably. For example, alcohol (CF 3) 3 C-OH due to fluorine atoms becomes so acidic that it is able to displace carbonic acid from its salts.