Basic properties of alcohols in organic chemistry. Alcohols: their nomenclature, physical and chemical properties

The word “alcohol” is familiar to everyone, but not everyone knows that in Latin it comes from the word “Spirit” - “Spiritus”. This unusual and slightly pretentious name was given to the alcohol by its discoverers, the alchemist Zhabir and the Alexandrian Zosimus de Panopolis, who worked at the court of the Egyptian caliph. It was they who first succeeded in isolating alcohol from wine using a distillation apparatus. These ancient scientists firmly believed that they managed to obtain the very spirit of wine. Since then, many scientists (first alchemists, and then simply chemists) from different historical eras have been studying alcohol and its physical and chemical properties. So in our time, alcohols occupy a prominent and important place in organic chemistry, and our article today is about them.

Alcohols are important organic and oxygen-containing compounds that contain the hydroxyl group OH. Also, all alcohols are divided into monohydric and polyhydric. The importance of alcohols in chemistry, and not only in it, is simply enormous; alcohols are actively used in the chemical, cosmetic and food industries (yes, for the creation of alcoholic drinks, too, but not only for them).

History of the discovery of alcohol

The history of alcohol goes back to ancient times, because according to archaeological finds, already 5000 years ago people knew how to make alcoholic drinks: wine and beer. They knew how to do this, but they did not fully understand what kind of magical element was in these drinks that made them intoxicating. However, the inquisitive minds of scientists of the past have repeatedly tried to isolate this magical component from wine, which is responsible for its alcohol content (or strength, as we say now).

And it was soon discovered that alcohol could be isolated using the process of liquid distillation. Distillation of alcohol is a chemical process in which volatile components (vapors) are removed, and alcohol is obtained from the fermented mixture. By the way, the distillation process itself was first described by the great scientist and natural philosopher Aristotle. In practice, the alchemists Jabiru and Zosimus de Panopolis managed to obtain alcohol using distillation; it was they, as we wrote at the beginning, who gave the alcohol its name - “spiritus vini” (spirit of wine), which over time became simply alcohol.

Alchemists of later times improved the process of distillation and production of alcohol, for example, the French physician and alchemist Arnaud de Villeguerre in 1334 developed a convenient technology for producing wine alcohol. And already from 1360, his achievements were adopted by Italian and French monasteries, which began to actively produce alcohol, which they called “Aqua vita” - “living water”.

In 1386, “living water” first came to Russia (more precisely, Muscovy, as this state was then called). The alcohol brought by the Genoese embassy as a gift to the royal court was very popular with the local boyars (though not only the boyars). And “living water” subsequently became the basis of a well-known alcoholic drink (which, however, we strongly do not recommend that you drink).

But let's get back to chemistry.

Classification of alcohols

In fact, there are many different types alcohols, which chemists divide depending on:

Nomenclature of alcohols

The nomenclature of monohydric alcohols, like polyhydric ones, depends on the name of the surrounding radicals and the structure of their molecules. For example:

Physical properties of alcohols

Low molecular weight alcohol is usually a colorless liquid with a pungent and characteristic odor. The boiling point of alcohol is higher than others organic compounds. This is due to the fact that alcohol molecules have a special type of interaction - bonds. Here's what they look like.

Chemical properties of alcohols

Due to their structure, alcohols exhibit amphoteric properties: basic and acidic, we will discuss them in detail below:

• The acidic properties of alcohols are manifested in the ability to remove the proton of the hydroxy group. As the length of the carbon chain, the volume of its radical increases, as well as the degree of branching and the presence of donors in the molecule, the acidity decreases.
• The basic properties of alcohols are the opposite of their acidic properties, since they are expressed in their ability, on the contrary, to attach a proton.

Alcohols and glycols have the ability to undergo chemical reactions of substitution, elimination and oxidation. Let's describe them in more detail:

Preparation of alcohols

Monohydric alcohols can be obtained from alkenes, esters, oxo compounds, carboxylic acids and halogen derivatives.

But ethanol alcohol, which can be obtained by fermentation of sugary substances, will have this appearance.

Polyhydric alcohols are formed from polybasic acids, esters, alkenes and oxo compounds.

And to obtain glycerin, you can use hydrolysis in an acidic environment of triacylglycerols - the main components of the lipid fraction of fats and vegetable oils.

Use of alcohols

In addition to alcoholic drinks of various strengths, alcohols are used in cosmetology to create various cosmetics (for example, colognes), and, of course, in medicine, both in the creation of various medicines, ethers, and in household use, alcohol can serve as a disinfectant.

Alcohols, video

And finally, an educational video on the topic of our article.

These are derivatives of hydrocarbons in which one hydrogen atom is replaced by a hydroxy group. The general formula of alcohols is CnH 2 n +1 OH.

Classification of monohydric alcohols.

Depending on the position where it is located HE-group, distinguish:

Primary alcohols:

Secondary alcohols:

Tertiary alcohols:

.

Isomerism of monohydric alcohols.

For monohydric alcohols characterized by isomerism of the carbon skeleton and isomerism of the position of the hydroxy group.

Physical properties of monohydric alcohols.

The reaction follows Markovnikov’s rule, so only song alcohol can be obtained from primary alkenes.

2. Hydrolysis of alkyl halides under the influence of aqueous solutions of alkalis:

If the heating is weak, then intramolecular dehydration occurs, resulting in the formation of ethers:

B) Alcohols can react with hydrogen halides, with tertiary alcohols reacting very quickly, while primary and secondary alcohols react slowly:

The use of monohydric alcohols.

Alcohols used primarily in industrial organic synthesis, in the food industry, medicine and pharmacy.

Which contain one or more hydroxyl groups. Depending on the number of OH groups, these are divided into monohydric alcohols, trihydric alcohols, etc. Most often these complex substances are considered as derivatives of hydrocarbons, the molecules of which have undergone changes, because one or more hydrogen atoms have been replaced by a hydroxyl group.

The simplest representatives of this class are monohydric alcohols, the general formula of which looks like this: R-OH or

Cn+H 2n+1OH.

1. Alcohols containing up to 15 carbon atoms are liquids, 15 or more are solids.
2. Solubility in water depends on molecular weight The higher it is, the less soluble alcohol is in water. Thus, lower alcohols (up to propanol) are mixed with water in any proportions, while higher alcohols are practically insoluble in it.
3. The boiling point also increases with increasing atomic mass, for example, t bp. CH3OH = 65 °C, and boiling point. C2H5OH =78 °C.
4. The higher the boiling point, the lower the volatility, i.e. the substance does not evaporate well.

These physical properties of saturated alcohols with one hydroxyl group can be explained by the occurrence of intermolecular hydrogen bonds between individual molecules of the compound itself or the alcohol and water.

Monohydric alcohols are capable of entering into the following chemical reactions:

Having considered Chemical properties alcohols, we can conclude that monohydric alcohols are amphoteric compounds, because they can react with alkali metals, exhibiting weak properties, and with hydrogen halides, exhibiting basic properties. All chemical reactions occur with a discontinuity O-N connections or S-O.

Thus, saturated monohydric alcohols are complex compounds with one OH group that do not have free valences after formation S-S connections and exhibiting weak properties of both acids and bases. Due to their physical and chemical properties, they are widely used in organic synthesis, in the production of solvents, fuel additives, as well as in the food industry, medicine, and cosmetology (ethanol).

The content 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. Tertiary carbon atom (highlighted green) is bonded simultaneously to three neighboring carbon atoms, for example, tertiary butanol and pentanol (Fig. 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 where the structure of an organic group is more complex, rules common to all organic chemistry are used. 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. Next, this numbering is used to indicate the position of 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, e.g. 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 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); in addition, 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 monoatomic 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 an 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 occurs (elimination of water), 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) intramolecular dehydration produces alkenes - 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 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. eleven. 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 the production and transportation of 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 the textile industry for 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

Ethyl alcohol or wine alcohol is a widespread representative of alcohols. There are many known substances that contain oxygen, along with carbon and hydrogen. Among the oxygen-containing compounds, I am primarily interested in the class of alcohols.

Ethanol

Physical properties alcohol . Ethyl alcohol C 2 H 6 O is a colorless liquid with a peculiar odor, lighter than water (specific gravity 0.8), boils at a temperature of 78 °.3, dissolves well many inorganic and organic matter. Rectified alcohol contains 96% ethyl alcohol and 4% water.

The structure of the alcohol molecule .According to the valency of the elements, the formula C 2 H 6 O corresponds to two structures:

To resolve the question of which of the formulas actually corresponds to alcohol, let us turn to experience.

Place a piece of sodium in a test tube with alcohol. A reaction will immediately begin, accompanied by the release of gas. It is not difficult to establish that this gas is hydrogen.

Now let’s set up the experiment so that we can determine how many hydrogen atoms are released during the reaction from each alcohol molecule. To do this, add a certain amount of alcohol, for example 0.1 gram molecule (4.6 grams), drop by drop from a funnel to a flask with small pieces of sodium (Fig. 1). The hydrogen released from the alcohol displaces water from the two-necked flask into the measuring cylinder. The volume of displaced water in the cylinder corresponds to the volume of released hydrogen.

Fig.1. Quantitative experience in producing hydrogen from ethyl alcohol.

Since 0.1 gram of alcohol molecule was taken for the experiment, it is possible to obtain about 1.12 hydrogen (in terms of normal conditions) liters This means that sodium displaces 11.2 from a gram molecule of alcohol liters, i.e. half a gram molecule, in other words 1 gram atom of hydrogen. Consequently, sodium displaces only one hydrogen atom from each alcohol molecule.

Obviously, in the alcohol molecule, this hydrogen atom is in a special position compared to the other five hydrogen atoms. Formula (1) does not explain this fact. According to it, all hydrogen atoms are equally bonded to carbon atoms and, as we know, are not displaced by metallic sodium (sodium is stored in a mixture of hydrocarbons - in kerosene). On the contrary, formula (2) reflects the presence of one atom located in a special position: it is connected to carbon through an oxygen atom. We can conclude that it is this hydrogen atom that is less tightly bound to the oxygen atom; it turns out to be more mobile and is replaced by sodium. Hence, structural formula ethyl alcohol:

Despite the greater mobility of the hydrogen atom of the hydroxyl group compared to other hydrogen atoms, ethyl alcohol is not an electrolyte and does not dissociate into ions in an aqueous solution.

To emphasize that the alcohol molecule contains a hydroxyl group - OH, connected to a hydrocarbon radical, the molecular formula of ethyl alcohol is written as follows:

Chemical properties of alcohol . We saw above that ethyl alcohol reacts with sodium. Knowing the structure of alcohol, we can express this reaction with the equation:

The product of replacing hydrogen in alcohol with sodium is called sodium ethoxide. It can be isolated after the reaction (by evaporation of excess alcohol) as a solid.

When ignited in air, alcohol burns with a bluish, barely noticeable flame, releasing a lot of heat:

If you heat ethyl alcohol with a hydrohalic acid, for example with HBr, in a flask with a refrigerator (or a mixture of NaBr and H 2 SO 4, which gives hydrogen bromide during the reaction), then an oily liquid will be distilled off - ethyl bromide C 2 H 5 Br:

This reaction confirms the presence of a hydroxyl group in the alcohol molecule.

When heated with concentrated sulfuric acid as a catalyst, the alcohol easily dehydrates, that is, it splits off water (the prefix “de” indicates the separation of something):

This reaction is used to produce ethylene in the laboratory. When alcohol is heated weaker with sulfuric acid (not higher than 140°), each molecule of water is split off from two molecules of alcohol, resulting in the formation of diethyl ether - a volatile, flammable liquid:

Diethyl ether (sometimes called sulfuric ether) is used as a solvent (tissue cleaning) and in medicine for anesthesia. He belongs to the class ethers - organic substances whose molecules consist of two hydrocarbon radicals connected through an oxygen atom: R - O - R1

Use of ethyl alcohol . Ethyl alcohol is of great practical importance. A lot of ethyl alcohol is consumed to produce synthetic rubber using the method of Academician S.V. Lebedev. By passing ethyl alcohol vapor through a special catalyst, divinyl is obtained:

which can then polymerize into rubber.

The alcohol is used to produce dyes, diethyl ether, various “fruit essences” and a number of other organic substances. Alcohol as a solvent is used to make perfumes and many medicines. Various varnishes are prepared by dissolving resins in alcohol. High calorific value alcohol determines its use as a fuel (motor fuel = ethanol).

Obtaining ethyl alcohol . World alcohol production is measured in millions of tons per year.

A common method for producing alcohol is the fermentation of sugary substances in the presence of yeast. These lower plant organisms (fungi) produce special substances - enzymes, which serve as biological catalysts for the fermentation reaction.

Cereal seeds or potato tubers rich in starch are taken as starting materials in the production of alcohol. Starch is first converted into sugar using malt containing the enzyme diastase, which is then fermented into alcohol.

Scientists have worked hard to replace food raw materials for alcohol production with cheaper non-food raw materials. These searches were crowned with success.

Recently, due to the fact that when cracking oil a lot of ethylene is formed, steel

The reaction of ethylene hydration (in the presence of sulfuric acid) was studied by A. M. Butlerov and V. Goryainov (1873), who also predicted its industrial significance. A method of direct hydration of ethylene by passing it in a mixture with water vapor over solid catalysts has also been developed and introduced into industry. Producing alcohol from ethylene is very economical, since ethylene is part of the cracking gases of oil and other industrial gases and, therefore, is a widely available raw material.

Another method is based on the use of acetylene as the starting product. Acetylene undergoes hydration according to the Kucherov reaction, and the resulting acetaldehyde is catalytically reduced with hydrogen in the presence of nickel into ethyl alcohol. The entire process of acetylene hydration followed by reduction with hydrogen on a nickel catalyst into ethyl alcohol can be represented by a diagram.

Homologous series of alcohols

In addition to ethyl alcohol, other alcohols are known that are similar to it in structure and properties. All of them can be considered as derivatives of the corresponding saturated hydrocarbons, in the molecules of which one hydrogen atom is replaced by a hydroxyl group:

Table

Hydrocarbons	Alcohols	Boiling point of alcohols in º C
Methane CH 4	Methyl CH 3 OH	64,7
Ethane C 2 H 6	Ethyl C 2 H 5 OH orCH 3 - CH 2 - OH	78,3
Propane C 3 H 8	Propyl C 4 H 7 OH or CH 3 - CH 2 - CH 2 - OH	97,8
Butane C 4 H 10	Butyl C 4 H 9 OH orCH 3 - CH 2 - CH 2 - OH	117

Being similar in chemical properties and differing from each other in the composition of the molecules by a group of CH 2 atoms, these alcohols form a homologous series. Comparing the physical properties of alcohols, in this series, as well as in the series of hydrocarbons, we observe the transition of quantitative changes into qualitative changes. The general formula of alcohols in this series is R - OH (where R is a hydrocarbon radical).

Alcohols are known whose molecules contain several hydroxyl groups, for example:

Groups of atoms that determine the characteristic chemical properties of compounds, i.e., their chemical function, are called functional groups.

Alcohols are organic substances whose molecules contain one or more functional hydroxyl groups connected to a hydrocarbon radical .

In their composition, alcohols differ from hydrocarbons corresponding to them in the number of carbon atoms by the presence of oxygen (for example, C 2 H 6 and C 2 H 6 O or C 2 H 5 OH). Therefore, alcohols can be considered as products of partial oxidation of hydrocarbons.

Genetic relationship between hydrocarbons and alcohols

It is quite difficult to directly oxidize hydrocarbons into alcohol. In practice, it is easier to do this through a halogen derivative of a hydrocarbon. For example, to obtain ethyl alcohol starting from ethane C 2 H 6, you can first obtain ethyl bromide by the reaction:

and then convert ethyl bromide into alcohol by heating with water in the presence of alkali:

In this case, an alkali is needed to neutralize the resulting hydrogen bromide and eliminate the possibility of its reaction with alcohol, i.e. move this reversible reaction to the right.

In a similar way, methyl alcohol can be obtained according to the following scheme:

Thus, hydrocarbons, their halogen derivatives and alcohols are in a genetic connection with each other (relationship by origin).