Physical properties

METHANOL (wood alcohol) is a liquid (t boil = 64.5; t pl = -98; ρ = 0.793 g/cm 3), with the smell of alcohol, soluble in water. Poisonous– causes blindness, death occurs from paralysis of the upper respiratory tract.

ETHANOL (wine alcohol) is a non-colored liquid with the smell of alcohol, mixes well with water.

The first representatives of the homologous series of alcohols are liquids, the higher ones are solids. Methanol and ethanol are mixed with water in any ratio. As the molecular weight increases, the solubility of alcohols in water decreases. Higher alcohols are practically insoluble in water.

In chemical reactions of hydroxy compounds, destruction of one of two bonds is possible:

C–OH with elimination of the OH group

O–H with hydrogen abstraction

These could be reactions substitution, in which OH or H is replaced, or the reaction splitting off(elimination) when a double bond is formed.

The polar nature of the C–O and O–H bonds contributes to their heterolytic cleavage and the occurrence of reactions along ionic mechanism. When the O–H bond is broken with the elimination of a proton (H+), the acidic properties of the hydroxy compound appear, and when the C–O bond is broken, the properties of a base and a nucleophilic reagent appear.

With the rupture of the O–H bond, oxidation reactions occur, and with the C–O bond, reduction reactions occur.

Thus, hydroxy compounds can undergo numerous reactions, yielding different classes of compounds. Due to the availability of hydroxyl compounds, especially alcohols, each of these reactions is one of the best ways to obtain certain organic compounds.

I. Acid-base

R.O. — + H + ↔ ROH ↔ R + + OH —

alcoholate ion

Acid properties decrease in the series, and basic properties increase:

HOH → R-CH 2 -OH → R 2 CH-OH → R 3 C-OH water primary secondary tertiary

Acid properties

With active alkali metals:

2C 2 H 5 OH + 2 Na → 2 C 2 H 5 ONa+H2

sodium ethoxide

Alcohols undergo hydrolysis, which proves that water has stronger acidic properties.

C 2 H 5 ONa + H 2 O ↔ C 2 H 5 OH + NaOH

Basic properties

With hydrohalic acids:

C 2 H 5 OH + HBr H2SO4( conc. ) ↔ C2H5Br+H2O

bromoethane

The ease of the reaction depends on the nature of the hydrogen halide and alcohol - an increase in reactivity occurs in the following series:

HF< HCl < HBr < HI

primary< вторичные < третичные

II. Oxidation

1). In the presence of oxidizing agents [O] – K 2 Cr 2 O 7 orKMnO 4 alcohols are oxidized to carbonyl compounds:

Primary alcohols upon oxidation form aldehydes, which are then easily oxidized to carboxylic acids.

The oxidation of secondary alcohols produces ketones.

Tertiary alcohols are more resistant to oxidizing agents. They oxidize only under harsh conditions (acidic environment, elevated temperature), which leads to the destruction of the carbon skeleton of the molecule and the formation of a mixture of products (carboxylic acids and ketones with lower molecular weight).

In an acidic environment:

For primary and secondary monohydric alcohols, the qualitative reaction is their interaction with an acidic solution of potassium dichromate. The orange color of the hydrated Cr 2 O 7 2- ion disappears and a greenish color characteristic of the Cr 3+ ion appears. This color change makes it possible to detect even trace amounts of alcohols.

CH 3 - OH + K 2 Cr 2 O 7 + 4H 2 SO 4 → CO 2 + K 2 SO 4 + Cr 2 (SO 4) 3 + 6H 2 O

3CH 3 -CH 2 -OH + K 2 Cr 2 O 7 + 4H 2 SO 4 → 3CH 3 COH + K 2 SO 4 + Cr 2 (SO 4) 3 + 7H 2 O

Under more severe conditions, the oxidation of primary alcohols proceeds directly to carboxylic acids:

3CH 3 -CH 2 -OH + 2K 2 Cr 2 O 7 + 8H 2 SO 4 t → 3CH 3 COOH + 2K 2 SO 4 + 2Cr 2 (SO 4) 3 + 11H 2 O

Tertiary alcohols are resistant to oxidation in alkaline and neutral environments. Under harsh conditions (when heated, in an acidic environment), they are oxidized with the cleavage of C-C bonds and the formation of ketones and carboxylic acids.

In a neutral environment:

CH 3 – OH + 2 KMnO 4 → K 2 CO 3 + 2 MnO 2 + 2 H 2 O, and the remaining alcohols to salts of the corresponding carboxylic acids.

2). Qualitative reaction to primary alcohols!

3). Combustion(with an increase in the mass of the hydrocarbon radical, the flame becomes more and more smoky)

C n H 2n+1 -OH + O 2 t→ CO 2 + H 2 O + Q

III.Elimination reactions

1) Intramolecular dehydration

CH 3 -CH 2 -CH(OH)-CH 3 t>140,H2SO4( To ) → CH 3 -CH=CH-CH 3 + H 2 O

butanol-2 butene-2

dehydration occurs predominantly in direction I, i.e. By Zaitsev's rule– with the formation of a more substituted alkene. Zaitsev's rule : Hydrogen is removed from the least hydrogenated carbon atom adjacent to the hydroxyl-bearing carbon.

2) Intermolecular dehydration

2C2H5OH t<140,H2SO4( To ) → WITH 2 H5-O-C2H5+H2O

ether

— when moving from primary to tertiary alcohols, the tendency to eliminate water and form alkenes increases; the ability to form ethers decreases.

3) Reaction of dehydrogenation and dehydration of saturated monohydric alcohols – reaction of S.V. Lebedeva

2C2H5OH 425,ZnO,Al2O3→ CH 2 =CH-CH=CH 2 + H 2 + 2H 2 O

IV.Esterification reactions

Alcohols react with mineral and organic acids, forming esters. The reaction is reversible (the reverse process is hydrolysis of esters).

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 COH - 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, 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 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 through 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 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 in 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, 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).

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 of 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 that of other 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.

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 of 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, and dissolves well many inorganic and organic substances. 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. Therefore, the structural formula of ethyl alcohol is:

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. The high calorific value of 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).

Along with hydrocarbons C A N V, which contain two types of atoms - C and H, oxygen-containing organic compounds of type C are known A N V ABOUT With. In Topic 2 we will look at oxygen-containing compounds that differ:
1) the number of O atoms in the molecule (one, two or more);
2) the multiplicity of the carbon–oxygen bond (single C–O or double C=O);
3) the type of atoms connected to oxygen (C–O–H and C–O–C).

Lesson 16.
Monohydric saturated alcohols

Alcohols are derivatives of hydrocarbons with the general formula ROH, where R is a hydrocarbon radical. The formula of an alcohol is obtained from the formula of the corresponding alkane by replacing the H atom with an OH group: RH ROH.
The chemical formula of alcohols can be derived differently, including the oxygen atom O between the atoms
C–H of a hydrocarbon molecule:

RH ROH, CH 3 –H CH 3 –O–H.

The hydroxyl group OH is alcohol functional group. That is, the OH group is a feature of alcohols; it determines the main physical and chemical properties of these compounds.

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

Names of alcohols obtained from the names of hydrocarbons with the same number of C atoms as in alcohol by adding the suffix - ol-. For example:

The name alcohols as derivatives of the corresponding alkanes is characteristic of compounds with a linear chain. The position of the OH group in them is at the outer or inner atom
C – indicated with a number after the name:

The names of alcohols - derivatives of branched hydrocarbons - are compiled in the usual way. Select the main carbon chain, which must include a C atom connected to an OH group. The C atoms of the main chain are numbered so that the carbon with the OH group receives a lower number:

The name is compiled starting with a number indicating the position of the substituent in the main carbon chain: “3-methyl...” Then the main chain is named: “3-methylbutane...” Finally, the suffix is ​​added - ol-(name of the OH group) and the number indicates the carbon atom to which the OH group is bonded: “3-methylbutanol-2.”
If there are several substituents on the main chain, they are listed sequentially, indicating the position of each with a number. Repeating substituents in the name are written using the prefixes “di-,” “tri-,” “tetra-,” etc. For example:

Isomerism of alcohols. Alcohol isomers have the same molecular formula, but a different order of connection of atoms in the molecules.
Two types of isomerism of alcohols:
1) carbon skeleton isomerism;
2)isomerism of the position of the hydroxyl group in the molecule.
Let us present the alcohol isomers C 5 H 11 OH of these two types in linear-angular notation:

According to the number of C atoms bonded to the alcohol (–C–OH) carbon, i.e. neighboring alcohols are called primary(one neighbor C), secondary(two C) and tertiary(three C-substituents at carbon –C–OH). For example:

Task. Compose one isomer of alcohols with the molecular formula C 6 H 13 OH with a main carbon chain:

a) C 6, b) C 5, V) C 4, G) C 3

and name them.

Solution

1) We write down the main carbon chains with a given number of C atoms, leaving space for H atoms (we will indicate them later):

a) С–С–С–С–С–С; b) С–С–С–С–С; c) S–S–S–S; d) S–S–S.

2) We arbitrarily select the place of attachment of the OH group to the main chain and indicate carbon substituents at the internal C atoms:

In example d) it is not possible to place three CH 3 substituents at the C-2 atom of the main chain. Alcohol C 6 H 13 OH does not have isomers with a three-carbon main chain.

3) We arrange the H atoms at the carbons of the main chain of isomers a)–c), guided by the valence of carbon C(IV), and name the compounds:

EXERCISES.

1. Underline the chemical formulas of saturated monohydric alcohols:

CH 3 OH, C 2 H 5 OH, CH 2 = CH CH 2 OH, CH CH 2 OH, C 3 H 7 OH,

CH 3 CHO, C 6 H 5 CH 2 OH, C 4 H 9 OH, C 2 H 5 OC 2 H 5, HOCH 2 CH 2 OH.

2. Name the following alcohols:

3. Make up structural formulas based on the names of alcohols: a) hexanol-3;
b) 2-methylpentanol-2; c) n-octanol; d) 1-phenylpropanol-1; e) 1-cyclohexylethanol.

4. Compose the structural formulas of isomers of alcohols with the general formula C 6 H 13 OH :
a) primary; b) secondary; c) tertiary.Name these alcohols.

5. Using the linear-angular (graphical) formulas of the compounds, write down their structural formulas and give names to the substances:

Lesson 17. Preparation of alcohols

Low molecular alcohols - methanol CH 3 OH, ethanol C 2 H 5 OH, propanol C 3 H 7 OH, and isopropanol (CH 3) 2 CHOH - are colorless mobile liquids with a specific alcoholic odor. High boiling points: 64.7 °C – CH 3 OH, 78 °C – C 2 H 5 OH, 97 °C – n-C 3 H 7 OH and 82 °C – (CH 3) 2 CHOH – are due to intermolecular hydrogen bond, existing in alcohols. Alcohols C (1) – C (3) are mixed with water (dissolved) in any ratio. These alcohols, especially methanol and ethanol, are the most widely used in industry.

1. Methanol synthesized from water gas:

2. Ethanol get ethylene hydration(by adding water to C 2 H 4):

3. Another way to receive ethanol – fermentation of sugary substances under the action of yeast enzymes. The process of alcoholic fermentation of glucose (grape sugar) has the form:

4. Ethanol get from starch, and made of wood(cellulose) by hydrolysis to glucose and subsequent fermentation into alcohol:

5. Higher alcohols get from halogenated hydrocarbons by hydrolysis under the influence of aqueous solutions of alkalis:

Task.How to get 1-propanol from propane?

Solution

Of the five methods for producing alcohols proposed above, none of them considers the production of alcohol from an alkane (propane, etc.). Therefore, the synthesis of 1-propanol from propane will include several stages. According to method 2, alcohols are obtained from alkenes, which in turn are available by dehydrogenation of alkanes. The process diagram is as follows:

Another scheme for the same synthesis is one step longer, but it is easier to implement in the laboratory:

The addition of water to propene at the last stage proceeds according to Markovnikov’s rule and leads to a secondary alcohol - propanol-2. The task requires you to obtain 1-propanol. Therefore, the problem is not solved, we are looking for another way.
Method 5 consists of hydrolysis of haloalkanes. The necessary intermediate for the synthesis of 1-propanol, 1-chloropropane, is obtained as follows. Chlorination of propane gives a mixture of 1- and 2-monochloropropanes:

1-chloropropane is isolated from this mixture (for example, using gas chromatography or due to different boiling points: for 1-chloropropane t kip = 47 °C, for 2-chloropropane t kip = 36 °C). By treating 1-chloropropane with aqueous alkali KOH or NaOH, the target propanol-1 is synthesized:

Please note that the interaction of the same substances: CH 3 CH 2 CH 2 Cl and KOH - depending on the solvent (alcohol C 2 H 5 OH or water) leads to different products - propylene
(in alcohol) or propanol-1 (in water).

EXERCISES.

1. Give reaction equations for the industrial synthesis of methanol from water gas and ethanol by ethylene hydration.

2. Primary alcohols RCH 2 OH prepared by hydrolysis of primary alkyl halides RCH 2 Hal, and secondary alcohols are synthesized by hydration of alkenes. Complete the reaction equations:

3. Suggest methods for producing alcohols: a) butanol-1; b) butanol-2;
c) pentanol-3, starting from alkenes and alkyl halides.

4. During enzymatic fermentation of sugars, along with ethanol, a mixture of primary alcohols is formed in small quantities C 3 – C 5 – fusel oil. The main component in this mixture is isopentanol.(CH 3) 2 CHCH 2 CH 2 OH, minor components – n-C 3 H 7 OH, (CH 3) 2 CHCH 2 OH and CH 3 CH 2 CH(CH 3)CH 2 OH. Name these “fusel” alcohols according to the IUPAC nomenclature. Write an equation for the fermentation reaction of glucose C 6 H 12 O 6, in which all four impurity alcohols would be obtained in a molar ratio of 2:1:1:1, respectively. Enter gas CO 2 to the right side of the equation in the amount of 1/3 mol of all initial atoms WITH , as well as the required number of molecules H 2 O.

5. Give the formulas of all aromatic alcohols of the composition C 8 H 10 O. (In aromatic alcohols the group HE removed from the benzene ring by one or more atoms WITH:
C 6 H 5 – (CH 2)n – HE.)

Answers to exercises for topic 2

Lesson 16

1. The chemical formulas of saturated monohydric alcohols are underlined:

CH 3 HE, WITH 2 N 5 HE, CH 2 = CHCH 2 OH, CHCH 2 OH, WITH 3 N 7 HE,

CH 3 CHO, C 6 H 5 CH 2 OH, WITH 4 N 9 HE, C 2 H 5 OS 2 H 5 , HOCH 2 CH 2 OH.

2. Names of alcohols by structural formulas:

3. Structural formulas by alcohol names:

4. Isomers and names of alcohols of the general formula C 6 H 13 OH:

5. Structural formulas and names compiled from graphical connection diagrams: