DEFINITION
Alcohols– compounds containing one or more hydroxyl groups –OH associated with a hydrocarbon radical.
Depending on the number of hydroxyl groups, alcohols are divided into one- (CH 3 OH - methanol, 2 H 5 OH - ethanol), two- (CH 2 (OH)-CH 2 -OH - ethylene glycol) and trihydric (CH 2 (OH) -CH(OH)-CH 2 -OH - glycerol). Depending on which carbon atom the hydroxyl group is located at, primary (R-CH 2 -OH), secondary (R 2 CH-OH) and tertiary alcohols (R 3 C-OH) are distinguished. The names of alcohols contain the suffix – ol.
Monohydric alcohols
The general formula of the homologous series of saturated monohydric alcohols is C n H 2 n +1 OH.
Isomerism
Saturated monohydric alcohols are characterized by isomerism of the carbon skeleton (starting from butanol), as well as isomerism of the position of the hydroxyl group (starting from propanol) and interclass isomerism with ethers.
CH 3 -CH 2 -CH 2 -CH 2 -OH (butanol – 1)
CH 3 -CH (CH 3) - CH 2 -OH (2-methylpropanol - 1)
CH 3 -CH (OH) -CH 2 -CH 3 (butanol - 2)
CH 3 -CH 2 -O-CH 2 -CH 3 (diethyl ether)
Physical properties
Lower alcohols (up to C 15) are liquids, higher alcohols are solids. Methanol and ethanol are mixed with water in any ratio. As the molecular weight increases, the solubility of alcohols in alcohol decreases. Alcohols have high boiling and melting points due to the formation of hydrogen bonds.
Preparation of alcohols
The production of alcohols is possible using a biotechnological (fermentation) method from wood or sugar.
Laboratory methods for producing alcohols include:
- hydration of alkenes (the reaction occurs when heated and in the presence of concentrated sulfuric acid)
CH 2 = CH 2 + H 2 O → CH 3 OH
— hydrolysis of alkyl halides under the influence of aqueous solutions of alkalis
CH 3 Br + NaOH → CH 3 OH + NaBr
CH 3 Br + H 2 O → CH 3 OH + HBr
— reduction of carbonyl compounds
CH 3 -CH-O + 2[H] → CH 3 – CH 2 -OH
Chemical properties
1. Reactions that occur with the rupture of the O-H bond:
— the acidic properties of alcohols are very weakly expressed. Alcohols react with alkali metals
2C 2 H 5 OH + 2K → 2C 2 H 5 OK + H 2
but do not react with alkalis. In the presence of water, alcoholates are completely hydrolyzed:
C 2 H 5 OK + H 2 O → C 2 H 5 OH + KOH
This means that alcohols are weaker acids than water.
- formation of esters under the influence of mineral and organic acids:
CH 3 -CO-OH + H-OCH 3 ↔ CH 3 COOCH 3 + H 2 O
- oxidation of alcohols under the action of potassium dichromate or permanganate to carbonyl compounds. Primary alcohols are oxidized to aldehydes, which in turn can be oxidized to carboxylic acids.
R-CH 2 -OH + [O] → R-CH=O + [O] → R-COOH
Secondary alcohols are oxidized to ketones:
R-CH(OH)-R’ + [O] → R-C(R’)=O
Tertiary alcohols are more resistant to oxidation.
2. Reaction with breaking of the C-O bond.
- intramolecular dehydration with the formation of alkenes (occurs when alcohols with water-removing substances (concentrated sulfuric acid) are strongly heated):
CH 3 -CH 2 -CH 2 -OH → CH 3 -CH=CH 2 + H 2 O
— intermolecular dehydration of alcohols with the formation of ethers (occurs when alcohols are slightly heated with water-removing substances (concentrated sulfuric acid)):
2C 2 H 5 OH → C 2 H 5 -O-C 2 H 5 + H 2 O
— weak basic properties of alcohols manifest themselves in reversible reactions with hydrogen halides:
C 2 H 5 OH + HBr → C 2 H 5 Br + H 2 O
Examples of problem solving
EXAMPLE 1
| Exercise | Determine the molar mass and structure of the alcohol if it is known that when 7.4 g of this alcohol interacts with metallic sodium, 1.12 liters of gas (n.s.) are released, and when oxidized with copper(II) oxide, a compound is formed that gives the reaction “ silver mirror." |
| Solution | Let's create equations for the reactions of alcohol ROH with: a) sodium; b) oxidizing agent CuO: From equation (a), using the method of ratios, we determine the molar mass of the unknown alcohol: 7,4/2X = 1,12/22,4, X = M(ROH) = 74 g/mol. Alcohols C 4 H 10 O have this molar mass. Moreover, according to the conditions of the problem [equation (b)], these can be primary alcohols - butanol-1 CH 3 CH 2 CH 2 CH 2 OH or 2-methylpropanol-1 (CH 3) 2 CHSN 2 OH. |
| Answer | M(C 4 H 10 O) = 74 g/mol, this is 1-butanol or 2-methylpropanol-1 |
EXAMPLE 2
| Exercise | What volume (in l) of oxygen (n.s.) will be required for complete combustion of 31.25 ml of ethyl alcohol (density 0.8 g/ml) and how many grams of sediment will be obtained when passing the reaction products through lime water? |
| Solution | Let's find the mass of ethanol: m = × V= 0.8×31.25 = 25 g. The amount of substance corresponding to this mass: (C 2 H 5 OH) = m/M = 25/46 = 0.543 mol. Let us write the equation for the combustion reaction of ethanol: The volume of oxygen consumed during the combustion of ethanol: V(O 2) = 25 × 3 × 22.4/46 = 36.5 l. According to the coefficients in the reaction equation: (O 2) = 3 (C 2 H 5 OH) = 1.63 mol, (CO 2) = 2 (C 2 H 5 OH) = 1.09 mol. |
Student: Reu D.S. Course: 2 Groups: No. 25
Agroindustrial Lyceum No. 45
G. Velsk: 2011
Introduction
Alcohols are organic substances whose molecules contain one or more functional hydroxyl groups connected to a hydrocarbon radical.
They can therefore be considered as derivatives of hydrocarbons, in the molecules of which one or more hydrogen atoms are replaced by hydroxyl groups.
Depending on the number of hydroxyl groups, alcohols are divided into mono-, di-, trihydric, etc.
1. History of the discovery of alcohols
Ethyl alcohol, or rather, the intoxicating plant drink containing it, has been known to mankind since ancient times.
It is believed that at least 8000 BC, people were familiar with the effects of fermented fruits, and later, using fermentation, they obtained intoxicating drinks containing ethanol from fruits and honey. Archaeological finds indicate that winemaking existed in Western Asia as early as 5400-5000 BC. e., and in the territory of modern China, Henan Province, evidence was found of the production of “wine”, or rather fermented mixtures of rice, honey, grapes and, possibly, other fruits, in the early Neolithic era: from 6500 to 7000 BC. BC e.
For the first time, alcohol was obtained from wine in the 6th-7th centuries by Arab chemists, and the first bottle of strong alcohol (the prototype of modern vodka) was made by the Persian alchemist Ar-Razi in 860. In Europe, ethyl alcohol was obtained from fermentation products in the 11th-12th centuries, in Italy.
Alcohol first came to Russia in 1386, when the Genoese embassy brought it with them under the name “aqua vita” and presented it to the royal court.
In 1660, the English chemist and theologian Robert Boyle first obtained anhydrous ethyl alcohol, and also discovered some of its physical and chemical properties, in particular discovering the ability of ethanol to act as a high-temperature fuel for burners. Absolute alcohol was obtained in 1796 by the Russian chemist T. E. Lovitz.
In 1842, the German chemist J. G. Schil discovered that alcohols form a homologous series, differing by a certain constant amount. True, he was mistaken when he described it as C2H2. Two years later, another chemist Charles Gerard established the correct homological relation of CH2 and predicted the formula and properties of propyl alcohol, unknown in those years. In 1850, the English chemist Alexander Williamson, studying the reaction of alcoholates with ethyl iodide, established that ethyl alcohol is a derivative of water with one substituted hydrogen, experimentally confirming the formula C2H5OH. The synthesis of ethanol by the action of sulfuric acid on ethylene was first carried out in 1854 by the French chemist Marcelin Berthelot.
The first study of methyl alcohol was made in 1834 by French chemists Jean-Baptiste Dumas and Eugene Peligot; they called it "methyl or wood alcohol" because it was found in the products of dry distillation of wood. The synthesis of methanol from methyl chloride was carried out by the French chemist Marcelin Berthelot in 1857. He was the first to discover isopropyl alcohol in 1855 by treating propylene with sulfuric acid.
For the first time, tertiary alcohol (2-methyl-propan-2-ol) was synthesized in 1863 by the famous Russian scientist A. M. Butlerov, marking the beginning of a whole series of experiments in this direction.
Dihydric alcohol - ethylene glycol - was first synthesized by the French chemist A. Wurtz in 1856. Trihydric alcohol - glycerol - was discovered in natural fats back in 1783 by the Swedish chemist Carl Scheele, but its composition was discovered only in 1836, and the synthesis was carried out from acetone in 1873 by Charles Friedel.
2. Being in nature
Alcohols are most widely distributed in nature, especially in the form of esters, but they can also be found in a free state quite often.
Methyl alcohol is found in small quantities in some plants, for example: hogweed (Heracleum).
Ethyl alcohol is a natural product of alcoholic fermentation of organic products containing carbohydrates, often formed in sour berries and fruits without any human intervention. In addition, ethanol is a natural metabolite and is found in the tissues and blood of animals and humans.
Essential oils from the green parts of many plants contain “leaf alcohol,” which gives them their characteristic scent.
Phenylethyl alcohol is a fragrant component of rose essential oil.
Terpene alcohols are very widely represented in the plant world, many of which are aromatic substances
3. Physical properties
Ethyl alcohol (ethanol) C2H5OH is a colorless liquid that evaporates easily (boiling point 64.7 ºС, melting point - 97.8 ºС, optical density 0.7930). Alcohol containing 4-5% water is called rectified alcohol, and alcohol containing only a fraction of a percent of water is called absolute alcohol. Such alcohol is obtained by chemical treatment in the presence of water-removing agents (for example, freshly calcined CaO).
4. Chemical properties
Like all oxygen-containing compounds, the chemical properties of ethyl alcohol are determined primarily by functional groups and, to a certain extent, by the structure of the radical.
A characteristic feature of the hydroxyl group of ethyl alcohol is the mobility of the hydrogen atom, which is explained by the electronic structure of the hydroxyl group. Hence the ability of ethyl alcohol to undergo certain substitution reactions, for example, with alkali metals. On the other hand, the nature of the bond between carbon and oxygen is also important. Due to the greater electronegativity of oxygen compared to carbon, the carbon-oxygen bond is also somewhat polarized, with a partial positive charge on the carbon atom and a negative charge on the oxygen. However, this polarization does not lead to dissociation into ions; alcohols are not electrolytes, but are neutral compounds that do not change the color of indicators, but they have a certain electric dipole moment.
Alcohols are amphoteric compounds, that is, they can exhibit both the properties of acids and the properties of bases.
The physicochemical properties of alcohols are determined mainly by the structure of the hydrocarbon chain and the −OH functional group, as well as their mutual influence:
1) The larger the substituent, the more strongly it affects the functional group, reducing the polarity of the O-H bond. Reactions based on breaking this bond proceed more slowly.
2) The hydroxyl group –OH reduces the electron density along adjacent bonds of the carbon chain (negative inductive effect).
All chemical reactions of alcohols can be divided into three conditional groups associated with certain reaction centers and chemical bonds:
O−H bond cleavage;
Cleavage or addition at the C–OH bond;
Breaking the −COH bond.
5. Receipt and production
Until the early 30s of the 20th century, it was obtained exclusively by fermenting carbohydrate-containing raw materials and by processing grain (rye, barley, corn, oats, millet). In the 30s to 50s, several methods of synthesis from chemical raw materials were developed
The reaction begins with a hydrogen ion attacking the carbon atom that is bonded to a larger number of hydrogen atoms and is therefore more electronegative than the neighboring carbon. After this, water is added to the neighboring carbon, releasing H+. This method is used to prepare ethyl, sec-propyl and tert-butyl alcohols on an industrial scale.
To obtain ethyl alcohol, various sugary substances have long been used, for example, grape sugar, or glucose, which is converted into ethyl alcohol by “fermentation” caused by the action of enzymes produced by yeast fungi.
Alcohols can be obtained from a wide variety of classes of compounds, such as hydrocarbons, alkyl halides, amines, carbonyl compounds, epoxides. There are many methods for producing alcohols, among which we highlight the most common:
oxidation reactions - based on the oxidation of hydrocarbons containing multiple or activated C−H bonds;
reduction reactions - reduction of carbonyl compounds: aldehydes, ketones, carboxylic acids and esters;
hydration reactions - acid-catalyzed addition of water to alkenes (hydration);
addition reactions;
substitution reactions (hydrolysis) - nucleophilic substitution reactions in which existing functional groups are replaced by a hydroxyl group;
syntheses using organometallic compounds;
6. Application
Ethyl alcohol is widely used in various fields of industry, primarily in the chemical industry. Synthetic rubber, acetic acid, dyes, essences, photographic film, gunpowder, and plastics are obtained from it. Alcohol is a good solvent and antiseptic. Therefore, it is used in medicine.
The main alcohol used for medicinal purposes is ethanol. It is used as an external antiseptic and irritant for preparing compresses and rubdowns. Ethyl alcohol is even more widely used for the preparation of various tinctures, dilutions, extracts and other dosage forms.
Alcohols are quite widely used as fragrant substances for compositions in the perfumery and cosmetics industry.
In the food industry, the widespread use of alcohols is well known: the basis of all alcoholic drinks is ethanol, which is obtained by fermenting food raw materials - grapes, potatoes, wheat and other starch or sugar-containing products. In addition, ethyl alcohol is used as a component (solvent) of some food and aromatic essences (flavors), widely used in cooking, in baking confectionery, in the production of chocolate, sweets, drinks, ice cream, preserves, jellies, jams, confitures, etc.
Alcohols.
Alcohols are hydrocarbon derivatives in whose molecules one or more hydrogen atoms are replaced by hydroxyl groups (OH).
So methyl alcohol CH 3 -OH is a hydroxyl derivative methane CH 4, ethanol C 2 H 5 -OH– derivative ethane.
The name of alcohols is formed by adding the ending “- ol» to the name of the corresponding hydrocarbon (methanol, ethanol, etc.)
Derivatives of aromatic hydrocarbons with the group HE in the benzene ring are called phenols.
Properties of alcohols.
Like water molecules, molecules of lower alcohols are linked to each other by hydrogen bonds. For this reason, the boiling point of alcohols is higher than the boiling point of the corresponding hydrocarbons.
A common property of alcohols and phenols is the mobility of the hydrogen of the hydroxyl group. When alcohol is exposed to an alkali metal, this hydrogen is displaced by the metal and solid, alcohol-soluble compounds called alcoholates.
Alcohols react with acids to form esters.
Alcohols are much more easily oxidized than the corresponding hydrocarbons. In this case, aldehydes And ketones.
Alcohols are practically not electrolytes, i.e. do not conduct electric current.
Methyl alcohol.
Methyl alcohol(methanol) CH 3 OH– colorless liquid. It is very poisonous: taking small doses by mouth causes blindness, and large doses cause death.
Methyl alcohol is produced in large quantities by synthesis from carbon monoxide and hydrogen at high pressure ( 200-300 atm.) and high temperature ( 400 deg C) in the presence of a catalyst.
Methyl alcohol is formed by dry distillation of wood; therefore it is also called wood alcohol.
It is used as a solvent and also for the production of other organic substances.
Ethanol.
Ethanol(ethanol) C 2 H 5 OH– one of the most important starting materials in the modern organic synthesis industry.
To obtain it, various sugary substances have long been used, which are converted into ethyl alcohol through fermentation. Fermentation is caused by the action of enzymes (enzymes) produced by yeast fungi.
Grape sugar or glucose is used as sugary substances:
Free glucose is found, for example, in grape juice, during fermentation of which it turns out grape wine with an alcohol content of 8 to 16%.
The starting product for producing alcohol can be a polysaccharide starch, contained, for example, in potato tubers, rye grains, wheat, corn. To convert it into sugary substances (glucose), starch is first subjected to hydrolysis.
Currently, another polysaccharide is also subjected to saccharification - pulp(fiber), forming the main mass wood. Cellulose (eg. sawdust) are also preliminarily subjected to hydrolysis in the presence of acids. The product thus obtained also contains glucose and is fermented into alcohol using yeast.
Finally, ethyl alcohol can be obtained synthetically from ethylene. The net reaction is the addition of water to ethylene.
The reaction occurs in the presence of catalysts.
Polyhydric alcohols.
So far we have considered alcohols with one hydroxyl group ( HE). Such alcohols are called alcohols.
But alcohols are also known whose molecules contain several hydroxyl groups. Such alcohols are called polyhydric.
Examples of such alcohols are the dihydric alcohol ethylene glycol and the trihydric alcohol glycerin:
Ethylene glycol and glycerin are sweetish-tasting liquids that can be mixed with water in any ratio.
Use of polyhydric alcohols.
Ethylene glycol used as a component of the so-called antifreeze, i.e. substances with a low freezing point that replace water in radiators of automobile and aircraft engines in winter.
Also, ethylene glycol is used in the production of cellophane, polyurethanes and a number of other polymers, as a solvent for dyes, and in organic synthesis.
Application area glycerin diverse: food industry, tobacco production, medical industry, production of detergents and cosmetics, agriculture, textile, paper and leather industries, plastics production, paint and varnish industry, electrical engineering and radio engineering.
Glycerin belongs to the group stabilizers. At the same time, it has the properties of maintaining and increasing the degree of viscosity of various products, and thus changing their consistency. Registered as a food additive E422, and is used as emulsifier, with the help of which various immiscible mixtures are mixed.
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. 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:
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.
- Isomerism of the carbon skeleton, starting with C 3
CH 3 –CH 2 –CH 2 –OH CH 3 –CH–OH
propanol 2-methylethanol
- 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.
- 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
- 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.
Alcohols(or alkanols) are organic substances whose molecules contain one or more hydroxyl groups (-OH groups) connected to a hydrocarbon radical.
Classification of alcohols
According to the number of hydroxyl groups(atomicity) alcohols are divided into:
Monatomic, For example: 
Diatomic(glycols), for example:
Triatomic, For example: 
According to the nature of the hydrocarbon radical The following alcohols are released:
Limit containing only saturated hydrocarbon radicals in the molecule, for example: 
Unlimited containing multiple (double and triple) bonds between carbon atoms in the molecule, for example:
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, for example:
Organic substances containing hydroxyl groups in the molecule, connected directly to the carbon atom of the benzene ring, differ significantly in chemical properties from alcohols and therefore are classified as an independent class of organic compounds - phenols.
For example:
There are also polyhydric (polyhydric alcohols) containing more than three hydroxyl groups in the molecule. For example, the simplest hexahydric alcohol hexaol (sorbitol)
Nomenclature and isomerism of alcohols
When forming the names of alcohols, a (generic) suffix is added to the name of the hydrocarbon corresponding to the alcohol. ol.
The numbers after the suffix indicate the position of the hydroxyl group in the main chain, and the prefixes di-, tri-, tetra- etc. - their number:
In the numbering of carbon atoms in the main chain, the position of the hydroxyl group takes precedence over the position of multiple bonds:
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:
Let's give a name to the alcohol, the formula of which is given below:
Name construction order:
1. The carbon chain is numbered from the end closest to the –OH group.
2. The main chain contains 7 C atoms, which means the corresponding hydrocarbon is heptane.
3. The number of –OH groups is 2, the prefix is “di”.
4. Hydroxyl groups are located at 2 and 3 carbon atoms, n = 2 and 4.
Alcohol name: heptanediol-2,4
Physical properties of alcohols
Alcohols can form hydrogen bonds both between alcohol molecules and between alcohol and water molecules. Hydrogen bonds arise from the interaction of a partially positively charged hydrogen atom of one alcohol molecule and a partially negatively charged oxygen atom of another molecule. It is thanks to hydrogen bonds between molecules that alcohols have abnormally high boiling points 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 it is a liquid.
The lower and middle members of a series of saturated monohydric alcohols containing from 1 to 11 carbon atoms are liquids. Higher alcohols (starting from C12H25OH) at room temperature - solids. Lower alcohols have an alcoholic odor and a pungent taste; they are highly soluble in water. As the carbon radical increases, the solubility of alcohols in water decreases, and octanol no longer mixes with water.
Chemical properties of alcohols
The properties of organic substances are determined by their composition and structure. Alcohols confirm the general rule. Their molecules include hydrocarbon and hydroxyl groups, so the chemical properties of alcohols are determined by the interaction of these groups with each other.
The properties characteristic of this class of compounds are due to the presence of a hydroxyl group.
- 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)
- Interaction of alcohols with hydrogen halides. Substitution of a hydroxyl group with a halogen leads to the formation of haloalkanes. For example:
This reaction is reversible. - Intermolecular dehydrationalcohols- splitting off 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. Thus, when ethyl alcohol is heated with sulfuric acid to a temperature of 100 to 140°C, diethyl (sulfur) ether is formed. - 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, when ethyl alcohol and acetic acid react, ethyl acetate is formed:
- 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:
- Oxidation of alcohols usually carried out with strong oxidizing agents, for example, 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:
The oxidation of secondary alcohols produces ketones: 
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. - 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:
- Qualitative reaction to polyhydric alcohols.
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. For ethylene glycol we can write:
Monohydric alcohols are not able to enter into this reaction. Therefore, it is a qualitative reaction to polyhydric alcohols.
Preparation of alcohols:
Use of alcohols
Methanol(methyl alcohol CH 3 OH) 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 ways of its production by distilling hard wood (Greek methy - wine, get drunk; hule - substance, wood).
Methanol 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 C 2 H 5 OH) 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.
Prolactriol-1,2,3(glycerin) 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.