Not a single holiday is complete without alcoholic drinks. And, of course, everyone knows that any strong drink contains drinking ethyl alcohol. It is this substance that brings a person a feeling of pleasant euphoria and relaxation and the most severe symptoms of intoxication in case of its excessive use. But some alcohol brings death with it.
This is due to the production of surrogate alcohol, which uses not ethyl alcohol, but methyl alcohol, a toxic and extremely poisonous product. Both types of connections are practically no different in appearance, the only difference is their chemical composition. Let's figure out what the formula of drinking alcohol is in chemistry and what is the difference between it and methyl alcohol.
To avoid fatal poisoning, you should distinguish ethyl alcohol from methyl alcohol
The origins of acquaintance with alcohol go back to the legendary biblical past. Noah, having tasted fermented grape juice, experienced the feeling of a hangover for the first time. It is from this moment that the triumphal procession begins alcoholic products, the development of wine culture and numerous alcohol experiments.
Spiritus vini is the name given to drinking alcohol, which was created by distillation. That is, the distillation and evaporation of a liquid, followed by the deposition of vapor into a liquid form.
The ethanol formula was established in 1833
The starting point for winemaking and alcohol production was the 14th century.. It was from this time that the production of the “magic” liquid began in various countries with the creation and development of numerous techniques. The important stages in the spread of ethanol, as drinking alcohol is scientifically called, and its development include the following years:
- XIV century (30s). Wine alcohol was first discovered by the French alchemist Arnaud de'Villger, and the scientist was able to isolate it from wine.
- XIV century (80s). An Italian merchant introduced the ethyl alcohol compound to the ancient Slavs, bringing this substance to Moscow.
- XVI century (20s). The legendary Swiss doctor and alchemist Paracelsus began to study the properties of ethanol and discovered its main ability - to put people to sleep.
- XVIII century. For the first time, the hypnotic properties of ethyl alcohol were tested on humans. With his help, a patient who was being prepared for a complex operation was euthanized for the first time.
From that moment on, the rapid growth of the alcohol-vodka industry began. In our country alone, until the beginning of the revolution, more than 3,000 alcohol factories were actively operating. True, during the Second World War their number decreased sharply, by almost 90%. The revival began only in the late 40s of the last century. They began to remember ancient technologies and develop new ones.
Types of alcohol
Alcohol has many different modifications. Some types of alcohol come into close contact with food technologies, others are poisonous. To know their action and influence on the human body, you should understand their main characteristics.
Food (or drinking)
Or ethyl alcohol. It is obtained by rectification (the process of separating multicomponent mixtures using heat exchange between liquid and steam). The raw materials for its preparation are taken different kinds grains The chemical formula of drinking ethyl alcohol is as follows: C2H5OH.
How does ethyl alcohol work?
Food alcohol, which is part of alcohol, is perceived in most cases as vodka. It is precisely this that many individuals abuse, leading themselves to persistent alcohol dependence.
Food ethanol also has its own varieties (they depend on the types of raw materials that were used). The classification of drinking alcohol has the following types:
First grade alcohol (or medicinal)
It is not used to produce alcoholic beverages. This compound is intended for use exclusively for medical purposes as an antiseptic, disinfection of operating rooms and surgical instruments.
Alpha
Alcohol compound premium. For its production, selected high-quality wheat or rye is taken. It is on the basis of Alpha alcohol that elite super-premium alcoholic drinks are produced. For example:
- Bacardi rum;
- Absolut vodka;
- Jack Daniels whiskey;
- Johnnie Walker whiskey.
Lux
For the production of drinking ethanol this level use potatoes and grain, taking into account that the output volume of potato starch should not exceed 35%. The alcohol compound is passed through several stages of filtration. Premium vodka is produced from it. Such as:
- Husky;
- Rainbow;
- Beluga;
- Mammoth;
- Nemiroff;
- Stolichnaya;
- Russian gold;
- Russian standard.
These vodka drinks have several degrees of protection. They have a special bottle shape, specially designed holograms, and a unique cap.
How to check the quality of vodka products
Extra
On its basis, classic and familiar vodka of the mid-price segment is made. This drinking alcohol is diluted (its strength in undiluted form is about 95%) and, in addition, is subjected to additional purification. The final product has a lower content of esters and methanol. Alcohol based on this compound is considered environmentally friendly pure product, however, not as expensive as alcohol based on Alpha or Lux.
Basis
Practically not inferior to vodka ethanols Extra and Alpha. It has the same high strength (about 95%). Vodka made from this drinking alcohol is the most popular product, as it is the most accessible (average price segment market). This brand of alcohol is produced from potatoes and grain, taking into account that the volume of potato starch in the resulting product does not exceed 60%.
Ethyl alcohol is widely used in medicine
Alcohol of the highest purification category
It is made from a mixture of the following products:
- corn;
- potato;
- molasses;
- sugar beet.
This connection is technological process undergoes minimal processing and filtering from various impurities and fusel oils. It is used to make cheap economy-class vodka, various tinctures and liqueurs.
Methyl alcohol (or technical)
A colorless, transparent substance, similar in smell to classic ethanol. But, unlike the latter, methanol is a highly toxic compound. The chemical formula of methanol (or wood alcohol) is CH3OH. If it enters the human body, this compound causes acute poisoning. A fatal outcome cannot be ruled out.
What is methyl alcohol
According to statistics, about 1,500 cases of methyl alcohol poisoning are diagnosed annually. Every fifth intoxication resulted in the death of a person.
Methyl alcohol has nothing to do with the production of alcoholic beverages and the food industry. But surrogate alcohol is often diluted with this cheap product in order to reduce the cost of the resulting product. When interacting with organic structures, methanol turns into a terrible poison, which has already destroyed many lives.
How to distinguish alcohols
It is extremely difficult to distinguish poisonous industrial alcohol from drinking alcohol. It is for this reason that cases of fatal poisoning occur. When, under the guise of ethanol, methanol is used to prepare alcoholic beverages.
But it is still possible to distinguish alcohol compounds. There are simple ways to do this that you can apply at home.
- With the help of fire. This is the easiest verification method. Just set fire to an alcoholic drink. Ethanol burns with a blue flame when burned, but the color of burning methanol is green.
- Using potatoes. Pour alcohol over a piece of raw potato and leave for 2-3 hours. If the color of the vegetable has not changed, the vodka is of excellent quality and can be safely consumed for its intended purpose. But in the case when the potatoes have acquired a pinkish tint, this is a consequence of the presence of industrial alcohol in the alcohol.
- Using copper wire. The wire should be heated red-hot and lowered into the liquid. If there is a pungent, repulsive odor when it fizzes, there is methanol in the alcohol. Ethyl alcohol will not smell at all.
- Measuring the boiling point. Should be using regular thermometer measure the boiling point of alcohols. Please note that methanol boils at +64⁰С, and ethanol – at +78⁰С.
- Using soda and iodine. Pour the alcohol to be tested into a transparent container. Add a pinch to it regular soda. Stir well and add iodine to it. Now hold the liquid up to the light. If there is sediment in it, this is evidence of the “purity” of the alcohol. Ethanol, when interacting with iodoform (iodine + soda), gives a yellowish suspension. But methanol does not change at all and remains transparent.
- Using potassium permanganate. Add a few crystals of potassium permanganate to the alcohol being tested. Once it dissolves and the liquid turns pink, heat it. If gas bubbles begin to be released when heated, you have poisonous methyl alcohol.
But it is worth considering that all these and similar household methods will not work if technical alcohol is initially mixed with ethanol in one product. In this case, only chemical examination can help. And a responsible approach to purchasing alcohol.
If assistance is not provided, death from methanol poisoning occurs after 2-3 hours
To avoid purchasing potentially dangerous alcohol, buy alcohol only in trusted places and specialized stores that inspire trust. Avoid underground shops and small stalls. This is where counterfeit products often spread.
Ways to use ethanol
Ethyl alcohol is used not only in the beloved alcohol industry. Its uses are varied and quite interesting. Check out just a few of the major uses for ethanol:
- fuel (rocket internal combustion engines);
- chemical (base for the manufacture of many different drugs);
- perfumery (when creating various perfume compositions and concentrates);
- paint and varnish (as a solvent, included in antifreeze, detergent household chemicals, windshield washers);
- food (except for the production of alcohol, it is successfully used in the production of vinegar and various flavorings);
- medicine (the most popular area of application, as an antiseptic for disinfecting wounds, with artificial ventilation lungs as an antifoam, included in anesthesia and anesthesia, various medicinal tinctures, antibiotics and extracts).
By the way, ethyl alcohol is also used as an antidote for methanol poisoning. This is an effective antidote in case of industrial alcohol intoxication. It would be useful to recall the main signs of poisoning by alcohol surrogates:
- severe headache;
- profuse debilitating vomiting;
- piercing pain in the abdomen;
- feeling of complete weakness, immobility;
- respiratory depression, a person sometimes cannot even take a breath.
By the way, you can encounter exactly the same symptoms in the case of ordinary alcohol intoxication. Therefore, you should pay attention to the amount of alcohol consumed. Industrial alcohol causes the development of this symptomatology when it enters the human body even in small quantities (from 30 ml, this is the standard volume of an ordinary glass).
In this case, you should immediately call Ambulance. Remember that if qualified assistance is not provided, the risk of death is very high.
To summarize, we can understand that being able to understand the types of alcohol and distinguish a toxic compound from drinking ethanol is very important. Do not forget that even if you consume a tiny amount of toxic methanol, you are putting your life at risk and bringing your body to a fatal point.
These are derivatives of hydrocarbons in which one hydrogen atom is replaced by a hydroxy group. General formula alcohols - 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.
The next class of substances that I would like to consider are alcohols. These are compounds that contain an -OH group bonded to a carbon atom. Such a group is monovalent and any alkane can be converted into an alcohol by replacing one of the hydrogens with OH. For example, methane corresponds to methyl alcohol, ethane - ethyl alcohol, and so on. They are also abbreviated with the ending “ol”: methanol, ethanol, propanol.
Methanol, ethanol, propanol
Starting with propanol, alcohols exhibit isomerism - in addition to the fact that alkanes themselves have isomers, the hydroxyl group can also be attached to different carbon atoms. For example, the name “butanol” already corresponds to 4 molecules of different structure.
Four isomeric butyl alcohols: n-butanol, sec-butanol, tert-butanol, isobutanol.
As you can see, the alcohol that retains a linear structure is called “normal” by analogy with alkanes. Such alcohols are also primary alcohols because the carbon atom connected to the hydroxyl group is directly connected to only one carbon atom. There are also secondary and tertiary alcohols (the two middle structures in the picture).
Alcohols are somewhat similar in properties to water: water also contains hydroxyl (that’s what the -OH group is called), but bonded to a hydrogen atom (therefore it can be called hydrogen hydroxide, although no one does that). Thanks to hydroxyl groups, the molecules are more strongly bonded to each other (due to hydrogen bonds), so even the lowest alcohol - methanol - is a liquid, albeit one that evaporates quite easily. Almost all lower alcohols, up to octanol, are liquid. Again, complexity arises here due to the large number of isomers.
General formula of alcohols C n H 2n+1 OH.
The most famous of the alcohols is ethanol, also known as ethyl alcohol - the same one found in alcoholic drinks. It boils at 78 and can be isolated from solution by distillation, but the concentration cannot be raised above 96% in this way (which does not, however, prevent one from obtaining 100% ethanol in other ways, for example, by removing water from 96% ethanol using a desiccant) . Surely everyone has heard about methanol, which is indistinguishable from ethanol in appearance and smell, but is deadly poisonous. However, without tasting it, methanol is an excellent solvent, as well as a fuel and intermediate for many chemical processes.
Since methanol and ethanol are controlled by law, the next alcohol, propanol, is often used instead. Moreover, n-propanol is much less common than its isomer - isopropanol, which is often used as a solvent and degreaser (also suitable for alcohol lamps, if that happens). It has a different odor from methanol and ethanol, is more viscous (especially at low temperatures) and boils at a slightly higher temperature.
Butanol and impurities of heavier alcohols form the basis of fusel oils - they are formed in small quantities during fermentation and have an unpleasant heavy odor. Otherwise, such alcohols are used primarily as reagents for the preparation of other compounds.
There can be several functional groups in a molecule, in particular alcohol groups. All the compounds discussed above are called monohydric alcohols - based on the number of hydroxyl groups. There are also dihydric alcohol ethylene glycol and trihydric alcohol glycerin:
Ethylene glycol and glycerin
They have properties similar to primary alcohols, but even more pronounced: they are thick liquids with high temperature boiling (ethylene glycol is used as a component of coolants in heating, and also as a component of antifreeze "antifreeze"). Both of them are mixed with water in any proportions. Unlike ethylene glycol, glycerin is low-toxic, and in addition it also has a sweet taste (hence the name: “glycos” - sweet), due to some similarity in structure with carbohydrates, which are also formally alcohols. This explains, in particular, why carbohydrates (including sugar) are highly soluble in water.
Alcohols are similar to alkanes, in which an oxygen atom is “built” into the molecule. And indeed, in many textbooks they write that methanol can be obtained by incomplete oxidation of methane. This, however, requires very special conditions that can only be realized in industry: high pressure, temperature control, use of catalysts. It is also obtained from the so-called. “synthesis gas” is a mixture of carbon monoxide and hydrogen, and synthesis gas, in turn, is obtained from methane and water at high temperature.
Production of methanol from synthesis gas
In general, methanol is a large-scale product (in 2004 its production was estimated at 32 million tons worldwide), and industrial chemistry is usually very different from laboratory chemistry (compare distillation columns and laboratory distillation apparatus). Methanol is formed in small quantities during the dry distillation of wood, which is why its other name is wood alcohol.
To produce ethanol, fermentation is used: some types of microorganisms can convert sugars present in plant material (for example, wheat or sugar cane) into ethanol, thereby obtaining energy. Ethanol is then separated by rectification and used, for example, as an additive to automobile fuel (so-called biofuel). Thus, about 60 million are produced. tons of ethanol per year (mainly in the USA and Brazil). On such a scale, I don’t want to talk about getting it from petroleum products, but there is still a way to get it from ethylene: a hydrocarbon in which two carbon atoms are connected not by one, but double bond. Under certain conditions, this bond can open, attaching a water molecule. This produces ethanol; other alcohols can be prepared in the same way from the corresponding alkenes
Ethylene hydration reaction
Methanol is oxidized to formaldehyde or formic acid. Ethanol, respectively, turns into acetaldehyde or acetic acid.
How and under what conditions, as well as other reactions of alcohols will be described in the next article.
Bioethanol production statistics can be found here: http://ethanolrfa.org/resources/industry/statistics/
Depending on the type of hydrocarbon radical, as well as in some cases, the characteristics of the attachment of the -OH group to this hydrocarbon radical, compounds with hydroxyl functional group divided into alcohols and phenols.
Alcohols are compounds in which the hydroxyl group is connected to a hydrocarbon radical, but is not attached directly to the aromatic ring, if there is one in the structure of the radical.
Examples of alcohols:
If the structure of a hydrocarbon radical contains an aromatic ring and a hydroxyl group, and is connected directly to the aromatic ring, such compounds are called phenols .
Examples of phenols:
Why are phenols classified as a separate class from alcohols? After all, for example, the formulas
are very similar and give the impression of substances of the same class organic compounds.
However, the direct connection of the hydroxyl group with the aromatic ring significantly affects the properties of the compound, since the conjugated system of π-bonds of the aromatic ring is also conjugated with one of the lone electron pairs of the oxygen atom. Because of this, the O-H bond in phenols is more polar compared to alcohols, which significantly increases the mobility of the hydrogen atom in the hydroxyl group. In other words, phenols have much more pronounced acidic properties than alcohols.
Chemical properties of alcohols
Monohydric alcohols
Substitution reactions
Substitution of a hydrogen atom in the hydroxyl group
1) Alcohols react with alkali, alkaline earth metals and aluminum (purified from protective film Al 2 O 3), in which case metal alcoholates are formed and hydrogen is released:
The formation of alcoholates is possible only when using alcohols that do not contain water dissolved in them, since in the presence of water alcoholates are easily hydrolyzed:
CH 3 OK + H 2 O = CH 3 OH + KOH
2) Esterification reaction
The esterification reaction is the interaction of alcohols with organic and oxygen-containing inorganic acids, leading to the formation of esters.
This type of reaction is reversible, therefore, to shift the equilibrium towards the formation of an ester, it is advisable to carry out the reaction with heating, as well as in the presence of concentrated sulfuric acid as a water-removing agent:
Substitution of hydroxyl group
1) When alcohols are exposed to hydrohalic acids, the hydroxyl group is replaced by a halogen atom. As a result of this reaction, haloalkanes and water are formed:
2) By passing a mixture of alcohol vapor and ammonia through heated oxides of some metals (most often Al 2 O 3), primary, secondary or tertiary amines can be obtained:
The type of amine (primary, secondary, tertiary) will depend to some extent on the ratio of the starting alcohol to ammonia.
Elimination reactions
Dehydration
Dehydration, which actually involves the elimination of water molecules, in the case of alcohols differs by intermolecular dehydration And intramolecular dehydration.
At intermolecular dehydration In alcohols, one molecule of water is formed as a result of the abstraction of a hydrogen atom from one molecule of alcohol and a hydroxyl group from another molecule.
As a result of this reaction, compounds belonging to the class of ethers (R-O-R) are formed:
Intramolecular dehydration alcohols process occurs in such a way that one molecule of water is split off from one molecule of alcohol. This type of dehydration requires somewhat more stringent conditions, consisting in the need to use significantly stronger heating compared to intermolecular dehydration. In this case, from one molecule of alcohol one molecule of alkene and one molecule of water are formed:
Since the methanol molecule contains only one carbon atom, intramolecular dehydration is impossible for it. When methanol is dehydrated, only ether (CH 3 -O-CH 3) can be formed.
It is necessary to clearly understand the fact that in the case of dehydration of unsymmetrical alcohols, intramolecular elimination of water will proceed in accordance with Zaitsev’s rule, i.e. hydrogen will be removed from the least hydrogenated carbon atom:
Dehydrogenation of alcohols
a) Dehydrogenation of primary alcohols when heated in the presence of copper metal leads to the formation aldehydes:
b) In the case of secondary alcohols, similar conditions will lead to the formation ketones:
c) Tertiary alcohols do not enter into a similar reaction, i.e. are not subject to dehydrogenation.
Oxidation reactions
Combustion
Alcohols easily react in combustion. This creates a large number of heat:
2CH 3 -OH + 3O 2 = 2CO 2 + 4H 2 O + Q
Incomplete oxidation
Incomplete oxidation of primary alcohols can lead to the formation of aldehydes and carboxylic acids.
In the case of incomplete oxidation of secondary alcohols, only ketones can be formed.
Incomplete oxidation of alcohols is possible when they are exposed to various oxidizing agents, for example, air oxygen in the presence of catalysts (metallic copper), potassium permanganate, potassium dichromate, etc.
In this case, aldehydes can be obtained from primary alcohols. As you can see, the oxidation of alcohols to aldehydes essentially leads to the same organic products as dehydrogenation:
It should be noted that when using oxidizing agents such as potassium permanganate and potassium dichromate in an acidic environment, deeper oxidation of alcohols is possible, namely to carboxylic acids. In particular, this manifests itself when using an excess of oxidizing agent during heating. Secondary alcohols can only be oxidized to ketones under these conditions.
LIMITED POLYATHICAL ALCOHOLS
Substitution of hydrogen atoms of hydroxyl groups
Polyhydric alcohols are the same as monohydric ones react with alkali, alkaline earth metals and aluminum (removed from filmAl 2 O 3 ); in this case, a different number of hydrogen atoms of hydroxyl groups in the alcohol molecule can be replaced:
2. Because in molecules polyhydric alcohols contains several hydroxyl groups, they influence each other due to a negative inductive effect. In particular, this leads to a weakening O-N connections and increasing the acidic properties of hydroxyl groups.
B O The greater acidity of polyhydric alcohols is manifested in the fact that polyhydric alcohols, unlike monohydric alcohols, react with some hydroxides of heavy metals. For example, you need to remember the fact that freshly precipitated copper hydroxide reacts with polyhydric alcohols to form a bright blue solution of the complex compound.
Thus, the interaction of glycerol with freshly precipitated copper hydroxide leads to the formation of a bright blue solution of copper glycerate:
This reaction is quality for polyhydric alcohols. For passing the Unified State Exam It is enough to know the signs of this reaction, but it is not necessary to be able to write the interaction equation itself.
3. Just like monohydric alcohols, polyhydric alcohols can enter into an esterification reaction, i.e. react with organic and oxygen-containing inorganic acids with the formation of esters. This reaction is catalyzed by strong inorganic acids and is reversible. In this regard, when carrying out the esterification reaction, the resulting ester is distilled off from the reaction mixture in order to shift the equilibrium to the right according to Le Chatelier’s principle:
If carboxylic acids with a large number of carbon atoms in the hydrocarbon radical resulting from such a reaction react with glycerol, esters called fats.
In the case of esterification of alcohols with nitric acid, a so-called nitrating mixture is used, which is a mixture of concentrated nitric and sulfuric acids. The reaction is carried out under constant cooling:
Glycerol ester and nitric acid, called trinitroglycerin, is an explosive. In addition, a 1% solution of this substance in alcohol has a powerful vasodilating effect, which is used for medical indications to prevent a stroke or heart attack.
Substitution of hydroxyl groups
Reactions of this type proceed through the mechanism of nucleophilic substitution. Interactions of this kind include the reaction of glycols with hydrogen halides.
For example, the reaction of ethylene glycol with hydrogen bromide proceeds with the sequential replacement of hydroxyl groups by halogen atoms:
Chemical properties of phenols
As mentioned at the very beginning of this chapter, the chemical properties of phenols are markedly different from the chemical properties of alcohols. This is due to the fact that one of the lone electron pairs of the oxygen atom in the hydroxyl group is conjugated with the π-system of conjugated bonds of the aromatic ring.
Reactions involving the hydroxyl group
Acid properties
Phenols are stronger acids than alcohols and are dissociated to a very small extent in aqueous solution:
B O The greater acidity of phenols compared to alcohols in terms of chemical properties is expressed in the fact that phenols, unlike alcohols, are able to react with alkalis:
However, the acidic properties of phenol are less pronounced than even one of the weakest inorganic acids - carbonic acid. So, in particular, carbon dioxide, when passing it through an aqueous solution of alkali metal phenolates, displaces free phenol from the latter as an even weaker acid than carbonic acid:
Obviously, any other stronger acid will also displace phenol from phenolates:
3) Phenols are stronger acids than alcohols, and alcohols react with alkali and alkaline earth metals. In this regard, it is obvious that phenols will react with these metals. The only thing is that, unlike alcohols, the reaction of phenols with active metals requires heating, since both phenols and metals are solids:
Substitution reactions in the aromatic ring
The hydroxyl group is a substituent of the first kind, which means that it facilitates the occurrence of substitution reactions in ortho- And pair- positions in relation to oneself. Reactions with phenol occur in much more mild conditions compared to benzene.
Halogenation
The reaction with bromine does not require any special conditions. When bromine water is mixed with a phenol solution, a white precipitate of 2,4,6-tribromophenol is instantly formed:
Nitration
When phenol is exposed to a mixture of concentrated nitric and sulfuric acids (nitrating mixture), 2,4,6-trinitrophenol is formed, a yellow crystalline explosive:
Addition reactions
Since phenols are unsaturated compounds, they can be hydrogenated in the presence of catalysts to the corresponding alcohols.
Hydrocarbon derivatives with one or more hydrogen atoms in the molecule replaced by an -OH group (hydroxyl group or hydroxy group) are alcohols. Chemical properties determined by a hydrocarbon radical and a hydroxyl group. Alcohols form a separate group in which each subsequent representative differs from the previous member by a homological difference corresponding to =CH2. All substances in this class can be represented by the formula: R-OH. For monatomic saturated compounds, the general chemical formula has the form CnH2n+1OH. According to international nomenclature, names can be derived from hydrocarbons with the addition of the ending -ol (methanol, ethanol, propanol, and so on).
This is a very diverse and broad class. chemical compounds. Depending on the number of -OH groups in the molecule, it is divided into one-, two-, triatomic and so on - polyatomic compounds. The chemical properties of alcohols also depend on the content of hydroxy groups in the molecule. These substances are neutral and do not dissociate into ions in water, such as strong acids or strong reasons. However, they can weakly exhibit both acidic (they decrease with increasing molecular weight and branching of the hydrocarbon chain in the series of alcohols) and basic (increasing with increasing molecular weight and branching of the molecule) properties.
The chemical properties of alcohols depend on the type and spatial arrangement of atoms: molecules come with chain isomerism and positional isomerism. Depending on the maximum number of single bonds of a carbon atom (linked to the hydroxy group) with other carbon atoms (with 1, 2 or 3), primary (normal), secondary or tertiary alcohols are distinguished. Primary alcohols have a hydroxyl group attached to the primary carbon atom. In secondary and tertiary - to secondary and tertiary, respectively. Starting with propanol, isomers appear that differ in the position of the hydroxyl group: propyl alcohol C3H7-OH and isopropyl alcohol CH3-(CHOH)-CH3.
It is necessary to name several main reactions that characterize the chemical properties of alcohols:
- When reacting with or their hydroxides (deprotonation reaction), alcoholates are formed (the hydrogen atom is replaced by a metal atom), depending on the hydrocarbon radical, methylates, ethylates, propylates and so on are obtained, for example, sodium propoxide: 2CH3CH2OH + 2Na → 2CH3CH2ONa + H2.
- When interacting with concentrated hydrohalic acids, HBr + CH3CH2OH ↔ CH3CH2Br + H2O are formed. This reaction is reversible. As a result, it happens nucleophilic substitution halogen ion of the hydroxyl group.
- Alcohols can be oxidized to carbon dioxide, to aldehydes, or to ketones. Alcohols burn in the presence of oxygen: 3O2 + C2H5OH →2CO2 + 3H2O. Under the influence of a strong oxidizing agent (chromic acid, etc.), primary alcohols are converted into aldehydes: C2H5OH → CH3COH + H2O, and secondary alcohols are converted into ketones: CH3—(CHOH)—CH3 → CH3—(CHO)—CH3 + H2O.
- The dehydration reaction occurs when heated in the presence of water-removing substances sulfuric acid and so on). As a result, alkenes are formed: C2H5OH → CH2=CH2 + H2O.
- The esterification reaction also occurs when heated in the presence of water-subtracting compounds, but, unlike the previous reaction, at a lower temperature and with the formation of 2C2H5OH → C2H5-O-C2H5O. With sulfuric acid the reaction occurs in two stages. First, an ester of sulfuric acid is formed: C2H5OH + H2SO4 → C2H5O—SO2OH + H2O, then when heated to 140 ° C and in excess of alcohol, diethyl (often called sulfuric) ether is formed: C2H5OH + C2H5O—SO2OH → C2H5—O—C2H5O + H2SO4 .
Chemical properties of polyhydric alcohols, by analogy with their physical properties, depend on the type of hydrocarbon radical forming the molecule and, of course, the number of hydroxyl groups in it. For example, ethylene glycol CH3OH-CH3OH (boiling point 197 °C), which is a 2-atomic alcohol, is a colorless liquid (has a sweetish taste), which mixes with H2O, as well as lower alcohols in any ratio. Ethylene glycol, like its higher homologues, enter into all reactions characteristic of monohydric alcohols. Glycerol CH2OH—CHOH—CH2OH (boiling point 290 °C) is the simplest representative of 3-hydroxy alcohols. This is a thick, sweet-tasting liquid that cannot be mixed with it in any proportion. Dissolves in alcohol. Glycerol and its homologues are also characterized by all reactions of monohydric alcohols.
The chemical properties of alcohols determine the areas of their use. They are used as fuel (bioethanol or biobutanol and others), as solvents in various industries; as a raw material for the production of surfactants and detergents; for synthesis polymer materials. Some members of this class of organic compounds are widely used as lubricants or hydraulic fluids, as well as in the manufacture of medicines and biologically active substances.