Oxygen gives organic substances a whole complex of characteristic properties.
Oxygen is divalent, has two valence electron pairs and is characterized by high electronegativity (x = 3.5). Strong chemical bonds are formed between carbon and oxygen atoms, which can already be seen in the example of CO 2 molecules. A single C-0 bond (£ sv \u003d 344 kJ / mol) is almost as strong as a C-C bond (E ca = 348 kJ/mol), and the double bond C=0 ( E St = 708 kJ/mol) is much stronger than the C=C bond (E St == 620 kJ/mol). Therefore, transformations leading to the formation of C=0 double bonds are common in organic molecules. For the same reason, carbonic acid is unstable:
The hydroxo group located at the double bond is converted into an hydroxy group (see above).
Oxygen will give polarity to the molecules of organic substances. Attraction between molecules increases, the melting and boiling points increase significantly. Under normal conditions, among oxygen-containing substances, very macho gases are only CH 3 OCH 3 ether, formaldehyde CH 2 0 and ethylene oxide CH 2 CH 2 0.
Oxygen promotes the formation of hydrogen bonds both as a donor and an acceptor of hydrogen. Hydrogen bonds enhance the attraction of molecules, and in the case of sufficiently complex molecules, give them a certain spatial structure. The influence of polarity and hydrogen bonds on the properties of a substance is seen in the example of a hydrocarbon, ketone and alcohol
Polarity and the formation of hydrogen bonds are responsible for the good solubility of oxygen-containing organic substances in water.
Oxygen imparts acidic properties to organic substances to some extent. In addition to the class of acids, the properties of which are obvious from the name, phenols and alcohols exhibit acidic properties.
Another common property of oxygen-containing substances is the easy oxidizability of the carbon atom associated simultaneously with oxygen and hydrogen. This is evident from the following chains of reactions, which are terminated when the carbohydrate loses the last water conduit atom:
contains a hydroxy group and is considered a heterofunctional acid.
Alcohols and ethers
Name of a whole class of organic substances alcohols(from Latin "spiritus" - spirit) comes from the "active principle" of the mixture obtained by fermenting fruit juices and other systems containing sugar. This active principle - wine alcohol, ethanol C2H5OH, is separated from water and non-volatile solutes during the distillation of the mixture. Another name for alcohol is alcohol - Arabic origin.
Alcohols are called organic compounds in which there is a hydroxo group associated with the $ p 3 carbon atom of the hydrocarbon radical.
Alcohols can also be considered as products of substitution of one hydrogen atom in water for a hydrocarbon radical. Alcohols form homologous series (Table 22.5), differing in the nature of the radicals and the number of hydroxo groups.
Table 22.5
Some homologous series of alcohols
Tlicols and glycerols are polyfunctional alcohols with OH groups at adjacent carbon atoms.
The hydroxo group at unsaturated carbon atoms is unstable, as it turns into a carbonyl group. Vinyl alcohol is in an insignificant amount in equilibrium with aldehyde:
There are substances in which the hydroxo group is bonded to the n / z carbon atom of the aromatic ring, but they are considered as a special class of compounds - phenols.
In alcohols, isomerism of the carbon skeleton and the position of the functional group is possible. In unsaturated alcohols, there is also isomerism of the position of the multiple bond and spatial isomerism. Compounds of the class of ethers are isomeric to alcohols. Among the alcohols, there are varieties called primary, secondary and tertiary alcohols. This is due to the nature of the carbon atom at which the functional group is located.
Example 22.12. Write the formulas for primary, secondary, and tertiary alcohols with four carbon atoms.
Decision.
Let us consider in more detail the homologous series of saturated alcohols. The first 12 members of this series are liquids. Methanol, ethanol and propanol are miscible with water in any ratio due to their structural similarity to water. Further along the homologous series, the solubility of alcohols decreases, since large (in terms of the number of atoms) hydrocarbon radicals are more and more displaced from the aqueous medium, like hydrocarbons. This property is called hydrophobicity. In contrast to the radical, the hydroxo group is attracted to water, forming a hydrogen bond with water, i.e. shows hydrophilicity. Higher alcohols (five or more carbon atoms) exhibit the property surface activity- the ability to concentrate at the surface of the water due to the expulsion of a hydrophobic radical (Fig. 22.3).
Rice. 22.3.
Surfactants coat liquid droplets and promote the formation of stable emulsions. This is the basis for the action of detergents. Surface activity can be exhibited not only by alcohols, but also by substances of other classes.
Most water-soluble alcohols are poisonous. The least poisonous are ethanol and glycerin. But, as you know, ethanol is dangerous because it causes a person to become addicted to its use. The simplest of the alcohols, methanol is similar in smell to ethanol, but extremely poisonous. There are many known cases of human poisoning as a result of erroneous ingestion.
methanol instead of ethanol. This is facilitated by the huge volume of industrial use of methanol. The simplest dihydric alcohol ethylene glycol C 2 H 4 (OH) 2 is used in large quantities for the production of polymer fibers. Its solution is used as an antifreeze for cooling automobile engines.
Getting alcohols. Let's look at a few common ways.
1. Hydrolysis of halogen derivatives of hydrocarbons. The reactions are carried out in an alkaline medium:
Example 22.13. Write the reactions for obtaining ethylene glycol by the hydrolysis of halogen derivatives, taking the starting material ethylene.
2. Addition of water to alkenes. Of greatest importance is the addition reaction of water to ethylene with the formation of ethanol. The reaction proceeds quite rapidly at high temperature, but the equilibrium is strongly shifted to the left and the yield of alcohol decreases. Therefore, it is necessary to create a high pressure and use a catalyst that makes it possible to achieve the same process speed at a lower temperature (similar to the conditions for the synthesis of ammonia). Ethanol is obtained by hydration of ethylene at -300°C and a pressure of 60-70 atm:
The catalyst is phosphoric acid supported on alumina.
3. There are special ways to produce ethanol and methanol. The first is obtained by the well-known biochemical method of fermenting carbohydrates, which are first broken down to glucose:
Methanol is produced synthetically from inorganic substances:
The reaction is carried out at 200-300°C and a pressure of 40-150 atm using a complex catalyst Cu0/2n0/A1 2 0 3 /Cr 2 0 3 . The importance of this industrial process is clear from the fact that more than 14 million tons of methanol are produced annually. It is used mainly in organic synthesis for the methylation of organic substances. Approximately the same amount is produced and ethanol.
Chemical properties of alcohols. Alcohols can be handful and oxidize. A mixture of ethyl alcohol and hydrocarbons is sometimes used as fuel for automobile engines. The oxidation of alcohols without disturbing the carbon structure is reduced to the loss of hydrogen and the addition of oxygen atoms. In industrial processes, alcohol vapors are oxidized by oxygen. In solutions, alcohols are oxidized by potassium permanganate, potassium dichromate and other oxidizing agents. An aldehyde is obtained from a primary alcohol upon oxidation:
With an excess of an oxidizing agent, the aldehyde is immediately oxidized to an organic acid:
Secondary alcohols are oxidized to ketones:
Tertiary alcohols can only be oxidized under harsh conditions with partial destruction of the carbon skeleton.
acid properties. Alcohols react with active metals to release hydrogen and form derivatives with the general name alkoxides (methoxides, ethoxides, etc.):
The reaction proceeds more calmly than a similar reaction with water. The liberated hydrogen does not ignite. This method destroys sodium residues after chemical experiments. This kind of reaction means that alcohols exhibit acidic properties. This is a consequence of the polarity of the O-H bond. However, alcohol practically does not react with alkali. This fact allows us to clarify the strength of the acidic properties of alcohols: they are weaker acids than water. Sodium ethoxide is almost completely hydrolyzed to form a solution of alcohol and alkali. The acidic properties of glycols and glycerols are somewhat stronger due to the mutual inductive effect of OH groups.
Polyhydric alcohols form complex compounds with ions of some ^/-elements. In an alkaline environment, a copper ion replaces two hydrogen ions at once in a glycerol molecule to form a blue complex:
With an increase in the concentration of H + ions (acid is added for this), the equilibrium shifts to the left and the color disappears.
Reactions of nucleophilic substitution of the hydroxo group. Alcohols react with hydrogen chloride and other hydrogen halides:
The reaction is catalyzed by a hydrogen ion. First, H + joins oxygen, accepting its electron pair. This shows the main properties of alcohol:
The resulting ion is unstable. It cannot be isolated from solution as a solid salt like the ammonium ion. The addition of H + causes an additional shift of the electron pair from carbon to oxygen, which facilitates the attack of the nucleophilic particle on carbon:
The bond between carbon and chloride ion increases as the bond between carbon and oxygen is broken. The reaction ends with the release of a water molecule. However, the reaction is reversible, and upon neutralization of hydrogen chloride, the equilibrium shifts to the left. Hydrolysis takes place.
The hydroxo group in alcohols is also replaced in reactions with oxygen-containing acids to form esters. Glycerol with nitric acid forms nitroglycerine used as a means of relieving spasms of the vessels of the heart:
It is clear from the formula that the traditional name of the substance is inaccurate, since in fact it is glycerol nitrate - an ester of nitric acid and glycerol.
When ethanol is heated with sulfuric acid, one molecule of alcohol acts as a nucleophilic reagent in relation to another. As a result of the reaction, an ethoxyethane ether is formed:
Some atoms are highlighted in the diagram to make it easier to trace their transition to the reaction products. One alcohol molecule first attaches a catalyst - an H + ion, and the oxygen atom of another molecule transfers an electron pair to carbon. After the elimination of water and the dissociation of H 4, an ether molecule is obtained. This reaction is also called intermolecular dehydration of alcohol. There is also a method for obtaining ethers with different radicals:
Ethers are more volatile than alcohols because hydrogen bonds do not form between their molecules. Ethanol boils at 78°C, and its isomer ester CH3OCH3 boils at -23.6°C. Ethers do not hydrolyze to alcohols when boiled with alkali solutions.
Dehydration of alcohols. Alcohols can decompose with elimination of water in the same way as halogen derivatives of hydrocarbons decompose with elimination of hydrogen halide. In the production of alcohols from alkene and water (see above), the reverse reaction of water elimination is also present. The difference in the conditions for the addition and elimination of water is that the addition occurs under pressure with an excess of water vapor relative to the alkene, and the elimination occurs from a single alcohol. Such dehydration is called intramolecular. It also goes in a mixture of alcohol with sulfuric acid at ~150°C.
Target: to form the ability to make observations and draw conclusions, write down the equations of the corresponding reactions in molecular and ionic forms .
Security of the lesson
1. A collection of guidelines for students on the implementation of practical exercises and laboratory work in the academic discipline "Chemistry".
2. Sodium hydroxide solution, sodium carbonate, calcium carbonate, copper (II) oxide, acetic acid, litmus blue, zinc; stand with test tubes, water bath, heating device, matches, test tube holder.
Theoretical material
Carboxylic acids are organic compounds whose molecules contain one or more carboxyl groups connected to a hydrocarbon radical or a hydrogen atom.
Obtaining: In the laboratory, carboxylic acids can be obtained from their salts by treating them with sulfuric acid when heated, for example:
2CH 3 - COOHa + H 2 SO 4 ® 2CH 3 - COOH + Na 2 SO 4
In industry, it is obtained by oxidation of hydrocarbons, alcohols and aldehydes.
Chemical properties:
1. Due to the shift in electron density from the hydroxyl group O–H to strongly
polarized carbonyl group C=O, carboxylic acid molecules are capable of
electrolytic dissociation: R–COOH → R–COO - + H +
2.Carboxylic acids have properties characteristic of mineral acids. They react with active metals, basic oxides, bases, salts of weak acids. 2CH 3 COOH + Mg → (CH 3 COO) 2 Mg + H 2
2CH 3 COOH + CaO → (CH 3 COO) 2 Ca + H 2 O
H–COOH + NaOH → H–COONa + H2O
2CH 3 CH 2 COOH + Na 2 CO 3 → 2CH 3 CH 2 COONa + H 2 O + CO 2
CH 3 CH 2 COOH + NaHCO 3 → CH 3 CH 2 COONa + H 2 O + CO 2
Carboxylic acids are weaker than many strong mineral acids
CH 3 COONa + H 2 SO 4 (conc.) →CH 3 COOH + NaHSO 4
3. Formation of functional derivatives:
a) when interacting with alcohols (in the presence of concentrated H 2 SO 4), esters are formed.
The formation of esters by the interaction of an acid and an alcohol in the presence of mineral acids is called an esterification reaction. CH 3 - -OH + HO-CH 3 D CH 3 - -OCH 3 + H 2 O
acetic acid methyl methyl ester
acetic acid alcohol
The general formula of esters is R– –OR’ where R and R" are hydrocarbon radicals: in formic acid esters – formates –R=H.
The reverse reaction is the hydrolysis (saponification) of the ester:
CH 3 – –OCH 3 + HO–H DCH 3 – –OH + CH 3 OH.
Glycerin (1,2,3-trihydroxypropane; 1,2,3-propanetriol) (glycos - sweet) is a chemical compound with the formula HOCH2CH(OH)-CH2OH or C3H5(OH)3. The simplest representative of trihydric alcohols. It is a viscous transparent liquid.
Glycerin is a colorless, viscous, hygroscopic liquid, infinitely soluble in water. Sweet taste (glycos - sweet). It dissolves many substances well.
Glycerol is esterified with carboxylic and mineral acids.
Esters of glycerol and higher carboxylic acids are fats.
Fats -
these are mixtures of esters formed by the trihydric alcohol glycerol and higher fatty acids. The general formula of fats, where R are the radicals of higher fatty acids:
Most often, fats include saturated acids: palmitic C15H31COOH and stearic C17H35COOH, and unsaturated acids: oleic C17H33COOH and linoleic C17H31COOH.
The common name for compounds of carboxylic acids with glycerol is triglycerides.
b) when exposed to water-removing reagents as a result of intermolecular
dehydration anhydrides are formed
CH 3 – –OH + HO– –CH 3 →CH 3 – –O– –CH 3 + H 2 O
Halogenation. Under the action of halogens (in the presence of red phosphorus), α-halo-substituted acids are formed:
Application: in the food and chemical industries (production of cellulose acetate, from which acetate fiber, organic glass, film are obtained; for the synthesis of dyes, medicines and esters).
Questions to consolidate the theoretical material
1 Which organic compounds are carboxylic acids?
2 Why are there no gaseous substances among carboxylic acids?
3 What causes the acidic properties of carboxylic acids?
4 Why does the color of indicators change in acetic acid solution?
5 What chemical properties are common for glucose and glycerol, and how do these substances differ from each other? Write the equations for the corresponding reactions.
Exercise
1. Repeat the theoretical material on the topic of the practical lesson.
2. Answer questions to consolidate the theoretical material.
3. Investigate the properties of oxygen-containing organic compounds.
4. Prepare a report.
Execution instructions
1. Familiarize yourself with the safety rules for working in a chemical laboratory and sign in the safety journal.
2. Perform experiments.
3. Enter the results in the table.
Experience No. 1 Testing a solution of acetic acid with litmus
Dilute the resulting acetic acid with a little water and add a few drops of blue litmus or dip an indicator paper into the test tube.
Experience No. 2 Reaction of acetic acid with calcium carbonate
Pour a little chalk (calcium carbonate) into a test tube and add a solution of acetic acid.
Experience No. 3 Properties of glucose and sucrose
a) Add 5 drops of glucose solution, a drop of copper (II) salt solution and, while shaking, a few drops of sodium hydroxide solution into a test tube until a light blue solution is formed. This experiment was done with glycerin.
b) Heat the resulting solutions. What are you watching?
Experience No. 4 Qualitative reaction to starch
To 5-6 drops of starch paste in a test tube, add a drop of iodine alcohol solution.
Sample report
Laboratory work No. 9 Chemical properties of oxygen-containing organic compounds.
Purpose: to form the ability to make observations and draw conclusions, write down the equations of the corresponding reactions in molecular and ionic forms .
Make a conclusion in accordance with the purpose of the work
Literature 0-2 s 94-98
Lab #10
The formation of haloalkanes during the interaction of alcohols with hydrogen halides is a reversible reaction. Therefore, it is clear that alcohols can be obtained by hydrolysis of haloalkanes- reactions of these compounds with water:
Polyhydric alcohols can be obtained by hydrolysis of haloalkanes containing more than one halogen atom in the molecule. For example:
Hydration of alkenes
Hydration of alkenes- addition of water at π - bonds of an alkene molecule, for example:
Hydration of propene leads, in accordance with Markovnikov's rule, to the formation of a secondary alcohol - propanol-2:
Hydrogenation of aldehydes and ketones
Oxidation of alcohols under mild conditions leads to the formation of aldehydes or ketones. Obviously, alcohols can be obtained by hydrogenation (hydrogen reduction, hydrogen addition) of aldehydes and ketones:
Alkene oxidation
Glycols, as already noted, can be obtained by oxidizing alkenes with an aqueous solution of potassium permanganate. For example, ethylene glycol (ethanediol-1,2) is formed during the oxidation of ethylene (ethene):
Specific methods for obtaining alcohols
1. Some alcohols are obtained in ways characteristic only of them. So, methanol in industry is obtained reaction of interaction of hydrogen with carbon monoxide(II) (carbon monoxide) at elevated pressure and high temperature on the surface of the catalyst (zinc oxide):
The mixture of carbon monoxide and hydrogen necessary for this reaction, also called "synthesis gas", is obtained by passing water vapor over hot coal:
2. Glucose fermentation. This method of obtaining ethyl (wine) alcohol has been known to man since ancient times:
The main methods for obtaining oxygen-containing compounds (alcohols) are: hydrolysis of haloalkanes, hydration of alkenes, hydrogenation of aldehydes and ketones, oxidation of alkenes, as well as obtaining methanol from "synthesis gas" and fermentation of sugary substances.
Methods for obtaining aldehydes and ketones
1. Aldehydes and ketones can be obtained oxidation or alcohol dehydrogenation. During the oxidation or dehydrogenation of primary alcohols, aldehydes can be obtained, and secondary alcohols - ketones:
3CH 3 -CH 2 OH + K 2 Cr 2 O 7 + 4H 2 SO 4 \u003d 3CH 3 -CHO + K 2 SO 4 + Cr 2 (SO 4) 3 + 7H 2 O
2.Kucherov's reaction. From acetylene, as a result of the reaction, acetaldehyde is obtained, from acetylene homologs - ketones:
3. When heated calcium or barium salts of carboxylic acids a ketone and a metal carbonate are formed:
Methods for obtaining carboxylic acids
1. Carboxylic acids can be obtained oxidation of primary alcohols or aldehydes:
3CH 3 -CH 2 OH + 2K 2 Cr 2 O 7 + 8H 2 SO 4 \u003d 3CH 3 -COOH + 2K 2 SO 4 + 2Cr 2 (SO 4) 3 + 11H 2 O
5CH 3 -CHO + 2KMnO 4 + 3H 2 SO 4 \u003d 5CH 3 -COOH + 2MnSO 4 + K 2 SO 4 + 3H 2 O,
3CH 3 -CHO + K 2 Cr 2 O 7 + 4H 2 SO 4 \u003d 3CH 3 -COOH + Cr 2 (SO 4) 3 + K 2 SO 4 + 4H 2 O,
CH 3 -CHO + 2OH CH 3 -COONH 4 + 2Ag + 3NH 3 + H 2 O.
But when methanal is oxidized with an ammonia solution of silver oxide, ammonium carbonate is formed, and not formic acid:
HCHO + 4OH \u003d (NH 4) 2 CO 3 + 4Ag + 6NH 3 + 2H 2 O.
2. Aromatic carboxylic acids are formed when oxidation of homologues benzene:
5C 6 H 5 -CH 3 + 6KMnO 4 + 9H 2 SO 4 \u003d 5C 6 H 5 COOH + 6MnSO 4 + 3K 2 SO 4 + 14H 2 O,
5C 6 H 5 -C 2 H 5 + 12KMnO 4 + 18H 2 SO 4 \u003d 5C 6 H 5 COOH + 5CO 2 + 12MnSO 4 + 6K 2 SO 4 + 28H 2 O,
C 6 H 5 -CH 3 + 2KMnO 4 \u003d C 6 H 5 COOK + 2MnO 2 + KOH + H 2 O
3. Hydrolysis of various carboxylic derivatives acids also produces acids. So, during the hydrolysis of an ester, an alcohol and a carboxylic acid are formed. Acid-catalyzed esterification and hydrolysis reactions are reversible:
4. Ester hydrolysis under the action of an aqueous solution of alkali proceeds irreversibly, in this case, not an acid is formed from the ester, but its salt:
Alcohols- derivatives of hydrocarbons containing a functional group IS HE(hydroxyl). Alcohols containing one OH group are called monatomic, and alcohols with several OH groups - polyatomic.
The names of some common alcohols are given in Table. nine.
Alcohols are classified according to their structure. primary, secondary and tertiary, depending on which carbon atom (primary, secondary or tertiary) the OH group is located:
Monohydric alcohols are colorless liquids (up to Cl 2 H 25 OH), soluble in water. The simplest alcohol methanol CH 3 OH is extremely poisonous. As the molar mass increases, the boiling point of alcohols increases.
Molecules of liquid monohydric alcohols ROH are associated through hydrogen bonds:
(these bonds are analogous to hydrogen bonds in pure water).
When dissolved in water, ROH molecules form hydrogen bonds with water molecules:
Aqueous solutions of ROH alcohols are neutral; in other words, alcohols practically do not dissociate in an aqueous solution in either the acidic or basic type.
The chemical properties of monohydric alcohols are due to the presence of the OH functional group in them.
Hydrogen of the OH group in alcohols can be replaced by a metal:
Ethanolates and derivatives of other alcohols (alcoholates) easily hydrolyzed:
The OH group in alcohols can be replaced by Cl or Br:
Under the action of water-removing agents on alcohols, for example, concentrated H 2 SO 4, intermolecular dehydration:
The reaction product is diethyl ether(C 2 H 5) 2 O - belongs to the class ethers.
Under more severe conditions, dehydration becomes intramolecular and the corresponding alkene is formed:
Polyhydric alcohols consider the example of the simplest representatives of two- and trihydric alcohols:
At room temperature, they are colorless viscous liquids with boiling points of 198 and 290 °C, respectively, and are infinitely miscible with water. Ethylene glycol is poisonous.
The chemical properties of polyhydric alcohols are similar to those of ROH alcohols. So, in ethylene glycol, one or two OH groups can be replaced by a halogen:
The acidic properties of polyhydric alcohols are manifested in the fact that (unlike monohydric alcohols) the hydrogen of the OH group is replaced by a metal under the action of not only metals, but also metal hydroxides:
(arrows in the formula of copper glycolate show the formation of copper-oxygen covalent bonds by the donor-acceptor mechanism).
Glycerin reacts similarly with copper (II) hydroxide:
Copper (II) glycolate and glycerate, which have a bright blue color, allow high-quality find polyhydric alcohols.
Receipt monohydric alcohols in industry- hydration of alkenes in the presence of catalysts (H 2 SO 4 , Al 2 O 3), and the addition of water to unsymmetrical alkenes occurs according to the Markovnikov rule:
(a method for obtaining secondary alcohol), or addition of CO and H 2 to alkenes in the presence of a cobalt catalyst (the process is called hydroforgylation):
(method of obtaining primary alcohol).
AT laboratories(and sometimes in industry) alcohols are obtained by the interaction of halogen derivatives of hydrocarbons with water or an aqueous solution of alkali when heated:
Ethanol C 2 H 5 OH is also formed when alcoholic fermentation sugary substances, such as glucose:
Ethylene glycol is produced in a two-stage process:
a) ethylene oxidation:
b) ethylene oxide hydration:
Glycerol was previously obtained by saponification of fats (see 20.3), the modern three-stage method is the gradual oxidation of propene (only the process diagram is given):
Alcohols are used as raw materials in organic synthesis, as solvents (for varnishes, paints, etc.), as well as in the paper, printing, perfumery, pharmacological and food industries.
Ethers- a class of organic compounds containing a bridging oxygen atom - O - between two hydrocarbon radicals: R - O-R ". The most famous and widely used simple ether is - diethyl ether C 2 H 5 -O - C 2 H 5. A colorless, mobile liquid with a characteristic ("ethereal") odor; in laboratory practice, it is simply called ether. Almost immiscible with water, bp = 34.51 °C. Ether vapor ignites in air. Diethyl ether is obtained by intermolecular dehydration of ethanol (see above), the main use is as a solvent.
Phenols are alcohols in which the OH group is directly bonded to the benzene ring. The simplest representative phenol C 6 H 5 -OH. White (turning pink in the light) crystals with a strong odor, t pl = 41 °C. Causes skin burns, poisonous.
Phenol is characterized by a significantly higher acidity than acyclic alcohols. As a result, phenol in aqueous solution easily reacts with sodium hydroxide:
Hence the trivial name of phenol - carbolic acid.
Note that the OH group in phenol is never replaced by any other groups or atoms, but does more mobile hydrogen atoms of the benzene ring. So, phenol easily reacts with bromine in water and nitric acid, forming 2,4,6-tribromophenol (I) and 2,4,6-trinitrophenol, respectively. (II, traditional name - picric acid):
Phenol in industry obtained by heating chlorobenzene with a solution of sodium hydroxide under pressure at 250 ° C:
Phenol is used as a raw material for the production of plastics and resins, intermediates for the paint and varnish and pharmaceutical industries, as a disinfectant.
10.2. Aldehydes and ketones
Aldehydes and ketones are derivatives of hydrocarbons containing a functional carbonyl group SO. In aldehydes, the carbonyl group is bonded to a hydrogen atom and one radical, and in ketones to two radicals.
General formulas:
The names of common substances of these classes are given in Table. ten.
Methanal is a colorless gas with a pungent suffocating odor, highly soluble in water (the traditional name for a 40% solution is formalin), poisonous. Subsequent members of the homologous series of aldehydes are liquids and solids.
The simplest ketone is propanone-2, better known as acetone, at room temperature - a colorless liquid with a fruity odor, t bp = 56.24 ° C. Mixes well with water.
The chemical properties of aldehydes and ketones are due to the presence of a CO carbonyl group in them; they easily enter into reactions of addition, oxidation and condensation.
As a result accession hydrogen to aldehydes formed primary alcohols:
When reduced with hydrogen ketones formed secondary alcohols:
Reaction accession sodium hydrosulfite is used to isolate and purify aldehydes, since the reaction product is slightly soluble in water:
(by the action of dilute acids, such products are converted into aldehydes).
Oxidation aldehydes passes easily under the action of atmospheric oxygen (the products are the corresponding carboxylic acids). Ketones are relatively resistant to oxidation.
Aldehydes are able to participate in reactions condensation. Thus, the condensation of formaldehyde with phenol proceeds in two stages. First, an intermediate product is formed, which is a phenol and an alcohol at the same time:
The intermediate then reacts with another phenol molecule to give the product polycondensation -phenol-formaldehyde resin:
Qualitative reaction on the aldehyde group - the reaction of the "silver mirror", i.e., the oxidation of the C (H) O group with silver (I) oxide in the presence of ammonia hydrate:
The reaction with Cu (OH) 2 proceeds similarly; when heated, a red precipitate of copper oxide (I) Cu 2 O appears.
Receipt: general method for aldehydes and ketones - dehydrogenation(oxidation) of alcohols. When dehydrogenating primary alcohols are obtained aldehydes, and in the dehydrogenation of secondary alcohols - ketones. Usually, dehydrogenation proceeds when heated (300 °C) over finely divided copper:
When oxidizing primary alcohols strong oxidizing agents (potassium permanganate, potassium dichromate in an acidic environment) the process is difficult to stop at the stage of obtaining aldehydes; aldehydes are easily oxidized to the corresponding acids:
A more suitable oxidizing agent is copper (II) oxide:
Acetaldehyde in industry obtained by the Kucherov reaction (see 19.3).
The most widely used aldehydes are methanal and ethanal. Metanal used for the production of plastics (phenolic plastics), explosives, varnishes, paints, medicines. Ethanal- the most important intermediate in the synthesis of acetic acid and butadiene (production of synthetic rubber). The simplest ketone, acetone, is used as a solvent for various varnishes, cellulose acetates, in the production of film and explosives.
10.3. carboxylic acids. Complex ethers. Fats
Carboxylic acids are derivatives of hydrocarbons containing the COOH functional group ( carboxyl).
Formulas and titles some common carboxylic acids are given in table. eleven.
The traditional names for acids are HCOOH ( formic), CH 3 COOH (vinegar), C 6 H 5 COOH (benzoic) and (COOH) 2 (sorrel) it is recommended to use instead of their systematic names.
Formulas and titles acid residues are given in table. 12.
The traditional names are usually used to name the salts of these carboxylic acids (and also their esters, see below), for example:
Lower carboxylic acids are colorless liquids with a pungent odor. As the molar mass increases, the boiling point increases.
Carboxylic acids are found in nature:
The simplest carboxylic acids are soluble in water, reversibly dissociate in an aqueous solution to form hydrogen cations:
and exhibit the general properties of acids:
Of great practical importance is the interaction of carboxylic acids with alcohols (for more details, see below):
Note that HCOOH acid enters into the "silver mirror" reaction as aldehydes:
and decomposes under the action of water-removing reagents:
Receipt:
Oxidation of aldehydes:
Hydrocarbon oxidation:
In addition, formic acid is obtained according to the scheme:
and acetic acid - according to the reaction:
Apply formic acid as a mordant for dyeing wool, fruit juice preservative, bleach, disinfectant. Acetic acid used as a raw material in the industrial synthesis of dyes, medicines, acetate fibers, non-combustible film, organic glass. Sodium and potassium salts of higher carboxylic acids are the main components of soap.
Esters- products of the exchange interaction of carboxylic acids with alcohols. This interaction is called a reaction. esterification:
The mechanism of the esterification reaction was established using an alcohol labeled with the isotope 18 O; this oxygen after the reaction turned out to be in the composition ether(not water):
Therefore, in contrast to the reaction of neutralization of an inorganic acid with an alkali (H + + OH - \u003d H 2 O), in the esterification reaction, a carboxylic acid always gives a group IS HE, alcohol - atom H(water is formed). The esterification reaction is reversible; it flows better acidic medium, the reverse reaction ( hydrolysis, saponification)- in an alkaline environment.
Formulas and titles common esters are given in table. thirteen.
Among the esters there are colorless, low-boiling, flammable liquids with a fruity odor, for example:
Esters are used as solvents for varnishes, paints and cellulose nitrates, carriers of fruit flavors in the food industry.
Esters of a trihydric alcohol - glycerol and higher carboxylic acids (in the general form RCOOH), for example with formulas and names:
are called fats. An example of a fat would be a mixed ester of glycerol and these acids:
The higher the content of oleic acid residues (or other unsaturated acids), the lower the melting point of the fat. Fats that are liquid at room temperature are called oils. By hydrogenation, that is, the addition of hydrogen to the double bond, oils are converted into solid fats (for example, vegetable oil into margarine). The esterification reaction (fat formation) is reversible:
Direct reaction is better acidic environment, the reverse reaction - hydrolysis, or saponification, fat - in alkaline environment; during digestion, fat is saponified (broken down) with the help of enzymes.
10.4. Carbohydrates
Carbohydrates (Sahara) are the most important natural compounds consisting of carbon, hydrogen and oxygen. Carbohydrates are divided into monosaccharides, disaccharides and polysaccharides. Monosaccharides do not undergo hydrolysis, and the remaining carbohydrates are broken down into monosaccharides when boiled in the presence of acids.
Monosaccharides(and all other carbohydrates) are polyfunctional compounds. In a monosaccharide molecule, there are functional groups of different types: groups IS HE(alcohol function) and groups SO(aldehyde or ketone function). Therefore, they distinguish aldoses(aldehyde alcohols, alcohol aldehydes) and ketosis(ketone alcohols, alcohol ketones).
The most important representative of aldose is glucose:
and representative of ketosis - fructose:
Glucose (grape sugar) and fructose (fruit sugar) are structural isomers, their molecular formula is C 6 H 12 O 6 .
Glucose can be distinguished from fructose in the same way as any aldehyde from ketone, according to the “silver mirror” reaction in an ammonia solution of Ag 2 O:
The esterification of glucose and fructose (for example, with acetic acid) leads to the formation of esters at all five OH groups (replaced by OCOCH 3).
However, not all reactions characteristic of aldehydes occur with glucose; for example, there is no addition reaction involving sodium hydrosulfite. The reason is that a glucose molecule can exist in three isomeric forms, of which two forms (? and?) - cyclic. In solution, all three forms are in equilibrium, with the open (aldehyde) form above being contained in least quantity:
Cyclic forms of glucose do not contain an aldehyde group. They differ from each other only in the spatial arrangement of the H atom and the OH group at the carbon atom C 1 (next to oxygen in the cycle):
disaccharides are formed from two molecules of monosaccharides by intermolecular dehydration. So, sucrose(normal sugar) C 12 H 22 O 11 is a product of the combination of glucose and fructose residues due to the elimination of water:
Upon hydrolysis in an acidic environment, sucrose again turns into monosaccharides:
The resulting mixture invert sugar- found in honey. At 200 °C, sucrose, losing water, turns into a brown mass. (caramel).
polysaccharides - starch and cellulose (fiber) - products of polycondensation (intermolecular dehydration), respectively?- and?-forms of glucose, their general formula is (C 6 H 10 O 5) n. The degree of polymerization of starch is 1000–6000, and that of cellulose is 10,000–14,000. Cellulose is the most common organic substance in nature (in wood, the mass fraction of cellulose reaches 75%). Starch (lighter) and cellulose (harder) undergo hydrolysis (conditions: H 2 SO 4 or HCl, > 100 °C); end product is glucose.
Cellulose esters with acetic acid are of great practical importance:
They are used in the production of artificial acetate fibers and motion picture films.
Examples of tasks of parts A, B1-2. To connect with formula
the correct name is
1) 2-methylpropanol-2
2) 2,2-dimethylethanol
3) propyl ethyl ether
4) ethyl propyl ether
3-4. To connect with formula
the correct name is
1) 1,1-dimethylpropanoic acid
2) 3-methylbutanoic acid
3) 2-methylpropanal
4) dimethylethanal
5. The correct name of the substance CH 3 COOCH 2 CH 3 is
1) methyl acetate
2) ethyl acetate
3) methyl formate
4) ethyl formate
6. Hydrogen bonds are formed between compound molecules
3) acetic acid
4) acetaldehyde
7. For the composition C 4 H 8 O 2, the names of structural isomers from the class of esters are
1) propyl formate
2) diethyl ether
3) ethyl acetate
4) methyl propionate
8-11. Title compound formula
8. sucrose
9. starch
10. fructose
11. fiber
complies with the composition
1) C 6 H 12 O 6
2) (C 6 H 10 O 5) n
3) Cl 2 H 22 O n
12. For limiting monohydric alcohols, the characteristic reactions are
1) hydrolysis
2) hydration
3) esterification
4) dehydration
13. The molecule of the final product of the reaction between phenol and bromine in water contains the total number of atoms of all elements equal to
14-17. In the reaction equation
14. oxidation of ethanol with copper (II) oxide
15. Phenol bromination
16. intermolecular dehydration of ethanol
17. Phenol nitration
the sum of the coefficients is
18. In the esterification reaction, the OH group is split off from the molecule
2) aldehyde
4) acids
19. With the help of chlorophyll in a green plant,
1) oxygen
3) glucose
20-21. Chemical properties of glucose characteristic of
20. alcohols
21. aldehydes
appear in the reaction
1) alcoholic fermentation
2) "silver mirror"
3) esterification
4) neutralization
22-24. When heated with water in the presence of H 2 SO 4 carbohydrate
22. starch
23. cellulose
24. sucrose
after hydrolysis is completed
2) fructose
3) gluconic acid
4) glucose
25. Methods for producing ethanol are
1) ethene hydration
2) glucose fermentation
3) ethane recovery
4) ethanol oxidation
26. Methods for obtaining ethylene glycol are
1) ethene oxidation
2) ethene hydration
3) the action of alkali on 1,2-C 2 H 4 Cl 2
4) Ethine Hydration
27. Methods for obtaining formic acid are
1) methane oxidation
2) phenol oxidation
3) methanol oxidation
4) the reaction of CH 3 OH with CO
28. For the synthesis of acetic acid, compounds are used
1) C 2 H 5 OH
29. Methanol is used in production
1) plastics
2) rubbers
3) gasolines
4) fats and oils
30. To recognize phenol (mixed with butanol-1) use
1) indicator and alkali solution
2) bromine water
3) copper (II) hydroxide
4) ammonia solution of silver oxide (I)
31. The same reagent is suitable for recognition in their solutions of glycerin, acetic acid, acetaldehyde and glucose
3) H 2 SO 4 (conc.)
4) Ag 2 O (in NH 3 solution)
32. Organic matter - a product of the hydration of acetylene, which enters into the "silver mirror" reaction, and upon reduction forms ethanol, is
1) acetaldehyde
2) acetic acid
33. Products A, B, and C in the reaction scheme CO 2 + H 2 O > photosynthesis A > fermentation - CO 2 B > HCOOH B
- is accordingly
2) glucose
3) propanoic acid
4) ethyl formate
34. Phenol will participate in the processes:
1) dehydration
2) bromination
3) isomerization
4) neutralization
5) nitration
6) "silver mirror"
35. Reactions are possible:
1) solid fat + hydrogen >…
2) formic acid + formaldehyde >…
3) methanol + copper (II) oxide >…
4) sucrose + water (in conc. H 2 SO 4) > ...
5) methanal + Ag 2 O (in NH 3 solution) >…
6) ethylene glycol + NaOH (solution) >…
36. For the industrial synthesis of phenol-formaldehyde resin, you should take a set of reagents
1) C 6 H 6, HC (H) O
2) C 6 H 6, CH 3 C (H) O
3) C 6 H 5 OH, HC (H) O
4) C 6 H 5 OH, CH 3 C (H) O
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