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. 10.
Methanal is a colorless gas with a pungent suffocating odor, highly soluble in water (the traditional name for a 40% solution is formalin), and poisonous. Subsequent members of the homologous series of aldehydes are liquids and solids.
The simplest ketone, propanone-2, better known as acetone, is a colorless liquid with a fruity odor at room temperature, 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:
A qualitative reaction to the aldehyde group is the “silver mirror” reaction, 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) Cu2O appears.
Obtaining: a common method for aldehydes and ketones is the 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. Methanal is used for the production of plastics (phenolic plastics), explosives, varnishes, paints, medicines. Ethanal is 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.
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Aldehydes- organic substances whose molecules contain a carbonyl group C=O, connected to a hydrogen atom and a hydrocarbon radical.
The general formula for aldehydes is:
In the simplest aldehyde, formaldehyde, the role of the hydrocarbon radical is played by another hydrogen atom:
The carbonyl group attached to the hydrogen atom is often referred to as aldehyde:
Ketones- organic substances in the molecules of which the carbonyl group is bonded to two hydrocarbon radicals. Obviously, the general formula for ketones is:
The carbonyl group of ketones is called keto group.
In the simplest ketone, acetone, the carbonyl group is bonded to two methyl radicals:
Nomenclature and isomerism of aldehydes and ketones
Depending on the structure of the hydrocarbon radical associated with the aldehyde group, limiting, unsaturated, aromatic, heterocyclic and other aldehydes are distinguished:
In accordance with the IUPAC nomenclature, the names of saturated aldehydes are formed from the name of an alkane with the same number of carbon atoms in the molecule using the suffix -al. For example:
The numbering of carbon atoms of the main chain starts from the carbon atom of the aldehyde group. Therefore, the aldehyde group is always located at the first carbon atom, and it is not necessary to indicate its position.
Along with the systematic nomenclature, trivial names of widely used aldehydes are also used. These names are usually derived from the names of carboxylic acids corresponding to aldehydes.
For the name of ketones according to the systematic nomenclature, the keto group is denoted by the suffix -He and a number that indicates the number of the carbon atom of the carbonyl group (numbering should start from the end of the chain closest to the keto group). For example:
For aldehydes, only one type of structural isomerism is characteristic - the isomerism of the carbon skeleton, which is possible from butanal, and for ketones also the isomerism of the position of the carbonyl group. In addition, they are also characterized by interclass isomerism (propanal and propanone).
Physical properties of aldehydes
In an aldehyde or ketone molecule, due to the greater electronegativity of the oxygen atom compared to the carbon atom, the bond C=O strongly polarized due to electron density shift π -bonds to oxygen:
Aldehydes and ketones are polar substances with excess electron density on the oxygen atom. The lower members of the series of aldehydes and ketones (formaldehyde, acetaldehyde, acetone) are infinitely soluble in water. Their boiling points are lower than those of the corresponding alcohols. This is due to the fact that in the molecules of aldehydes and ketones, unlike alcohols, there are no mobile hydrogen atoms and they do not form associates due to hydrogen bonds. Lower aldehydes have a pungent odor; aldehydes containing from four to six carbon atoms in the chain have an unpleasant odor; higher aldehydes and ketones have floral odors and are used in perfumery .
Chemical properties of aldehydes and ketones
The presence of an aldehyde group in a molecule determines the characteristic properties of aldehydes.
1. Recovery reactions.
The addition of hydrogen to aldehyde molecules occurs via a double bond in the carbonyl group. The product of hydrogenation of aldehydes are primary alcohols, ketones are secondary alcohols. So, when acetaldehyde is hydrogenated on a nickel catalyst, ethyl alcohol is formed, and when acetone is hydrogenated, propanol-2 is formed.
Hydrogenation of aldehydes- reduction reaction, in which the degree of oxidation of the carbon atom included in the carbonyl group decreases.
2. Oxidation reactions. Aldehydes are able not only to recover, but also oxidize. When oxidized, aldehydes form carboxylic acids.
Air oxygen oxidation. For example, propionic acid is formed from propionaldehyde (propanal):
Oxidation with weak oxidizing agents(ammonia solution of silver oxide).
If the surface of the vessel in which the reaction is carried out was previously degreased, then the silver formed during the reaction covers it with a thin, even film. It turns out a wonderful silver mirror. Therefore, this reaction is called the "silver mirror" reaction. It is widely used for making mirrors, silvering decorations and Christmas decorations.
3. Polymerization reaction:
n CH 2 \u003d O → (-CH 2 -O-) n paraforms n \u003d 8-12
Obtaining aldehydes and ketones
The use of aldehydes and ketones
Formaldehyde(methanal, formic aldehyde) H 2 C=O:
a) to obtain phenol-formaldehyde resins;
b) obtaining urea-formaldehyde (urea) resins;
c) polyoxymethylene polymers;
d) synthesis medicines(urotropin);
e) disinfectant;
f) preservative of biological preparations (due to the ability to fold the protein).
Acetic aldehyde(ethanal, acetaldehyde) CH 3 CH \u003d O:
a) production of acetic acid;
b) organic synthesis.
Acetone CH 3 -CO-CH 3:
a) solvent for varnishes, paints, cellulose acetates;
b) raw materials for the synthesis of various organic substances.
The material contains a brief theoretical introduction, examples of solving tasks and tasks for independent work, which can be used both to control knowledge in the 10th grade, but also to prepare for the exam in the 11th grade. Answers are provided for the tasks.
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Alcohols, aldehydes, ketones
Theoretical introduction
Alcohols - these are derivatives of hydrocarbons in which one or more hydrogen atoms are replaced by hydroxyl groups −OH.
The chemical properties of alcohols are determined by the hydroxyl group −OH. The chemical reactions of alcohols can proceed with the participation of the entire group (with C–O bond cleavage) or proceed along the hydrogen of the hydroxyl group (with O–H bond cleavage), for example, the esterification reaction.
Phenols - These are organic compounds in which the hydroxyl group is connected directly to the carbon atom of the benzene ring. The simplest representative of phenols is hydroxybenzene or phenol, which has one hydroxyl group in the benzene ring (C 6 H 5 -OH).
Phenol is a solid crystalline substance with a characteristic odor, poorly soluble in water. The chemical properties of phenols are determined by the hydroxyl group and the benzene ring associated with it.
acid properties.Phenols exhibit acidic properties and interact with alkali metals and alkalis:
2C 6 H 5 OH + 2Na → 2C 6 H 5 ONa + H 2 ;
C 6 H 5 OH + NaOH → C 6 H 5 ONa + H 2 O.
Substitution reactions in the benzene ring. The hydroxyl group is very big influence on the benzene ring, increasing its reactivity. Therefore, phenol easily enters into electrophilic substitution reactions (with substituents oriented in o - and p -provisions). For example, it is easily brominated with bromine water to form 2,4,6-tribromophenol.
Qualitative reaction to phenol. Phenol forms with FeCl 3 complex salt, colored purple.
Under the action of oxidizing agents (K 2 Cr 2 O 7 , KMnO 4 ) in the presence of H 2 SO 4 alcohols are oxidized to form aldehydes and ketones, for example:
3C 2 H 5 OH + K 2 Cr 2 O 7 + 4H 2 SO 4 → Cr 2 (SO) 3 + K 2 SO 4 + 3CH 3 - SON + 7H 2 O
acetaldehyde
Aldehydes and ketones contain a carbonyl group C \u003d O in the molecule
In aldehyde molecules, the carbonyl group is connected to a hydrocarbon radical and a hydrogen atom. The first member of the homologous series of aldehydes is methanal HSON (formaldehyde), a 40% aqueous solution of formaldehyde is called formalin.
In ketone molecules, the carbonyl group is linked to two different R−CO−R′ or the same radicals. For example, N 3 C-C-CH 3
║ acetone
According to their chemical propertiesaldehydes are reducing agents, which are easily oxidized to acids. For example, when aldehydes are oxidized with an ammonia solution of silver oxide, carboxylic acid is formed and metallic silver is released (“silver mirror reaction”) and is qualitative for aldehydes:
CH 3 -CH 2 -SON + 2OH → CH 3 -CH 2 -COOH + 2Ag ↓ + 4NH 3 + H 2 O.
Propanal propanoic acid
Ketones are much more difficult to oxidize than aldehydes and only by strong oxidizing agents. In this case, the carbon chain is broken and a mixture of products is formed. Ketones do not react with the silver mirror.
Examples of problem solving
Example 1
C 2 H 4 → X → Y → C 2 H 5 −O−C 2 H 5.
Specify the conditions for the reactions to take place. Name substances X and Y.
Solution . The final product - diethyl ether - is obtained from ethyl alcohol, therefore, substance Y is ethanol. You can go from ethylene to ethanol through an intermediate compound - a halogen derivative of ethane (substance X).
When ethylene reacts with hydrogen bromide, bromoethane is formed:
C 2 H 4 + HBr → C 2 H 5 Br.
Bromoethane is hydrolyzed to alcohol by the action of an aqueous solution of NaOH:
C 2 H 5 Br + NaOH → C 2 H 5 OH + NaBr.
When ethanol is heated to 140 °C in the presence of sulfuric acid, diethyl ether is formed as a catalyst:
C 2 H 5 OH → C 2 H 5 −O−C 2 H 5 + H 2 O. (t, H + )
Example 2 What mass of sodium propylate can be obtained by reacting 15 g of propanol-1 with 9.2 g of sodium?
Solution . We write the reaction equation between propanol-1 and metallic sodium:
2CH 3 -CH 2 -CH 2 -OH + 2Na → 2CH 3 -CH 2 -CH 2 -ONa + H 2.
We determine the amount of propanol-1 substance and sodium:
υ (C 3 H 7 OH) \u003d m / M \u003d 15/60 \u003d 0.25 mol;
υ (Na) \u003d m / M \u003d 9.2 / 23 \u003d 0.4 mol (Na)
It follows from the reaction equation that the number of moles of alcohol and sodium must be equal, therefore, sodium is taken in excess.
Based on the reaction equation, we write:
υ (C 3 H 7 ONa) \u003d υ (C 3 H 7 OH); υ (C 3 H 7 ONa) = 0.25 mol.
Determine the mass of sodium propylate, which can be obtained:
m (C 3 H 7 ONa) \u003d υ (C 3 H 7 ONa) ∙ M (C 3 H 7 ONa);
m (C 3 H 7 ONa) \u003d 0.25 ∙ 82 \u003d 20.5 g.
Example 3 Formalin is a 40% aqueous solution of formaldehyde. Calculate the mass of methanol that must be oxidized to obtain 600 g of formalin.
Solution . We calculate the mass of formaldehyde, which is required for the preparation of formalin:
m (CH 2 O) \u003d 40 * 600/100 \u003d 240 g.
The amount of substance required formaldehyde is equal to
υ (CH2O) = 240/30 = 8 mol.
We compose the equation for the oxidation of methanol:
CH 3 OH + [O] → CH 2 O + H 2 O.
It follows from the reaction equation that υ (CH 3 OH) \u003d υ (CH 2 O); υ(CH 2 O) = 8 mol.
The mass of required methanol is
m (CH 3 OH) \u003d υ (CH 3 OH) ∙ M (CH 3 OH);
m (CH 3 OH) \u003d 8 ∙ 32 \u003d 256 g.
Tasks and exercises for independent solution
1 . During the interaction of butanol-1 with an excess of metallic sodium, hydrogen was released, occupying at normal conditions volume 2.8 l. Determine the amount of butanol-1 substance that has reacted.
(Answer: 0.25 mol).
2. Name the substances X and Y and write the reaction equations with which the following transformations can be carried out:
a) propanol-1 → X → propanol-2;
b) ethanol → Y → 1,2-dichloroethane.
Specify the conditions for the reactions to take place.
3 . To obtain methanol, 2 m3 of carbon monoxide (II) and 5 m3 of hydrogen were used under normal conditions. Received 2.04 kg of alcohol. Determine the yield of alcohol. ( Answer: 71.4%.
4 . Write the reaction equations that can be used to carry out the following transformations:
C → CH 4 → C 2 H 6 → C 2 H 4 → C 2 H 5 OH → C 2 H 5 ONa.
5. Determine the mass of sodium phenolate, which can be obtained by reacting 4.7 g of phenol with 4.97 ml of a 35% NaOH solution (ρ = 1.38 g/ml). ( Answer: 5.8 g).
6. Write the reaction equations with which you can carry out the following transformations:
chloroethane → ethanol → ethylene → propanal.
7. Oxidation of 13.8 g of ethanol with an excess of copper (II) oxide yielded aldehyde, the mass of which was 9.24 g. Determine the yield of the reaction product. ( Answer: 70%.
8. Determine the mass of silver that will be obtained if 50 g of an 11.6% aqueous solution of propanal is added to an excess of an ammonia solution of silver oxide. ( Answer: 21.6 g).
9. What amount of substance HCHO is contained in its 30% aqueous solution with a volume of 3 liters and a density of 1.06 g/ml? ( Answer: 31.8 mol).
10. 280 ml of acetylene was used to obtain acetaldehyde, the yield of which was 80%. What mass of silver can be formed by adding all the resulting aldehyde to an excess of ammonia solution of silver oxide? ( Answer: 1.08 g).
11. Write reaction equations that can be used to carry out the following transformations:
C → CaC 2 → C 2 H 2 → C 2 H 4 → C 2 H 6 → C 2 H 5 Cl → C 2 H 5 OH.
12. During the oxidation of 6 g of the technical preparation of ethanal with an ammonia solution of silver oxide, 20 g of the metal was formed. Determine the mass fraction (%) of ethanal in the technical preparation. ( Answer: 67.9%. C O O C O
13. Write reaction equations that can be used to carry out the following transformations: methane → acetylene → acetaldehyde → ethyl alcohol → acetaldehyde.
14. Write reaction equations for the following reactions:
C → CH 4 → C 2 H 2 → C 6 H 6 → C 6 H 5 Cl → C 6 H 5 OH.
16. Write reaction equations that can be used to carry out the following transformations:
acetaldehyde → ethanol → ethylene → acetylene → acetaldehyde.
17. Write the reaction equations that must be carried out to carry out the following transformations:
a) CH4 → X → CH3OH → CH3-O-CH3;
b) ethanol → ethylene → Y → ethanol.
Name substances X and Y.
18. During the dehydration of propanol-2, propylene was obtained, which discolored bromine water weighing 200 g. The mass fraction of bromine in bromine water is 3.2%. Determine the mass of propanol-2 taken for the reaction. ( Answer: 2.4 g).
(Answer: 11.28 g).
20. Compose the equations of the reactions that must be carried out to carry out the following transformations: propyne → X → acetone.
Name the substance X, indicate the conditions for the reaction.
The first group of properties is addition reactions. In the carbonyl group, between carbon and oxygen, there is a double bond, which, as you remember, consists of a sigma bond and a pi bond. In addition reactions, the pi bond breaks and two sigma bonds are formed, one with carbon and the other with oxygen. Carbon has a partial positive charge, and oxygen has a partial negative charge. Therefore, a negatively charged particle of the reagent, an anion, is attached to carbon, and a positively charged part of the molecule is attached to oxygen.
First property hydrogenation, addition of hydrogen.
The reaction takes place when heated. The hydrogenation catalyst already known to you, nickel, is used. Primary alcohols are obtained from aldehydes, secondary alcohols from ketones.
In secondary alcohols, the hydroxo group is bonded to a secondary carbon atom.
Second property hydration, water addition. This reaction is possible only for formaldehyde and acetaldehyde. Ketones do not react with water at all.
All addition reactions proceed in such a way that plus goes to minus, and minus to plus.
As you remember from the video about alcohols, the presence of two hydroxo groups on one atom is an almost impossible situation, such substances are extremely unstable. So, specifically, these two cases formaldehyde hydrate and acetaldehyde are possible, although they exist only in solution.
It is not necessary to know the reactions themselves. Most likely, the question on the exam may sound like a statement of fact, for example, they react with water and substances are listed. Among their list of which may be methanal or ethanal.
Third property addition of hydrocyanic acid.
Again, plus goes to minus, and minus to plus. Substances called hydroxynitriles are obtained. Again, the reaction itself is not common, but you need to know about this property.
Fourth property addition of alcohols.
Here again, you do not need to know the reaction equation by heart, you just need to understand that such an interaction is possible.
As usual in reactions of addition to a carbonyl group, plus to minus, and minus to plus.
Fifth property reaction with sodium hydrosulfite.
And again, the reaction is quite complicated, it is unlikely to learn it, but this is one of the qualitative reactions for aldehydes, because the resulting sodium salt precipitates. That is, in fact, you should know that aldehydes react with sodium hydrosulfite, this will be enough.
This concludes the first group of reactions. The second group is polymerization and polycondensation reactions.
2. Polymerization and polycondensation of aldehydes
You are familiar with polymerization: polyethylene, butadiene and isoprene rubbers, polyvinyl chloride are the products of combining many molecules (monomers) into one large, into a single polymer chain. That is, one product is obtained. During polycondensation, the same thing happens, but in addition to the polymer, low molecular weight products, such as water, are also obtained. That is, there are two products.
So, sixth property polymerization. Ketones do not enter into these reactions; only the polymerization of formaldehyde is of industrial importance.
The pi bond breaks and two sigma bonds are formed with neighboring monomers. It turns out polyformaldehyde, also called paraform. Most likely, the question on the exam may sound like this: substances enter into the polymerization reaction. And a list of substances is given, among which there may be formaldehyde.
The seventh property is polycondensation. Once again: during polycondensation, in addition to the polymer, a low-molecular compound is also obtained, for example, water. Formaldehyde enters into such a reaction with phenol. For clarity, we first write the equation with two phenol molecules.
As a result, such a dimer is obtained and a water molecule is split off. Now we write the reaction equation in general form.
The polycondensation product is phenol-formaldehyde resin. It has a wide range of applications ranging from adhesives and varnishes to plastics and particle board components.
Now the third group of properties oxidation reactions.
3. Oxidation of aldehydes and ketones
Eighth the reaction in the general list is a qualitative reaction to the aldehyde group oxidation with an ammonia solution of silver oxide. Silver mirror reaction. I will say right away that ketones do not enter into this reaction, only aldehydes.
The aldehyde group is oxidized to a carboxyl, acidic group, but in the presence of ammonia, which is a base, a neutralization reaction immediately occurs and a salt, ammonium acetate, is obtained. The silver precipitates, coating the inside of the tube and creating a mirror-like surface. This reaction occurs on the exam all the time.
By the way, the same reaction is qualitative for other substances that have an aldehyde group, for example, formic acid and its salts, as well as glucose.
ninth the reaction is also qualitative for the aldehyde group oxidation with freshly precipitated copper hydroxide two. Here, too, I note that ketones do not enter into this reaction.
Visually, the formation of a yellow precipitate will be observed first, which then turns red. In some textbooks, information is found that copper hydroxide alone is first formed, which has a yellow color, which then decomposes into red copper oxide alone and water. So this is not true according to the latest data, in the process of precipitation, the size of copper oxide particles changes, which ultimately reach sizes that are painted exactly in red. The aldehyde is oxidized to the corresponding carboxylic acid. The reaction occurs on the exam very often.
The tenth reaction is the oxidation of aldehydes with an acidified solution of potassium permanganate when heated.
Discoloration of the solution occurs. The aldehyde group is oxidized to a carboxyl group, that is, the aldehyde is oxidized to the corresponding acid. For ketones, this reaction has no practical meaning, since the destruction of the molecule occurs and the result is a mixture of products.
It is important to note that formic aldehyde, formaldehyde, oxidizes to carbon dioxide, because the corresponding formic acid itself is not resistant to strong oxidizing agents.
As a result, carbon goes from oxidation state 0 to oxidation state +4. Let me remind you that methanol, as a rule, under such conditions is oxidized to the maximum to CO 2, skipping the stage of both aldehyde and acid. This feature must be remembered.
Eleventh reaction combustion, complete oxidation. Both aldehydes and ketones burn to carbon dioxide and water.
Let us write the reaction equation in general form.
According to the law of conservation of mass, there should be as many atoms on the left as there are atoms on the right. Because in fact chemical reactions atoms do not go anywhere, but the order of bonds between them simply changes. So there will be as many carbon dioxide molecules as there are carbon atoms in a molecule of a carbonyl compound, since the molecule contains one carbon atom. That is n CO 2 molecules. There will be half as many water molecules as hydrogen atoms, that is, 2n / 2, which means just n.
There are the same number of oxygen atoms on the left and on the right. On the right, there are 2n of them from carbon dioxide, because each molecule has two oxygen atoms, plus n of water, for a total of 3n. On the left, there are the same number of oxygen atoms 3n, but one of the atoms is in the aldehyde molecule, which means it must be subtracted from the total to get the number of atoms per molecular oxygen. It turns out that 3n-1 atoms contain molecular oxygen, which means there are 2 times fewer molecules, because one molecule contains 2 atoms. That is (3n-1)/2 oxygen molecules.
Thus, we have compiled the equation for the combustion of carbonyl compounds in a general form.
And finally twelfth property related to substitution reactions halogenation at the alpha carbon atom. Let us turn once again to the structure of the aldehyde molecule. Oxygen pulls electron density onto itself, creating a partial positive charge on carbon. The methyl group tries to compensate for this positive charge by shifting electrons from hydrogen to it along a chain of sigma bonds. The carbon-hydrogen bond becomes more polar and the hydrogen breaks off more easily when attacked with a reagent. This effect is observed only for the alpha carbon atom, that is, the atom following the aldehyde group, regardless of the length of the hydrocarbon radical.
Thus, it is possible to obtain, for example, 2-chloroacetaldehyde. Further substitution of hydrogen atoms to trichloroethane is possible.
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. 10.
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:
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