Aldehydes – organic matter, whose molecules contain a carbonyl group C=O, connected to a hydrogen atom and a hydrocarbon radical.
The general formula of aldehydes is:
In the simplest aldehyde, formaldehyde, the role of a hydrocarbon radical is played by another hydrogen atom:
A carbonyl group bonded to a hydrogen atom is often called aldehydic:
Ketones– organic substances in the molecules of which the carbonyl group is associated with two hydrocarbon radicals. Obviously, general formula ketones looks like:
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 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 highly polarized due to a shift in electron density π -bonds to oxygen:
Aldehydes and ketones are polar substances with excess electron density on the oxygen atom. Lower members of a series of aldehydes and ketones (formaldehyde, acetaldehyde, acetone) are unlimitedly 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 can not only be reduced, but also oxidize. When oxidized, aldehydes form carboxylic acids.
Oxidation by air oxygen. 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. This makes 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 =O → (-CH 2 -O-) n paraforms n=8-12
Preparation of aldehydes and ketones
Application of aldehydes and ketones
Formaldehyde(methanal, formic aldehyde) H 2 C=O:
a) for the production of phenol-formaldehyde resins;
b) obtaining urea-formaldehyde (urea) resins;
c) polyoxymethylene polymers;
d) synthesis of drugs (urotropine);
e) disinfectant;
f) a preservative for biological preparations (due to the ability to coagulate proteins).
Acetaldehyde(ethanal, acetaldehyde) CH 3 CH=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 first group of properties are addition reactions. In the carbonyl group, there is a double bond between carbon and oxygen, which, as you remember, consists of a sigma bond and a pi bond. In addition reactions, the pi bond is broken and two sigma bonds are formed, one with carbon and the other with oxygen. A partial positive charge is concentrated on carbon, and a partial negative charge on oxygen. Therefore, a negatively charged reagent particle, 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 occurs when heated. The already known hydrogenation catalyst nickel is used. Primary alcohols are obtained from aldehydes, and secondary alcohols from ketones.
In secondary alcohols, the hydroxo group is bonded to a secondary carbon atom.
Second property hydration, addition of water. This reaction is only possible 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 these two specific cases - hydrate of formaldehyde 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, substances react with water and are listed. Among them, the list may include methanal or ethanal.
Third property addition of hydrocyanic acid.
Again, plus goes to minus, and minus to plus. The resulting substances are called hydroxynitriles. Again, the reaction itself is not common, but it is a property you should be aware of.
Fourth property addition of alcohols.
Here again, you don’t 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 complex, it is unlikely that you will be able to learn it, but this is one of the qualitative reactions to 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 with 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 - these are products of combining many molecules (monomers) into one large, 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 are also obtained, for example, water. That is, two products are obtained.
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. The result is polyformaldehyde, also called paraform. Most likely, the exam question may sound like this: substances enter into polymerization reactions. And there is a list of substances that may include formaldehyde.
The seventh property is polycondensation. Once again: during polycondensation, in addition to the polymer, a low molecular weight compound is also obtained, for example, water. Formaldehyde reacts with phenol in this way. For clarity, we first write the equation with two phenol molecules.
As a result, such a dimer is formed and a water molecule is split off. Now let's write the reaction equation in general form.
The polycondensation product is phenol-formaldehyde resin. It has a wide range of applications, from adhesives and varnishes to plastics and chipboard 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. The “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 the salt ammonium acetate is obtained. The silver precipitates, coating the inside of the test tube and creating a mirror-like surface. This reaction occurs on the Unified State 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 I will also note that ketones do not enter into this reaction.
Visually, the formation of a yellow precipitate will first be observed, which then turns red. In some textbooks there is information that first copper hydroxide one is formed, which has a yellow color, which then breaks down into red copper oxide one and water. So this is not true - according to the latest data, during the process of precipitation, the size of the copper oxide particles changes, which ultimately reach sizes that are colored red. The aldehyde is oxidized to the corresponding carboxylic acid. The reaction occurs on the exam very often.
Tenth reaction: 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 molecule is destroyed and the result is a mixture of products.
It is important to note that formic aldehyde, formaldehyde, is oxidized to carbon dioxide, because its corresponding formic acid is itself 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 a maximum of 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, after all, in 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 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 displacing electrons from the hydrogen to it through a chain of sigma bonds. The carbon-hydrogen bond becomes more polar and the hydrogen breaks off more easily when attacked by a reagent. This effect is observed only for the alpha carbon atom, that is, the atom next to the aldehyde group, regardless of the length of the hydrocarbon radical.
In this way, it is possible to obtain, for example, 2-chloroacetaldehyde. Further substitution of hydrogen atoms to trichloroethanal is possible.
Aldehydes and ketones– these are hydrocarbon derivatives containing a functional carbonyl group CO
In aldehydes, the carbonyl group is associated with a hydrogen atom and one radical, and in ketones with two radicals.
General formulas:
The names of common substances of these classes are given in table. 10.
Methanal is a colorless gas with a sharp suffocating odor, highly soluble in water (the traditional name for a 40% solution is formalin), and poisonous. The 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 it is a colorless liquid with a fruity odor, boiling point = 56.24 °C. Mixes well with water.
Chemical properties aldehydes and ketones are due to the presence of the carbonyl group CO; they easily enter into addition, oxidation and condensation reactions.
As a result accession
hydrogen to aldehydes are formed primary alcohols:
When reduced with hydrogen ketones are formed secondary alcohols:
Reaction accession
sodium hydrosulfite is used to isolate and purify aldehydes, since the reaction product is slightly soluble in water:
(such products are converted into aldehydes by the action of dilute acids).
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 capable of participating in reactions condensation
Thus, the condensation of formaldehyde with phenol occurs 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; upon heating, a red precipitate of copper (I) oxide Cu2O appears.
Receipt: general method for aldehydes and ketones – dehydrogenation (oxidation) of alcohols. When dehydrogenating primary
alcohols are obtained aldehydes
And when dehydrogenating secondary alcohols - ketones
Typically, dehydrogenation occurs by heating (300 °C) over finely crushed copper:
During the oxidation of primary alcohols strong oxidizing agents (potassium permanganate, potassium dichromate in an acidic environment) make it difficult to stop the process at the stage of producing 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 (phenoplasts), explosives, varnishes, paints, and 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, and in the production of film and explosives.
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The material contains a brief theoretical introduction, examples of problem solving and tasks for independent work, which can be used to control knowledge in the 10th grade, but also to prepare for the exam in the 11th grade. Answers are provided for the problems.
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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. Chemical reactions 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 – This 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 - 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 acid 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 has a very large effect on the benzene ring, increasing its reactivity. Therefore, phenol easily enters into electrophilic substitution reactions (with substituents oriented in o - and p -positions). For example, it is easily brominated bromine water with the formation of 2,4,6-tribromophenol.
Qualitative reaction to phenol. Phenol forms with FeCl 3 complex salt, colored purple.
Under the influence 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 = 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 НСО (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 its chemical propertiesaldehydes are reducing agents, which are easily oxidized into acids. For example, when aldehydes are oxidized with an ammonia solution of silver oxide, a 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 oxidized much more difficult 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.
Indicate the reaction conditions. 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 1-propanol and sodium metal:
2CH 3 −CH 2 −CH 2 −OH + 2Na → 2CH 3 −CH 2 −CH 2 −ONa + H 2 .
Determine the amounts of the substance 1-propanol 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) = υ (C 3 H 7 OH); υ (C 3 H 7 ONa) = 0.25 mol.
Determine the mass of sodium propylate that can be obtained:
m (C 3 H 7 ONa) = υ(C 3 H 7 ONa) ∙ M (C 3 H 7 ONa);
m (C 3 H 7 ONa) = 0.25 ∙ 82 = 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 formaldehyde.
Solution . We calculate the mass of formaldehyde that will be required to prepare formaldehyde:
m (CH 2 O) = 40*600/100 = 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) = υ(CH 2 O); υ(CH 2 O) = 8 mol.
The mass of required methanol is
m (CH 3 OH) = υ(CH 3 OH) ∙ M (CH 3 OH);
m (CH 3 OH) = 8 ∙ 32 = 256 g.
Tasks and exercises for independent solution
1 . When 1-butanol interacts with excess metallic sodium, hydrogen is released, occupying a volume of 2.8 liters under normal conditions. Determine the amount of butanol-1 substance that has reacted.
(Answer: 0.25 mol).
2. Name the substances X and Y and write reaction equations with which you can carry out the following transformations:
a) propanol-1 → X → propanol-2;
b) ethanol → Y → 1,2-dichloroethane.
Specify the conditions for the reactions to take place.
3 . To produce methanol, 2 m3 of carbon (II) monoxide 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 . Draw up 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 OHa.
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 reaction equations that can be used to carry out the following transformations:
chloroethane → ethanol → ethylene → propanal.
7. When 13.8 g of ethanol was oxidized with an excess of copper (II) oxide, an aldehyde was obtained, 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 ammonia solution of silver oxide. ( Answer: 21.6 g).
9. How much of the substance HCHO is contained in its 30% aqueous solution volume 3 l and density 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. When 6 g of technical preparation of ethanal was oxidized with an ammonia solution of silver oxide, 20 g of metal was formed. Determine the mass fraction (%) of ethanal in the technical preparation. ( Answer: 67.9%). C OH C O
13. Draw up reaction equations that can be used to carry out the following transformations: methane → acetylene → acetaldehyde → ethyl alcohol → acetaldehyde.
14. Draw up reaction equations using which reactions can carry out the following transformations:
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. When dehydrating propanol-2, propylene was obtained, which decolorized 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. Draw up reaction equations that must be carried out to carry out the following transformations: propyne → X → acetone.
Name the substance X, indicate the reaction conditions.
Phenol is used as a raw material for the production of plastics and resins, intermediate products for the paint and varnish and pharmaceutical industries, and as a disinfectant.
10.2. Aldehydes and ketones
Aldehydes and ketones– these are hydrocarbon derivatives containing a functional carbonyl group CO. In aldehydes, the carbonyl group is associated with a hydrogen atom and one radical, and in ketones with two radicals.
General formulas:
The names of common substances of these classes are given in table. 10.
Methanal is a colorless gas with a sharp suffocating odor, highly soluble in water (the traditional name for a 40% solution is formalin), poisonous. The 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 – colorless liquid with a fruity odor, boiling point = 56.24 °C. Mixes well with water.
The chemical properties of aldehydes and ketones are due to the presence of the carbonyl group CO; they easily enter into addition, oxidation and condensation reactions.
As a result accession hydrogen to aldehydes are formed primary alcohols:
When reduced with hydrogen ketones are formed secondary alcohols:
Reaction accession sodium hydrosulfite is used to isolate and purify aldehydes, since the reaction product is slightly soluble in water:
(such products are converted into aldehydes by the action of dilute acids).
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 capable of participating in reactions condensation. Thus, the condensation of formaldehyde with phenol occurs 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 “silver mirror” reaction, i.e. 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; upon heating, a red precipitate of copper (I) oxide Cu 2 O appears.
Receipt: General method for aldehydes and ketones – dehydrogenation(oxidation) of alcohols. When dehydrogenating primary alcohols are obtained aldehydes, and during dehydrogenation of secondary alcohols – ketones. Typically, dehydrogenation occurs by heating (300 °C) over finely crushed copper:
During the oxidation of primary alcohols strong oxidizing agents (potassium permanganate, potassium dichromate in an acidic environment) make it difficult to stop the process at the stage of producing 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 used for the production of plastics (phenoplasts), explosives, varnishes, paints, and medicines. Ethanal– the most important intermediate product 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, and in the production of film and explosives.
10.3. carboxylic acids. Esters. Fats
Carboxylic acids are hydrocarbon derivatives containing the functional group COOH ( carboxyl).
Formulas And titles Some common carboxylic acids are given in table. eleven.
Traditional names of acids HCOOH ( formic), CH 3 COOH (vinegar), C 6 H 5 COOH (benzoic) and (COOH) 2 (oxalic) it is recommended to use them instead of their systematic names.
Formulas And titles acid residues are given in table. 12.
To compile the names of the salts of these carboxylic acids (as well as their esters, see below) traditional names are usually used, for example:
