Aldehydes and ketones. Aldehydes are isomeric to another class of compounds, ketones.

Aldehydes are a class of organic compounds containing a carbonyl group -СНThe name of aldehydes comes from the name of hydrocarbon radicals with the addition of the suffix -al. The general formula of saturated aldehydes is CnH2n + 1COH. Nomenclature and isomerism

The nomenclature of these two groups of compounds is constructed differently. Trivial names of aldehydes associate them with the trivial names of the acids into which they turn during oxidation

From ketones only a few have trivial names (eg, acetone). Widely used for them radical functional nomenclature, in which the names of ketones are given using the names of the radicals associated with the carbonyl group. According to IUPAC nomenclature, names of aldehydes are derived from the name of a hydrocarbon with the same number of carbon atoms by adding the ending –al.For ketones, this nomenclature requires ending -He. The number indicates the position of the functional group in the ketone chain.

Compound	Names according to trivial and radical functional nomenclatures	IUPAC names
	formicaldehyde; formaldehyde	methanal
	acetaldehyde; acetaldehyde	ethanal
	propionaldehyde	propional
	butyraldehyde	butanal
	isobutyraldehyde	methylpropanal
	valeraldehyde	pentanal
	isovaleraldehyde	3-methylbutanal
	acetone; dimethyl ketone	propanone
	methyl ethyl ketone	butanone
	methylpropyl ketone	pentanone-2
	methyl isopropyl ketone	3-methylbutanone-2

Isomerism of aldehydes and ketones is fully reflected by the nomenclature and does not require comment. Aldehydes and ketones with the same number of carbon atoms are isomers. For example:

Methods of preparation – Oxidation or catalytic dehydrogenation of primary alcohols to aldehydes, secondary alcohols to ketones. These reactions have already been mentioned when considering the chemical properties of alcohols.

– Pyrolysis of calcium or barium salts of carboxylic acids, one of which is the salt of formic acid, produces aldehydes.

– Hydrolysis of geminal ( substituents on one carbon ) dihaloalkanes

– Hydration of acetylene and its homologues occurs in the presence of mercury sulfate (Kucherov reaction) or over a heterogeneous catalyst

Physical properties. Formic aldehyde is a gas. The remaining lower aldehydes and ketones are liquids that are poorly soluble in water. Aldehydes have a suffocating odor. Ketones usually smell nice. 1. R. Oxidation. Aldehydes are easily oxidized to carboxylic acids. Oxidizing agents can be copper (II) hydroxide, silver oxide, air oxygen:

Aromatic aldehydes are more difficult to oxidize than aliphatic ones. Ketones, as mentioned above, are more difficult to oxidize than aldehydes. Oxidation of ketones is carried out under harsh conditions, in the presence of strong oxidizing agents. Formed as a result of a mixture of carboxylic acids. This produces metallic silver. A silver oxide solution is prepared immediately before the experiment:

Aldehydes also reduce freshly prepared light blue ammonia solution of copper(II) hydroxide (Fehling's reagent) to yellow copper(I) hydroxide, which decomposes when heated to release a bright red precipitate of copper(I) oxide. CH3-CH=O + 2Cu(OH)2 - CH3COOH+2CuOH+H2O 2CuOH->Cu2O+H2O

2. R. Accessions. Hydrogenation is the addition of hydrogen. Carbonyl compounds are reduced to alcohols with hydrogen, lithium aluminum hydride, and sodium borohydride. Hydrogen is added via the C=O bond. The reaction is more difficult than the hydrogenation of alkenes: heating is required, high pressure and metal catalyst (Pt,Ni

Organic drugs

We study drugs divided into groups according to chemical classification. The advantage of this classification is the ability to identify and study general patterns in the development of methods for obtaining drugs that make up the group, methods of pharmaceutical analysis based on the physical and chemical properties of substances, and establishing a connection between chemical structure and pharmacological action.

All drugs are divided into inorganic and organic. Inorganic, in turn, are classified according to the position of the elements in the PS. And organic ones are divided into derivatives of the aliphatic, alicyclic, aromatic and heterocyclic series, each of which is divided into classes: hydrocarbons, halogen derivatives of hydrocarbons, alcohols, aldehydes, ketones, acids, ethers and esters, etc.

ALIPHATIC COMPOUNDS, LIKE DRUGS.

Preparations of aldehydes and their derivatives. Carbohydrates

Aldehydes

This group of compounds includes organic medicinal substances containing an aldehyde group or their functional derivatives.

General formula:

Pharmacological properties

The introduction of an aldehyde group into the structure of an organic compound gives it a narcotic and antiseptic effect. In this regard, the action of aldehydes is similar to the action of alcohols. But unlike the alcohol group, the aldehyde group increases the toxicity of the compound.

Factors influencing the structure on the pharmacological action :

elongation of the alkyl radical increases activity, but at the same time toxicity increases;

the introduction of unsaturated bonds and halogens has the same effect;

the formation of the hydrated form of aldehyde leads to a decrease in toxicity. But the ability to form a stable hydrate form is manifested only in chlorinated aldehydes. Thus, formaldehyde is a protoplasmic poison, used for disinfection, acetaldehyde and chloral are not used in medicine due to their high toxicity, and chloral hydrate is a drug used as a sleeping pill and sedative.

The strength of the narcotic (pharmacological) effect and toxicity increased from formaldehyde to acetaldehyde and chloral. The formation of the hydrate form (chloral hydrate) can dramatically reduce toxicity while maintaining the pharmacological effect.

According to physical condition aldehydes may be gaseous (low molecular weight), liquids and solids. Low molecular weight ones have a sharp bad smell, high molecular weight – pleasant floral.

Chemical properties

Chemically, these are highly reactive substances, which is due to the presence of a carbonyl group in their molecule.

The high reactivity of aldehydes is explained by:

a) the presence of a polarized double bond

b) carbonyl dipole moment

c) the presence of a partial positive charge on the carbonyl carbon atom

σ -

σ + H

The double bond between C and O, unlike the double bond between two carbons, is highly polarized, since oxygen has a much higher electronegativity than carbon, and the electron density of the π bond is shifted towards oxygen. Such high polarization determines the electrophilic properties of the carbon of the carbonyl group and its ability to react with nucleophilic compounds (to enter into nucleophilic addition reactions). The oxygen group has nucleophilic properties.

Characteristic reactions are oxidation and nucleophilic addition

I. Oxidation reactions.

Aldehydeseasily oxidize. Oxidation of aldehydes to acids occurs under the influence as strongand weak oxidizing agents .

Many metals - silver, mercury, bismuth, copper - are reduced from solutions of their salts, especially in the presence of alkali. This distinguishes aldehydes from other organic compounds capable of oxidation - alcohols, unsaturated compounds, the oxidation of which requires stronger oxidizing agents. Consequently, the oxidation reactions of aldehydes with complexly bound cations of mercury, copper, and silver in an alkaline medium can be used to prove the authenticity of aldehydes.

I. 1 .Reactionwith ammonia solution of silver nitrate (silver mirror reaction) FS is recommended to confirm the authenticity of substances with an aldehyde group. It is based on the oxidation of aldehyde to acid and the reduction of Ag + to Ag↓.

AgNO 3 + 2NH 4 OH → NO 3 +2H 2 O

NSSON+ 2NO 3 + H 2 O → HCOONH 4 + 2Ag↓+ 2NH 4 NO 3 + NH 3

Formaldehyde, oxidizing to the ammonium salt of formic acid, reduces metallic silver, which is precipitatedon the walls of the test tube in the form shiny coating "mirror" or gray sediment.

I. 2. Reactionwith Fehling's reagent (a complex compound of copper (II) with potassium-sodium salt of tartaric acid). Aldehydes reduce the copper(II) compound to copper(I) oxide, A brick-red precipitate forms. Prepare before use).

Felling's reagent 1 - CuSO 4 solution

Felling's reagent 2 – alkaline solution of potassium-sodium salt of tartaric acid

When mixing 1:1 Felling's reagents 1 and 2 a blue copper complex compound is formed (II) with potassium-sodium tartaric acid:

blue coloring

When the aldehyde is added and heated, the blue color of the reagent disappears, and an intermediate product is formed - a yellow precipitate of copper (I) hydroxide, which immediately decomposes into a red precipitate of copper (I) oxide and water.

2KNa+ R- COH+2NaOH+ 2KOH→ R- COONa+4KNaC 4 H 4 O 6 + 2 CuOH ↓ +H2O

2 CuOH ↓ →Cu 2 O ↓ +H2O

Yellow sediment brick red sediment

The textbooks have a different general reaction scheme

I. 3. Reactionwith Nessler's reagent (alkaline solution of potassium tetraiodomercurate (II). Formaldehyde reduces the mercury ion to metallic mercury - a dark gray precipitate.

R-COH + K 2 +3KOH → R-COOK + 4KI + Hg↓ + 2H 2 O

Aldehydes and their chemical properties

Aldehydes are those organic substances whose molecules contain a carbonyl group bonded to at least one hydrogen atom and a hydrocarbon radical.

Chemical properties aldehydes are predetermined in their molecule by the presence of a carbonyl group. In this regard, addition reactions can be observed in the carbonyl group molecule.

So, for example, if you take formaldehyde vapor and pass it along with hydrogen over a heated nickel catalyst, then hydrogen will join and formaldehyde will be reduced to methyl alcohol. In addition, the polar nature of this bond also gives rise to reactions of aldehydes such as the addition of water.

Now let's look at all the features of reactions from the addition of water. It should be noted that a hydroxyl group is added to the carbon atom of the carbonyl group, which carries a partial positive charge due to the electron pair of the oxygen atom.

The following reactions are typical for this addition:

First, hydrogenation occurs and primary alcohols RCH2OH are formed.
Secondly, alcohols are added and hemiacetals R-CH (OH) – OR are formed. And in the presence of hydrogen chloride HCl, acting as a catalyst, and with an excess of alcohol, we observe the formation of acetal RCH (OR)2;
Thirdly, sodium hydrosulfite NaHSO3 is added and derivatives of hydrosulfite aldehydes are formed. During the oxidation of aldehydes, one can observe such special reactions as interaction with an ammonia solution of silver (I) oxide and with copper (II) hydroxide and the formation of carboxylic acids.

The polymerization of aldehydes is characterized by such special reactions as linear and cyclic polymerization.

If we talk about the chemical properties of aldehydes, the oxidation reaction should also be mentioned. Such reactions include the “silver mirror” reaction and the traffic light reaction.

You can observe the unusual reaction of the “silver mirror” by conducting an interesting experiment in the classroom. To do this, you will need a cleanly washed test tube, into which you should pour a few milliliters of an ammonia solution of silver oxide, and then add four or five drops of formaldehyde to it. The next step in carrying out this experiment is to place the test tube in a glass with hot water and then you can see how a shiny layer appears on the walls of the test tube. This resulting coating is a deposit of metallic silver.

And here is the so-called “traffic light” reaction:

Physical properties of aldehydes

Now let's begin to consider the physical properties of aldehydes. What properties do these substances have? It should be noted that a number of simple aldehydes are colorless gases, more complex ones are presented in the form of a liquid, but higher aldehydes are solids. The more molecular mass aldehydes, the higher the boiling point. For example, propionaldehyde reaches its boiling point at 48.8 degrees, but propyl alcohol boils at 97.8 0C.

If we talk about the density of aldehydes, then it less than one. For example, acetaldehyde and formic aldehyde tend to dissolve well in water, while more complex aldehydes have a weaker ability to dissolve.

Aldehydes, which belong to the lowest category, have a sharp and unpleasant odor, while solid and insoluble in water, on the contrary, are characterized by a pleasant floral odor.

Finding aldehydes in nature

In nature, representatives are found everywhere various groups aldehydes. They are present in the green parts of plants. This is one of the simplest groups of aldehydes, which includes formic aldehyde CH2O.

Aldehydes with a more complex composition are also found. These types include vanillin or grape sugar.

But since aldehydes have the ability to easily enter into all sorts of interactions and have a tendency to oxidize and reduce, we can say with confidence that aldehydes are very capable of various reactions and therefore they are extremely rare in their pure form. But their derivatives can be found everywhere, both in plant and animal environments.

Application of aldehydes

The aldehyde group is present in a number of natural substances. Their distinctive feature, at least many of them, is the smell. For example, representatives of higher aldehydes have various aromas and are part of essential oils. Well, as you already know, such oils are present in floral, spicy and fragrant plants, fruits and vegetables. They have found large-scale use in the production of industrial goods and in the production of perfumes.

Aliphatic aldehyde CH3(CH2)7C(H)=O can be found in essential oils citrus fruits. Such aldehydes have an orange odor and are used in Food Industry, as a flavoring agent, and also in cosmetics, perfumery and household chemicals, as a fragrance.

Formic aldehyde is a colorless gas that has a sharp, specific odor and easily dissolves in water. This aqueous solution of formaldehyde is also called formalin. Formaldehyde is very poisonous, but in medicine it is used in diluted form as a disinfectant. It is used to disinfect instruments, and it weak solution Used to wash the skin when sweating heavily.

In addition, formaldehyde is used in tanning leather, as it has the ability to combine with protein substances that are present in the leather.

IN agriculture formaldehyde has proven itself to be effective in treating grain before sowing. It is used to produce plastics, which are so necessary for equipment and household needs.

Acetaldehyde is a colorless liquid that has the smell of rotten apples and easily dissolves in water. It is used to obtain acetic acid and other substances. But since it is a toxic substance, it can cause poisoning of the body or inflammation of the mucous membranes of the eyes and respiratory tract.

1. R. Oxidation.

Aldehydes are easily oxidized to carboxylic acids. Oxidizing agents can be copper(II) hydroxide, oxidesilver, air oxygen:

Aromatic aldehydes are more difficult to oxidize than aliphatic ones. Ketones, as mentioned above, are more difficult to oxidize than aldehydes. Oxidation of ketones is carried out under harsh conditions, in the presence of strong oxidizing agents. Formed as a result of a mixture of carboxylic acids. How to distinguish aldehydes from ketones? The difference in oxidation ability serves as the basis for qualitative reactions that distinguish aldehydes from ketones. Many mild oxidizing agents react readily with aldehydes but are inert towards ketones. a) Tollens' reagent (ammonia solution of silver oxide), containing complex ions +, gives a “silver mirror” reaction with aldehydes. This produces metallic silver. A silver oxide solution is prepared nepo indirectly d experience:

Tollens' reagent oxidizes aldehydes to the corresponding carboxylic acids, which form ammonium salts in the presence of ammonia. The oxidizing agent itself is reduced to metallic silver in this reaction. Due to the thin silver coating on the walls of the test tube that is formed during this reaction, the reaction of aldehydes with an ammonia solution of silver oxide is called the “silver mirror” reaction. CH3-CH=O)+2OH->CH3COONH4+2Ag+3NH3+H2O. Aldehydes also reduce freshly prepared light blue ammonia solution of copper(II) hydroxide (Fehling's reagent) to yellow copper(I) hydroxide, which decomposes when heated to release a bright red precipitate of copper(I) oxide. CH3-CH=O + 2Cu(OH)2 - CH3COOH+2CuOH+H2O 2CuOH->Cu2O+H2O

2. R. Accessions

Hydrogenation is the addition of hydrogen.

Carbonyl compounds are reduced to alcohols with hydrogen, lithium aluminum hydride, and sodium borohydride. Hydrogen is added via the C=O bond. The reaction is more difficult than the hydrogenation of alkenes: heat, high pressure and a metal catalyst (Pt, Ni) are required:

3. Interaction with water Ouch.

4. Interaction with alcohols.

When aldehydes react with alcohols, hemiacetals and acetals can be formed. Hemiacetals are compounds that contain a hydroxyl and an alkoxy group at one carbon atom. Acetals include substances whose molecules contain a carbon atom with two alkoxy substituents.

Acetals, unlike aldehydes, are more resistant to oxidation. Due to the reversibility of interaction with alcohols, they are often used in organic synthesis to “protect” the aldehyde group.

4.Addition of hydrosulfites.

Hydrosulfite NaHSO3 also adds at the C=O bond to form a crystalline derivative from which the carbonyl compound can be regenerated. Bisulfite derivatives are used for the purification of aldehydes and ketones.

As a result of the polycondensation of phenol with formaldehyde in the presence of catalysts, phenol-formaldehyde resins are formed, from which plastics - phenol plastics (bakelites) are obtained. Phenolic plastics are the most important substitutes for non-ferrous and ferrous metals in many industries. They are made from a large number of consumer products, electrical insulating materials and construction parts. A fragment of phenol-formaldehyde resin is shown below:

The starting compounds for the production of aldehydes and ketones can be hydrocarbons, halogen derivatives, alcohols and acids.

Application of carbonyl compounds

Formaldehyde is used to produce plastics, such as bakelite, leather tanning, disinfection, and seed dressing. More recently, a method for producing polyformaldehyde (-CH2-O-)n, which has high chemical and thermal stability, has been developed in our country.

This is the most valuable structural plastic, capable of replacing metals in many cases. Acetaldehyde is used to produce acetic acid and some plastics. Acetone is used as a starting material for the synthesis of many compounds (for example, methyl methacrylate, the polymerization of which produces plexiglass); it is also used as a solvent.

Among oxygen-containing organic compounds great value have two whole classes of substances, which are always studied together for their similarity in structure and manifested properties. These are aldehydes and ketones. It is these molecules that underlie many chemical syntheses, and their structure is interesting enough to become the subject of study. Let's take a closer look at what these classes of compounds are.

Aldehydes and ketones: general characteristics

From a chemical point of view, the class of aldehydes should include organic molecules containing oxygen as part of the functional group -SON, called carbonyl. The general formula in this case will look like this: R-COH. By their nature, these can be both limiting and non-limiting compounds. Also among them there are aromatic representatives, along with aliphatic ones. The number of carbon atoms in the radical chain varies quite widely, from one (formaldehyde or methanal) to several dozen.

Ketones also contain a carbonyl group -CO, but it is not connected to a hydrogen cation, but to another radical, different or identical to the one in the chain. The general formula looks like this: R-CO-R, . It is obvious that aldehydes and ketones are similar in the presence of a functional group of this composition.

Ketones can also be saturated and unsaturated, and the properties exhibited are similar to those of a closely related class. Several examples can be given to illustrate the composition of molecules and reflect the accepted designations for the formulas of the substances in question.

1. Aldehydes: methanal - HCOH, butanal - CH 3 -CH 2 -CH 2 -CH, phenylacetic - C 6 H 5 -CH 2 -CH.
2. Ketones: acetone or dimethyl ketone - CH 3 -CO-CH 3, methyl ethyl ketone - CH 3 -CO-C 2 H 5 and others.

Obviously, the name of these compounds is formed in two ways:

• according to rational nomenclature according to the radicals included in the composition and the class suffix -al (for aldehydes) and -on (for ketones);
• trivial, historically established.

If you bring general formula for both classes of substances, it will become clear that they are isomers of each other: C n H 2n O. They themselves are characterized by the following types of isomerism:

To distinguish between representatives of both classes, qualitative reactions are used, most of which allow the identification of the aldehyde. Since the chemical activity of these substances is slightly higher, due to the presence of a hydrogen cation.

Molecule structure

Let's look at what aldehydes and ketones look like in space. The structure of their molecules can be reflected in several points.

1. The carbon atom directly included in the functional group has sp 2 hybridization, which allows part of the molecule to have a flat spatial shape.
2. In this case, the polarity of the C=O bond is strong. Being more electronegative, oxygen takes the bulk of the density, concentrating a partially negative charge on itself.
3. In aldehydes O-H connection is also highly polarized, which makes the hydrogen atom mobile.

As a result, it turns out that such a structure of molecules allows the compounds in question to be both oxidized and reduced. The formula of an aldehyde and a ketone with a redistributed electron density makes it possible to predict the products of reactions in which these substances participate.

History of discovery and study

Like many organic compounds, people succeeded in isolating and studying aldehydes and ketones only in the 19th century, when vitalistic views completely collapsed and it became clear that these compounds could be formed synthetically, artificially, without the participation of living beings.

However, back in 1661, R. Boyle managed to obtain acetone (dimethyl ketone) when he exposed calcium acetate to heat. But study this substance in detail and name it, determine systematic position among others, he failed. It was only in 1852 that Williamson was able to bring this matter to completion, and then the history of the detailed development and accumulation of knowledge about carbonyl compounds began.

Physical properties

Let's consider what physical properties aldehydes and ketones. Let's start with the first ones.

1. The first representative of methanal state of aggregation- gas, the next eleven are liquids, over 12 carbon atoms are part of solid aldehydes of normal structure.
2. Boiling point: depends on the number of C atoms; the more there are, the higher it is. In this case, the more branched the chain, the lower the temperature drops.
3. For liquid aldehydes, the viscosity, density, and refractive indexes also depend on the number of atoms. The more there are, the higher they are.
4. Gaseous and liquid aldehydes dissolve in water very well, but solid ones practically cannot do this.
5. The smell of representatives is very pleasant, often the aromas of flowers, perfumes, and fruits. Only those aldehydes in which the number of carbon atoms is 1-5 are strong and unpleasant-smelling liquids.

If we denote the properties of ketones, we can also highlight the main ones.

1. Aggregate states: lower representatives are liquids, more massive ones are solid compounds.
2. The smell is pungent and unpleasant in all representatives.
3. Solubility in water is good for the lower ones, and excellent in organic solvents for all.
4. Volatile substances, this indicator exceeds that of acids and alcohols.
5. The boiling and melting points depend on the structure of the molecule and vary greatly depending on the number of carbon atoms in the chain.

These are the main properties of the compounds under consideration, which belong to the group of physical ones.

Chemical properties

The most important thing is what aldehydes and ketones react with and the chemical properties of these compounds. Therefore, we will definitely consider them. First, let's deal with aldehydes.

1. Oxidation to the corresponding carboxylic acids. General form reaction equation: R-COH + [O] = R-COOH. Aromatic representatives enter into such interactions even more easily; they are also capable of forming esters, which have important industrial value. The following oxidizing agents are used: oxygen, Tollens' reagent, copper (II) hydroxide and others.
2. Aldehydes manifest themselves as strong reducing agents, while turning into saturated monohydric alcohols.
3. Interaction with alcohols to form acetals and hemiacetals.
4. Special reactions are polycondensation. As a result, phenol-formaldehyde resins are formed, which are important for the chemical industry.
5. Several specific reactions with the following reagents:

• hydroalcoholic alkali;
• Grignard reagent;
• hydrosulfites and others.

A qualitative reaction to this class of substances is the “silver mirror” reaction. As a result, metallic reduced silver and the corresponding carboxylic acid are formed. It requires an ammonia solution of silver oxide or Tollins reagent.

Chemical properties of ketones

Alcohols, aldehydes, and ketones are compounds with similar properties, since they are all oxygen-containing. However, already at the oxidation stage it becomes clear that alcohols are the most active and easily affected compounds. Ketones are the most difficult to oxidize.

1. Oxidative properties. As a result, secondary alcohols are formed.
2. Hydrogenation also leads to the products mentioned above.
3. Keto-enol tautomerism is a special specific property of ketones to take the beta form.
4. Aldol condensation reactions with the formation of beta-keto alcohols.
5. Ketones can also interact with:

• ammonia;
• hydrocyanic acid;
• hydrosulfites;
• hydrazine;
• orthosilicic acid.

Obviously, the reactions of such interactions are very complex, especially those that are specific. These are all the main features that aldehydes and ketones exhibit. Chemical properties underlie many syntheses of important compounds. Therefore, knowing the nature of molecules and their character during interactions is extremely necessary in industrial processes.

Addition reactions of aldehydes and ketones

We have already examined these reactions, but did not give them such a name. All interactions as a result of which the carbonyl group exhibited activity can be classified as addition. Or rather, a mobile hydrogen atom. That is why in this matter preference is given to aldehydes, due to their better reactivity.

With what substances are reactions of aldehydes and ketones possible by nucleophilic substitution? This:

1. Hydrocyanic acid produces cyanohydrins - the starting material for the synthesis of amino acids.
2. Ammonia, amines.
3. Alcohols.
4. Water.
5. Sodium hydrogen sulfate.
6. Grignard reagent.
7. Thiols and others.

These reactions are of great industrial importance, since the products are used in various areas of human activity.

Methods of obtaining

There are several main methods by which aldehydes and ketones are synthesized. Production in laboratory and industry can be expressed in the following ways.

1. The most common method, including in laboratories, is the oxidation of the corresponding alcohols: primary to aldehydes, secondary to ketones. The following can act as an oxidizing agent: chromates, copper ions, potassium permanganate. General form of the reaction: R-OH + Cu (KMnO 4) = R-COH.
2. In industry, a method based on the oxidation of alkenes - oxosynthesis - is often used. The main agent is synthesis gas, a mixture of CO 2 + H 2. The result is an aldehyde with one more carbon in the chain. R=R-R + CO 2 + H 2 = R-R-R-COH.
3. Oxidation of alkenes with ozone - ozonolysis. The result also suggests an aldehyde, but also a ketone in the mixture. If the products are mentally combined by removing the oxygen, it will become clear which original alkene was taken.
4. Kucherov reaction - hydration of alkynes. An obligatory agent is mercury salts. One of the industrial methods for the synthesis of aldehydes and ketones. R≡R-R + Hg 2+ + H 2 O = R-R-COH.
5. Hydrolysis of dihalogenated hydrocarbons.
6. Reduction of: carboxylic acids, amides, nitriles, acid chlorides, esters. As a result, both an aldehyde and a ketone are formed.
7. Pyrolysis of mixtures of carboxylic acids over catalysts in the form of metal oxides. The mixture should be steamy. The essence is the splitting between carbon dioxide and water molecules. As a result, an aldehyde or ketone is formed.

Aromatic aldehydes and ketones are prepared by other methods, since these compounds have an aromatic radical (phenyl, for example).

1. According to Friedel-Crafts: in the starting reagents aromatic hydrocarbon and a dihalogenated ketone. Catalyst - ALCL 3. As a result, an aromatic aldehyde or ketone is formed. Another name for the process is acylation.
2. Oxidation of toluene by the action of various agents.
3. Reduction of aromatic carboxylic acids.

Naturally, industry tries to use those methods in which the feedstock is as cheap as possible and the catalysts are less toxic. For the synthesis of aldehydes, this is the oxidation of alkenes with oxygen.

Industrial Applications and Significance

The use of aldehydes and ketones is carried out in such industries as:

• pharmaceuticals;
• chemical synthesis;
• medicine;
• perfume area;
• food industry;
• paint and varnish production;
• synthesis of plastics, fabrics, etc.

It is possible to identify more than one area, because approximately 6 million tons of formaldehyde alone are synthesized annually! Its 40% solution is called formalin and is used for storing anatomical objects. He's going into production medicines, antiseptics and polymers.

Acetaldehyde, or ethanal, is also a mass-produced product. The amount of annual consumption in the world is about 4 million tons. It is the basis of many chemical syntheses in which important products are formed. For example:

• acetic acid and its anhydride;
• cellulose acetate;
• medicines;
• butadiene - the basis of rubber;
• acetate fiber.

Aromatic aldehydes and ketones are component many flavorings, both food and perfume. Most of them have very pleasant floral, citrus, herbal aromas. This makes it possible to produce on their basis:

• air fresheners of various kinds;
• toilet and perfume waters;
• various cleaning products and detergents.

Some of them are aromatic food additives approved for consumption. Their natural content in essential oils, fruits and resins proves the possibility of such use.

Individual representatives

An aldehyde such as citral is a liquid with high viscosity and a strong lemon aroma. It is found in nature in essential oils of the latter. Also contains eucalyptus, sorghum, kebab.

Its areas of application are well known:

• pediatrics - decreased intracranial pressure;
• normalization blood pressure in adults;
• component of a medicine for the organs of vision;
• an integral part of many aromatic substances;
• anti-inflammatory and antiseptic;
• raw materials for the synthesis of retinol;
• flavoring for food purposes.