Aldehydes and their chemical properties

Aldehydes are called such organic substances, in which the molecules have a carbonyl group associated, minimum, with a single hydrogen atom and a hydrocarbon radical.

The chemical properties of the aldehydes are predetermined in their molecule by the presence of a carbonyl group. In this regard, in the molecule of the carbonyl group, you can observe the connection reaction.

For example, if you take and skip the formaldehyde pairs with a hydrogen over a preheated nickel catalyst, it will take the addition of hydrogen and formaldehyde to recover in methyl alcohol. In addition, the polar nature of this coupling gives rise to such a reaction of aldehydes as water joining.

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

With such an accession, the following reactions are characteristic:

First, hydrogenation occurs and primary alcohols are formed.
Secondly, the addition of alcohols and the formation of semi-acetals R-CH (OR) - OR. And in the presence of HCL chloride, protruding with a catalyst and with an excess of alcohol, we observe the formation of RSN (OR) 2;
Thirdly, the sodium sodium hydrosulfite occurs and derivatives of hydrosulfite aldehydes are formed. In the oxidation of aldehydides, such special reactions can be observed as interaction with ammonia solution of silver oxide (I) and with hydroxide of copper (II) and the formation of carboxylic acids.

In the polymerization of aldehydes, such special reactions as linear and cyclic polymerization are characteristic.

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

You can pass for an unusual reaction of the "silver mirror" by spending an interesting experience in the class. To do this, you need a purely washed test tube, into which several milliliters of ammonia silver oxide solution should be pouring, and then add four or five drops of formalin to it. The next stage, when carrying out this experience, you need to put a test tube in a glass with hot water And then you can see how a brilliant layer appears on the walls of the test tube. This coating is a precipitate of metallic silver.

And here is the so-called traffic light:

Physical properties of aldehydes

Now let's get to consider physical properties Aldehydes. What properties do these substances have? It should be paid to the fact that a number of simple aldehydes are colorless gas, more complex are represented as a liquid, but higher aldehydes are solids. The bigger molecular mass Aldehydes, the higher the boiling point. For example, propionic aldehyde reaches the boiling point at 48.8 degrees, but the propyl alcohol is accumulated at 97.8 0.

If we talk about density of aldehydes, then it is less than one. Thus, for example, acetic and ant aldehyde has a property to dissolve well in water, and more complex aldehydes have a weaker dissolution ability.

Aldehydes, which relate to the lower discharge, have a sharp and unpleasant odor, and solid and insoluble in water, on the contrary are characterized by a pleasant flower smell.

Finding aldehydes in nature

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

Aldehydes are also found with a more complex composition. Such species include vanillin or grape sugar.

But since the aldehydes have the ability to easily enter into all sorts of interactions, they have a tendency to oxidation and restoration, then it is safe to say that aldehydes are very capable of different reactions and therefore they are extremely rare in its pure form. But their derivatives can be found everywhere, both in a plant medium and an animal.

Application Aldehydes

Aldehyde group is present in a number of natural substances. Their distinctive feature, at least many of them, is the smell. So, for example, representatives of higher aldehydes are owned by various flavors and are part of essential oils. Well, as you already know, such oils are present in flower, spicy and fragrant plants, fruits and fruits. They found large-scale use in the production of industrial goods and in the production of perfumery.

Aliphatic aldehyde CH3 (CH2) 7C (H) \u003d O can be found in citrus essential oils. Such aldehydes have the smell of orange, and is used in the food industry, as an aroma, as well as in cosmetics, perfumery and household chemicals, as a fragrance.

The formic aldehyde is a colorless gas that has a sharp specific smell and easily dissolved in water. Such an aqueous solution of formaldehyde is also called formalin. Formaldehyde is very poisonous, but in medicine it is used in a diluted form as a disinfectant. It is used for disinfection of tools, and its weak solution is used to wash the skin with severe sweating.

In addition, formaldehyde is used when torn skin, as it has the ability to connect with protein substances that are available in the skin.

In agriculture, formaldehyde has perfectly proven itself in the processing of grain in front of the sowing work. It is used for the production of plastics that are so necessary for technology and household needs.

Acetic aldehyde is a colorless liquid, which has the smell of heavy apples and is easily dissolved in water. It is used to obtain acetic acid and other substances. But since it is a poisonous substance, it can cause the body poisoning or inflammation of the mucous membranes of the eyes and respiratory tract.

Workers notebooks

Continued. Beginning see in № 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 26, 28, 29, 30, 31, 32/2004

Lesson 24. Chemical properties and applying aldehydes

Chemical properties. Consider the behavior of aldehydes regarding the standard set of reagents: air oxygen O 2, oxidizing agents [O], as well as H 2, H 2 O, alcohols, Na, NCl.

Aldehydes are slowly oxidized by air oxygen in carboxylic acids:

A high-quality reaction to aldehydes is the "silver mirror" reaction. The reaction consists in the interaction of aldehyde with an aqueous-ammonium solution of silver oxide (I), which represents a soluble comprehensive OH connection. The reaction is carried out at temperatures close to water boiling temperature (80-100 ° C). As a result on the walls of the glass vessel (test tubes, the flasks), the precipitate of metallic silver is formed - "SERVICE MIRROR":

Restoration of copper (II) hydroxide in copper oxide (I) is another characteristic reaction of aldehydes. The reaction occurs when the mixture is boiled and consists in the oxidation of aldehyde. More precisely, the introduction of an atom [O] of the Cu (OH) 2 oxidizing agent for the connection of the CU (OH) 2. In this case, the degrees of oxidation of carbonyl carbon (from +1 to +3) and the copper atom (from +2 to +1). When heating a blue sediment Cu (OH) 2 in a mixture with aldehyde, there is a disappearance of blue coloring and the formation of a red sediment Cu 2 O:

Aldehydes join hydrogen H 2 double bond C \u003d O when heated in the presence of a catalyst (Ni, Pt, Pd). The reaction is accompanied by a break-down-connection in the carbonyl group C \u003d O and addition at the place of its rupture of two atoms of hydrogen molecules nn. Thus, allegations are obtained from aldehydes:

Aldehydes with electronized substituents inPutting to the aldehyde group attach water With the formation of hydrates of aldehydes (diol-1,1):

In order to hold two electronegative hydroxyl groups, the carbon atom must carry a sufficient positive charge. The creation of an additional positive charge on carbonyl carbon is facilitated by three electro-coceptor chlorine atoms with a neighboring chlorine-carbon.

The reaction of aldehydes with alcohols. Synthesis of semi-acetals and acetals. In favorable conditions (for example: a) when heated with acid or in the presence of water-based drugs; b) with intramolecular condensation with the formation of five and six-membered cycles) aldehydes react with alcohols. At the same time, either one alcohol molecule (semi-acetal product) can be joined to one alpidage molecule (product - semi-acetal), or two alcohol molecules (product - acetal):

Aldehydes do not join Nsl double bond C \u003d O. Alporee also do not reactwith Na, i.e. The aldehyde hydrogen group does not have noticeable acid properties.

Application Aldehydes Based on their high reactivity. Aldehydes are used as source and intermediate compounds in the synthesis of substances with the useful properties of other classes.
Formaldehyde NNO - a colorless gas with a sharp smell - used for production polymeric materials. Substances with movable H atoms in the molecule (usually with C-H or N-H connections, but not O-H) are connected to formaldehyde CH 2 O by type:

If two or more movable protons (at phenol with 6 H 5, it is three such protons), then a polymer is obtained in the reaction with formaldehyde. For example, with phenol - phenol formaldehyde resin:

Similarly, urea with formaldehyde gives urea formaldehyde resins:

Formaldehyde serves as an initial substance for production dyes, pharmaceutical preparations, synthetic rubber, explosives And many others organic compounds.

Formalin (40% aqueous solution of formaldehyde) is used as antiseptic (disinfectant). The property of formalin rolling protein is used in leather manufacturing and to preserve biological products.

Acetaldehyde CH 3 SNO - colorless liquid ( t. Kip \u003d 21 ° C) with a sharp smell, well soluble in water. The main use of acetaldehyde - getting acetic acid. From it also get synthetic resins, medicines etc.

EXERCISES

1. Describe, with what chemical reactions The following pairs of substances can be distinguished:
a) benzaldehyde and benzyl alcohol; b) Propionic aldehyde and propyl alcohol. Specify what will be observed during each reaction.

2. Bring equations reactionsconfirming the presence in the molecule
P-hydroxybenzaldehyde of the corresponding functional groups.

3. Write the equations of boutanal reactions with the following reagents:
but) H 2, t., cat. Pt; b) KMNO 4, H 3 O +, t.; in) Oh. in NH 3 / H 2 O; d) NASN 2 CH 2 t, Cat. Nsl.

4. Make the equations of reactions for the chain of chemical transformations:

5. As a result of acetal hydrolysis aldehyde is formed Rcho and alcohol R "ON. in a molar ratio 1:2. Make the equation of reactions of hydrolysis of the following acets:

6. When oxidizing the limit singo-name alcohol The oxide of copper (II) was formed 11.6 g of organic compound with a yield of 50%. With the interaction of the resulting substance with an excess of ammonia solution of silver oxide, 43.2 g of sediment was separated. What alcohol was taken and what is his mass?

7. The 5-hydroxygexanal in the acidified aqueous solution is mainly in the form of a six-membered cyclic semi-aotic. Make the equation of the appropriate reaction:

Answers to the exercises to the topic 2

Lesson 24.

1. Two substances can be distinguished by reactions characteristic only for one of these substances. For example, aldehydes are oxidized into acids under the action of weak oxidizers. Heating the mixture of benzaldehyde and ammonia solution of silver oxide proceeds with the formation of a silver mirror flasks on the walls:

Benzaldehyde is restored during catalytic hydrogenation into benzyl alcohol:

Benzyl alcohol reacts with sodium, hydrogen is highlighted in the reaction:

2C 6 H 5 CH 2 H + 2NA 2C 6 H 5 CN 2 ONA + H 2.

When heated in the presence of copper catalyst, the benzyl alcohol is oxidized by air oxygen into benzaldehyde, which is detected by the characteristic smell of Gorky Almond:

Similarly, the propionic aldehyde and propyl alcohol can be distinguished.

2. IN p- Hydroxibenzaldehyde Three functional groups: 1) aromatic ring; 2) phenolic hydroxyl; 3) Aldehyde group. IN special conditions - when protecting the aldehyde group from oxidation (designation - [-CO]) - can be chlorinated p- Hydroxibenzaldehyde in the benzene ring:

6. Equations of these reactions:

Consistently we find the amount of substance - silver, aldehyde RCHO and alcohol RCH 2 OH:

(AG) \u003d 43.2 / 108 \u003d 0.4 mol;

(RCho) \u003d 1/2 (Ag) \u003d 0.2 mol.

C for the exit of 50% in the reaction (1):

(RSN 2) \u003d 2 (RChO) \u003d 0.4 mol.

Molar mass of aldehyde:

M.(RCho) \u003d m. / \u003d 11.6 / 0.2 \u003d 58 g / mol.

This is propionic aldehyde CH 3 CH 2 SNO.

The corresponding alcohol - propanol-1 CH 3 CH 2 CH 2.

Alcohol Mass: m. = M. \u003d 0.4 60 \u003d 24 g

Answer. The alcohol of Propanol-1 weighing 24 g.

Aldehydes and Ketones refer to carbonyl Organic compounds.

Carbonyl compounds Call organic substances, in the molecules of which there is a group\u003e C \u003d O (carbonyl or an oxo group).

General formula of carbonyl compounds:

Depending on the type of substituent, these compounds are divided into:

 aldehydes (x \u003d n);

 ketones (x \u003d r, r ");

 carboxylic acids (x \u003d it) and their derivatives (x \u003d OR, NH 2, NHR, HAL, etc.).

Aldehydes and Ketones - characterized by the presence in the molecule carbony groups,or carbonyl radical,\u003e c \u003d o. In aldehydes, the carbon atom of this radical is associated with no less than one hydrogen atom, so it turns out a monovalent radical radical aldehyde group.In ketones, the carbonyl group is associated with two hydrocarbon radicals and is called also ketogroupor oxo group.

Homological series of aldehydes and their nomenclature

Aldehydes - Organic compounds, in the molecules of which carbonyl carbon atom (carbonyl carbon) is associated with a hydrogen atom.

General formula: R-CN \u003d O or

Functional group - SN \u003d O called aldehyde.

Aldehydes can also be considered as substances that occurred from substitutions in paraffin hydrocarbons of the hydrogen atom on the aldehyde group, i.e., as unused derivatives of hydrocarbon derivatives of a homologous series of methane. Consequently, homology and isomeria are here as for other single-dismembered derivatives of limit hydrocarbons.

The names of the aldehydes are made from the trivial names of acids with the same number of carbon atoms in the molecule. So, aldehyde CH 3 is called acetate aldehydeor acetaldehyde,CH 3 CH 2 - propione aldehyde,CH 3 CH 2 CH 2 -Cly - Normal oil aldehydeor butyraldehyd,(CH 3) 2 SN-SNO - isomaslyanya aldehyde,aldehydes with 4 H 9 - valerian aldehydamietc.

According to the Geneva nomenclature, the names of the aldehydes are made from the names of hydrocarbons, having the same number of carbon atoms, with the accession of cocoon an.slut al, eg metanalN-SNO, ethanalCH 3 -Cly, 2 -MethylpropanalCH 3 CH (CH 3) -Con

Homological row of ketones and their nomenclature

Ketones - organic substances whose molecules contain a carbonyl group connected to two hydrocarbon radicals.

General formulas: R. 2 C \u003d O, R-CO-R " or

The simplest of the ketones has the structure of CH 3 -CH-CH 3 and is called dimethylketonor acetone.From acetone you can produce a homologous series to the consistent replacement of hydrogen atoms on methyl. Thus, the next homolog of acetone - methyl ethyl ketoneit has the structure of CH 3 -CO-CH 2 -CH 3.

The names of the ketones, as well as the names of the aldehydes, in the Geneva nomenclature, are made from the names of hydrocarbons with the same number of carbon atoms, with the accession of cocoon an.slut is heand adding a figure denoting the place of carbonyl carbonyl carbon atom, counting from the beginning of a normal carbon chain; acetone, so wears a name propanonediethyl ketone - pentanon3, methylisopropyl ketone - 2. -Methylbutanoneetc

Aldehydes and ketones with the same number of carbon atoms in a molecule are amomer to each other. General formula for homologous series of limit aldehydes and ketones: with n. H 2 n. ABOUT.

Aldehydes and ketones contain a molecule of the same carbonyl group that causes a lot of common typical properties. Therefore, there is a lot of total and the ingestion of the preparation and the vcchimical reactions of both of these related classes of substances. The presence of Valdehydes of the hydrogen atom associated with the carbonyl group determines the number of differences in this class of substances from ketones.

In the presence of aldehydium mineral acids and ketones react with one or two alcohol miles:

If you take a carbonyl connection and an excess of alcohol, then the equilibrium will be shifted to the right and acetal or ketal will be formed. In contrast, when heating acetals and ketals with an excess of water in an acidic medium, hydrolysis occurs with the formation of aldehyde or ketone:

In the second example, both hydroxyl groups participating in the formation of Kethala were in the same alcohol -ethadiola alcohol molecule), so Ketal has a cyclical structure.

Comparatively inert acetals and ketali are used as protecting groups to protect the carbonyl group from unwanted reactions during multi-stage synthesis. The particle synthesis is shown below, which includes the protection of the carbonyl group:

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The initial compound A has two carbonyl groups, and in the final product of the hydrocortisone, one of the ketone groups should be restored to the alcohol. Alumohydride lithium will restore both ketone groups, and the one, which is desirable to maintain unchanged, will restore even faster, since the reagent approach to another group is difficult due to steric obstacles. To eliminate this difficulty, the substance is reacted and with one mole of 1,2-ethadiola (ethylene glycol). At the same time, Ketal forms steric

a more affordable carbonyl group, which thus turns out to be protected from the action of reducing agents or other reagents interacting with ketones. Now you can restore the free carbonyl group of lithium aluminum hydride and get the connection of C. Please note that alumohydride also restores the essential group to alcohol, but does not affect the double carbon-carbon bond. Further, having carried out the acylation of the alcohol group of the side chain necessary for further transformations and obtaining a compound remove the protecting group with an acid action. A few more stages are required to turn the substance into hydrocortisone which is used in medicine during arthritis, rheumatism and inflammatory processes.

Another example of using the reaction of ketage formation is the synthesis of Guadarel, which has a hypotensive effect (the ability to reduce pressure):

(Some details of this and previous synthesis are omitted to focus on the problem under discussion.)

Restoration

Aldehydes and ketones are restored respectively to primary and secondary alcohols. You can use hydrogen gas in the yrisutics of the catalyst, however, it is inconvenient in the laboratory, as working with gases requires special equipment and skills.

Comprehensive hydrides are much more often used, such as lithium aluminum hydride and sodium borohydride. The symbol denote any reducing agent or

Specific examples:

Sodium borohydride can be used in the form of aqueous or alcohol solution, lithium aluminum hydride can be dissolved only on the air.

With one of the two methods shown below, carbonyl compounds can be restored to alkanes:

wolf - Kizhner Reaction

clemensen reaction

Both of these methods are applicable to most carbonyl compounds, but if there are groups that are sensitive to the action of acid in the molecule, the Wolf - Kižner reaction should be used (restoration of hydrazine in the presence of alkali), and if the compound is unstable to the action of the base, it is preferred to restore Clemensen amalgam ( mortar in mercury) zinc in hydrochloric acid:

In the latter example, the use of hydrazine and base is undesirable, since this will replace the chlorine atom. It is better to use the Clemensen reaction.

Oxidation

While the ketones are not subjected to oxidation, the aldehydes are oxidized to carboxylic acids very easily. At the same time, a variety of oxidants can be used (we have already mentioned it in Ch. 7 and in this chapter):

When interacting with two alcohol moles or one mole of the aldehyde and ketones form acetal and ketali, respectively. Aldehydes and ketones can be restored to alcohols using a wide variety of reducing agents. The restoration of carbonyl compounds on Wolf - Kleyer or Clemensen is obtained by alkanes. Aldehydes are easily oxidized to carboxylic acids, the ketones do not react under the same conditions.

Ammonia derivative reactions

Ammonia derivatives are often used to identify aldehydes and ketones. In the interaction of these compounds, the following happens:

A carbonyl carbon atom forms a double bond with a nitrogen atom and the water molecule is cleaved. Many nitrogen derivatives of carbonyl compounds are solids, while the aldehydes and ketones themselves are mostly fluid. After obtaining a solid aldehyde or ketone derivative, comparing its melting point with table values, you can determine which aldehyde or ketone was taken. The three most common types of compounds used for this purpose are shown below. Especially convenient 2,4-dinitrophenyl hydrazones, painted in bright yellow, orange or red, which also helps identify aldehyde or ketone.

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Below are the melting temperatures of nitrogenic derivatives of some aldehydes and ketones (melting temperatures are determined with an accuracy of ± 3 ° C):

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For example, if you received a 2,4-dinitrophenyl hydronex of an unknown aldehyde or ketone with a melting point of 256 ° C, therefore, an unknown carbonyl connection is probably cinnamine aldehyde or fbrombenzaldehyde. If in the future you installed that oxim has a melting point means your connection -brombenzaldehyde. Since there are data on the derivative of almost all aldehydes and ketones, they can be identified by obtaining one or more nitrogen derivatives and comparing the experimentally found melting temperatures with table values.

Haloiding

Aldehydes and ketones react with halogens in the presence of acid or base, as well as with hypathaloenites, forming -ed-shaped connections:

For example:

For methylketones, a haloforous reaction is characteristic. In the processing of these compounds, the excess of halogen in an alkaline medium occurs three-time halogenation of the methyl group and cleavage of trigalomethane to form an anion of carboxylic acid:

If the iodoform is formed as a halogen, which is a yellow crystalline substance with a melting point of 119 ° C. This reaction is a breakdown on methylketones. The formation of a yellow sediment in the processing of a sample with an excess of iodine in an alkaline medium indicates the presence in the methyl ketone sample.

Reaction of joining

The presence in the carbonyl group is connected between carbon and oxygen atoms makes it possible to attach various substances To aldehydam and ketone:

This group of reactions includes the already discussed formation of semi-acetals and semi-binding:

Most attachment reactions refers to nucleophil to BC. Since the carbonal carbon atom carries a partial positive charge, at the first stage of the nucleophile joins the carbon atom. The typical nucleophilic connection reaction is the interaction of aldehydes and ketones with cyanides:

Anion formed at the first stage takes off the proton from the solvent molecule. As a result, organic cyanide is formed - nitrile, the vortex can be hydrolyzed to carboxylic acid:

the reaction of this type is used in the synthesis of an important non-nancotic analgesic ibuprofen:

The reactions of nucleophilic addition relates the reaction of aldehydes and ketones with Grignar reactors (see ch. 7). We give a few more examples, giving the product of hydrolysis at once:

All these reactions allow you to create a new carbon skeleton to synthesize almost any alcohols. From formaldehyde

primary alcohols are formed, from other aldehydes - secondary, and from Keto new - tertiary alcohols.

Aldol condensation

Aldehydes, having a-hydrogen atoms (hydrogen atoms with a carbon atom adjacent to carbonyl), in an alkaline medium, come into the condensation reaction, which is an important method of creating a new carbon skeleton. For example, when processing acetaldehyde, the following happens:

In the first stage, it is formed - pyrechayaldehyde, having a trivial name Aldol, so all the reactions of this type have a general name of the aldol condensation. - Hydroxyaldehydes are easily dehydrated with the formation of -Evennodeldehydes. As a result, a compound is formed, containing twice as much carbon atoms than the original aldehyde.

The overall mechanism of condensation is as follows: 1. Hydroxide-ion cleaves the model in a small part of the aldehyde molecules. A-hydrogen atoms have a weakness due to the resonant stabilization of the formed anion:

2. The formed anion, speaking as a nucleophile, attacks the carbonyl group of another aldehyde molecule, forming a new carbon-carbon connection:

3. A new anion takes off the proton from the water molecule, regenerating the catalyst - hydroxide ion:

4. Hydroxyaldehyde easily (often self-acrossal) loses water, turning into a-terminal aldehyde:

As a result, the carbonyl carbon atom of one aldehyde molecule turns out to be a connected double bond with a carbonic atom of another molecule. In the examples below, part of different source molecules are circled into the frame:

Unfoluble aldehydes can serve as the initial substances in the synthesis of various organic compounds with a new carbon skeleton, since both carbonyl group and double carbon-carbon bond are capable of many transformations. For example:

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Vittiga reaction

Aldehydes and ketones react with the so-called phosphorus or substances with the formation of substances having a new carbon skeleton. Ilda are pre-obtained from trialkylphosphines, halogen and a strong base, for example, butyl lithium:

Note that the resulting alkene contains carbon fragments of carbonyl compound and halolyanka, and double communication Connect carbon atoms previously connected to oxygen and halogen atoms. For example:

In order to identify aldehyde and ketones are converted into solid derivatives. Both types of carbonyl compounds under conditions of sour or alkaline catalysis are halogenated into a-position. Methyl ketones when processing iodom in an alkaline medium form iodoform, which is qualitative reaction on methylketones. Aldehydes and ketones in aqueous medium interact with cyanides, giving nitriles, which can be hydrolyzed to carboxylic acid, converting one carbon atom more than the original connection. In the interaction of aldehydes and ketones with Raactivities of Grignar, alcohols are formed. Aldol condensation and the Vittig reaction make it possible to create a new carbon skeleton.

Summary of the main provisions of ch. eight

1. In accordance with the IUPAC nomenclature, the names of the aldehydes and ketones are constructed by adding the suffixes "al" or "it", respectively, to the names of hydrocarbons. Aldehydes

have trivial namescoinciding with the names of carboxylic acids. The names of the ketones in the radical-functional nomenclature consist of the names of the radicals connected to the carbonyl group, and the words "ketone".

2. Aldehydes and ketones are obtained by oxidation of primary and secondary alcohols. The restoration of acyllhalides leads to the formation of aldehydes, while the interaction of acyllhalides with dialkuldmeum gives ketones. As a result of ozonolysis of alkenes, aldehydes and (or) ketones are also formed.

3. Aldehydes and ketones react with alcohols, giving acetal and ketali. This reaction is used to protect the carbonyl group. Restoration of aldehydes and ketones with hydrogen or hydrides gives alcohol. When restoring Clemensen or Wolf - hydrocarbons are formed. Aldehydes are easily oxidized to carboxylic acids. For identification, carbonyl compounds are translated into solid derivatives having characteristic melting points. In the halogenation of aldehydes and ketones, halogens are selectively sent to position. When processing methyl ketones, iodine in an alkaline medium is formed by iodoform carbonyl compounds react with cyanides, forming nitriles (which can be hydrolyzed to carboxylic acids) and join the Grignar reagents, giving alcohols. The construction of a new carbon skeleton is achieved using the aldol condensation and the Vittig reaction.

Keywords

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Questions for the development of skills

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Aldehydes and ketones.

Aldehydes and ketones are similar chemical structure. Therefore, the story about them is combined in the same chapter.

In the structure of both compounds, a bivalent carbonyl group is suited:

The difference of aldehydes and ketones the following. In aldehydes, the carbonyl group is associated with one hydrogen atom and with a hydrocarbon radical, while in the ketone, it is associated with two hydrocarbon radicals.

Chemical properties of aldehydes and ketones.

The presence in the aldehydes and in the ketones of the carbonyl group determines the similar similarity of their properties. However, there are differences. This difference is explained by the presence in the aldehyde molecule of the hydrogen atom associated with the carbonyl group. (In the molecule of ketones there is no such atom).

Carbonyl group and a hydrogen-associated hydrogen atom highlighted in separate functional group. This group was named aldehyde functional group.

Due to the presence of hydrogen in the aldehyde molecule, the latter are easily oxidized (oxygen is connected) and turn into carboxylic acids.

For example, at oxidation of acetic aldehyde, acetic acid is formed:

As a result, the light oxidation of aldehydes are energetic reducing agents. By this, they differ significantly from ketones that are much more difficult.

Obtaining aldehydes and ketones.

Aldehydes and ketones can be obtained by oxidation of the corresponding alcohols.having the same carbon skeleton and hydroxyl with the same carbon atom, which in the obtained aldehyde or ketone forms a carbonyl group.

If the primary alcohol is used as an oxidized alcohol, then a aldehyde is obtained as a result of oxidation.

Aldehyde (formaldehyde).

- This is the simplest aldehyde with the formula:

Formaldehyde is obtained from methyl alcohol - the simplest of alcohols.

In formaldehyde, a hydrogen atom is performed as a radical.

Properties:

- It is a gas with a sharp unpleasant smell, well soluble in water. It has antiseptic, as well as bubble properties.

Getting:

Receive formaldehyde From methyl alcohol by the catalytic oxidation of its air oxygen or by dehydrogenation (hydrogen cleavage).

Application:

Water solution formaldehyde (usually 40%) is called formalin. Formalin is widely reduced for disinfecting, preserving anatomical preparations. Significant amounts of formaldehyde are used to obtain phenol formaldehyde resins.

This is one of the most important aldehydes. It corresponds ethyl alcohol And it can be obtained by oxidation.

Acetic Aldehyde It is widely found in nature and produced in large quantities industrial. It is present in coffee, in ripe fruits, bread, and synthesized by plants as the result of their metabolism.

Properties:

Acetic Aldehyde - Easily boiling colorless liquid (boiling point 21 degrees C). It has a characteristic smell of heavy apples, well soluble in water.

Getting:

In the vernacility acetic Aldehyde It turns out:

1. ethylene oxidation,
2. joining water to acetylene,
3. oxidation or dehydrogenation of ethyl alcohol.

Application:

Apply acetic Aldehyde To obtain acetic acid, butadiene, some organic substances, aldehyde polymers.

Dimethyl ketone (acetone).

Dimethyl ketone (acetone) It is the simplest ketone. In his molecule, the role of hydrocarbon radicals performs methyl CH 3. (residue of methane).

Properties:

Acetone - Colorless liquid with a characteristic smell.

Boiling temperature 56,2 degrees FROM.

Acetone Mixed with water in all relations.

It is one of the metabolites produced by the human body.

Getting:

1. Acetone can be obtained by oxidation of propulsion,
2. Methods of obtaining are used acetone from isopropyl alcohol and acetylene,
3. Main part acetone It is obtained as a coin in the preparation of phenol from benzene by a cumen method.

Application:

Acetone - highly good solvent Many organic substances. It is widely used in the paint industry, in the production of certain types of artificial fiber, unbalanced organic glass, film, smokeless powder. Acetone It is also used as a starting material for the synthesis of a number of organic compounds.