Aldehydes in perfume mythology. Properties of alcohols, aldehydes, acids, esters, phenol

Characteristic chemical properties of saturated monohydric and polyhydric alcohols, phenol

Saturated monohydric and polyhydric alcohols

Alcohols (or alkanols) are organic substances whose molecules contain one or more hydroxyl groups ($—OH$ groups) connected to a hydrocarbon radical.

Based on the number of hydroxyl groups (atomicity), alcohols are divided into:

- monoatomic, for example:

$(CH_3-OH)↙(methanol(methyl alcohol))$ $(CH_3-CH_2-OH)↙(ethanol(ethyl alcohol))$

— dihydric (glycols), For example:

$(OH-CH_2-CH_2-OH)↙(ethanediol-1,2(ethylene glycol))$

$(HO-CH_2-CH_2-CH_2-OH)↙(propanediol-1,3)$

— triatomic, For example:

Based on the nature of the hydrocarbon radical, the following alcohols are distinguished:

— limit containing only saturated hydrocarbon radicals in the molecule, for example:

— unlimited containing multiple (double and triple) bonds between carbon atoms in the molecule, for example:

$(CH_2=CH-CH_2-OH)↙(propen-2-ol-1 (allylic alcohol))$

— aromatic, i.e. alcohols containing a benzene ring and a hydroxyl group in the molecule, connected to each other not directly, but through carbon atoms, for example:

Organic substances containing hydroxyl groups in the molecule, connected directly to the carbon atom of the benzene ring, differ significantly in chemical properties from alcohols and therefore are classified as an independent class of organic compounds - phenols. For example:

There are also polyhydric (polyhydric) alcohols containing more than three hydroxyl groups in the molecule. For example, the simplest hexahydric alcohol hexaol (sorbitol):

Nomenclature and isomerism

When forming the names of alcohols, a generic suffix is ​​added to the name of the hydrocarbon corresponding to the alcohol -ol. The numbers after the suffix indicate the position of the hydroxyl group in the main chain, and the prefixes di-, tri-, tetra- etc. - their number:

In the numbering of carbon atoms in the main chain, the position of the hydroxyl group takes precedence over the position of multiple bonds:

Starting from the third member of the homologous series, alcohols exhibit isomerism of the position of the functional group (propanol-1 and propanol-2), and from the fourth, isomerism of the carbon skeleton (butanol-1, 2-methylpropanol-1). They are also characterized by interclass isomerism - alcohols are isomeric to ethers:

$(CH_3-CH_2-OH)↙(ethanol)$ $(CH_3-O-CH_3)↙(dimethyl ether)$

alcohols

Physical properties.

Alcohols can form hydrogen bonds both between alcohol molecules and between alcohol and water molecules.

Hydrogen bonds occur when a partially positively charged hydrogen atom of one alcohol molecule interacts with a partially negatively charged oxygen atom of another molecule. It is thanks to hydrogen bonds between molecules that alcohols have boiling points that are abnormally high for their molecular weight. Thus, propane with a relative molecular weight of $44$ is a gas under normal conditions, and the simplest of alcohols, methanol, with a relative molecular weight of $32$, is a liquid under normal conditions.

The lower and middle members of a series of saturated monohydric alcohols, containing from $1$ to $11$ carbon atoms, are liquids. Higher alcohols (starting from $C_(12)H_(25)OH$) are solids at room temperature. Lower alcohols have a characteristic alcoholic odor and pungent taste; they are highly soluble in water. As the hydrocarbon radical increases, the solubility of alcohols in water decreases, and octanol no longer mixes with water.

Chemical properties.

The properties of organic substances are determined by their composition and structure. Alcohols confirm the general rule. Their molecules include hydrocarbon and hydroxyl radicals, so the chemical properties of alcohols are determined by the interaction and influence of these groups on each other. The properties characteristic of this class of compounds are due to the presence of a hydroxyl group.

1. Interaction of alcohols with alkali and alkaline earth metals. To identify the effect of a hydrocarbon radical on a hydroxyl group, it is necessary to compare the properties of a substance containing a hydroxyl group and a hydrocarbon radical, on the one hand, and a substance containing a hydroxyl group and not containing a hydrocarbon radical, on the other. Such substances can be, for example, ethanol (or other alcohol) and water. The hydrogen of the hydroxyl group of alcohol molecules and water molecules is capable of being reduced by alkali and alkaline earth metals (replaced by them):

$2Na+2H_2O=2NaOH+H_2$,

$2Na+2C_2H_5OH=2C_2H_5ONa+H_2$,

$2Na+2ROH=2RONa+H_2$.

2. Interaction of alcohols with hydrogen halides. Substitution of a hydroxyl group with a halogen leads to the formation of haloalkanes. For example:

$C_2H_5OH+HBr⇄C_2H_5Br+H_2O$.

This reaction is reversible.

3. Intermolecular dehydration of alcohols— splitting off a water molecule from two alcohol molecules when heated in the presence of water-removing agents:

As a result of intermolecular dehydration of alcohols, ethers. Thus, when ethyl alcohol is heated with sulfuric acid to a temperature from $100$ to $140°C$, diethyl (sulfuric) ether is formed:

4. Interaction of alcohols with organic and inorganic acids to form esters ( esterification reaction):

The esterification reaction is catalyzed by strong inorganic acids.

For example, when ethyl alcohol and acetic acid react, ethyl acetate is formed - ethyl acetate:

5. Intramolecular dehydration of alcohols occurs when alcohols are heated in the presence of water-removing agents to a higher temperature than the temperature of intermolecular dehydration. As a result, alkenes are formed. This reaction is due to the presence of a hydrogen atom and a hydroxyl group at adjacent carbon atoms. An example is the reaction of producing ethene (ethylene) by heating ethanol above $140°C in the presence of concentrated sulfuric acid:

6. Oxidation of alcohols usually carried out with strong oxidizing agents, for example, potassium dichromate or potassium permanganate in an acidic environment. In this case, the action of the oxidizing agent is directed to the carbon atom that is already bonded to the hydroxyl group. Depending on the nature of the alcohol and the reaction conditions, various products can be formed. Thus, primary alcohols are oxidized first to aldehydes, and then in carboxylic acids:

The oxidation of secondary alcohols produces ketones:

Tertiary alcohols are quite resistant to oxidation. However, under harsh conditions (strong oxidizing agent, high temperature), oxidation of tertiary alcohols is possible, which occurs with the rupture of carbon-carbon bonds closest to the hydroxyl group.

7. Dehydrogenation of alcohols. When alcohol vapor is passed at $200-300°C over a metal catalyst, such as copper, silver or platinum, primary alcohols are converted into aldehydes, and secondary alcohols into ketones:

The presence of several hydroxyl groups in the alcohol molecule at the same time determines the specific properties polyhydric alcohols, which are capable of forming water-soluble bright blue complex compounds when interacting with a freshly prepared precipitate of copper (II) hydroxide. For ethylene glycol we can write:

Monohydric alcohols are not able to enter into this reaction. Therefore, it is a qualitative reaction to polyhydric alcohols.

Phenol

Structure of phenols

The hydroxyl group in molecules of organic compounds can be associated with the aromatic ring directly, or can be separated from it by one or more carbon atoms. It can be expected that, depending on this property, substances will differ significantly from each other due to the mutual influence of groups of atoms. Indeed, organic compounds containing the aromatic radical phenyl $C_6H_5$—, directly bonded to the hydroxyl group, exhibit special properties that differ from the properties of alcohols. Such compounds are called phenols.

Phenols are organic substances whose molecules contain a phenyl radical associated with one or more hydroxo groups.

Just like alcohols, phenols are classified according to their atomicity, i.e. by the number of hydroxyl groups.

Monohydric phenols contain one hydroxyl group in the molecule:

Polyhydric phenols contain more than one hydroxyl group in molecules:

There are other polyhydric phenols containing three or more hydroxyl groups on the benzene ring.

Let's take a closer look at the structure and properties of the simplest representative of this class - phenol $C_6H_5OH$. The name of this substance formed the basis for the name of the entire class - phenols.

Physical and chemical properties.

Physical properties.

Phenol is a solid, colorless, crystalline substance, $t°_(pl.)=43°C, t°_(boiling)=181°C$, with a sharp characteristic odor. Poisonous. Phenol is slightly soluble in water at room temperature. An aqueous solution of phenol is called carbolic acid. If it comes into contact with the skin, it causes burns, so phenol must be handled with care!

Chemical properties.

Acidic properties. As already mentioned, the hydrogen atom of the hydroxyl group is acidic in nature. The acidic properties of phenol are more pronounced than those of water and alcohols. Unlike alcohols and water, phenol reacts not only with alkali metals, but also with alkalis to form phenolates:

However, the acidic properties of phenols are less pronounced than those of inorganic and carboxylic acids. For example, the acidic properties of phenol are approximately $3000$ times weaker than those of carbonic acid. Therefore, by passing carbon dioxide through an aqueous solution of sodium phenolate, free phenol can be isolated:

Adding hydrochloric or sulfuric acid to an aqueous solution of sodium phenolate also leads to the formation of phenol:

Qualitative reaction to phenol.

Phenol reacts with iron (III) chloride to form an intensely purple complex compound.

This reaction allows it to be detected even in very limited quantities. Other phenols containing one or more hydroxyl groups on the benzene ring also produce bright blue-violet colors when reacted with iron(III) chloride.

Reactions of the benzene ring.

The presence of a hydroxyl substituent greatly facilitates the occurrence of electrophilic substitution reactions in the benzene ring.

1. Bromination of phenol. Unlike benzene, the bromination of phenol does not require the addition of a catalyst (iron (III) bromide).

In addition, the interaction with phenol occurs selectively: bromine atoms are directed to ortho- and para positions, replacing the hydrogen atoms located there. The selectivity of substitution is explained by the features of the electronic structure of the phenol molecule discussed above.

Thus, when phenol reacts with bromine water, a white precipitate is formed 2,4,6-tribromophenol:

This reaction, like the reaction with iron (III) chloride, serves for the qualitative detection of phenol.

2. Nitration of phenol also occurs more easily than benzene nitration. The reaction with dilute nitric acid occurs at room temperature. As a result, a mixture is formed ortho- And pair- isomers of nitrophenol:

When concentrated nitric acid is used, an explosive is formed - 2,4,6-trinitrophenol(picric acid):

3. Hydrogenation of the aromatic core of phenol in the presence of a catalyst occurs easily:

4.Polycondensation of phenol with aldehydes, in particular with formaldehyde, occurs with the formation of reaction products - phenol-formaldehyde resins and solid polymers.

The interaction of phenol with formaldehyde can be described by the following scheme:

You probably noticed that “mobile” hydrogen atoms are retained in the dimer molecule, which means that further continuation of the reaction is possible with a sufficient number of reagents:

Reaction polycondensation, those. the polymer production reaction, which occurs with the release of a low-molecular-weight by-product (water), can continue further (until one of the reagents is completely consumed) with the formation of huge macromolecules. The process can be described by the summary equation:

The formation of linear molecules occurs at ordinary temperatures. Carrying out this reaction when heated leads to the fact that the resulting product has a branched structure, it is solid and insoluble in water. As a result of heating a linear phenol-formaldehyde resin with an excess of aldehyde, hard plastic masses with unique properties are obtained. Polymers based on phenol-formaldehyde resins are used for the manufacture of varnishes and paints, plastic products that are resistant to heating, cooling, water, alkalis and acids, and have high dielectric properties. The most critical and important parts of electrical appliances, power unit housings and machine parts, and the polymer base of printed circuit boards for radio devices are made from polymers based on phenol-formaldehyde resins. Adhesives based on phenol-formaldehyde resins are capable of reliably connecting parts of a wide variety of natures, maintaining the highest joint strength over a very wide temperature range. This glue is used to attach the metal base of lighting lamps to a glass bulb. Now you understand why phenol and products based on it are widely used.

Characteristic chemical properties of aldehydes, saturated carboxylic acids, esters

Aldehydes and ketones

Aldehydes are organic substances whose molecules contain a carbonyl group , 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 the second hydrogen atom:

A carbonyl group bonded to a hydrogen atom is called aldehydic:

Organic substances in whose molecules a carbonyl group is linked to two hydrocarbon radicals are called ketones.

Obviously, the general formula for ketones is:

The carbonyl group of ketones is called keto group.

In the simplest ketone, acetone, the carbonyl group is linked to two methyl radicals:

Nomenclature and isomerism

Depending on the structure of the hydrocarbon radical associated with the aldehyde group, saturated, 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 the carbon atoms of the main chain begins with the carbon atom of the aldehyde group. Therefore, the aldehyde group is always located at the first carbon atom, and there is no need to indicate its position.

Along with 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.

To name ketones according to systematic nomenclature, the keto group is designated 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:

Aldehydes are characterized by only one type of structural isomerism - isomerism of the carbon skeleton, which is possible with butanal, and for ketones - also isomerism of the position of the carbonyl group. In addition, they are characterized by interclass isomerism (propanal and propanone).

Trivial names and boiling points of some aldehydes.

Physical and chemical properties

Physical properties.

In an aldehyde or ketone molecule, due to the greater electronegativity of the oxygen atom compared to the carbon atom, the $C=O$ bond is highly polarized due to a shift in the electron density of the $π$ bond towards oxygen:

Aldehydes and ketones are polar substances with excess electron density on the oxygen atom. The lower members of the series of aldehydes and ketones (formaldehyde, acetaldehyde, acetone) are 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 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

The presence of an aldehyde group in a molecule determines the characteristic properties of aldehydes.

Recovery reactions.

Hydrogen addition to aldehyde molecules occurs via a double bond in the carbonyl group:

The product of hydrogenation of aldehydes is primary alcohols, and ketones are secondary alcohols.

Thus, when hydrogenating acetaldehyde on a nickel catalyst, ethyl alcohol is formed, and when hydrogenating acetone, propanol-2 is formed:

Hydrogenation of aldehydes - recovery reaction at which the oxidation state of the carbon atom included in the carbonyl group decreases.

Oxidation reactions.

Aldehydes can not only be reduced, but also oxidize. When oxidized, aldehydes form carboxylic acids. This process can be schematically represented as follows:

From propionic aldehyde (propanal), for example, propionic acid is formed:

Aldehydes are oxidized even by atmospheric oxygen and such weak oxidizing agents as an ammonia solution of silver oxide. In a simplified form, this process can be expressed by the reaction equation:

For example:

This process is more accurately reflected by the equations:

If the surface of the vessel in which the reaction is carried out has been previously degreased, then the silver formed during the reaction covers it with an even thin film. Therefore this reaction is called reaction "silver mirror". It is widely used for making mirrors, silvering decorations and Christmas tree decorations.

Freshly precipitated copper(II) hydroxide can also act as an oxidizing agent for aldehydes. Oxidizing the aldehyde, $Cu^(2+)$ is reduced to $Cu^+$. The copper (I) hydroxide $CuOH$ formed during the reaction immediately decomposes into red copper (I) oxide and water:

This reaction, like the “silver mirror” reaction, is used to detect aldehydes.

Ketones are not oxidized either by atmospheric oxygen or by such a weak oxidizing agent as an ammonia solution of silver oxide.

Individual representatives of aldehydes and their significance

Formaldehyde(methanal, formicaldehyde$HCHO$ ) - a colorless gas with a pungent odor and a boiling point of $-21C°$, highly soluble in water. Formaldehyde is poisonous! A solution of formaldehyde in water ($40%$) is called formaldehyde and is used for disinfection. In agriculture, formaldehyde is used to treat seeds, and in the leather industry - for treating leather. Formaldehyde is used to produce methenamine, a medicinal substance. Sometimes methenamine compressed in the form of briquettes is used as fuel (dry alcohol). A large amount of formaldehyde is consumed in the production of phenol-formaldehyde resins and some other substances.

Acetaldehyde(ethanal, acetaldehyde$CH_3CHO$ ) - a liquid with a sharp unpleasant odor and a boiling point of $21°C$, highly soluble in water. Acetic acid and a number of other substances are produced from acetaldehyde on an industrial scale; it is used for the production of various plastics and acetate fiber. Acetaldehyde is poisonous!

Carboxylic acids

Substances containing one or more carboxyl groups in a molecule are called carboxylic acids.

Group of atoms called carboxyl group, or carboxyl.

Organic acids containing one carboxyl group in the molecule are monobasic.

The general formula of these acids is $RCOOH$, for example:

Carboxylic acids containing two carboxyl groups are called dibasic. These include, for example, oxalic and succinic acids:

There are also polybasic carboxylic acids containing more than two carboxyl groups. These include, for example, tribasic citric acid:

Depending on the nature of the hydrocarbon radical, carboxylic acids are divided into saturated, unsaturated, aromatic.

Saturated, or saturated, carboxylic acids are, for example, propanoic (propionic) acid:

or the already familiar succinic acid.

It is obvious that saturated carboxylic acids do not contain $π$ bonds in the hydrocarbon radical. In molecules of unsaturated carboxylic acids, the carboxyl group is associated with an unsaturated, unsaturated hydrocarbon radical, for example, in molecules of acrylic (propene) $CH_2=CH—COOH$ or oleic $CH_3—(CH_2)_7—CH=CH—(CH_2)_7—COOH $ and other acids.

As can be seen from the formula of benzoic acid, it is aromatic, since it contains an aromatic (benzene) ring in the molecule:

Nomenclature and isomerism

The general principles of the formation of the names of carboxylic acids, as well as other organic compounds, have already been discussed. Let us dwell in more detail on the nomenclature of mono- and dibasic carboxylic acids. The name of a carboxylic acid is derived from the name of the corresponding alkane (alkane with the same number of carbon atoms in the molecule) with the addition of the suffix -ov-, endings -and I and the words acid. The numbering of carbon atoms begins with the carboxyl group. For example:

The number of carboxyl groups is indicated in the name by prefixes di-, tri-, tetra-:

Many acids also have historically established, or trivial, names.

Names of carboxylic acids.

After getting acquainted with the diverse and interesting world of organic acids, we will consider in more detail the saturated monobasic carboxylic acids.

It is clear that the composition of these acids is expressed by the general formula $C_nH_(2n)O_2$, or $C_nH_(2n+1)COOH$, or $RCOOH$.

Physical and chemical properties

Physical properties.

Lower acids, i.e. acids with a relatively small molecular weight, containing up to four carbon atoms per molecule, are liquids with a characteristic pungent odor (remember the smell of acetic acid). Acids containing from $4$ to $9$ carbon atoms are viscous oily liquids with an unpleasant odor; containing more than $9$ carbon atoms per molecule - solids that do not dissolve in water. The boiling points of saturated monobasic carboxylic acids increase with increasing number of carbon atoms in the molecule and, consequently, with increasing relative molecular weight. For example, the boiling point of formic acid is $100.8°C$, acetic acid is $118°C$, and propionic acid is $141°C$.

The simplest carboxylic acid is formic $HCOOH$, having a small relative molecular weight $(M_r(HCOOH)=46)$, under normal conditions it is a liquid with a boiling point of $100.8°C$. At the same time, butane $(M_r(C_4H_(10))=58)$ under the same conditions is gaseous and has a boiling point of $-0.5°C$. This discrepancy between boiling points and relative molecular weights is explained by the formation of carboxylic acid dimers, in which two acid molecules are linked by two hydrogen bonds:

The occurrence of hydrogen bonds becomes clear when considering the structure of carboxylic acid molecules.

Molecules of saturated monobasic carboxylic acids contain a polar group of atoms - carboxyl and a practically non-polar hydrocarbon radical. The carboxyl group is attracted to water molecules, forming hydrogen bonds with them:

Formic and acetic acids are unlimitedly soluble in water. It is obvious that with an increase in the number of atoms in a hydrocarbon radical, the solubility of carboxylic acids decreases.

Chemical properties.

The general properties characteristic of the class of acids (both organic and inorganic) are due to the presence in the molecules of a hydroxyl group containing a strong polar bond between hydrogen and oxygen atoms. Let us consider these properties using the example of water-soluble organic acids.

1. Dissociation with the formation of hydrogen cations and anions of the acid residue:

$CH_3-COOH⇄CH_3-COO^(-)+H^+$

More accurately, this process is described by an equation that takes into account the participation of water molecules in it:

$CH_3-COOH+H_2O⇄CH_3COO^(-)+H_3O^+$

The dissociation equilibrium of carboxylic acids is shifted to the left; the vast majority of them are weak electrolytes. However, the sour taste of, for example, acetic and formic acids is due to dissociation into hydrogen cations and anions of acidic residues.

It is obvious that the presence of “acidic” hydrogen in the molecules of carboxylic acids, i.e. hydrogen of the carboxyl group, due to other characteristic properties.

2. Interaction with metals, standing in the electrochemical voltage series up to hydrogen: $nR-COOH+M→(RCOO)_(n)M+(n)/(2)H_2$

Thus, iron reduces hydrogen from acetic acid:

$2CH_3-COOH+Fe→(CH_3COO)_(2)Fe+H_2$

3. Interaction with basic oxides with the formation of salt and water:

$2R-COOH+CaO→(R-COO)_(2)Ca+H_2O$

4. Interaction with metal hydroxides with the formation of salt and water (neutralization reaction):

$R—COOH+NaOH→R—COONa+H_2O$,

$2R—COOH+Ca(OH)_2→(R—COO)_(2)Ca+2H_2O$.

5. Interaction with salts of weaker acids with the formation of the latter. Thus, acetic acid displaces stearic acid from sodium stearate and carbonic acid from potassium carbonate:

$CH_3COOH+C_(17)H_(35)COONa→CH_3COONa+C_(17)H_(35)COOH↓$,

$2CH_3COOH+K_2CO_3→2CH_3COOK+H_2O+CO_2$.

6. Interaction of carboxylic acids with alcohols with the formation of esters - esterification reaction (one of the most important reactions characteristic of carboxylic acids):

The interaction of carboxylic acids with alcohols is catalyzed by hydrogen cations.

The esterification reaction is reversible. The equilibrium shifts toward ester formation in the presence of dewatering agents and when the ester is removed from the reaction mixture.

In the reverse reaction of esterification, called ester hydrolysis (the reaction of an ester with water), an acid and an alcohol are formed:

It is obvious that reacting with carboxylic acids, i.e. Polyhydric alcohols, for example glycerol, can also enter into an esterification reaction:

All carboxylic acids (except formic acid), along with the carboxyl group, contain a hydrocarbon residue in their molecules. Of course, this cannot but affect the properties of acids, which are determined by the nature of the hydrocarbon residue.

7. Multiple addition reactions- they contain unsaturated carboxylic acids. For example, the hydrogen addition reaction is hydrogenation. For an acid containing one $π$ bond in the radical, the equation can be written in general form:

$C_(n)H_(2n-1)COOH+H_2(→)↖(catalyst)C_(n)H_(2n+1)COOH.$

Thus, when oleic acid is hydrogenated, saturated stearic acid is formed:

$(C_(17)H_(33)COOH+H_2)↙(\text"oleic acid"))(→)↖(catalyst)(C_(17)H_(35)COOH)↙(\text"stearic acid") $

Unsaturated carboxylic acids, like other unsaturated compounds, add halogens via a double bond. For example, acrylic acid decolorizes bromine water:

$(CH_2=CH—COOH+Br_2)↙(\text"acrylic (propenoic) acid")→(CH_2Br—CHBr—COOH)↙(\text"2,3-dibromopropanoic acid").$

8. Substitution reactions (with halogens)- saturated carboxylic acids are capable of entering into them. For example, by reacting acetic acid with chlorine, various chlorinated acids can be obtained:

$CH_3COOH+Cl_2(→)↖(P(red))(CH_2Cl-COOH+HCl)↙(\text"chloroacetic acid")$,

$CH_2Cl-COOH+Cl_2(→)↖(P(red))(CHCl_2-COOH+HCl)↙(\text"dichloroacetic acid")$,

$CHCl_2-COOH+Cl_2(→)↖(P(red))(CCl_3-COOH+HCl)↙(\text"trichloroacetic acid")$

Individual representatives of carboxylic acids and their significance

Ant(methane) acid HTSOOKH- a liquid with a pungent odor and a boiling point of $100.8°C$, highly soluble in water. Formic acid is poisonous Causes burns upon contact with skin! The stinging fluid secreted by ants contains this acid. Formic acid has disinfectant properties and therefore finds its use in the food, leather and pharmaceutical industries, and medicine. It is used in dyeing fabrics and paper.

Vinegar (ethane)acid $CH_3COOH$ is a colorless liquid with a characteristic pungent odor, miscible with water in any ratio. Aqueous solutions of acetic acid are sold under the name vinegar ($3-5% solution) and vinegar essence ($70-80% solution) and are widely used in the food industry. Acetic acid is a good solvent for many organic substances and is therefore used in dyeing, tanning, and the paint and varnish industry. In addition, acetic acid is a raw material for the production of many technically important organic compounds: for example, substances used to control weeds - herbicides - are obtained from it.

Acetic acid is the main component wine vinegar, the characteristic smell of which is due precisely to it. It is a product of ethanol oxidation and is formed from it when wine is stored in air.

The most important representatives of higher saturated monobasic acids are palmitic$C_(15)H_(31)COOH$ and stearic$C_(17)H_(35)COOH$ acid. Unlike lower acids, these substances are solid and poorly soluble in water.

However, their salts - stearates and palmitates - are highly soluble and have a detergent effect, which is why they are also called soaps. It is clear that these substances are produced on a large scale. Of the unsaturated higher carboxylic acids, the most important is oleic acid$C_(17)H_(33)COOH$, or $CH_3 - (CH_2)_7 - CH=CH -(CH_2)_7COOH$. It is an oil-like liquid without taste or odor. Its salts are widely used in technology.

The simplest representative of dibasic carboxylic acids is oxalic (ethanedioic) acid$HOOC—COOH$, the salts of which are found in many plants, such as sorrel and sorrel. Oxalic acid is a colorless crystalline substance that is highly soluble in water. It is used for polishing metals, in the woodworking and leather industries.

Esters

When carboxylic acids react with alcohols (esterification reaction), they form esters:

This reaction is reversible. The reaction products can interact with each other to form the starting materials - alcohol and acid. Thus, the reaction of esters with water—ester hydrolysis—is the reverse of the esterification reaction. The chemical equilibrium established when the rates of forward (esterification) and reverse (hydrolysis) reactions are equal can be shifted towards the formation of ester by the presence of water-removing agents.

Fats- derivatives of compounds that are esters of glycerol and higher carboxylic acids.

All fats, like other esters, undergo hydrolysis:

When hydrolysis of fat is carried out in an alkaline environment $(NaOH)$ and in the presence of soda ash $Na_2CO_3$, it proceeds irreversibly and leads to the formation not of carboxylic acids, but of their salts, which are called soaps. Therefore, the hydrolysis of fats in an alkaline environment is called saponification.

What are aldehydes anyway? The answer to this question is not as simple as it might seem at first glance. Ask an experienced perfume lover about this - most likely he will tell you about synthetic materials with a difficult-to-describe smell that made the scent so unusual, abstract and innovative.

A chemist or even an ordinary eleventh grader who regularly attends chemistry lessons will also not think much and say that aldehydes are a class of organic compounds containing the group -SNO, which is called the aldehyde group. All aldehydes have common chemical properties, for example, they are easily oxidized to form the corresponding acids. The reaction of the silver mirror is based on this - remember, when the test tube is heated and a shiny metallic layer appears on the surface of the glass. The word “aldehyde” itself, coined by the German chemist Eustace von Liebig, is an abbreviation alcohol dehydrogenatum, what does " alcohol without hydrogen».

In trivial names of aldehydes often* (see footnote) either the word “aldehyde” itself or a suffix is ​​present -al , for example, “dumpling aldehyde”, “jabaldehyde”, “kochergal”. Substances such as vanillin and heliotropin are also aldehydes from a chemical point of view. In general, a perfumer has a huge number of aldehydes with completely different odors: melonal smells like melon adoxal smells of the sea and egg whites, citronellal- lemongrass, lyral- lily of the valley, triplel- green grass. There are cyclamenaldehyde, cinnamaldehyde, anise, cumin, tangerine.

Okay, you ask, what does Chanel have to do with it? If there are so many aldehydes and they all smell differently, then what kind of “aldehyde note” is this, what does it smell like and what specific aldehydes are included in Chanel No. 5? Remember Kharms’s “Anecdotes from the Life of Pushkin”: “Pushkin really fell in love with Zhukovsky and began to call him Zhukov in a friendly manner”? What perfumers often casually call simply aldehydes is actually a certain subtype and special case: saturated aliphatic or so-called fatty aldehydes. They are usually named after the number of carbon atoms in the molecule. In "aldehyde C-7", or heptanal, - seven carbon atoms, “aldehyde C-10”, decanal, as you might guess, ten.

Chanel No. 5 contains a mixture of aldehydes" S-11 undecylic" or "S-110"(undekanala) , "S-11 undecylenic"(10-undecenal) and S-12(dodecanal). It is worth noting that aldehydes appeared in perfumes long before the appearance of this legendary aroma [ Chanel No. 5 was released in 1921]. Many historians of perfumery agree that aldehydes were first used in the creation, or rather, its re-release in 1905, created by perfumer Pierre Armigeant. There are aldehydes in both (1912) and Bouquet de Catherine (1913) from the Moscow factory Alphonse Rallet & Co, created, like Chanel No. 5, by perfumer Ernest Beaux (by the way, a native Muscovite). But it was Chanel that undoubtedly became the main aldehyde scent of all times, giving rise to a huge number of imitations and copies.

Fatty aldehydes have a characteristic waxy odor, similar to the smell of a blown out candle (in fact, this candle smell is caused by fatty aldehydes, products of incomplete combustion of paraffin). The odor of fatty aldehydes is very intense and pungent; it becomes pleasant when diluted to 1% or less. The smell of decanal (C-10) has a hint of zest, the smell of aldehyde C-12 has nuances of lily and violet. The simplest aldehydes, formaldehyde and acetaldehyde, have an extremely pungent and rather unpleasant odor (nevertheless, even acetaldehyde is used by flavorists and is part of some flavoring additives), while hexanal (C-6 aldehyde) can already distinguish relatively pleasant green and apple aspects. Fatty aldehydes, which have 15 carbon atoms or more in their chain, are already practically odorless.

The smell of fatty aldehydes has one more common property - a certain “soapiness”. Aldehydes have long been actively used to fragrance soap due to their low cost, intensity of odor, and ability to well mask the unpleasant odor of a soap base. Often the aldehydic smell is associated with abstract cleanliness or the feeling of freshly ironed linen.

Another important point that is worth paying special attention to is that aldehydes are not something artificial, the result of human labor. Many of them are widely found in nature. Decanal, for example, is found in essential oils of citrus fruits (up to 4% in orange!), conifers and many flower plants; there is a lot of it in coriander essential oil. Unsaturated aliphatic aldehydes are also ubiquitous in nature, they have an even more intense odor, for example, (E)-2-decenal is responsible for the characteristic odor of cilantro, it is indeed often present in the “chemical weapons” of bedbugs, and the epoxy derivative, trans-4, 5-epoxy-(E)-2-decenal causes the characteristic smell of blood, which gives it a pronounced metallic aspect. It is by the smell of this substance that predators track their prey.

In the wake of the success of the first floral-aldehydic fragrances, chemists worked tirelessly to synthesize new materials with similar olfactory properties. In 1905, the French E.E.Blaise and L.Huillon (Bull.Soc.Chim.Fr. 1905, 33, 928) synthesized gamma-undecalactone; a little later, in 1908, two Russian chemists A.A. published a similar work. Zhukov and P.I. Shestakov (ZHRHO 40, 830, 1908). This compound had an interesting aroma, reminiscent of a ripe peach heated in the sun - fruity, waxy and somewhat coconut-creamy.

Manufacturers decided to sell this substance under the name “aldehyde C-14” in order, on the one hand, to satisfy the thirst of perfumers for new “aldehydes with numbers”, and on the other hand, to mislead competitors, because in fact, from a chemical point of view, it was not an aldehyde , but a lactone (cyclic ester), and the atoms in the molecule of this compound are not 14, but 11. As in the joke, “not in chess, but in preference, you didn’t win, but you lost.”

The so-called “aldehyde C-14” debuted with great success in the Guerlain Mitsouko fragrance in 1919, and a little later new similar materials appeared: “aldehyde C-16 (strawberry)”, “aldehyde C-18 (coconut)”, “aldehyde C-20 (raspberry)" and some others. So it turns out that, on the one hand, almost every third fragrant substance is an aldehyde, and on the other hand, some of the most important aldehydes are not aldehydes at all.

* Chemists use several types of names. The first type is systematic, or nomenclatural. A nomenclature name is a kind of code, an algorithm, thanks to which you can recreate the structure of a substance, that is, understand which atoms and how they are connected inside a molecule. Each name corresponds to a single structure and vice versa - for each substance there is only one nomenclature name. Aldehydes, according to nomenclature, must have the suffix “al”. The only, but very significant, disadvantage of such names is cumbersomeness. For example, the iso e super discussed last time, according to nomenclature rules, should be called “1-(1,2,3,4,5,6,7,8-octahydro-2,3,8,8,-tetramethyl-2-naphthyl )ethanone-1". It’s hard to imagine what everyday life in laboratories would become if chemists used only nomenclature names (“Vasily, please pass that flask with cis-3-dimethylmethoxy…”).

For this reason, trivial names are often used. A trivial name is like a nickname, nickname of a substance. It doesn't tell us anything about structure or structure, but it's short and memorable. Vanillin, dichlorvos, promedol, paraben - these are all trivial names. Different companies may market the same compound under different names; these names are usually called trademarks. 2acetylhydroxybenzoic acid is a nomenclature name, acetylsalicylic acid is a trivial one, and aspirin is a trademark. Manufacturers of synthetic fragrances like to give their materials bright, sonorous names. Often aldehydes (from a chemical point of view) are named with the suffix “al” at the end. But knowing the love of perfumers for aldehydes, sometimes names with “al” are given to substances that are something completely different. For example, Clonal, a product from IFF, is actually a nitrile, and Mystikal, a captive material from Givaudan, is a carboxylic acid. Essentially the same trick as with “aldehyde C-14”.

Aldehydes and ketones are carbonyl organic compounds. Carbonyl compounds are organic substances whose molecules contain a >C=O group (carbonyl or oxo group).

General formula of carbonyl compounds:

The functional group –CH=O is called aldehyde. Ketones- organic substances whose molecules contain a carbonyl group connected to two hydrocarbon radicals. General formulas: R 2 C=O, R–CO–R" or

Nomenclature of aldehydes and ketones.

Systematic names aldehydes built by the name of the corresponding hydrocarbon and adding a suffix -al. Chain numbering begins with the carbonyl carbon atom. Trivial names are derived from the trivial names of those acids into which aldehydes are converted during oxidation.

Systematic names ketones simple structure is derived from the names of radicals (in increasing order) with the addition of the word ketone. For example: CH 3 –CO–CH 3 - dimethyl ketone(acetone); CH 3 CH 2 CH 2 –CO–CH 3 - methylpropyl ketone. More generally, the name of a ketone is based on the name of the corresponding hydrocarbon and the suffix -He; Chain numbering starts from the end of the chain closest to the carbonyl group (IUPAC substitutive nomenclature). Examples: CH 3 –CO–CH 3 - propane He(acetone); CH 3 CH 2 CH 2 –CO–CH 3 - pentane He- 2; CH 2 =CH–CH 2 –CO–CH 3 - pentene-4 -He- 2.

Isomerism of aldehydes and ketones.

Aldehydes and ketones are characterized by structural isomerism.

Isomerism aldehydes:

interclass isomerism (similar to aldehydes).

Structure of the carbonyl group C=O.

 The properties of aldehydes and ketones are determined by the structure of the carbonyl group >C=O.

The C=O bond is highly polar. Its dipole moment (2.6-2.8D) is significantly higher than that of the C–O bond in alcohols (0.70D). The electrons of the C=O multiple bond, especially the more mobile -electrons, are shifted towards the electronegative oxygen atom, which leads to the appearance of a partial negative charge on it. The carbonyl carbon acquires a partial positive charge.

 Therefore, carbon is attacked by nucleophilic reagents, and oxygen is attacked by electrophilic reagents, including H +.

The molecules of aldehydes and ketones lack hydrogen atoms capable of forming hydrogen bonds. Therefore, their boiling points are lower than those of the corresponding alcohols. Methanal (formaldehyde) is a gas, aldehydes C 2 -C 5 and ketones C 3 -C 4 are liquids, higher substances are solids. Lower homologs are soluble in water due to the formation of hydrogen bonds between the hydrogen atoms of water molecules and the carbonyl oxygen atoms. As the hydrocarbon radical increases, solubility in water decreases.

Reaction centers of aldehydes and ketones

sp 2 -The hybridized carbon atom of the carbonyl group forms three σ bonds lying in the same plane and a π bond with the oxygen atom due to the unhybridized p orbital. Due to the difference in electronegativity of carbon and oxygen atoms, the π bond between them is highly polarized (Fig. 5.1). As a result, a partial positive charge δ+ appears on the carbon atom of the carbonyl group, and a partial negative charge δ- appears on the oxygen atom. Since the carbon atom is electron deficient, it provides a site for nucleophilic attack.

Distribution of electron density in molecules of aldehydes and ketones, taking into account the transfer of electronic influence by electron-

Rice. 5.1. Electronic structure of the carbonyl group

the deficient carbon atom of the carbonyl group along σ-bonds is presented in Scheme 5.1.

Scheme 5.1. Reaction centers in the molecule of aldehydes and ketones

There are several reaction centers in the molecules of aldehydes and ketones:

The electrophilic center - the carbon atom of the carbonyl group - determines the possibility of nucleophilic attack;

The main center - the oxygen atom - makes it possible to attack with a proton;

A CH acid center whose hydrogen atom has weak proton mobility and can, in particular, be attacked by a strong base.

In general, aldehydes and ketones are highly reactive.

The name aldehyde is applied to compounds containing a carbonyl group bonded to a hydrogen atom (-COH)

Aldehydes most often have trivial names, usually the same as the acids into which they transform upon oxidation.

The name of a straight acyclic aldehyde is formed by adding the ending " –AL" ("–AL" in Russian terminology) to the name of a hydrocarbon containing the same number of carbon atoms, for example:

The presence of multiple bonds or side chains in the aldehyde molecule is designated similarly to alkanes:

3-methylpentanal

By rational In nomenclature, fatty aldehydes are sometimes considered derivatives of acetaldehyde, for example: trimethylacetic aldehyde, methylethylacetic aldehyde, etc.

Non-systematic - trivial names are widely used for aldehydes. They are formed from the corresponding trivial names of carboxylic acids. These names are given in Table 7.

Table 7

Names of aldehydes

Exception: Ethanedialdehyde is commonly called glyoxal.

The name ketone is applied to compounds containing a carbonyl group linked to two hydrocarbon radicals.

Ketone names are formed by adding the ending " -HE" or " –DION" etc. to the name of the hydrocarbon corresponding to the main chain.

2-butanone 2,4-hescandione

By radical-functional In nomenclature, the names of ketones are derived from the names of the hydrocarbon radicals associated with the carbonyl group, adding the ending " –KETONE"

Table 8

Ketone names

diethyl ketone dimethyl ketone

3-pentanone propanone

Some ketones, as well as aldehydes, retain trivial names

acetone diacetyl

4.3. "Carboxylic acids"

TO
Arboxylic acids are compounds containing a carboxyl group (-COOH) in their structure.

The names of monobasic carboxylic acids are based on three types of nomenclatures.

Trivial names do not express the structure of a compound and usually reflect the history, origin of substances, their isolation from natural products, the route of synthesis, etc.

By rational In the nomenclature, carboxylic acids are considered as substituted acetic acid (methylethylacetic acid, trimethylacetic acid, etc.).

IUPAC nomenclature. There are two options for forming the name.

1st option: the carbon atom of the carboxyl group is considered an integral part of the carbon skeleton, and the name of the acid is formed from the name of the corresponding hydrocarbon by adding the ending " –OVA ACID". This option is most preferable for simple aliphatic acids.

hexanoic acid

2nd option: the carboxyl group is considered as a substituent in the hydrocarbon chain. The name of the corresponding hydrocarbon is appended with the suffix " –CARBOXYLIC ACID"

1-pentanecarboxylic acid

saturated monobasic carboxylic acids are formed from the names of alkanes with the same number of carbon atoms with the addition of a suffix.

DEFINITION

Aldehydes– organic substances belonging to the class of carbonyl compounds containing the functional group –CH = O, which is called carbonyl.

The general formula for saturated aldehydes and ketones is C n H 2 n O. The names of aldehydes contain the suffix –al.

The simplest representatives of aldehydes are formaldehyde (formaldehyde) -CH 2 = O, acetaldehyde (acetic aldehyde) - CH 3 -CH = O. There are cyclic aldehydes, for example, cyclohexane-carbaldehyde; aromatic aldehydes have trivial names - benzaldehyde, vanillin.

The carbon atom in the carbonyl group is in a state of sp 2 hybridization and forms 3σ bonds (two C-H bonds and one C-O bond). The π bond is formed by the p electrons of the carbon and oxygen atoms. The C=O double bond is a combination of σ and π bonds. The electron density is shifted towards the oxygen atom.

Aldehydes are characterized by isomerism of the carbon skeleton, as well as interclass isomerism with ketones:

CH 3 -CH 2 -CH 2 -CH = O (butanal);

CH 3 -CH (CH 3) -CH = O (2-methylpentanal);

CH 3 -C (CH 2 -CH 3) = O (methyl ethyl ketone).

Chemical properties of aldehydes

Aldehyde molecules have several reaction centers: an electrophilic center (carbonyl carbon atom), which participates in nucleophilic addition reactions; the main center is an oxygen atom with lone electron pairs; α-CH acid center responsible for condensation reactions; a C-H bond that is broken in oxidation reactions.

1. Addition reactions:

- water with the formation of heme-diols

R-CH = O + H 2 O ↔ R-CH(OH)-OH;

— alcohols with the formation of hemiacetals

CH 3 -CH = O + C 2 H 5 OH ↔CH 3 -CH(OH)-O-C 2 H 5 ;

— thiols with the formation of dithioacetals (in an acidic environment)

CH 3 -CH = O + C 2 H 5 SH ↔ CH 3 -CH(SC 2 H 5) -SC 2 H 5 + H 2 O;

— sodium hydrosulfite with the formation of sodium α-hydroxysulfonates

C 2 H 5 -CH = O + NaHSO 3 ↔ C 2 H 5 -CH(OH)-SO 3 Na;

- amines with the formation of N-substituted imines (Schiff bases)

C 6 H 5 CH = O + H 2 NC 6 H 5 ↔ C 6 H 5 CH = NC 6 H 5 + H 2 O;

- hydrazines to form hydrazones

CH 3 -CH = O + 2 HN-NH 2 ↔ CH 3 -CH = N-NH 2 + H 2 O;

— hydrocyanic acid with the formation of nitriles

CH 3 -CH = O + HCN ↔ CH 3 -CH(N)-OH;

- recovery. When aldehydes react with hydrogen, primary alcohols are obtained:

R-CH = O + H 2 → R-CH 2 -OH;

2. Oxidation

- “silver mirror” reaction - oxidation of aldehydes with an ammonia solution of silver oxide

R-CH = O + Ag 2 O → R-CO-OH + 2Ag↓;

- oxidation of aldehydes with copper (II) hydroxide, which results in the formation of a red precipitate of copper (I) oxide

CH 3 -CH = O + 2Cu(OH) 2 → CH 3 -COOH + Cu 2 O↓ + 2H 2 O;

These reactions are qualitative reactions to aldehydes.

Physical properties of aldehydes

The first representative of the homologous series of aldehydes is formaldehyde (formaldehyde) - a gaseous substance (n.s.), aldehydes of unbranched structure and composition C 2 -C 12 - liquids, C 13 and longer - solids. The more carbon atoms a straight aldehyde contains, the higher its boiling point. With an increase in the molecular weight of aldehydes, the values ​​of their viscosity, density and refractive index increase. Formaldehyde and acetaldehyde are able to mix with water in unlimited quantities, however, with the growth of the hydrocarbon chain, this ability of aldehydes decreases. Lower aldehydes have a pungent odor.

Preparation of aldehydes

The main methods for obtaining aldehydes:

- hydroformylation of alkenes. This reaction consists of the addition of CO and hydrogen to an alkene in the presence of carbonyls of some Group VIII metals, for example, octacarbonyl dicobalt (Co 2 (CO) 8). The reaction is carried out by heating to 130 C and a pressure of 300 atm

CH 3 -CH = CH 2 + CO +H 2 →CH 3 -CH 2 -CH 2 -CH = O + (CH 3) 2 CHCH = O;

- hydration of alkynes. The interaction of alkynes with water occurs in the presence of mercury (II) salts and in an acidic environment:

HC≡CH + H 2 O → CH 3 -CH = O;

- oxidation of primary alcohols (the reaction occurs when heated)

CH 3 -CH 2 -OH + CuO → CH 3 -CH = O + Cu + H 2 O.

Application of aldehydes

Aldehydes are widely used as raw materials for the synthesis of various products. Thus, from formaldehyde (large-scale production) various resins (phenol-formaldehyde, etc.) and medicines (urotropine) are obtained; acetaldehyde is a raw material for the synthesis of acetic acid, ethanol, various pyridine derivatives, etc. Many aldehydes (butyric, cinnamon, etc.) are used as ingredients in perfumery.

Examples of problem solving

EXAMPLE 1

EXAMPLE 2