Oxygen-containing organic substances contain atoms. Physical and chemical properties of alcohols. V. Text of the lecture

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 polyatomic (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.

Benzene ring reactions

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, formic acid $HCOOH$, having a small relative molecular weight $(M_r(HCOOH)=46)$, under normal conditions 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.

This video lesson was created specifically for self-study of the topic “Oxygen-containing organic substances.” During this lesson, you will learn about a new type of organic substance containing carbon, hydrogen and oxygen. The teacher will talk about the properties and composition of oxygen-containing organic substances.

Topic: Organic matter

Lesson: Oxygen-containing organic substances

1. The concept of a functional group

The properties of oxygen-containing organic substances are very diverse, and they are determined by which group of atoms the oxygen atom belongs to. This group is called functional.

A group of atoms that significantly determines the properties of an organic substance is called a functional group.

There are several different oxygen-containing groups.

Hydrocarbon derivatives, in which one or more hydrogen atoms are replaced by a functional group, belong to a certain class of organic substances (Table 1).

Tab. 1. The belonging of a substance to a certain class is determined by the functional group

2. Alcohols

Monohydric saturated alcohols

Let's consider individual representatives and general properties of alcohols.

The simplest representative of this class of organic substances is methanol, or methyl alcohol. Its formula is CH3OH. It is a colorless liquid with a characteristic alcoholic odor, highly soluble in water. Methanol- this is very poisonous substance. A few drops taken orally lead to blindness, and a slightly larger amount leads to death! Previously, methanol was isolated from wood pyrolysis products, so its old name was retained - wood alcohol. Methyl alcohol is widely used in industry. Medicines, acetic acid, and formaldehyde are made from it. It is also used as a solvent for varnishes and paints.

No less common is the second representative of the class of alcohols - ethyl alcohol, or ethanol Its formula is C2H5OH. In terms of its physical properties, ethanol is practically no different from methanol. Ethyl alcohol is widely used in medicine and is also included in alcoholic beverages. A sufficiently large number of organic compounds are obtained from ethanol in organic synthesis.

Obtaining ethanol. The main method for producing ethanol is the hydration of ethylene. The reaction occurs at high temperature and pressure, in the presence of a catalyst.

CH2=CH2 + H2O → C2H5OH

The reaction of substances with water is called hydration.

Polyhydric alcohols

Polyhydric alcohols include organic compounds whose molecules contain several hydroxyl groups connected to a hydrocarbon radical.

One of the representatives of polyhydric alcohols is glycerin (1,2,3-propanetriol). The glycerol molecule contains three hydroxyl groups, each of which is located at its own carbon atom. Glycerin is a very hygroscopic substance. It is able to absorb moisture from the air. Due to this property, glycerin is widely used in cosmetology and medicine. Glycerin has all the properties of alcohols. A representative of two atomic alcohols is ethylene glycol. Its formula can be considered as the formula of ethane, in which the hydrogen atoms of each atom are replaced by hydroxyl groups. Ethylene glycol is a syrupy liquid with a sweet taste. But it is very poisonous, and under no circumstances should you taste it! Ethylene glycol is used as antifreeze. One of the common properties of alcohols is their interaction with active metals. In the hydroxyl group, a hydrogen atom can be replaced by an active metal atom.

2C2H5OH + 2Na→ 2С2Н5ОNa+ H2 &

Hydration of alkenes

In the presence of strong mineral acids, alkenes undergo hydration reactions to form alcohols:

In the case of unsymmetrical alkenes, addition occurs in accordance with Markovnikov’s rule - the hydrogen atom of a water molecule attaches to a more hydrogenated carbon atom, and the hydroxy group to a less hydrogenated one at a double bond:

Hydrogenation (reduction) of aldehydes and ketones

Hydrogenation of aldehydes on metal catalysts (Pt, Pd or Ni) when heated leads to the formation of primary alcohols:

Under similar conditions, secondary alcohols are obtained from ketones:

Hydrolysis of esters

When exposed to esters of strong mineral acids, they undergo hydrolysis to form alcohol and carboxylic acid:

Hydrolysis of esters in the presence of alkalis is called saponification. This process is irreversible and leads to the formation of an alcohol and a carboxylic acid salt:

This process occurs through the action of an aqueous alkali solution on monohalogen derivatives of hydrocarbons:

Other methods for obtaining individual representatives of monohydric alcohols

Alcoholic fermentation of glucose

In the presence of some yeast, or more precisely under the action of the enzymes they produce, the formation of ethyl alcohol from glucose is possible. In this case, carbon dioxide is also formed as a by-product:

Production of methanol from synthesis gas

Synthesis gas is a mixture of carbon monoxide and hydrogen. By acting on this mixture of catalysts, heating and high pressures, methanol is produced in industry:

Preparation of polyhydric alcohols

Wagner reaction (mild oxidation of alkenes)

When alkenes are exposed to a neutral solution of potassium permanganate in the cold (0 o C), vicinal dihydric alcohols (diols) are formed:

The diagram presented above is not a complete reaction equation. In this form it is easier to remember it in order to be able to answer individual test questions of the Unified State Examination. However, if this reaction occurs in tasks of high complexity, then its equation must be written in full form:

Chlorination of alkenes followed by hydrolysis

This method is a two-stage one and consists in the fact that in the first stage the alkene enters into an addition reaction with a halogen (chlorine or bromine). For example:

And on the second, the resulting dihaloalkane is treated with an aqueous solution of alkali:

Obtaining glycerol

The main industrial method for producing glycerin is alkaline hydrolysis of fats (saponification of fats):

Preparation of phenol

Three-step method via chlorobenzene

This method is three-stage. At the first stage, benzene is brominated or chlorinated in the presence of catalysts. Depending on the halogen used (Br 2 or Cl 2), the corresponding aluminum or iron (III) halide is used as a catalyst.

At the second stage, the halogen derivative obtained above is treated with an aqueous solution of alkali:

In the third stage, sodium phenolate is treated with a strong mineral acid. Phenol is displaced because it is a weak acid, i.e. low dissociating substance:

Cumene oxidation

Preparation of aldehydes and ketones

Dehydrogenation of alcohols

When primary and secondary alcohols are dehydrogenated over a copper catalyst upon heating, aldehydes and ketones are obtained, respectively.

Oxidation of alcohols

Incomplete oxidation of primary alcohols produces aldehydes, and secondary alcohols produce ketones. In general, the scheme of such oxidation can be written as:

As you can see, the incomplete oxidation of primary and secondary alcohols leads to the same products as the dehydrogenation of these same alcohols.

Copper oxide can be used as an oxidizing agent when heated:

Or other stronger oxidizing agents, for example a solution of potassium permanganate in an acidic, neutral, or alkaline medium.

Alkyne hydration

In the presence of mercuric salts (often together with strong acids), alkynes undergo a hydration reaction. In the case of ethylene (acetylene), an aldehyde is formed; in the case of any other alkyne, a ketone is formed:

Pyrolysis of carboxylic acid salts of divalent metals

When heating salts of carboxylic acids of divalent metals, for example, alkaline earth metals, a ketone and carbonate of the corresponding metal are formed:

Hydrolysis of geminal dihalogen derivatives

Alkaline hydrolysis of geminal dihalogen derivatives of various hydrocarbons leads to aldehydes if chlorine atoms were attached to the extreme carbon atom and to ketones, if not to the extreme:

Catalytic oxidation of alkenes

Acetaldehyde is produced by the catalytic oxidation of ethylene:

Preparation of carboxylic acids

Catalytic oxidation of alkanes

Oxidation of alkenes and alkynes

For this, an acidified solution of potassium permanganate or dichromate is most often used. In this case, the multiple carbon-carbon bond is broken:

Oxidation of aldehydes and primary alcohols

In this method of producing carboxylic acids, the most common oxidizing agents used are an acidified solution of potassium permanganate or dichromate:

By hydrolysis of trihalogenated hydrocarbons

At the first stage, the trihaloalkane is treated with an aqueous alkali solution. This produces a carboxylic acid salt:

The second stage involves treating the carboxylic acid salt with a strong mineral acid. Because carboxylic acids are weak; they are easily replaced by strong acids:

Hydrolysis of esters

From salts of carboxylic acids

This reaction has already been considered in the preparation of carboxylic acids through the hydrolysis of trihalogen derivatives (see above). The point is that carboxylic acids, being weak, are easily replaced by strong inorganic acids:

Specific methods for producing acids

Obtaining formic acid from carbon monoxide

This method is industrial and consists in the fact that in the first stage, carbon monoxide under pressure at high temperatures reacts with anhydrous alkali:

and the second resulting formate is treated with a strong inorganic acid:

2HCOONa + H 2 SO 4 > 2HCOOH + Na 2 SO 4

Oxygen-containing compounds may include hydroxyl, carbonyl and carboxyl groups. They correspond to a class of compounds - alcohols, aldehydes, ketones, carboxylic acids.

Alcohols

Let's attack the ethylene with water. We use sulfuric acid as a catalyst. It catalyzes both the addition and removal of water. As a result of the cleavage of the double bond, one carbon atom will attach a hydrogen atom, and the other will attach the hydroxyl group of the water molecule. This is how compounds of the alcohol class are obtained.

The simplest alcohol is methyl CH3–OH. Ethyl alcohol is the next homologue of a number of alcohols.

If an alcohol molecule contains one hydroxyl group, such an alcohol is called monohydric. There are also alcohols that contain two or more hydroxyl groups. Such alcohols are called polyhydric. An example of a polyhydric alcohol is the well-known glycerin.

Aldehydes

Under the influence of a weak oxidizing agent, a hydroxyl group can be converted into a carbonyl group. As a result, a new class of compounds is formed - aldehydes. For example, ethyl alcohol is oxidized by such a weak oxidizing agent as copper(II) oxide. The reaction occurs when heated. The reaction product is acetaldehyde.

This is a qualitative reaction to alcohols. It is produced like this. Copper wire is calcined until an oxide film forms and then dipped in hot alcohol. The alcohol is oxidized and the copper is reduced. The copper wire becomes shiny and smells of acetaldehyde.

Like alcohols, aldehydes can be oxidized by weak oxidizing agents. This reaction occurs when the aldehyde is oxidized with an ammonia solution of silver oxide. The precipitated silver forms a thin mirror-like layer on the walls of the test tube. This process is called the silver mirror reaction. It is used for the qualitative determination of aldehydes.

Carboxylic acids

During the oxidation of aldehydes, the carbonyl group adds an oxygen atom. This creates a carboxyl group. A new class of organic compounds is formed - carboxylic acids. In our case, acetic acid was obtained from acetaldehyde. As we can see, functional groups can transform into each other.

Many carboxylic acids are weak electrolytes. During dissociation under the influence of water molecules, hydrogen is split off from the carboxyl group of an organic acid molecule:

CH3COOH ó CH3COO- + H+

Acetic acid, like other organic acids, reacts with bases, basic oxides, and metals.

Aldehydes, alcohols and acids are of great importance in our lives. They are used for the synthesis of various substances. Alcohols are used to produce synthetic rubbers, fragrances, medicines, dyes, and as solvents.

Organic acids are widespread in nature and play an important role in biochemical reactions. In the chemical industry, organic acids are used in tanning and calico printing.

Alcohols are also toxic substances. Methanol is especially poisonous. If it enters the body, it causes blindness and even death. Ethyl alcohol has a negative effect on vital centers in the cerebral cortex, blood vessels, and on the psyche, destroying a person’s personality.

The formation of haloalkanes during the interaction of alcohols with hydrogen halides is a reversible reaction. Therefore, it is clear that alcohols can be obtained by hydrolysis of haloalkanes- reactions of these compounds with water:

Polyhydric alcohols can be obtained by hydrolysis of haloalkanes containing more than one halogen atom per molecule. For example:

Hydration of alkenes

Hydration of alkenes- addition of water at the π bond of the alkene molecule, for example:

Hydration of propene leads, in accordance with Markovnikov’s rule, to the formation of a secondary alcohol - propanol-2:

Hydrogenation of aldehydes and ketones

Oxidation of alcohols under mild conditions leads to the formation of aldehydes or ketones. It is obvious that alcohols can be obtained by hydrogenation (reduction with hydrogen, addition of hydrogen) of aldehydes and ketones:

Oxidation of alkenes

Glycols, as already noted, can be obtained by oxidation of alkenes with an aqueous solution of potassium permanganate. For example, ethylene glycol (ethanediol-1,2) is formed by the oxidation of ethylene (ethene):

Specific methods for producing alcohols

1. Some alcohols are obtained using methods that are characteristic only of them. Thus, methanol is produced in industry reaction between hydrogen and carbon monoxide(II) (carbon monoxide) at elevated pressure and high temperature on the surface of the catalyst (zinc oxide):

The mixture of carbon monoxide and hydrogen required for this reaction, also called “synthesis gas,” is obtained by passing water vapor over hot coal:

2. Glucose fermentation. This method of producing ethyl (wine) alcohol has been known to man since ancient times:

The main methods for producing oxygen-containing compounds (alcohols) are: hydrolysis of haloalkanes, hydration of alkenes, hydrogenation of aldehydes and ketones, oxidation of alkenes, as well as the production of methanol from “synthesis gas” and fermentation of sugary substances.

Methods for producing aldehydes and ketones

1. Aldehydes and ketones can be produced oxidation or dehydrogenation of alcohols. By oxidation or dehydrogenation of primary alcohols, aldehydes can be obtained, and secondary alcohols - ketones:

3CH 3 –CH 2 OH + K 2 Cr 2 O 7 + 4H 2 SO 4 = 3CH 3 –CHO + K 2 SO 4 + Cr 2 (SO 4) 3 + 7H 2 O

2.Kucherov's reaction. As a result of the reaction, acetylene produces acetaldehyde, and acetylene homologues produce ketones:

3. When heated calcium or barium salts of carboxylic acids ketone and metal carbonate are formed:

Methods for producing carboxylic acids

1. Carboxylic acids can be obtained oxidation of primary alcohols or aldehydes:

3CH 3 –CH 2 OH + 2K 2 Cr 2 O 7 + 8H 2 SO 4 = 3CH 3 –COOH + 2K 2 SO 4 + 2Cr 2 (SO 4) 3 + 11H 2 O

5CH 3 –CHO + 2KMnO 4 + 3H 2 SO 4 = 5CH 3 –COOH + 2MnSO 4 + K 2 SO 4 + 3H 2 O,

3CH 3 –CHO + K 2 Cr 2 O 7 + 4H 2 SO 4 = 3CH 3 –COOH + Cr 2 (SO 4) 3 + K 2 SO 4 + 4H 2 O,

CH 3 –CHO + 2OH CH 3 –COONH 4 + 2Ag + 3NH 3 + H 2 O.

But when methanal is oxidized with an ammonia solution of silver oxide, ammonium carbonate is formed, not formic acid:

HCHO + 4OH = (NH 4) 2 CO 3 + 4Ag + 6NH 3 + 2H 2 O.

2. Aromatic carboxylic acids are formed when oxidation of homologues benzene:

5C 6 H 5 –CH 3 + 6KMnO 4 + 9H 2 SO 4 = 5C 6 H 5 COOH + 6MnSO 4 + 3K 2 SO 4 + 14H 2 O,

5C 6 H 5 –C 2 H 5 + 12KMnO 4 + 18H 2 SO 4 = 5C 6 H 5 COOH + 5CO 2 + 12MnSO 4 + 6K 2 SO 4 + 28H 2 O,

C 6 H 5 –CH 3 + 2KMnO 4 = C 6 H 5 COOK + 2MnO 2 + KOH + H 2 O

3. Hydrolysis of various carbon derivatives acids also leads to the production of acids. Thus, the hydrolysis of an ester produces an alcohol and a carboxylic acid. Acid-catalyzed esterification and hydrolysis reactions are reversible:

4. Ester hydrolysis under the influence of an aqueous solution of alkali proceeds irreversibly; in this case, not an acid, but its salt is formed from the ester: