The physical properties of esters are summarized. Abstract: Esters
Introduction -3-
1. Structure -4-
2. Nomenclature and isomerism -6-
3. Physical properties and being in nature -7-
4. Chemical properties -8-
5. Getting -9-
6. Application -10-
6.1 Use of inorganic acid esters -10-
6.2 Use of organic acid esters -12-
Conclusion -14-
Used sources of information -15-
Appendix -16-
Introduction
Among the functional derivatives of acids, esters, derivatives of acids, in which the acidic hydrogen is replaced by alkyl (or generally hydrocarbon) radicals, occupy a special place.
Esters are divided depending on which acid they are derived from (inorganic or carboxylic).
Among the esters, a special place is occupied by natural esters - fats and oils, which are formed by the trihydric alcohol glycerol and higher fatty acids containing even number carbon atoms. Fats are part of plant and animal organisms and serve as one of the energy sources of living organisms, which is released during the oxidation of fats.
The purpose of my work is to familiarize yourself in detail with such a class of organic compounds as esters and in-depth consideration of the field of application of individual representatives of this class.
1. Structure
General formula of carboxylic acid esters:
where R and R "are hydrocarbon radicals (in esters of formic acid, R is a hydrogen atom).
General fat formula:
where R ", R", R "" are carbon radicals.
Fats are “simple” and “mixed”. The composition of simple fats contains the remains of the same acids (ie, R '= R "= R" "), the composition of mixed fats contains different ones.
The following fatty acids are most commonly found in fats:
Alkanoic acids
1. Butyric acid CH 3 - (CH 2) 2 - COOH
3. Palmitic acid CH 3 - (CH 2) 14 - COOH
4. Stearic acid CH 3 - (CH 2) 16 - COOH
Alkenic acids
5. Oleic acid C 17 H 33 COOH
CH 3 - (CH 2) 7 -CH === CH- (CH 2) 7 -COOH
Alkadienic acids
6. Linoleic acid C 17 H 31 COOH
CH 3 - (CH 2) 4 -CH = CH-CH 2 -CH = CH-COOH
Alcatrienoic acids
7. Linolenic acid C 17 H 29 COOH
CH 3 CH 2 CH = CHCH 2 CH == CHCH 2 CH = CH (CH 2) 4 COOH
2. Nomenclature and isomerism
Ester names are derived from the name of the hydrocarbon radical and the name of the acid, in which the suffix is used instead of the ending -ova - at , for example:
The following types of isomerism are characteristic of esters:
1. The isomerism of the carbon chain begins at the acid residue with butanoic acid, and at the alcohol residue with propyl alcohol, for example, ethyl butyrate isomerically ethyl isobutyrate, propyl acetate and isopropyl acetate.
2. Isomerism of the position of the ester group -CO-O-. This type of isomerism begins with esters that contain at least 4 carbon atoms, such as ethyl acetate and methyl propionate.
3. Interclass isomerism, e.g. isomeric propanoic acid methyl acetate.
For esters containing unsaturated acid or unsaturated alcohol, two more types of isomerism are possible: isomerism of the position of the multiple bond and cis-, trans-isomerism.
3. Physical properties and being in nature
Esters of lower carboxylic acids and alcohols are volatile, water-insoluble liquids. Many of them have a pleasant smell. So, for example, butyl butyrate has a pineapple smell, isoamyl acetate - pears, etc.
Esters of the higher fatty acids and alcohols - waxy substances, odorless, insoluble in water.
The pleasant aroma of flowers, fruits, berries is largely due to the presence of certain esters in them.
Fats are widespread in nature. Along with hydrocarbons and proteins, they are part of all plant and animal organisms and constitute one of the main parts of our food.
By aggregate state at room temperature, fats are divided into liquid and solid. Hard fats, as a rule, are formed by saturated acids, liquid fats (they are often called oils) - unsaturated. Fats are soluble in organic solvents and insoluble in water.
4. Chemical properties
1. Reaction of hydrolysis, or saponification. Since the esterification reaction is reversible, therefore, in the presence of acids, the reverse hydrolysis reaction occurs:
The hydrolysis reaction is also catalyzed by alkalis; in this case, hydrolysis is irreversible, since the resulting acid forms a salt with alkali:
2. Reaction of addition. Esters containing unsaturated acid or alcohol are capable of addition reactions.
3. Recovery reaction. The reduction of esters with hydrogen leads to the formation of two alcohols:
4. Reaction of amide formation. Under the action of ammonia, esters are converted to acid amides and alcohols:
5. Receiving
1. The reaction of esterification:
Alcohols react with mineral and organic acids to form esters. The reaction is reversible (reverse process - hydrolysis of esters).
The reactivity of monohydric alcohols in these reactions decreases from primary to tertiary.
2. Interaction of acid anhydrides with alcohols:
3. Interaction of acid halides with alcohols:
6. Application
6.1 Use of inorganic acid esters
Boric acid esters - trialkylborates- easily obtained by heating alcohol and boric acid with the addition of concentrated sulfuric acid. Boronomethyl ether (trimethyl borate) boils at 65 ° C, and boron ethyl (triethyl borate) at 119 ° C. Esters of boric acid are easily hydrolyzed with water.
The reaction with boric acid serves to establish the configuration polyhydric alcohols and was repeatedly used in the study of sugars.
Orthosilicon ethers- liquids. Methyl ether boils at 122 ° С, ethyl ether at 156 ° С.Hydrolysis with water proceeds easily even in the cold, but it proceeds gradually and with a lack of water leads to the formation of high molecular weight anhydride forms in which silicon atoms are connected to each other through oxygen (siloxane groups) :
These high molecular weight substances (polyalkoxysiloxanes) are used as binders that can withstand a fairly high fever, in particular for coating the surface of molds for precision metal casting.Dialkyl dichlorosilanes react similarly to SiCl 4, for example ((CH 3) 2 SiCl 2, forming dialkoxy derivatives:
Their hydrolysis with a lack of water gives the so-called polyalkylsiloxanes:
They have different (but very significant) molecular weights and are viscous liquids used as heat-resistant lubricants, and with even longer siloxane skeletons - heat-resistant electrical insulating resins and rubbers. These are liquids that are easily hydrolyzed to methyl alcohol and TiO 2 are used for impregnation fabrics to make them waterproof.
Esters of nitric acid. They are obtained by the action of a mixture of nitric and concentrated sulfuric acids on alcohols. Methyl nitrate CH 3 ONO 2 (bp 60 ° C) and ethyl nitrate C 2 H 5 ONO 2 (bp 87 ° C) can be distilled with careful work, but when heated above the boiling point or during detonation they are very strong blow up.
Ethylene glycol and glycerin nitrates, incorrectly called nitroglycol and nitroglycerin, are used as explosives. Nitroglycerin itself (a heavy liquid) is inconvenient and dangerous to handle.
Pentrite - tetranitrate of pentaerythritol C (CH 2 ONO 2) 4, obtained by treating pentaerythritol with a mixture of nitric and sulfuric acids, is also a strong explosive with blasting action.
Glycerin nitrate and pentaerythritol nitrate have a vasodilating effect and are used as symptomatic agents for angina pectoris.
Esters. Among the functional derivatives of acids, esters, derivatives of acids, in which the hydrogen atom in the carboxyl group is replaced by a hydrocarbon radical, occupy a special place. General formula of esters
where R and R "are hydrocarbon radicals (in esters of formic acid, R is a hydrogen atom).
Nomenclature and isomerism. Ester names are derived from the name of the hydrocarbon radical and the name of the acid, in which the suffix -am is used instead of the ending -ova, for example:
Esters are characterized by three types of isomerism:
- 1. The isomerism of the carbon chain begins at the acid residue with butanoic acid, for the alcohol residue - with propyl alcohol, for example, ethyl butyrate isomeric ethyl isobutyrate, propyl acetate and isopropyl acetate.
- 2. Isomerism of the position of the ester group --CO - O--. This type of isomerism begins with esters that contain at least 4 carbon atoms, such as ethyl acetate and methyl propionate.
- 3. Interclass isomerism, eg isomeric propanoic acid methyl acetate.
For esters containing unsaturated acid or unsaturated alcohol, two more types of isomerism are possible: isomerism of the position of the multiple bond and cis-, trans-isomerism.
Physical properties of esters. Esters of lower carboxylic acids and alcohols are volatile, water-insoluble liquids. Many of them have a pleasant smell. So, for example, butyl butyrate has a pineapple smell, isoamyl acetate - pears, etc.
Esters of higher fatty acids and alcohols are waxy substances, odorless, insoluble in water.
Chemical properties of esters. 1. Reaction of hydrolysis, or saponification. Since the esterification reaction is reversible, therefore, in the presence of acids, the reverse hydrolysis reaction occurs:
The hydrolysis reaction is also catalyzed by alkalis; in this case, hydrolysis is irreversible, since the resulting acid forms a salt with alkali:
- 2. Reaction of addition. Esters containing unsaturated acid or alcohol are capable of addition reactions.
- 3. Recovery reaction. The reduction of esters with hydrogen leads to the formation of two alcohols:
4. Reaction of amide formation. Under the action of ammonia, esters are converted to acid amides and alcohols:
17. Structure, classification, isomerism, nomenclature, production methods, physical properties, Chemical properties amino acids
Amino acids (aminocarbamic acids) - organic compounds, the molecule of which simultaneously contains carboxyl and amine groups.
Amino acids can be considered derivatives of carboxylic acids in which one or more hydrogen atoms are replaced by amine groups.
Amino acids are colorless crystalline substances that are readily soluble in water. Many of them have a sweet taste. All amino acids are amphoteric compounds, they can exhibit both acidic properties due to the presence of the carboxyl group --COOH in their molecules, and the main properties due to the amino group --NH2. Amino acids interact with acids and alkalis:
NH2 --CH2 --COOH + HCl> HCl * NH2 --CH2 --COOH (glycine hydrochloric salt)
NH 2 --CH 2 --COOH + NaOH> H 2 O + NH 2 --CH 2 --COONa (sodium salt of glycine)
Due to this, solutions of amino acids in water have the properties of buffer solutions, i.e. are in a state of internal salts.
NH 2 --CH 2 COOH N + H 3 --CH 2 COO -
Amino acids can usually enter into all reactions characteristic of carboxylic acids and amines.
Esterification:
NH 2 --CH 2 --COOH + CH 3 OH> H 2 O + NH 2 --CH 2 --COOCH 3 (glycine methyl ester)
An important feature of amino acids is their ability to polycondensate, leading to the formation of polyamides, including peptides, proteins, nylon, nylon.
Peptide formation reaction:
HOOC --CH2 --NH --H + HOOC --CH2 --NH2> HOOC --CH2 --NH --CO --CH2 --NH2 + H2O
The isoelectric point of an amino acid is the pH value at which the maximum fraction of amino acid molecules has zero charge. At this pH, the amino acid is the least mobile in the electric field, and this property can be used to separate amino acids, as well as proteins and peptides.
A zwitter ion is an amino acid molecule in which the amino group is represented as -NH 3 +, and the carboxy group as -COO? ... Such a molecule has a significant dipole moment at zero total charge. It is from these molecules that the crystals of most amino acids are built.
Some amino acids have multiple amino and carboxyl groups. For these amino acids, it is difficult to talk about any particular zwitterion.
Most amino acids can be obtained during protein hydrolysis or as a result of chemical reactions:
CH 3 COOH + Cl 2 + (catalyst)> CH 2 ClCOOH + HCl; CH 2 ClCOOH + 2NH 3> NH 2 --CH 2 COOH + NH 4 Cl
Now let's talk about complex ones. Esters are widespread in nature. To say that esters play a big role in human life is to say nothing. We encounter them when we smell a flower that owes its scent to the simplest esters. Sunflower or olive oil is also a complex ester, but it has a high molecular weight - just like animal fats. We wash, wash and wash with the means that we receive chemical reaction processing of fats, that is, esters. They are also used in various areas of production: they are used to make medicines, paints and varnishes, perfumes, lubricants, polymers, synthetic fibers and much, much more.
Esters are organic compounds based on oxygen-containing organic carboxylic or inorganic acids. The structure of a substance can be represented as an acid molecule in which the H atom in the OH- hydroxyl is replaced by a hydrocarbon radical.
Esters are obtained by the reaction of an acid and an alcohol (esterification reaction).
Classification
- Fruit esters - liquids with a fruity smell, the molecule contains no more than eight carbon atoms. Obtained from monohydric alcohols and carboxylic acids. Floral-scented esters are produced using aromatic alcohols.
- Waxes are solids containing from 15 to 45 C atoms in a molecule.
- Fats - contain 9-19 carbon atoms in a molecule. Obtained from glycerin a (trihydric alcohol) and higher carboxylic acids. Fats can be liquid (vegetable fats called oils) and solid (animal fats).
- Esters of mineral acids in their physical properties can also be both oily liquids (up to 8 carbon atoms) and solids (from nine C atoms).
Properties
V normal conditions esters can be liquid, colorless, with a fruity or floral odor, or solid, plastic; usually odorless. The longer the chain of the hydrocarbon radical, the harder the substance. Almost insoluble in water. They dissolve well in organic solvents. Combustible.
Reacts with ammonia to form amides; with hydrogen (it is this reaction that turns liquid vegetable oils into solid margarines).
As a result of the hydrolysis reaction, they decompose into alcohol and acid. Hydrolysis of fats in an alkaline medium leads to the formation of not acid, but its salt - soap.
Esters of organic acids are low-toxic, have a narcotic effect on humans, mainly belong to the 2nd and 3rd class of hazard. Some reagents in production require the use of special eye and respiratory protection. The longer the ether molecule is, the more toxic it is. Esters of inorganic phosphoric acids are poisonous.
Substances can enter the body through the respiratory system and skin. Symptoms of acute poisoning are excitement and impaired coordination of movements, followed by depression of the central nervous system. Regular exposure can lead to liver disease, kidney disease, of cardio-vascular system, violations of the blood formula.
Application
In organic synthesis.
- For the production of insecticides, herbicides, lubricants, impregnations for leather and paper, detergents, glycerin, nitroglycerin, drying oils, oil paints, synthetic fibers and resins, polymers, plexiglass, plasticizers, reagents for ore dressing.
- As an additive to engine oils. 
- In the synthesis of perfumery fragrances, food fruit essences and cosmetic flavors; medicines, for example, vitamins A, E, B1, validol, ointments.
- As solvents for paints, varnishes, resins, fats, oils, cellulose, polymers.
In the assortment of the PrimeChemicalsGroup store you can buy demanded esters, including butyl acetate and Tween-80.
Butyl acetate
It is used as a solvent; in the perfumery industry for the manufacture of fragrances; for tanning leather; in pharmaceuticals - during the manufacture of certain drugs.
Twin-80
It is also polysorbate-80, polyoxyethylene sorbitan monooleate (based on sorbitol olive oil). Emulsifier, solvent, technical lubricant, viscosity modifier, stabilizer essential oils, nonionic surfactant, moisturizer. Part of solvents and cutting fluids. It is used for the production of cosmetic, food, household, agricultural and technical products. Possesses unique property emulsify a mixture of water and oil.
If the initial acid is polybasic, then either complete esters can be formed - all HO groups are replaced, or acid esters are partially substituted. For monobasic acids, only complete esters are possible (Fig. 1).
Rice. 1. EXAMPLES OF ESTERS based on inorganic and carboxylic acid
Nomenclature of esters.
The name is created as follows: first, the R group attached to the acid is indicated, then the name of the acid with the suffix "at" (as in the names of inorganic salts: carbon at sodium, nitr at chromium). Examples in Fig. 2
Rice. 2. NAMES OF ESTERS... Fragments of molecules and their corresponding fragments of names are highlighted in the same color. Esters are usually thought of as reaction products between an acid and an alcohol, for example butyl propionate can be thought of as a reaction between propionic acid and butanol.
If you use the trivial ( cm... TRIVIAL NAMES OF SUBSTANCES) the name of the original acid, then the name of the compound includes the word "ester", for example, C 3 H 7 COOS 5 H 11 - amyl ester of butyric acid.
Classification and composition of esters.
Most of the studied and widely used esters are compounds derived from carboxylic acids. Esters based on mineral (inorganic) acids are not so diverse, because the class of mineral acids is less numerous than carboxylic acids (the variety of compounds is one of the hallmarks of organic chemistry).
When the number of C atoms in the starting carboxylic acid and alcohol does not exceed 6–8, the corresponding esters are colorless oily liquids, most often with a fruity odor. They make up the fruity ester group. If an aromatic alcohol (containing an aromatic nucleus) participates in the formation of an ester, then such compounds usually have a floral rather than a fruity odor. All compounds of this group are practically insoluble in water, but readily soluble in most organic solvents. These compounds are interesting for a wide range of pleasant aromas (Table 1), some of them were initially isolated from plants, and later synthesized artificially.
| Tab. 1. SOME ESTERS with a fruity or floral aroma (fragments of the initial alcohols in the formula of the compound and in the name are highlighted in bold) | ||
| Ester Formula | Name | Scent |
| CH 3 COO C 4 H 9 | Butyl acetate | pear |
| C 3 H 7 COO CH 3 | Methyl new butyric acid ester | apple |
| C 3 H 7 COO C 2 H 5 | Ethyl new butyric acid ester | pineapple |
| C 4 H 9 COO C 2 H 5 | Ethyl | crimson |
| C 4 H 9 COO C 5 H 11 | Isoamil new isovaleric acid ester | banana |
| CH 3 COO CH 2 C 6 H 5 | Benzyl acetate | jasmine |
| C 6 H 5 COO CH 2 C 6 H 5 | Benzyl benzoate | floral |
With an increase in the size of the organic groups that make up the esters, up to C 15-30, the compounds acquire the consistency of plastic, easily softening substances. This group is called waxes and is generally odorless. Beeswax contains a mixture of various esters, one of the components of the wax, which we managed to isolate and determine its composition, is palmitic acid myricyl ester С 15 Н 31 СООС 31 Н 63. Chinese wax (product of isolation of cochineal - insects of East Asia) contains ceryl ester of cerotinic acid C 25 H 51 SOOS 26 H 53. In addition, waxes also contain free carboxylic acids and alcohols containing large organic groups. Waxes are not wetted with water, soluble in gasoline, chloroform, benzene.
The third group is fats. Unlike the previous two groups based on monohydric alcohols ROH, all fats are esters formed from the trihydric alcohol glycerol HOCH 2 –CH (OH) –CH 2 OH. The carboxylic acids in fats usually have a hydrocarbon chain with 9-19 carbon atoms. Animal fats (cow oil, lamb, lard) are plastic low-melting substances. Vegetable fats (olive, cottonseed, sunflower oil) are viscous liquids. Animal fats mainly consist of a mixture of stearic and palmitic acid glycerides (Fig. 3A, B). Vegetable oils contain glycerides of acids with a slightly shorter carbon chain: lauric C 11 H 23 COOH and myristic C 13 H 27 COOH. (like stearic and palmitic are saturated acids). Such oils can be stored in air for a long time without changing their consistency, and therefore are called non-drying. In contrast, linseed oil contains the glyceride of unsaturated linoleic acid (Figure 3B). When applied in a thin layer to a surface, such oil dries out under the influence of atmospheric oxygen during polymerization along double bonds, thus forming an elastic film insoluble in water and organic solvents. Based linseed oil make natural drying oil.
Rice. 3. GLYCERIDES OF STEARIC AND PALMITIC ACID (A AND B)- components of animal fat. Linoleic acid glyceride (B) is a component of linseed oil.
Esters of mineral acids (alkyl sulfates, alkyl borates containing fragments of lower alcohols С 1–8) are oily liquids, esters of higher alcohols (starting from С 9) are solid compounds.
Chemical properties of esters.
The most characteristic of carboxylic acid esters is hydrolytic (under the action of water) cleavage of the ester bond, in neutral environment it proceeds slowly and is noticeably accelerated in the presence of acids or bases, because ions H + and HO - catalyze this process (Fig. 4A), and hydroxyl ions act more efficiently. Hydrolysis in the presence of alkalis is called saponification. If we take an amount of alkali sufficient to neutralize all the acid formed, then the ester is completely saponified. This process is carried out on an industrial scale, with the receipt of glycerin and higher carboxylic acids (C 15-19) in the form of alkali metal salts, which are soap (Fig. 4B). Fragments of unsaturated acids contained in vegetable oils, like any unsaturated compounds, can be hydrogenated, hydrogen is attached to double bonds and compounds close to animal fats are formed (Fig. 4B). This method is used in industry to obtain solid fats based on sunflower, soybean or corn oil. From products of hydrogenation of vegetable oils, mixed with natural animal fats and various food additives make margarine.
The main synthesis method is the interaction of carboxylic acid and alcohol, catalyzed by acid and accompanied by the release of water. This reaction is the opposite of that shown in Fig. 3A. In order for the process to go in the right direction (synthesis of an ester), water is distilled (distilled off) from the reaction mixture. Special studies using labeled atoms have established that during the synthesis, the O atom, which is part of the resulting water, is detached from the acid (marked with a red dotted frame), and not from alcohol (the unrealizable variant is highlighted in a blue dotted frame).
In the same way, esters of inorganic acids are obtained, for example, nitroglycerin (Fig. 5B). Instead of acids, acid chlorides can be used; the method is applicable to both carboxylic (Fig. 5B) and inorganic acids (Fig. 5D).
The interaction of carboxylic acid salts with alkyl halides RCl also leads to esters (Fig.5D), the reaction is convenient because it is irreversible - the released inorganic salt is immediately removed from the organic reaction medium in the form of a precipitate.
The use of esters.
Ethyl formate НСООС 2 Н 5 and ethyl acetate Н 3 СООС 2 Н 5 are used as solvents for cellulose varnishes (based on nitrocellulose and cellulose acetate).
Esters based on lower alcohols and acids (Table 1) are used in the food industry to create fruit essences, and esters based on aromatic alcohols - in the perfume industry.
Waxes are used to make polishes, lubricants, impregnating compositions for paper (waxed paper) and leather, they are also included in cosmetic creams and medicinal ointments.
Fats, along with carbohydrates and proteins, make up the set necessary for nutrition food products, they are part of all plant and animal cells, in addition, accumulating in the body, they play the role of an energy reserve. Due to the low thermal conductivity, the fat layer protects animals (in particular, sea whales or walruses) from hypothermia.
Animal and vegetable fats are raw materials for obtaining higher carboxylic acids, detergents and glycerin (Fig. 4), used in the cosmetic industry and as a component of various lubricants.
Nitroglycerin (Fig. 4) - known medicinal product and explosive, dynamite base.
On the basis of vegetable oils, drying oils are made (Fig. 3), which form the basis of oil paints.
Sulfuric acid esters (Fig. 2) are used in organic synthesis as alkylating reagents (introducing an alkyl group into the compound), and phosphoric acid esters (Fig. 5) are used as insecticides, as well as additives to lubricating oils.
Mikhail Levitsky
Derivatives of carboxylic or inorganic acids, in which the hydrogen atom in the hydroxyl group is replaced by a radical, are called esters. Usually general formula esters are designated as two hydrocarbon radicals attached to the carboxyl group - C n H 2n + 1 -COO-C n H 2n + 1 or R-COOR '.
Nomenclature
Ester names are composed of radical and acid names with the suffix "-at". For example:
- CH 3 COOH- methyl formate;
- HCOOCH 3- ethyl formate;
- CH 3 COOC 4 H 9- butyl acetate;
- CH 3 -CH 2 -COO-C 4 H 9- butyl propionate;
- CH 3 -SO 4 -CH 3- dimethyl sulfate.
The trivial names of the acid that make up the compound are also used:
- C 3 H 7 SOOS 5 H 11- amyl ester of butyric acid;
- HCOOCH 3- formic acid methyl ester;
- CH 3 -COO-CH 2 -CH (CH 3) 2- isobutyl acetic acid ester.
Rice. 1. Structural formulas of esters with names.
Classification
Depending on the origin, esters are divided into two groups:
- carboxylic acid esters- contain hydrocarbon radicals;
- inorganic acid esters- include the remainder of mineral salts (C 2 H 5 OSO 2 OH, (CH 3 O) P (O) (OH) 2, C 2 H 5 ONO).
The most diverse are esters of carboxylic acids. Their physical properties depend on the complexity of the structure. Esters of lower carboxylic acids are volatile liquids with a pleasant aroma, higher ones are solids. These are poorly soluble compounds that float on the surface of the water.
The types of esters of carboxylic acids are shown in the table.
|
View |
Description |
Examples of |
|
Fruit esters |
Liquids whose molecules contain no more than eight carbon atoms. They have a fruity aroma. Consist of monohydric alcohols and carboxylic acids |
|
|
Liquid (oils) and solids containing from nine to 19 carbon atoms. Consist of glycerin and carboxylic (fatty) acid residues |
Olive oil - a mixture of glycerin with residues of palmitic, stearic, oleic, linoleic acids |
|
|
Solids with 15-45 carbon atoms |
CH 3 (CH 2) 14 -CO-O- (CH 2) 29 CH 3-myricyl palmitate |
Rice. 2. Wax.
Esters of carboxylic acids are the main component of aromatic essential oils that are found in fruits, flowers, berries. Also included in beeswax.
Rice. 3. Essential oils.
Receiving
Esters are prepared in several ways:
- by the reaction of esterification of carboxylic acids with alcohols:
CH 3 COOH + C 2 H 5 OH → CH 3 COOC 2 H 5 + H 2 O;
- the reaction of carboxylic acid anhydrides with alcohols:
(CH 3 CO) 2 O + 2C 2 H 5 OH → 2CH 3 COOC 2 H 5 + H 2 O;
- the reaction of salts of carboxylic acids with halogenated hydrocarbons:
CH 3 (CH 2) 10 COONa + CH 3 Cl → CH 3 (CH 2) 10 COOCH 3 + NaCl;
- by the reaction of addition of carboxylic acids to alkenes:
CH 3 COOH + CH 2 = CH 2 → CH 3 COOCH 2 CH 3 + H 2 O.
Properties
The chemical properties of esters are due to functional group-COOH. The main properties of esters are described in the table.
Esters are used in cosmetology, medicine, food industry as flavors, solvents, fillers.
What have we learned?
From the topic of the 10th grade chemistry lesson, they learned what esters are. These are compounds containing two radicals and a carboxyl group. Depending on the origin, they may contain residues of mineral or carboxylic acids. Esters of carboxylic acids are divided into three groups: fats, waxes, fruit esters. They are poorly soluble in water substances with low density and pleasant aroma. Esters react with alkalis, water, halogens, alcohols and ammonia.
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