Esters ending. Esters - concept, properties, application. Nomenclature of esters
Esters are derivatives of oxoacids (both carboxylic and mineral) RkE(=O)l(OH)m, (l ≠ 0), formally being the products of the replacement of hydrogen atoms of hydroxyls -OH acidic function with a hydrocarbon residue (aliphatic, alkenyl, aromatic or heteroaromatic); are also considered as acyl derivatives of alcohols. In the IUPAC nomenclature, esters also include acyl derivatives of chalcogenide analogues of alcohols (thiols, selenols and tellurenes).
They differ from ethers, in which two hydrocarbon radicals are connected by an oxygen atom (R1-O-R2).
General formula esters:
Nomenclature of esters.
The name is created as follows: first, the group R 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, nitrate at chromium). Examples in Fig. 2
Rice. 2. NAMES OF ESTERS. Fragments of molecules and 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 the result of the reaction between propionic acid and butanol.
If the trivial name of the starting acid is used, then the word “ester” is included in the name of the compound, for example, C 3 H 7 COOC 5 H 11 - amyl ester of butyric acid.
Homologous series esters.
The general formula of esters is R1--CO---R2, where R1 and R2 are carbohydrate radicals. Esters are derivatives of acids in which the H in the hydroxyl is replaced by a radical. Esters are named after their acids and alcohols. who participate in education
H-CO-O-CH3-- methyl formate or methyl formic acid ester or methyl formic ester.
CH3-CO-O-C2H5 - ethyl acetate or ethyl ester of acetic acids or acetic ethyl ether..
C3H7-CO-O-CH3 - butyric acid methyl ester or methyl butyrate
C3H7-CO-O-C2H5 - ethyl ester of butyric acid or ethyl butyrate
In short, you need to write down the table of carboxylic acids. and to them the name of the salt (formic - formate, acetic - acetate, propionic - propinate, butyrate, valeric - valeriat, capronic - capronate, enanthic - enantonate, oxalic - oxalate, malonic - malonate, succinic - succinate .... Look How are the names of ethers formed?
CH3-CO-O (this is acetic acid without H) --C5H11- (this is a monovalent pentyl(amyl) radical - table) this is the name of this ester.
Amyl acetate ester, acetic acid amine ester, amyl acetate. Look again.
CH3CH2CH2CH2-CO-O (pentane or valeric acid) ---C4H9 (this is butyl) - butyl valerate, valerian butyl ether, butyl ester of valeric acid.
Isomerism.
Esters are characterized by isomerism of the hydrocarbon skeleton. For example, isomers are propyl acetate and isopropyl acetate. Since the ester molecule contains two hydrocarbon radicals - an acid residue and an alcohol residue - isomerism of each of the radicals is possible. For example, isomers are propyl acetate and isopropyl acetate (isomerism in the alcohol radical) or ethyl butyrate and ethyl isobutyrate (isomerism in the acid radical).
Physical properties. Esters are colorless liquids, slightly soluble or not at all soluble in water, and have a specific odor (in low concentrations - pleasant, often fruity or floral). Esters of higher alcohols and higher acids are solids.
Chemical properties . The most characteristic reaction for esters is hydrolysis. Hydrolysis occurs in the presence of acids or alkalis. When an ester is hydrolyzed in the presence of acids, a carboxylic acid and an alcohol are formed:
When an ester is hydrolyzed in the presence of alkalis, a carboxylic acid salt and an alcohol are formed:
Methods of obtaining.
Methods for producing esters. Main products and their areas of application. Conditions for the esterification reaction of organic acids with alcohols. Process catalysts. Features of the technological design of the esterification reaction unit.
1. Interaction of acids with alcohols:
This is the most common method for producing esters.
2. Synthesis of esters by aldehyde condensation:
The synthesis of esters from aldehydes (Tishchenko reaction) is carried out in the presence of aluminum alkoxide activated with ferric chloride or, better, aluminum chloride and zinc oxide. This method is of industrial importance.
3. Addition of organic acids to alkenes:
4. Synthesis of esters by dehydrogenation of alcohols:
5. Obtaining esters by transesterification.
This reaction has two varieties: the exchange reaction between ether and alcohol with alcohol radicals (alcoholysis reaction):
and the exchange reaction of acid radicals at the alcohol group of the ester:
6. Synthesis of esters from acid anhydrides and alcohols:
7. Interaction of ketones with alcohols:
8. Interaction between acid halides and alcohols:
9. Reaction between silver or potassium salts of acids and aliphatic halide derivatives:
10. Interaction of acids with aliphatic diazo compounds
Application.
Some esters are used as solvents (ethyl acetate is of greatest practical importance). Many esters, due to their pleasant smell, are used in the food and perfume and cosmetic industries. Esters of unsaturated acids are used to produce plexiglass; methyl methacrylate is most widely used for this purpose.
On the topic
"Esters and esters"
Completed by: Manzhieva A.A.
Lesson topic: Esters. Compound. Nomenclature. Properties. Application.
Lesson Objectives :
Consider the composition and structure of the simplest esters, the essence of the esterification reaction.
Create conditions for the development of skills to independently acquire knowledge using various
information sources.
Contribute to: 1. the formation of experience creative activity, business communication experience.
2. development creative thinking, memory, attention, observation.
Continue to develop students’ abilities to independently analyze, correct and
evaluate knowledge;
The most important task of a teacher is to support and guide students, not to give ready-made knowledge, but to teach them how to obtain it from various sources.
Lesson type : A lesson in learning new material with elements of research and using a presentation on a given topic.
Form of organization of cognitive activity : work in groups using ICT.
On the teacher's desk: soap different types, perfumes, varnishes, flowers (geranium, violets), fresh fruits: lemon, orange, tangerine, bergamot oil, lavender, etc.
Epigraph of the lesson :
There is a persuasiveness in the aroma that is stronger than words, evidence, feelings and will. The persuasiveness of the aroma is irrefutable, irresistible, it enters us just as the air we breathe enters our lungs, it fills us, fills us to capacity. There is no remedy against it. Patrick Suskind. “Perfumer”(Slide 1)(Slide2)
During the classes :
Teacher's opening speech (motivation on the topic being studied)
Indeed, pleasant aromas can not only give us pleasure, but also cause a good mood, increase efficiency, they can lower blood pressure and increase skin temperature. When an unpleasant odor enters the human olfactory organ, the person involuntarily holds his breath, trying to inhale as little unpleasant air as possible. Undesirable odor reduces performance and significantly depresses a person. (I draw the students’ attention to the objects on the teacher’s desk.) They all have smells. What substances cause various odors? These are mainly esters. (The topic of the lesson is announced) (Slide 3)
Survey :
Exercise 1 (for 4 minutes), then control the students’ answers at the board. (Slide 4)
1 group: Write down the general formula of saturated monohydric alcohols. Give examples of any four alcohols; give them names according to the international and trivial nomenclature.
WITHnH2n+2 Oh orWITHnH2n+1 HE R- OH CH3OH - methanol, methyl alcohol, C2 H5OH-ethanol, ethyl alcohol
C3 H7OH - propanol, propyl alcohol C4 H9OH - butanol, butyl alcohol
2nd group: Write down the general formula of saturated monobasic carboxylic acids, give examples of any four carboxylic acids; give them names according to international and trivial nomenclature. WITHnH2nABOUT R- CO- OH H-CO-OH methane. formic,
СH3 - CO-OH ethane, acetic. CH3 - CH2 - CO-OH propane, propionic
CH3 - CH2 - CH2 - CO-OH butane, oil.
3 group: create an equation for the interaction of methanol with formic and acetic carboxylic acids, give the name of the resulting org. substances.
Studying new material: Please remember the name of the reaction between a carboxylic acid and an alcohol (based on materials previous lessons) and what substance is formed as a result of this interaction.
This reaction is called an esterification reaction (Slide 5)
R-CO-OH + HO-R1 ↔ RCO-OR1 + H2O
General formula of esters
|
R-C–O-R |
WITHnH2nO2 |
Question: What class organic compounds has the same general formula? (saturated monobasic carboxylic acids)
I suggest students write down the definitions of esters in their notebooks (Slide 6)
Esters- these are substances formed as a result of the dehydration reaction of carboxylic acids and alcohols.
Esters are called organic substances that have the general formula RCOOR1.
Esters are called organic substances that contain a functional group of atoms - COO - connected to two hydrocarbon radicals.
I ask a question: What are esters called according to the international nomenclature? (Slide 7)
According to the international nomenclature, the names of esters are given as follows: to the name of the saturated hydrocarbon radical in alcohol, the name of the corresponding acid is added, in which the ending - vaya is replaced by the suffix - at.
Task 2
Groups 1 and 2: Write down in the table the names of esters according to the international nomenclature using the proposed formulas (printed in files). (Slide 8)
Ether formula | Broadcast name |
||
S4N9-SOO-S5N11 C3H7-COO-S2H5 CH3-CH(CH3)-CH2COO-C2H5 CH3-COO - C2H5 H – COO – C2H5 | Orange Apricot Apple Pear Cherry |
Group 3: Create formulas of esters by name
Ether formula | Broadcast name |
||
Pear Cherry Apricot Orange Apple | Ethyl ethanate Ethyl methanate Ethyl butanoate Pentyl tentanate Ethyl,3-methylbutanate |
Students compare the table data on the slide with the entries in the notebook, correct mistakes (Slide 9)
Task3 (use of table) (slide 10)
1g. Write an equation for the esterification reaction to produce ester - with cherry aroma.
1.H-COOH + C2H5OH ↔ H - COOC2H5 + H2O
2 gr. Write an equation for the esterification reaction to produce an ester with pear aroma.
2.CH3 - COOH + C2H5OH ↔ H - COOC2H5 + H2O
3 g Write an equation for the esterification reaction to produce ester with apple aroma.
3. CH3-CH(CH3)-CH2COOH + HO - C2H5↔ CH3-CH(CH3)-CH2COO- C2H5+ H2O
Types of isomerism of esters: (Slide 11)
1. Carbon skeleton
2. Interclass (limit monobasic carboxylic acids)
Task4 (Slide 12)
С5Н10О2 |
1g. Compose 2 formulas of isomers with different carbon skeletons and name them by MN.
2g. Make 2 formulas of isomers from different classes and name them by MN.
3gr. Compose one formula of isomers with different carbon skeletons and from the class of carboxylic acids and name them by MN.
Physical properties of esters (Slide13)
Esters are liquids, lighter than water, volatile, with a pleasant odor in most cases, boiling point. and t° pl. lower than boiling point and t°pl. initial carboxylic acids, poorly soluble in water, with the exception of esters with a lower content of carbon atoms, highly soluble in alcohols.
Chemical properties of esters (Slide 14)
The esterification reaction proceeds very slowly and, as a rule, not completely because hydrolysis of esters occurs (saponification), and the starting substances are formed again - alcohol and acid. Saponification occurs much faster if the reaction takes place in an alkaline environment.
RCO-OR1 + H2O ↔ R-CO-OH + HO-R1
For example:
H - COOC2H5 + H2O ↔ H-COOH + C2H5OH
Research element in the lesson
Task 5 (Slide15)
Using the information provided (files with materials on the tables), prepare small messages in groups:
1 gr. What is perfume made of?
2 gr. Esters in medicinal plants
3 gr. What is wax?
Verification test for consolidation of the studied material (Slide 16)
1. General formula of esters:
A) CnH2nO B) CnH2nO2 C) CnH2n+2O D) CnH2n
2. Esters are a product of the interaction:
1. Carboxylic acids and aldehydes
2. Alcohols and aldehydes
3. Carboxylic acids and alcohols
4. Alcohols and ethers
3. As a result of what reaction are esters formed?:
1. Esterification
2. Polymerization
3. Polycondensation
4. Hydrolysis
A
Homework: §21 pages 190-192 No. 1,2,3.page 195 (diagram 5 in notebook)
a class of compounds based on mineral (inorganic) or organic carboxylic acids, in which the hydrogen atom in the HO group is replaced by an organic group R . The adjective “complex” in the name of esters helps to distinguish them from compounds called ethers.If the starting acid is polybasic, then the formation of either full esters all HO groups are substituted, or acid esters partial substitution is possible. For monobasic acids, only full 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 group is indicated R , attached to the acid, then the name of the acid with the suffix “at” (as in the names of inorganic salts: carbon at sodium, nitrate at chromium). Examples in Fig.2
If you use trivial ( cm. TRIVIAL NAMES OF SUBSTANCES) is the name of the starting acid, then the name of the compound includes the word “ester”, for example, C 3 H 7 COOC 5 H 11 amyl ester of butyric acid.
Classification and composition of esters. Among the studied and widely used esters, the majority 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 (variety of compounds one of distinctive features organic chemistry).When the number of C atoms in the original carboxylic acid and alcohol does not exceed 68, the corresponding esters are colorless oily liquids, most often with a fruity odor. They form a group of fruit esters. If an aromatic alcohol (containing an aromatic nucleus) is involved in the formation of an ester, then such compounds, as a rule, have a floral rather than a fruity odor. All compounds in this group are practically insoluble in water, but easily soluble in most organic solvents. These compounds are interesting because of their wide range of pleasant aromas (Table 1); some of them were first isolated from plants and later synthesized artificially.
| Table 1. SOME ESTERS, having a fruity or floral aroma (fragments of the original alcohols in the compound formula and in the name are highlighted in bold) | ||
| Ester Formula | Name | Aroma |
| CH 3 COO C 4 H 9 | Butyl acetate | pear |
| C 3 H 7 COO CH 3 | Methyl Butyric acid ester | apple |
| C 3 H 7 COO C 2 H 5 | Ethyl 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 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 |
The third group is fats. Unlike the previous two groups based on monohydric alcohols
ROH , all fats are esters of glycerol alcohol HOCH 2 CH(OH)CH 2 OH. Carboxylic acids that make up fats, as a rule, have a hydrocarbon chain with 919 carbon atoms. Animal fats (cow butter, lamb, lard) plastic, fusible substances. Vegetable fats (olive, cottonseed, sunflower oil) viscous liquids. Animal fats mainly consist of a mixture of glycerides of stearic and palmitic acid (Fig. 3A, B). Vegetable oils contain glycerides of acids with a slightly shorter carbon chain length: lauric C 11 H 23 COOH and myristic C 13 H 27 COOH. (like stearic and palmitic these 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, flaxseed oil contains unsaturated linoleic acid glyceride (Figure 3B). When applied in a thin layer to the surface, such oil dries under the influence of atmospheric oxygen during polymerization along double bonds, and an elastic film is formed that is insoluble in water and organic solvents. Natural drying oil is made from linseed oil.
Rice. 3. GLYCERIDES OF STEARIC AND PALMITIC ACID (A AND B) components of animal fat. Linoleic acid glyceride (B) component of linseed oil.
Esters of mineral acids (alkyl sulfates, alkyl borates containing fragments of lower alcohols C 18) oily liquids, esters of higher alcohols (starting from C 9) solid compounds.
Chemical properties of esters. Most characteristic of esters of carboxylic acids is the hydrolytic (under the influence of water) cleavage of the ester bond; in a neutral environment it proceeds slowly and noticeably accelerates in the presence of acids or bases, because H + and HO ions catalyze this process (Fig. 4A), with hydroxyl ions acting more efficiently. Hydrolysis in the presence of alkalis is called saponification. If you take an amount of alkali sufficient to neutralize all the acid formed, then complete saponification of the ester occurs. This process is carried out on an industrial scale, and glycerin and higher carboxylic acids (C 1519) are obtained 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 attaches to double bonds and compounds similar to animal fats are formed (Fig. 4B). Using this method, solid fats are produced industrially based on sunflower, soybean or corn oil. Margarine is made from hydrogenation products of vegetable oils mixed with natural animal fats and various food additives.The main method of synthesis is the interaction of a carboxylic acid and an alcohol, catalyzed by the 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 proceed in the desired direction (ester synthesis), water is distilled (distilled) from the reaction mixture. Through special studies using labeled atoms, it was possible to establish that during the synthesis process, the O atom, which is part of the resulting water, is detached from the acid (marked with a red dotted frame), and not from the alcohol (the unrealized option is highlighted with a blue dotted frame).
Using the same scheme, esters of inorganic acids, for example, nitroglycerin, are obtained (Fig. 5B). Instead of acids, acid chlorides can be used; the method is applicable for both carboxylic (Fig. 5C) and inorganic acids (Fig. 5D).
Interaction of carboxylic acid salts with alkyl halides
RCl also leads to esters (Fig. 5D), the reaction is convenient in that it is irreversible; the released inorganic salt is immediately removed from the organic reaction medium in the form of a precipitate.Use of esters. Ethyl formate HCOOC 2 H 5 and ethyl acetate H 3 COOC 2 H 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 Food Industry when creating fruit essences, and esters based on aromatic alcohols in the perfume industry.
Polishes, lubricants, impregnating compositions for paper (waxed paper) and leather are made from waxes; they are also included in cosmetic creams and medicinal ointments.
Fats, together with carbohydrates and proteins, make up a set of foods necessary for nutrition; they are part of all plant and animal cells; in addition, when they accumulate in the body, they play the role of an energy reserve. Due to its low thermal conductivity, the fat layer protects animals (especially sea whales or walruses) well from hypothermia.
Animal and vegetable fats are raw materials for the production of higher carboxylic acids, detergents and glycerol (Fig. 4), used in the cosmetics industry and as a component of various lubricants.
Nitroglycerin (Fig. 4) known medicinal product And explosive, the basis of dynamite.
Drying oils are made from vegetable oils (Fig. 3), which form the basis of oil paints.
Esters of sulfuric acid (Fig. 2) are used in organic synthesis as alkylating (introducing an alkyl group into a compound) reagents, and esters of phosphoric acid (Fig. 5) are used as insecticides, as well as additives to lubricating oils.
Mikhail Levitsky
LITERATURE Kartsova A.A. Conquest of matter. Organic chemistry . Khimizdat Publishing House, 1999Pustovalova L.M. Organic chemistry. Phoenix, 2003
Derivatives of carboxylic or inorganic acids in which the hydrogen atom in the hydroxyl group is replaced by a radical are called esters. Typically, the general formula of esters is denoted as two hydrocarbon radicals attached to a carboxyl group - C n H 2n+1 -COO-C n H 2n+1 or R-COOR’.
Nomenclature
The names of esters are composed of the names of the radical and the acid with the suffix “-at”. For example:
- CH3COOH- methyl formate;
- HCOOCH 3- ethyl formate;
- CH 3 COOC 4 H 9- butyl acetate;
- CH 3 -CH 2 -COO-C 4 H 9- butylpropionate;
- CH 3 -SO 4 -CH 3- dimethyl sulfate.
Trivial names for the acid contained in the compound are also used:
- C 3 H 7 SOOS 5 H 11- amyl ester of butyric acid;
- HCOOCH 3- methyl ester of formic acid;
- CH 3 -COO-CH 2 -CH(CH 3) 2- isobutyl ester of acetic acid.
Rice. 1. Structural formulas of esters with names.
Classification
Depending on their origin, esters are divided into two groups:
- carboxylic acid esters- contain hydrocarbon radicals;
- esters of inorganic acids- 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. They depend on the complexity of the structure physical properties. Esters of lower carboxylic acids are volatile liquids with a pleasant aroma, higher ones - solids. These are poorly soluble compounds that float on the surface of the water.
The types of carboxylic acid esters are given in the table.
|
View |
Description |
Examples |
|
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 glycerol and carboxylic (fatty) acid residues |
Olive oil is 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, which are found in fruits, flowers, and berries. Also included in beeswax.
Rice. 3. Essential oils.
Receipt
Esters are prepared in several ways:
- esterification reaction of carboxylic acids with alcohols:
CH 3 COOH + C 2 H 5 OH → CH 3 COOC 2 H 5 + H 2 O;
- 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;
- 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;
- 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 the -COOH functional group. The main properties of esters are described in the table.
Esters are used in cosmetology, medicine, and the food industry as flavoring agents, solvents, and fillers.
What have we learned?
From the topic of the 10th grade chemistry lesson we 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. These are poorly soluble substances in water with low density and a pleasant aroma. Esters react with alkalis, water, halogens, alcohols and ammonia.
Test on the topic
Evaluation of the report
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Among the functional derivatives of carboxylic acidsA special place is occupied by esters - compoundsions representing carboxylic acids with a water atomkind in the carboxyl group is replaced hydrocarbon radical. General formula of esters
Esters are often named after their acid residues andalcohols of which they are composed. So, discussed above esters may be called: ethanoethyl ether, crotonovomethyl ether.
Esters are characterized by three types of isomerism:
1. Isomerism of the carbon chain, begins at the acidic position the residue from butanoic acid, the alcohol residue from propyl alcohol, for example:
2. Isomerism of the position of the ester group /> -SO-O-. This type of isomerism begins with esters, inmolecules containing at least 4 carbon atoms, example: />
3. Interclass isomerism, for example:
For esters containing unsaturated acid orunsaturated alcohol, two more types of isomerism are possible: isomerismmultiple bond positions; cis-trans isomerism.
Physical properties esters. Esters /> lower carboxylic acids and alcohols are volatile, sparingly soluble or practically insoluble in waterliquids. Many of them have a pleasant smell. For example, butyl butyrate smells like pineapple, isoamyl acetate smells like pear, etc.
Esters tend to have a lower temperatureboiling point than their corresponding acids. For example, stearic acid boils at 232 °C (P = 15 mm Hg), and metilstearate - at 215 °C (P = 15 mm Hg). This is explained bythat there are no hydrogen bonds between the molecules of esters communications.
Esters of higher fatty acids and alcohols - waxesfigurative substances, odorless, insoluble in water, althoughhighly soluble in organic solvents. For example, bee the wax is mainly myricyl palmitate(C 15 H 31 COOC 31 H 63 ).