Oxygen-containing organic compounds general characteristics
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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 in the molecule. For example:
Hydration of alkenes
Hydration of alkenes- addition of water at π - bonds of an 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
The oxidation of alcohols in mild conditions leads to the formation of aldehydes or ketones. Obviously, alcohols can be obtained by hydrogenation (hydrogen reduction, hydrogen addition) of aldehydes and ketones:
Alkene oxidation
Glycols, as already noted, can be obtained by oxidizing alkenes with an aqueous solution of potassium permanganate. For example, ethylene glycol (ethanediol-1,2) is formed during the oxidation of ethylene (ethene):
Specific methods for obtaining alcohols
1. Some alcohols are obtained in ways characteristic only of them. So, methanol in industry is obtained reaction of interaction of hydrogen with carbon monoxide(II) (carbon monoxide) at high blood pressure And high temperature on the surface of the catalyst (zinc oxide):
The mixture required for this reaction carbon monoxide and hydrogen, also called "synthesis gas", is obtained by passing water vapor over hot coal:
2. Glucose fermentation. This method of obtaining ethyl (wine) alcohol has been known to man since ancient times:
The main ways to get oxygenated 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 the fermentation of sugary substances.
Methods for obtaining aldehydes and ketones
1. Aldehydes and ketones can be obtained oxidation or alcohol dehydrogenation. During the 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 \u003d 3CH 3 -CHO + K 2 SO 4 + Cr 2 (SO 4) 3 + 7H 2 O
2.Kucherov's reaction. From acetylene, as a result of the reaction, acetaldehyde is obtained, from acetylene homologs - ketones:
3. When heated calcium or barium salts of carboxylic acids a ketone and a metal carbonate are formed:
Methods for obtaining 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 \u003d 3CH 3 -COOH + 2K 2 SO 4 + 2Cr 2 (SO 4) 3 + 11H 2 O
5CH 3 -CHO + 2KMnO 4 + 3H 2 SO 4 \u003d 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 \u003d 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, and not formic acid:
HCHO + 4OH \u003d (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 \u003d 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 \u003d 5C 6 H 5 COOH + 5CO 2 + 12MnSO 4 + 6K 2 SO 4 + 28H 2 O,
C 6 H 5 -CH 3 + 2KMnO 4 \u003d C 6 H 5 COOK + 2MnO 2 + KOH + H 2 O
3. Hydrolysis of various carboxylic derivatives acids also produces acids. So, during the hydrolysis of an ester, an alcohol and a carboxylic acid are formed. Acid-catalyzed esterification and hydrolysis reactions are reversible:
4. Ester hydrolysis under the action of an aqueous solution of alkali proceeds irreversibly, in this case, not an acid is formed from the ester, but its salt:
METHODOLOGICAL DEVELOPMENT
For a lecture
in the discipline "Chemistry"
for cadets of the 2nd course in the specialty 280705.65 -
« Fire safety»
SECTION IV
PHYSICO-CHEMICAL PROPERTIES OF ORGANIC SUBSTANCES
TOPIC 4.16
SESSION № 4.16.1-4.16.2
OXYGEN-CONTAINING ORGANIC COMPOUNDS
Discussed at the PMC meeting
protocol No. ____ dated "___" _______ 2015
Vladivostok
I. Goals and objectives
Training: give a definition of oxygen-containing organic compounds, draw the attention of cadets to their diversity and prevalence. Show the dependence of the physicochemical and fire hazardous properties of oxygen-containing organic compounds on their chemical structure.
Educational: to educate students in the responsibility for preparing for practical activities.
II. Calculation of study time
III. Literature
1. Glinka N.L. General chemistry. - Tutorial for universities / Ed. A.I. Ermakov. - ed.30, corrected. - M.: Integral-Press, 2010. - 728 p.
2. Svidzinskaya G.B. Laboratory works By organic chemistry: Tutorial. - St. Petersburg: SPbI GPS EMERCOM of Russia, 2003. - 48p.
IV. Educational and material support
1. Teaching aids: TV, overhead projector, VCR, DVD player, computer equipment, interactive whiteboard.
2. Periodic system of elements D.I. Mendeleev, demonstration posters, diagrams.
V. Text of the lecture
INTRODUCTION (5 min.)
The teacher checks the presence of students (cadets), announces the topic, learning goals and lesson questions.
MAIN PART (170 min)
Question No. 1. Classification of oxygen-containing organic compounds (20 min).
All these substances (like most organic matter) in accordance with Technical regulation on fire safety requirements. Federal Law No. 123-FZ refer to substances that can form an explosive mixture (a mixture of air and an oxidizer with combustible gases or vapors of flammable liquids), which, at a certain concentration, is capable of exploding (Article 2. P.4). This is what determines the fire and explosion hazard of substances and materials, i.e. their ability to form a combustible environment, characterized by their physico-chemical properties and (or) behavior in fire conditions (P.29) .
Properties of this type compounds are due to the presence of functional groups.
| Functional group | Name of the functional group | Connection class | Connection examples |
| DREAM | hydroxyl | Alcohols | CH 3 - CH 2 - OH |
| C=O | carbonyl | Aldehydes | CH 3 - C \u003d O ç H |
| Ketones | CH 3 - C - CH 3 ll O | ||
| - C \u003d O ç OH | carboxyl | carboxylic acids | CH 3 - C \u003d O ç OH |
| C - O - C | ethers | CH 3 - O - CH 2 - CH 3 | |
| C - C \u003d O ç O - C | esters | C 2 H 5 - C \u003d O ç O - CH 3 | |
| C - O - O - C | peroxide compounds | CH 3 - O - O - CH 3 |
It is easy to see that all classes of oxygen-containing compounds can be considered as hydrocarbon oxidation products. In alcohols, only one of the four carbon atom valences is used for connection with an oxygen atom, and therefore alcohols are the least oxidized compounds. More oxidized compounds are aldehydes and ketones: their carbon atom has two bonds with oxygen. The most oxidized carboxylic acids, because. in their molecules, the carbon atom used up its three valences per bond to the oxygen atom.
On carboxylic acids, the oxidation process is completed, leading to the formation of organic substances resistant to the action of oxidizing agents:
alcohol D aldehyde D carboxylic acid ® CO 2
Question number 2. Alcohols (40 min)
Alcohols - organic compounds whose molecules contain one or more hydroxyl groups (-OH) connected to hydrocarbon radicals.
Alcohol classification
I. Depending on the number of hydroxyl groups:
II. According to the saturation of the hydrocarbon radical:
III. By the nature of the hydrocarbon radical associated with the OH group:
Monohydric alcohols
The general formula of saturated monohydric alcohols: C n H 2 n +1 OH.
Nomenclature
Two possible names for the class of alcohols are used: "alcohols" (from the Latin "spiritus" - spirit) and "alcohols" (Arabic).
According to the international nomenclature, the name of alcohols is formed from the name of the corresponding hydrocarbon with the addition of the suffix ol:
CH 3 OH methanol
C 2 H 5 OH ethanol, etc.
The main chain of carbon atoms is numbered from the end closest to which the hydroxyl group is located:
5 CH 3 - 4 CH - 3 CH 2 - 2 CH 2 - 1 CH 2 -OH
4-methylpentanol-2
Isomerism of alcohols
The structure of alcohols depends on the structure of the radical and the position of the functional group, i.e. in the homologous series of alcohols, there can be two types of isomerism: isomerism of the carbon skeleton and isomerism of the position of the functional group.
In addition, the third type of alcohol isomerism is interclass isomerism with ethers.
So, for example, for pentanols (general formula C 5 H 11 OH), all 3 indicated types of isomerism are characteristic:
1. Isomerism of the skeleton
pentanol-1
CH 3 - CH - CH 2 - CH 2 -OH
3-methylbutanol-1
CH 3 - CH 2 - CH - CH 2 -OH
2-methylbutanol-1
CH 3 - CH - CH 2 - OH
2,2-dimethylpropanol-1
The above isomers of pentanol, or amyl alcohol, are trivially called "fusel oils".
2. Isomerism of the position of the hydroxyl group
CH 3 - CH 2 - CH 2 - CH 2 - CH 2 - OH
pentanol-1
CH 3 - CH - CH 2 - CH 2 -CH 2
pentanol-2
CH 3 - CH 2 - CH - CH 2 -CH 2
pentanol-3
3. Interclass isomerism
C 2 H 5 - O - C 3 H 7
ethyl propyl ether
The number of isomers in the series of alcohols is growing rapidly: an alcohol with 5 carbon atoms has 8 isomers, with 6 carbon atoms - 17, with 7 carbon atoms - 39, and with 10 carbon atoms - 507.
Methods for obtaining alcohols
1. Obtaining methanol from synthesis gas
400 0 C, ZnO, Cr 2 O 3
CO + 2H 2 ¾¾¾¾¾® CH 3 OH
2. Hydrolysis of halocarbons (in aqueous solutions of alkalis):
CH 3 - CH - CH 3 + KOH water ® CH 3 - CH - CH 3 + KCl
2-chloropropane propanol-2
3. Hydration of alkenes. The reaction proceeds according to the rule of V.V. Markovnikov. The catalyst is dilute H 2 SO 4 .
CH 2 \u003d CH 2 + HOH ® CH 3 - CH 2 - OH
ethylene ethanol
CH 2 \u003d CH - CH 3 + HOH ® CH 2 - CH - CH 3
propene propanol-2
4. Recovery of carbonyl compounds (aldehydes and ketones).
When aldehydes are reduced, primary alcohols are obtained:
CH 3 - CH 2 - C \u003d O + H 2 ® CH 3 - CH 2 - CH 2 - OH
propanol-1 propanal
When ketones are reduced, secondary alcohols are obtained:
CH 3 - C - CH 3 + H 2 ® CH 3 - CH - CH 3
propanone (acetone) propanol-2
5. Obtaining ethanol by fermentation of sugary substances:
enzymes enzymes
C 12 H 22 O 11 + H 2 O ¾¾¾® 2C 6 H 12 O 6 ¾¾¾® 4C 2 H 5 OH + 4CO 2
sucrose glucose ethanol
enzymes enzymes
(C 6 H 10 O 5) n + H 2 O ¾¾¾® nC 6 H 12 O 6 ¾¾¾® C 2 H 5 OH + CO 2
cellulose glucose ethanol
Alcohol obtained by fermentation of cellulose is called hydrolysis alcohol and is used only for technical purposes, because contains a large amount of harmful impurities: methanol, acetaldehyde and fusel oils.
6. Hydrolysis of esters
H + or OH -
CH 3 - C - O - CH 2 - CH 2 -CH 3 + H 2 O ¾¾® CH 3 - C - OH + OH - CH 2 - CH 2 -CH 3
acetic acid propyl ester acetic propanol-1
(propylethanoate) acid
7. Recovery of esters
CH 3 - C - O - CH 2 - CH 2 -CH 3 ¾¾® CH 3 - CH 2 - OH + OH - CH 2 - CH 2 -CH 3
propyl ester of acetic acid ethanol propanol-1
(propyl ethanoate)
Physical Properties alcohols
Limit alcohols containing from 1 to 12 carbon atoms are liquids; from 13 to 20 carbon atoms - oily (ointment-like) substances; more than 21 carbon atoms are solids.
Lower alcohols (methanol, ethanol and propanol) have a specific alcoholic smell, butanol and pentanol have a sweet suffocating smell. Alcohols containing more than 6 carbon atoms are odorless.
Methyl, ethyl and propyl alcohols dissolve well in water. As the molecular weight increases, the solubility of alcohols in water decreases.
A significantly higher boiling point of alcohols compared to hydrocarbons containing the same number of carbon atoms (for example, t bale (CH 4) \u003d - 161 0 C, and t bale (CH 3 OH) \u003d 64.7 0 C) is associated with the ability alcohols form hydrogen bonds, and hence the ability of molecules to associate.
××× Н – О ×××Н – О ×××Н – О ×××R – alcohol radical
When alcohol is dissolved in water, hydrogen bonds also occur between the molecules of alcohol and water. As a result of this process, energy is released and volume decreases. So, when mixing 52 ml of ethanol and 48 ml of water, the total volume of the resulting solution will not be 100 ml, but only 96.3 ml.
fire hazard represent both pure alcohols (especially lower ones), the vapors of which can form explosive mixtures, and aqueous solutions of alcohols. Aqueous solutions of ethanol in water with an alcohol concentration of more than 25% or more are flammable liquids.
Chemical properties alcohols
The chemical properties of alcohols are determined by the reactivity of the hydroxyl group and the structure of the radical associated with the hydroxyl group.
1. Reactions of hydroxyl hydrogen R - O - H
Due to the electronegativity of the oxygen atom in alcohol molecules, there is a partial distribution of charges:
Hydrogen has a certain mobility and is able to enter into substitution reactions.
1.1. Interaction with alkali metals - the formation of alcoholates:
2CH 3 - CH - CH 3 + 2Na ® 2CH 3 - CH - CH 3 + H 2
propanol-2 sodium isopropoxide
(sodium salt of propanol-2)
Salts of alcohols (alcoholates) are solids. When they are formed, alcohols act as very weak acids.
Alcoholates are easily hydrolyzed:
C 2 H 5 ONa + HOH ® C 2 H 5 OH + NaOH
sodium ethoxide
1.2. Interaction with carboxylic acids (esterification reaction) - formation of esters:
H 2 SO 4 conc.
CH 3 - CH - OH + HO - C - CH 3 ¾¾® CH 3 - CH - O - C - CH 3 + H 2 O
CH 3 O CH 3 O
acetic acid isopropyl acetate
(isopropyl ether
acetic acid)
1.3. Interaction with inorganic acids:
CH 3 - CH - OH + HO -SO 2 OH ® CH 3 - CH - O - SO 2 OH + H 2 O
sulfuric acid isopropylsulfuric acid
(isopropyl ether
sulfuric acid)
1.4. Intermolecular dehydration - the formation of ethers:
H 2 SO 4 conc., t<140 0 C
CH 3 - CH - OH + BUT - CH - CH 3 ¾¾¾® CH 3 - CH - O - CH - CH 3 + H 2 O
CH 3 CH 3 CH 3 CH 3
diisopropyl ether
2. Reactions of the hydroxyl group R - OH
2.1. Interaction with hydrogen halides:
H 2 SO 4 conc.
CH 3 - CH - CH 3 + HCl ¾¾® CH 3 - CH - CH 3 + H 2 O
2-chloropropane
2.2. Interaction with halogen derivatives of phosphorus:
CH 3 - CH - CH 3 + PCl 5 ¾® CH 3 - CH - CH 3 + POCl 3 + HCl
2-chloropropane
2.3. Intramolecular dehydration - obtaining alkenes:
H 2 SO 4 conc., t> 140 0 C
CH 3 - CH - CH 2 ¾¾¾® CH 3 - CH \u003d CH 2 + H 2 O
½ ½ propene
During the dehydration of an asymmetric molecule, the elimination of hydrogen proceeds predominantly from least hydrogenated carbon atom ( rule A.M. Zaitsev).
3. Oxidation reactions.
3.1. Complete oxidation - combustion:
C 3 H 7 OH + 4.5O 2 ® 3CO 2 + 4H 2 O
Partial (incomplete) oxidation.
Oxidizers can be potassium permanganate KMnO 4 , a mixture of potassium dichromate with sulfuric acid K 2 Cr 2 O 7 + H 2 SO 4 , copper or platinum catalysts.
When primary alcohols are oxidized, aldehydes are formed:
CH 3 - CH 2 - CH 2 - OH + [O] ® [CH 3 - C - OH] ® CH 3 - CH 2 - C \u003d O + H 2 O
propanol-1 propanal
The oxidation reaction of methanol when this alcohol enters the body is an example of the so-called “lethal synthesis”. Methyl alcohol itself is a relatively harmless substance, but in the body, as a result of oxidation, it turns into extremely toxic substances: methanal (formaldehyde) and formic acid. As a result, ingestion of 10 g of methanol leads to loss of vision, and 30 g leads to death.
The reaction of alcohol with copper (II) oxide can be used as a qualitative reaction for alcohols, because As a result of the reaction, the color of the solution changes.
CH 3 - CH 2 - CH 2 - OH + CuO ® CH 3 - CH 2 - C \u003d O + Cu¯ + H 2 O
propanol-1 propanal
As a result of partial oxidation of secondary alcohols, ketones are formed:
CH 3 - CH - CH 3 + [O] ® CH 3 - C - CH 3 + H 2 O
propanol-2 propanone
Tertiary alcohols do not oxidize under such conditions, and when oxidized under more severe conditions, the molecule is split, and a mixture of carboxylic acids is formed.
The use of alcohols
Alcohols are used as excellent organic solvents.
Methanol is obtained from large volume and used for the preparation of dyes, non-freezing mixtures, as a source for the production of various polymeric materials (obtaining formaldehyde). It should be remembered that methanol is highly toxic.
Ethyl alcohol is the first organic substance that was isolated in pure form in 900 in Egypt.
Currently, ethanol is a large-tonnage product of the chemical industry. It is used to produce synthetic rubber, organic dyes, and the manufacture of pharmaceuticals. In addition, ethyl alcohol is used as an environmentally friendly fuel. Ethanol is used in the manufacture of alcoholic beverages.
Ethanol is a drug that stimulates the body; its prolonged and excessive use leads to alcoholism.
Butyl and amyl alcohols (pentanols) are used in industry as solvents, as well as for the synthesis of esters. All of them are highly toxic.
Polyhydric alcohols
Polyhydric alcohols contain two or more hydroxyl groups at different carbon atoms.
CH 2 - CH 2 CH 2 - CH - CH 2 CH 2 - CH - CH - CH - CH 2
ç ç ç ç ç ç ç ç ç ç
OH OH OH OH OH OH OH OH
ethanediol-1,2 propanetriol-1,2,3 pentanpentol-1,2,3,4,5
(ethylene glycol) (glycerin) (xylitol)
Physical properties of polyhydric alcohols
Ethylene glycol (“glycols” is the common name for dihydric alcohols) is a colorless viscous liquid, highly soluble in water and in many organic solvents.
Glycerin - the most important trihydric alcohol - is a colorless, thick liquid that is highly soluble in water. Glycerin has been known since 1779 after its discovery by the Swedish chemist K Scheele.
Polyhydric alcohols containing 4 or more carbon atoms are solids.
The more hydroxyl groups in a molecule, the better it dissolves in water and the higher its boiling point. In addition, a sweet taste appears, and the more hydroxyl groups in a substance, the sweeter it is.
Substances such as xylitol and sorbitol are used as sugar substitutes:
CH 2 - CH - CH - CH - CH 2 CH 2 - CH - CH - CH - CH - CH 2
ç ç ç ç ç ç ç ç ç ç ç
OH OH OH OH OH OH OH OH OH
xylitol sorbitol
The six-hydric alcohol “inositol” also tastes sweet. Inositol is found in legumes, kidneys, liver, muscles. Inositol has a common formula with glucose:
NO -HC CH - OH
NO -NS CH - OH C 6 H 12 O 6.
cyclohexanehexol
Methods for obtaining polyhydric alcohols
1. Incomplete oxidation of alkenes
Partial oxidation with KMnO 4 potassium permanganate solution.
1.1. Ethylene oxidation
CH 2 \u003d CH 2 + [O] + HOH ® CH 2 - CH 2
ethylene ½ ½
ethanediol-1,2
(ethylene glycol)
1.2. propene oxidation
CH 2 \u003d CH - CH 3 + [O] + HOH ® CH 2 - CH - CH 2
propene ½ ½ ½
propanetriol-1,2,3,
(glycerol)
2. Saponification of vegetable and animal fats
Glycerin is obtained as a by-product in the soap industry during the processing of fats.
CH - O - OS - C 17 H 35 + 3NaOH® CH - OH + 3 C 17 H 35 COOHa
CH 2 - O - OS - C 17 H 35 CH 2 - OH
triglyceride glycerin sodium stearate
stearic acid(soap)
Chemical properties of polyhydric alcohols
The chemical properties of polyhydric alcohols are in many respects similar to those of monohydric alcohols.
1. Interaction with active metals
CH 2 - OH CH 2 - ONa
ç + 2Na®ç + H 2
CH 2 - OH CH 2 - ONa
ethylene glycol sodium salt of ethylene glycol
2. Formation of esters with mineral acids
CH 2 - OH + HO - NO 2 CH 2 - O - NO 2
CH - OH + HO - NO 2 ® CH - O - NO 2 + 3H 2 O
CH 2 - OH + HO - NO 2 CH 2 - O - NO 2
glycerin nitric trinitroglycerin
Trinitroglycerin is one of the strongest explosives; it explodes from impact, concussion, fuse, as a result of self-decomposition. For practical use, in order to increase safety when working with trinitroglycerin, it is transferred to dynamite(porous materials impregnated with trinitroglycerin - diatomaceous earth, wood flour, etc.).
3. Interaction with copper (II) hydroxide - a qualitative reaction to glycerol
CH 2 - OH CH 2 - O m H / O - CH 2
2 CH - OH + Cu (OH) 2 ® CH - O / HO - C H
CH 2 - OH CH 2 - OH HO - CH 2
copper diglycerate
(bright blue coloration)
4. Dehydration of glycerol with the formation of acrolein
C 3 H 8 O 3 ® CH 2 \u003d CH - C \u003d O + 2H 2 O
glycerin ç
acrolein (suffocating odor when calcined fats)
5. Oxidation reactions
Ethylene glycol and glycerin, when interacting with strong oxidizing agents (potassium permanganate KMnO 4, chromium oxide (VI) CrO 3), are prone to spontaneous combustion.
5C 3 H 8 O 3 + 14KMnO 4 + 21H 2 SO 4 ® 15CO 2 + 14MnSO 4 + 7K 2 SO 4 + 41H 2 O
The use of polyhydric alcohols
Ethylene glycol and glycerin are used to make antifreeze liquids - antifreeze. So, an aqueous 50% solution of glycerin freezes only at -34 0 C, and a solution composed of 6 parts of ethylene glycol and 1 part of water freezes at a temperature of -49 0 C.
Propylene glycol CH 3 - CH (OH) - CH 2 - CH 2 OH is used to obtain water-free foams (such foams are more stable), and is also integral part sun creams.
Ethylene glycol is used to produce lavsan fiber, and glycerin is used to produce glyptal resins.
In large quantities, glycerin is used in the perfumery, medical and food industries.
Phenols
Phenols- derivatives of aromatic hydrocarbons, in which the hydroxyl group OH- is attached directly to the carbon atom of the benzene ring.
The hydroxyl group is linked to an aromatic radical (phenyl). p-electrons of the benzene ring involve the lone electrons of the oxygen atom of the OH group into their system, as a result of which the hydrogen of the hydroxyl group becomes more mobile than in aliphatic alcohols.
Physical Properties
The simplest representative - phenol - is a colorless crystalline substance (melting point 42 0 C) with a characteristic odor. The trivial name of phenol is carbolic acid.
Monatomic phenols are sparingly soluble in water; with an increase in the number of hydroxyl groups, the solubility in water increases. Phenol at a temperature of 60 0 C dissolves in water without limit.
All phenols are highly toxic. Phenol causes burns on contact with skin.
Methods for obtaining phenol
1. Obtaining from coal tar
This is the most important technical way obtaining phenol. It consists in the fact that the fractions of coal tar obtained by coking hard coal, are treated with alkalis, and then for neutralization with acids.
2. Obtaining from halogen derivatives of benzene
C 6 H 5 Cl + NaOH conc. aq. solution ® C 6 H 5 OH + NaCl
chlorobenzenephenol
Chemical properties of phenols
1. Reactions involving hydroxyl hydrogen C 6 H 5 - O - H
1.1. Interaction with active metals
2C 6 H 5 OH + 2Na® 2C 6 H 5 ONa + H 2
phenol phenolate
sodium (salt)
1.2. Interaction with alkalis
Phenol is a stronger acid than monohydric alcohols and therefore, unlike the latter, phenol reacts with alkali solutions:
C 6 H 5 OH + NaOH ® C 6 H 5 ONa + H 2 O
phenol phenolate
Phenol is a weaker acid than carbonic acid H 2 CO 3 (about 300 times) or hydrosulfide acid H 2 S, so phenolates are decomposed by weak acids:
C 6 H 5 ONa + H 2 O + CO 2 ® C 6 H 5 OH + NaHCO 3
1.3. Formation of ethers and esters
H 2 SO 4 conc.
C 6 H 5 OH + HO - C 2 H 5 ¾¾¾®C 6 H 5 O - C 2 H 5 + H 2 O
2. Reactions involving the benzene ring
Phenol without heating And without catalysts vigorously enters into reactions of substitution of hydrogen atoms, while trisubstituted derivatives are almost always formed
2.1. Interaction with bromine water - a qualitative reaction to phenol
2.2. Interaction with nitric acid
Picric acid is a yellow crystalline substance. When heated carefully, it melts at a temperature of 122 0 C, and when heated rapidly, it explodes. Salts of picric acid (picrates) explode on impact and friction.
3. Polycondensation reaction with formaldehyde
The interaction of phenol with formaldehyde with the formation of resinous products was studied as early as 1872 by Bayer. wide practical use this reaction took place much later - in the 20-30s of the 20th century, when in many countries so-called bakelites began to be prepared from phenol and formaldehyde.
4. Staining reaction with ferric chloride
All phenols, when interacting with ferric chloride FeCl 3, form colored compounds; monatomic phenols give violet or of blue color. This reaction can serve as a qualitative reaction for phenol.
The use of phenols
Phenols kill many microorganisms, which is used in medicine, using phenols and their derivatives as disinfectants and antiseptics. Phenol (carbolic acid) was the first antiseptic introduced into surgery by Lister in 1867. The antiseptic properties of phenols are based on their ability to fold proteins.
"Phenolic coefficient" - a number showing how many times the antiseptic effect of a given substance is greater (or less) than the action of phenol, taken as a unit. Benzene homologues - cresols - have a stronger bactericidal effect than phenol itself.
Phenol is used to produce phenol-formaldehyde resins, dyes, picric acid, and drugs such as salicylates, aspirin and others are obtained from it.
One of the most well-known derivatives of dihydric phenols is adrenaline. Adrenaline is a hormone produced by the adrenal glands and has the ability to constrict blood vessels. It is often used as a hemostatic agent.
Question #3
Ethers called organic compounds in which two hydrocarbon radicals are linked by an oxygen atom. Ethers can be considered as products of substitution of a hydrogen atom in the hydroxyl of an alcohol by a radical:
R – O – H ® R – O – R /
General formula of ethers C n H 2 n +2 O.
The radicals in an ether molecule can be the same, for example, in CH 3 - O - CH 3 ether, or different, for example, in CH 3 - O - C 3 H 7 ether. Ether having different radicals is called mixed.
Ether nomenclature
Esters are usually named according to the radicals that are part of their composition (rational nomenclature).
According to the international nomenclature, ethers are designated as derivatives of hydrocarbons in which the hydrogen atom is substituted alkoxy group(RO -), for example, a methoxy group CH 3 O -, an ethoxy group C 2 H 5 O -, etc.
Ether isomerism
1. The isomerism of ethers is determined by the isomerism of the radicals associated with oxygen.
CH 3 - O - CH 2 - CH 2 - CH 3 methyl propyl ether
C 2 H 5 - O - C 2 H 5 diethyl ether
CH 3 - O - CH - CH 3 methyl isopropyl ether
2. Interclass isomers of ethers are monohydric alcohols.
CH 3 - CH 2 - CH 2 - CH 2 - OH
butanol-1
Physical properties of ethers
Dimethyl and methyl ethyl ethers are gaseous substances under normal conditions.
Starting with diethyl ether, substances of this class are colorless, easily mobile liquids with a characteristic odor.
Ethers are lighter than water and almost insoluble in it. Due to the absence of hydrogen bonds between molecules, ethers boil at a lower temperature than the corresponding alcohols.
In organic solvents, ethers dissolve easily and dissolve many substances themselves.
The most common compound of this class is diethyl ether C 2 H 5 - O - C 2 H 5, first obtained in the 16th century by Kordus. Very often it is called "sulfuric ether". This name, received in the 18th century, is associated with a method for obtaining ether: the interaction ethyl alcohol with sulfuric acid.
Diethyl ether is a colorless, very mobile liquid with a strong characteristic odor. This substance is extremely explosive and flammable. The boiling point of diethyl ether is 34.6 0 C, the freezing point is 117 0 C. The ether is poorly soluble in water (1 volume of ether dissolves in 10 volumes of water). Ether is lighter than water (density 714 g/l). Diethyl ether is prone to electrification: discharges of static electricity can occur at the time of transfusion of ether and cause it to ignite. Vapors of diethyl ether are 2.5 times heavier than air and form explosive mixtures with it. Concentration limits of flame propagation (CPR) 1.7 - 49%.
Ether vapor can spread over considerable distances, while maintaining the ability to burn. Basic precautions when working with ether - this is the distance from open flames and very hot appliances and surfaces, including electric stoves.
The flash point of the ether is 45 0 С, the self-ignition temperature is 164 0 С. When burning, the ether burns with a bluish flame with the release of a large amount of heat. The flame of the ether is growing rapidly, because. upper layer it quickly heats up to boiling point. When burning, the ether heats up in depth. The growth rate of the heated layer is 45 cm/hour, and the rate of its burnout from the free surface is 30 cm/hour.
Upon contact with strong oxidizing agents (KMnO 4 , CrO 3 , halogens), diethyl ether ignites spontaneously. In addition, upon contact with atmospheric oxygen, diethyl ether can form peroxide compounds, which are extremely explosive substances.
Methods for obtaining ethers
1. Intermolecular dehydration of alcohols
H 2 SO 4 conc.
C 2 H 5 - OH + BUT - C 2 H 5 ¾¾¾® C 2 H 5 - O - C 2 H 5 + H 2 O
ethanol diethyl ether
Chemical properties of ethers
1. Ethers are rather inert substances, not prone to chemical reactions. However, under the action of concentrated acids, they decompose
C 2 H 5 - O - C 2 H 5 + HI conc. ® C 2 H 5 OH + C 2 H 5 I
diethyl ethanol iodoethane
2. Oxidation reactions
2.1. Complete oxidation - combustion:
C 4 H 10 O + 6 (O 2 + 3.76N 2) ® 4CO 2 + 5H 2 O + 6 × 3.76N 2
2.2. incomplete oxidation
When standing, especially in the light, the ether under the influence of oxygen is oxidized and decomposed with the formation of poisonous and explosive products– peroxide compounds and products of their further decomposition.
O - C - CH 3
C 2 H 5 - O - C 2 H 5 + 3 [O] ® ½
O - C - CH 3
hydroxyethyl hydroperoxide
The use of ethers
Diethyl ether is a good organic solvent. It is used to extract various useful substances from plants, for cleaning fabrics, in the manufacture of gunpowder and artificial fibers.
In medicine, ether is used for general anesthesia. For the first time for this purpose, during a surgical operation, ether was used by the American physician Jackson in 1842. The Russian surgeon N.I. ardently fought for the introduction of this method. Pirogov.
Question number 4. Carbonyl compounds (30 min)
Aldehydes and ketones- derivatives of hydrocarbons, the molecules of which contain one or more carbonyl groups С = O.
| Aldehydes | Ketones |
| Aldehydes contain a carbonyl group associated with one radical and one hydrogen atom - C \u003d O ½ H | Ketones contain a carbonyl group linked to two radicals - C - ll O |
| The general formula of carbonyl compounds C n H 2 n O | |
| Nomenclature of carbonyl compounds | |
| The name “aldehydes” comes from the general method for obtaining these compounds: alcohol dehydrogenation, i.e. removal of hydrogen. According to the IUPAC nomenclature, the name of aldehydes is derived from the names of the corresponding hydrocarbons, adding the suffix “al” to them. The chain numbering starts from the aldehyde group. | According to the IUPAC nomenclature, the name of ketones is derived from the names of the corresponding hydrocarbons, adding the suffix “on” to them. The numbering is carried out from the end of the chain closest to the carbonyl. The first representative of the ketone series contains 3 carbon atoms. |
| H - C \u003d O methanal ½ (formaldehyde, H formaldehyde) CH 3 - C \u003d O ethanal ½ (acetic aldehyde, H acetaldehyde) 5 4 3 2 1 CH 3 - CH - CH 2 - CH 2 - C \u003d O ½ ½ CH 3 H 4-methylpentanal | CH 3 - C - CH 3 propanone ll (acetone) O 6 5 4 3 2 1 CH 3 - CH 2 - CH - CH 2 - C - CH 3 ½ ll CH 3 O 4-methylhexanone-2 |
| Isomerism of unsaturated compounds | |
| 1. Isomerism of the carbon chain | |
| CH 3 - CH 2 - CH 2 - CH 2 - CH 2 - C \u003d O ½ hexanal H CH 3 - CH - CH - C \u003d O ½ ½ ½ CH 3 CH 3 H 2,3-dimethylbutanal | CH 3 - CH 2 - CH 2 - CH 2 - CH 2 - C - CH 3 ll heptanone-2 O CH 3 - CH 2 - CH - C - CH 3 ½ ll C 2 H 5 O 3-ethylpentanone-2 |
| 2. Isomerism of the position of the carbonyl group | |
| CH 3 - CH 2 - CH 2 - CH 2 - CH 2 - C - CH 3 ll heptanone-2 O CH 3 - CH 2 - CH 2 - C - CH 2 - CH 2 - CH 3 ll heptanone-4 O | |
| 3. Aldehydes and ketones are interclass isomers | |
| Physical properties of carbonyl compounds | |
| Formaldehyde (methanal) under normal conditions is a gas with a sharp unpleasant “pungent” odor, highly soluble in water. A 40% solution of formaldehyde in water is called formalin. Acetic aldehyde (ethanal) is a volatile, flammable liquid. Its boiling point is 20.2 0 C, the flash point is -33 0 C. In high concentrations, it has an unpleasant suffocating odor; in small concentrations, it has a pleasant smell of apples (in which it is contained in a small amount). Acetic aldehyde is highly soluble in water, alcohol, and many other organic solvents. | The simplest ketone, propanone (acetone), is a flammable liquid. Subsequent representatives are also liquids. Higher aliphatic (> 10 C atoms) as well as aromatic ketones are solids. Acetone has low temperature boiling point 56.1 0 C and flash point -20 0 C. The simplest ketones are mixed with water. Aqueous solutions of acetone are also dangerous. So, a 10% solution of it in water has a flash point of 11 0 C. All ketones are readily soluble in alcohol and ether. The simplest ketones have a characteristic odor; average homologues have a rather pleasant smell, reminiscent of the smell of mint. |
| Methods for the preparation of carbonyl compounds | |
| 1. Reactions of partial (incomplete) oxidation of alcohols | |
| Primary alcohols, when oxidized, give aldehydes: CH 3 - CH 2 - CH 2 - OH + [O]® H 2 O + propanol-1 + CH 3 - CH 2 - C \u003d O propanal ½ H | Secondary alcohols form ketones during oxidation: CH 3 - CH - CH 2 -CH 3 + [O] ® H 2 O + ½ OH + CH 3 - C - CH 2 - CH 3 butanol-2 ll O butanone-2 |
| 2. Hydration of alkynes (Kucherov reaction) | |
| Aldehyde is obtained only when acetylene is hydrated; in all other cases, ketones are formed. Hg 2+ CH º CH + HOH ® CH 3 - C \u003d O + H 2 O acetylene ½ H ethanal | Hg 2+ CH º C - CH 2 - CH 3 + HOH ® H 2 O + butin-1 + CH 3 - C - CH 2 - CH 3 ll O butanone-2 |
| 3. Hydrolysis of dihalogen derivatives. (Halogen atoms are located on the same carbon atom). The reaction proceeds in an aqueous solution of alkali. | |
| Cl ½ CH 3 - CH 2 - CH + 2KOH water ® Cl 1,1-dichloropropane ® 2KCl + CH 3 - CH 2 - C \u003d O + H 2 O ½ H propanal | Cl ½ CH 3 - CH 2 - C - CH 3 + 2KOH water ® ½ Cl 2,2-dichlorobutane ® 2KCl + CH 3 - CH 2 - C - CH 3 + H 2 O ll O butanone-2 |
| 4. Recovery of carboxylic acids | |
| CH 3 - CH 2 - C \u003d O + H 2 ® ½ OH propanoic acid ® H 2 O + CH 3 - CH 2 - C \u003d O ½ H propanal | |
| Chemical properties of carbonyl compounds | |
| In terms of chemical activity, aldehydes are superior to ketones and are more reactive. The radicals associated with the carbonyl group have the so-called positive inductive effect: they increase the electron density of the bond of the radical with other groups, i.e. as if extinguished positive charge carbon atom of carbonyl. As a result, carbonyl compounds, according to the decrease in their chemical activity, can be arranged in the following row: H - C d + - H> H 3 C ® C d + - H> H 3 C ® C d + CH 3 II II II O d - O d - About d - (straight arrows in the formulas show the shift of electrons, the quenching of a positively charged carbon atom of the carbonyl group). | |
| 1. Addition reactions at the double bond break >C = O. Recovery reactions. | |
| CH 3 - CH 2 - C \u003d O + H 2 ® ½ H propanal ® CH 3 - CH 2 - CH 2 - OH (propanol-1) | CH 3 - CH 2 - C - CH 3 + H 2 ® II O butanone-2 ® CH 3 - CH 2 - CH - CH 3 ½ OH butanol-2 |
| 2. Oxidation reactions | |
| 2.1. Complete oxidation - combustion | |
| C 3 H 6 O + 4O 2 ® 3CO 2 + 3H 2 O | C 4 H 8 O + 5.5 O 2 ® 4CO 2 + 4H 2 O |
| 2.2. Partial (incomplete) oxidation | |
| Oxidation reactions with silver oxide ("silver mirror reaction"), copper (II) hydroxide - qualitative reactions for aldehydes. NH 3, t CH 3 - CH 2 - C \u003d O + Ag 2 O ¾¾® ½ H propanal ¾¾® 2Ag¯ + CH 3 - CH 2 - C \u003d O ½ OH propanoic acid In this case, silver precipitates. CH 3 - CH 2 - C \u003d O + 2Cu (OH) 2 ® ½ H propanal ® Cu 2 O + CH 3 - CH 2 - C \u003d O + H 2 O ½ OH propanoic acid The blue precipitate of copper hydroxide turns into a red precipitate of nitrous oxide copper. | The oxidation of ketones is very difficult only with strong oxidizing agents (chromium mixture, KMnO 4), as a result, a mixture of acids is formed: t CH 3 - CH 2 - C - CH 3 + [O] ® II O butanone-2 ® 2CH 3 - C \u003d O ½ OH acetic (ethanoic) acid or ® CH 3 - CH 2 - C \u003d O + H - C \u003d O ½ ½ OH OH propanoic formic acid (methanoic) acid |
| Upon contact with strong oxidizing agents (KMnO 4 , CrO 3 , HNO 3 conc., H 2 SO 4 conc.), aldehydes and ketones ignite spontaneously. | |
| 3. Reactions due to transformations in radicals. Replacement of hydrogen in radicals by halogens | |
| CH 3 - C \u003d O + Cl 2 ® HCl + CH 2 Cl - C \u003d O ½ ½ H H ethanal chloroacetic aldehyde When methanal is chlorinated, poisonous phosgene gas is formed: H - C \u003d O + 2Cl 2 ®Cl - C \u003d O + 2HCl ½½ HCl phosgene | CH 3 - C - CH 3 + Br 2 ® HBr + CH 3 - C - CH 2 Br II II O O acetone bromoacetone Bromoacetone and chloroacetone are tear chemical warfare agents ( lachrymators). |
| Application of carbonyl compounds | |
| Formaldehyde is used in industry for the production of phenol-formaldehyde and carbamide polymers, organic dyes, adhesives, varnishes, and in the leather industry. Formaldehyde in the form of an aqueous solution (formalin) is used in medical practice. Acetaldehyde is the starting material for the production of acetic acid, polymeric materials, medicines, ethers. | Acetone very well dissolves a number of organic substances (for example, varnishes, nitrocellulose, etc.) and therefore in large quantities used as a solvent (production of smokeless powder, rayon, paints, film). Acetone is used as a raw material for the production of synthetic rubber. Pure acetone is used for extraction food products, vitamins and drugs, as well as a solvent for the storage and transportation of acetylene. |
Question #5. Carboxylic acids (30 min)
carboxylic acids called derivatives of hydrocarbons that contain one or more carboxyl groups - C \u003d O.
The carboxyl group is a combination of carbonyl and hydroxyl groups: - C \u003d O + - C - ® - C \u003d O.
carbo nile + hydro xyl® carboxyl.
Carboxylic acids are oxidation products of aldehydes, which, in turn, are oxidation products of alcohols. On acids, the oxidation process is completed (with the preservation of the carbon skeleton) in the following series:
hydrocarbon ® alcohol ® aldehyde ® carboxylic acid.
Similar information.
One of the most common chemical elements included in the vast majority chemical substances is oxygen. Oxides, acids, bases, alcohols, phenols and other oxygen-containing compounds are studied in the course of inorganic and organic chemistry. In our article, we will study the properties, as well as give examples of their application in industry, agriculture and medicine.
oxides
The simplest in structure are binary compounds of metals and non-metals with oxygen. The classification of oxides includes the following groups: acidic, basic, amphoteric and indifferent. The main criterion for the division of all these substances is which element combines with oxygen. If it is metal, then they are basic. For example: CuO, MgO, Na 2 O - oxides of copper, magnesium, sodium. Their main chemical property is the reaction with acids. So, copper oxide reacts with hydrochloric acid:
CuO + 2HCl -> CuCl2 + H2O + 63.3 kJ.
The presence of atoms of non-metallic elements in the molecules of binary compounds indicates their belonging to acidic hydrogen H 2 O, carbon dioxide CO 2, phosphorus pentoxide P 2 O 5 . The ability of such substances to react with alkalis is their main chemical characteristic.
As a result of the reaction, species can be formed: acidic or medium. This will depend on how many moles of alkali react:
- CO2 + KOH => KHCO3;
- CO2+ 2KOH => K2CO3 + H2O.
Another group of oxygen-containing compounds, which include such chemical elements as zinc or aluminum, is referred to as amphoteric oxides. In their properties, there is a tendency to chemical interaction with both acids and alkalis. The products of the interaction of acid oxides with water are acids. For example, in the reaction of sulfuric anhydride and water, acids are formed - this is one of the most important classes of oxygen-containing compounds.
Acids and their properties
Compounds consisting of hydrogen atoms associated with complex ions of acidic residues are acids. Conventionally, they can be divided into inorganic, for example, carbonic acid, sulfate, nitrate, and organic compounds. The latter include acetic acid, formic, oleic acids. Both groups of substances have similar properties. So, they enter into a neutralization reaction with bases, react with salts and basic oxides. Almost all oxygen-containing acids in aqueous solutions dissociate into ions, being conductors of the second kind. It is possible to determine the acidic nature of their environment, due to the excessive presence of hydrogen ions, using indicators. For example, purple litmus turns red when added to an acid solution. A typical representative of organic compounds is acetic acid containing a carboxyl group. It includes a hydrogen atom, which causes acid acids. It is a colorless liquid with a specific pungent odor, crystallizing at temperatures below 17 ° C. CH 3 COOH, like other oxygen-containing acids, is perfectly soluble in water in any proportion. Its 3 - 5% solution is known in everyday life under the name of vinegar, which is used in cooking as a seasoning. The substance has also found its application in the production of acetate silk, dyes, plastics and some medicines.
Organic compounds containing oxygen
In chemistry, one can distinguish a large group of substances containing, in addition to carbon and hydrogen, also oxygen particles. These are carboxylic acids, esters, aldehydes, alcohols and phenols. All their chemical properties are determined by the presence in the molecules of special complexes - functional groups. For example, alcohol containing only limit bonds between atoms - ROH, where R is a hydrocarbon radical. These compounds are usually considered as derivatives of alkanes, in which one hydrogen atom is replaced by a hydroxo group.
Physical and chemical properties of alcohols
The state of aggregation of alcohols is liquids or solid compounds. There are no gaseous substances among alcohols, which can be explained by the formation of associates - groups consisting of several molecules connected by weak hydrogen bonds. This fact also determines the good solubility of lower alcohols in water. However, in aqueous solutions, oxygen-containing organic substances - alcohols, do not dissociate into ions, do not change the color of indicators, that is, they have a neutral reaction. The hydrogen atom of the functional group is weakly bound to other particles, therefore, in chemical interactions, it is able to leave the molecule. At the same place of free valency, it is replaced by other atoms, for example, in reactions with active metals or with alkalis - by metal atoms. In the presence of catalysts such as platinum mesh or copper, alcohols are oxidized by vigorous oxidizing agents, potassium bichromate or potassium permanganate, to aldehydes.
esterification reaction
One of the most important chemical properties of oxygen-containing organic substances: alcohols and acids is a reaction leading to the production of esters. She has great practical value and is used in industry for the extraction of esters used as solvents in the food industry (in the form of fruit essences). In medicine, some of the esters are used as antispasmodics, for example, ethyl nitrite dilates peripheral blood vessels, and isoamyl nitrite is a spasm protector. coronary arteries. The esterification reaction equation has the following form:
CH3COOH+C2H5OH<--(H2SO4)-->CH3COOC2H5+H2O
In it, CH 3 COOH is acetic acid, and C 2 H 5 OH is chemical formula alcohol ethanol.
Aldehydes
If a compound contains the -COH functional group, then it is classified as an aldehyde. They are presented as products of further oxidation of alcohols, for example, with oxidizing agents such as copper oxide.
The presence of a carbonyl complex in the molecules of formic or acetaldehyde determines their ability to polymerize and attach atoms of other chemical elements. Qualitative reactions that can be used to prove the presence of a carbonyl group and the belonging of a substance to aldehydes are the reaction of a silver mirror and interaction with copper hydroxide when heated:
Acetaldehyde, used in industry for the production of acetic acid, a large tonnage product of organic synthesis, has received the greatest use.
Properties of oxygen-containing organic compounds - carboxylic acids
The presence of a carboxyl group - one or more - is distinguishing feature carboxylic acids. Due to the structure of the functional group, dimers can form in acid solutions. They are linked together by hydrogen bonds. The compounds dissociate into hydrogen cations and acid residue anions and are weak electrolytes. An exception is the first representative of a number of limiting monobasic acids - formic, or methane, which is a conductor of the second kind of medium strength. The presence of only simple sigma bonds in molecules indicates the limit, but if substances have double pi bonds in their composition, these are unsaturated substances. The first group includes such acids as methane, acetic, butyric. The second is represented by compounds that are part of liquid fats - oils, for example, oleic acid. The chemical properties of oxygen-containing compounds: organic and inorganic acids are largely similar. So, they can interact with active metals, their oxides, with alkalis, and also with alcohols. For example, acetic acid reacts with sodium, oxide, and to form a salt - sodium acetate:
NaOH + CH3COOH→NaCH3COO + H2O
A special place is occupied by compounds of higher carboxylic oxygen-containing acids: stearic and palmitic, with a trihydric saturated alcohol - glycerin. They belong to esters and are called fats. The same acids are part of the sodium and potassium salts as an acid residue, forming soaps.
Important organic compounds that are widely distributed in wildlife and play a leading role as the most energy-intensive substance are fats. They are not an individual compound, but a mixture of heterogeneous glycerides. These are compounds of the limiting polyhydric alcohol - glycerin, which, like methanol and phenol, contains hydroxyl functional groups. Fats can be subjected to hydrolysis - heating with water in the presence of catalysts: alkalis, acids, oxides of zinc, magnesium. The products of the reaction will be glycerol and various carboxylic acids, further used for the production of soap. In order not to use expensive natural essential carboxylic acids in this process, they are obtained by oxidizing paraffin.
Phenols
Finishing to consider the classes of oxygen-containing compounds, let us dwell on phenols. They are represented by a phenyl radical -C 6 H 5 connected to one or more functional hydroxyl groups. The simplest representative of this class is carbolic acid, or phenol. As a very weak acid, it can interact with alkalis and active metals - sodium, potassium. A substance with pronounced bactericidal properties - phenol is used in medicine, as well as in the production of dyes and phenol-formaldehyde resins.
In our article, we studied the main classes of oxygen-containing compounds, and also considered their chemical properties.
Oxygen gives organic substances a whole complex of characteristic properties.
Oxygen is divalent, has two valence electron pairs and is characterized by high electronegativity (x = 3.5). Strong chemical bonds are formed between carbon and oxygen atoms, which can already be seen in the example of CO 2 molecules. A single C-0 bond (£ sv \u003d 344 kJ / mol) is almost as strong as C-C connection (E ca = 348 kJ/mol), and the double bond C=0 ( E St = 708 kJ/mol) is much stronger than the C=C bond (E St == 620 kJ/mol). Therefore, transformations leading to the formation of C=0 double bonds are common in organic molecules. For the same reason, carbonic acid is unstable:
The hydroxo group located at the double bond is converted into an hydroxy group (see above).
Oxygen will give polarity to the molecules of organic substances. Attraction between molecules increases, the melting and boiling points increase significantly. Under normal conditions among oxygenated substances very macho gases - only ether CH 3 OCH 3, formaldehyde CH 2 0 and ethylene oxide CH 2 CH 2 0.
Oxygen promotes the formation of hydrogen bonds both as a donor and an acceptor of hydrogen. Hydrogen bonds enhance the attraction of molecules, and in the case of sufficiently complex molecules, give them a certain spatial structure. The influence of polarity and hydrogen bonds on the properties of a substance is seen in the example of a hydrocarbon, ketone and alcohol
Polarity and the formation of hydrogen bonds are responsible for the good solubility of oxygen-containing organic substances in water.
Oxygen imparts acidic properties to organic substances to some extent. In addition to the class of acids, the properties of which are obvious from the name, phenols and alcohols exhibit acidic properties.
Another common property oxygen-containing substances lies in the easy oxidizability of the carbon atom associated simultaneously with oxygen and hydrogen. This is evident from the following chains of reactions, which are terminated when the carbohydrate loses the last water conduit atom:
contains a hydroxy group and is considered a heterofunctional acid.
Alcohols and ethers
Name of a whole class of organic substances alcohols(from Latin "spiritus" - spirit) comes from the "active principle" of the mixture obtained by fermenting fruit juices and other systems containing sugar. This active principle - wine alcohol, ethanol C2H5OH, is separated from water and non-volatile solutes during the distillation of the mixture. Another name for alcohol is alcohol - Arabic origin.
Alcohols are called organic compounds in which there is a hydroxo group associated with the $ p 3 carbon atom of the hydrocarbon radical.
Alcohols can also be considered as products of substitution of one hydrogen atom in water for a hydrocarbon radical. Alcohols form homologous series (Table 22.5), differing in the nature of the radicals and the number of hydroxo groups.
Table 22.5
Some homologous series of alcohols
Tlicols and glycerols are polyfunctional alcohols with OH groups at adjacent carbon atoms.
The hydroxo group at unsaturated carbon atoms is unstable, as it turns into a carbonyl group. Vinyl alcohol is in an insignificant amount in equilibrium with aldehyde:
There are substances in which the hydroxo group is bonded to the n / z carbon atom of the aromatic ring, but they are considered as a special class of compounds - phenols.
In alcohols, isomerism of the carbon skeleton and the position of the functional group is possible. In unsaturated alcohols, isomerism of the position of the multiple bond and spatial isomerism also arise. Compounds of the class of ethers are isomeric to alcohols. Among the alcohols, there are varieties called primary, secondary And tertiary alcohols. This is due to the nature of the carbon atom at which the functional group is located.
Example 22.12. Write the formulas for primary, secondary, and tertiary alcohols with four carbon atoms.
Solution.
Let us consider in more detail the homologous series of saturated alcohols. The first 12 members of this series are liquids. Methanol, ethanol and propanol are miscible with water in any ratio due to their structural similarity to water. Further along the homologous series, the solubility of alcohols decreases, since large (in terms of the number of atoms) hydrocarbon radicals are more and more displaced from aquatic environment like hydrocarbons. This property is called hydrophobicity. In contrast to the radical, the hydroxo group is attracted to water, forming a hydrogen bond with water, i.e. shows hydrophilicity. Higher alcohols (five or more carbon atoms) exhibit the property surface activity- the ability to concentrate at the surface of the water due to the expulsion of a hydrophobic radical (Fig. 22.3).
Rice. 22.3.
Surfactants coat liquid droplets and promote the formation of stable emulsions. This is the basis for the action of detergents. Surface activity can be exhibited not only by alcohols, but also by substances of other classes.
Most water-soluble alcohols are poisonous. The least poisonous are ethanol and glycerin. But, as you know, ethanol is dangerous because it causes a person to become addicted to its use. The simplest of the alcohols, methanol is similar in smell to ethanol, but extremely poisonous. There are many known cases of human poisoning as a result of erroneous ingestion.
methanol instead of ethanol. This is facilitated by the huge volume of industrial use of methanol. The simplest dihydric alcohol ethylene glycol C 2 H 4 (OH) 2 is used in large quantities for the production of polymer fibers. Its solution is used as an antifreeze for cooling automobile engines.
Getting alcohols. Let's look at a few common ways.
1. Hydrolysis of halogen derivatives of hydrocarbons. The reactions are carried out in an alkaline medium:
Example 22.13. Write the reactions for obtaining ethylene glycol by the hydrolysis of halogen derivatives, taking the starting material ethylene.
2. Addition of water to alkenes. Highest value has the addition reaction of water to ethylene to form ethanol. The reaction proceeds quite rapidly at high temperature, but the equilibrium is strongly shifted to the left and the yield of alcohol decreases. Therefore, it is necessary to create a high pressure and use a catalyst that makes it possible to achieve the same process speed at a lower temperature (similar to the conditions for the synthesis of ammonia). Ethanol is obtained by hydration of ethylene at -300°C and a pressure of 60-70 atm:
The catalyst is phosphoric acid supported on alumina.
3. There are special ways to produce ethanol and methanol. The first is obtained by the well-known biochemical method of fermenting carbohydrates, which are first broken down to glucose:
Methanol is produced synthetically from inorganic substances:
The reaction is carried out at 200-300°C and a pressure of 40-150 atm using a complex catalyst Cu0/2n0/A1 2 0 3 /Cr 2 0 3 . The importance of this industrial process is clear from the fact that more than 14 million tons of methanol are produced annually. It is used mainly in organic synthesis for the methylation of organic substances. Approximately the same amount is produced and ethanol.
Chemical properties of alcohols. Alcohols can be handful and oxidize. A mixture of ethyl alcohol and hydrocarbons is sometimes used as fuel for automobile engines. The oxidation of alcohols without disturbing the carbon structure is reduced to the loss of hydrogen and the addition of oxygen atoms. In industrial processes, alcohol vapors are oxidized by oxygen. In solutions, alcohols are oxidized by potassium permanganate, potassium dichromate and other oxidizing agents. An aldehyde is obtained from a primary alcohol upon oxidation:
With an excess of an oxidizing agent, the aldehyde is immediately oxidized to an organic acid:
Secondary alcohols are oxidized to ketones:
Tertiary alcohols can only be oxidized under harsh conditions with partial destruction of the carbon skeleton.
acid properties. Alcohols react with active metals to release hydrogen and form derivatives with common name alkoxides (methoxides, ethoxides, etc.):
The reaction proceeds more calmly than a similar reaction with water. The liberated hydrogen does not ignite. This method destroys sodium residues after chemical experiments. This kind of reaction means that alcohols exhibit acidic properties. This is a consequence of the polarity of the O-H bond. However, alcohol practically does not react with alkali. This fact allows us to clarify the strength of the acidic properties of alcohols: they are weaker acids than water. Sodium ethoxide is almost completely hydrolyzed to form a solution of alcohol and alkali. The acidic properties of glycols and glycerols are somewhat stronger due to the mutual inductive effect of OH groups.
Polyhydric alcohols form complex compounds with ions of some ^/-elements. In an alkaline environment, a copper ion replaces two hydrogen ions at once in a glycerol molecule to form a blue complex:
With an increase in the concentration of H + ions (acid is added for this), the equilibrium shifts to the left and the color disappears.
Reactions of nucleophilic substitution of the hydroxo group. Alcohols react with hydrogen chloride and other hydrogen halides:
The reaction is catalyzed by a hydrogen ion. First, H + joins oxygen, accepting its electron pair. This shows the main properties of alcohol:
The resulting ion is unstable. It cannot be isolated from solution as a solid salt like the ammonium ion. The addition of H + causes an additional shift of the electron pair from carbon to oxygen, which facilitates the attack of the nucleophilic particle on carbon:
The bond between carbon and chloride ion increases as the bond between carbon and oxygen is broken. The reaction ends with the release of a water molecule. However, the reaction is reversible, and upon neutralization of hydrogen chloride, the equilibrium shifts to the left. Hydrolysis takes place.
The hydroxo group in alcohols is also replaced in reactions with oxygen-containing acids to form esters. Glycerol with nitric acid forms nitroglycerine used as a means of relieving spasms of the vessels of the heart:
It is clear from the formula that the traditional name of the substance is inaccurate, since in fact it is glycerol nitrate - an ester of nitric acid and glycerol.
When ethanol is heated with sulfuric acid, one molecule of alcohol acts as a nucleophilic reagent in relation to another. As a result of the reaction, an ethoxyethane ether is formed:
Some atoms are highlighted in the diagram to make it easier to trace their transition to the reaction products. One alcohol molecule first attaches a catalyst - an H + ion, and the oxygen atom of another molecule transfers an electron pair to carbon. After the elimination of water and the dissociation of H 4, an ether molecule is obtained. This reaction is also called intermolecular dehydration of alcohol. There is also a method for obtaining ethers with different radicals:
Ethers are more volatile than alcohols because hydrogen bonds do not form between their molecules. Ethanol boils at 78°C, and its isomer ester CH3OCH3 boils at -23.6°C. Ethers do not hydrolyze to alcohols when boiled with alkali solutions.
Dehydration of alcohols. Alcohols can decompose with elimination of water in the same way as halogen derivatives of hydrocarbons decompose with elimination of hydrogen halide. In the production of alcohols from alkene and water (see above), the reverse reaction of water elimination is also present. The difference in the conditions for the addition and elimination of water is that the addition occurs under pressure with an excess of water vapor relative to the alkene, and the elimination occurs from a single alcohol. Such dehydration is called intramolecular. It also goes in a mixture of alcohol with sulfuric acid at ~150°C.
