Formula - C2H5OH
The structural formula of ethyl alcohol is as follows-
H H
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H-C-C-O-H or CH3–CH2–OH or C2H5OH
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H H
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H-C-C-O-H or CH3–CH2–OH or C2H5OH
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H H
In this the —OH group is attached to the saturated carbon atom. Hence alcoholic group is present in it. Hence it is an alcohol. It is an important member of the alcohol group and is also known simply as alcohol. Its name is ethanol in the IUPAC system. In nature it is found in the form of esters in aromatic oils and fruits. Ethyl alcohol is usually made from starch-containing grain materials, hence it is also called grain alcohol in the trade.
Method of Preparation
1. From ethyl bromide - Ethyl alcohol is obtained by treating ethyl chloride, ethyl bromide or ethyl iodide with aqueous KOH or NaOH.
For example
C2H5Br + KOH (aqueous) → C2H5OH + KBr
2. From ethyl acetate - Ethyl alcohol is obtained as a result of reaction of ethyl acetate with water in the presence of acid or base.
CH3COOC2H5 + HOH → CH3COOH + C2H5OH
In this reaction, acid or base acts as a catalyst.
3. From ethylene - Ethyl hydrogen sulphate is obtained by passing ethylene in concentrated sulfuric acid, which is hydrolysed by steam to obtain ethyl alcohol.
CH2 CH3 CH3
|| + H2SO4 | |
CH2 CH2HSO4 CH2OH
|| + H2SO4 | |
CH2 CH2HSO4 CH2OH
4. By Fermentation – The gradual decomposition of organic compounds into simple organic substances by micro-organisms is called fermentation. The molecular organisms due to which this action takes place are called ferments. Curdling of milk, setting of curd, rancidity of meat and cheese after some time and preparation of wine and vinegar from sugarcane juice are examples of fermentation. In the process of fermentation, some complex nitrogenous organic compounds obtained from yeasts act as catalysts. These compounds are called enzymes.
Ethyl alcohol is also obtained by fermentation of sugar-containing and starch-containing substances. The following reactions take place in the fermentation of sugary substances—
C12H22O11 + H2O → invertase (from yeast) → C6H12O6 + C6H12O6
Physical properties
- It is a colorless and sweet smelling liquid. Its taste is pungent. Its boiling point is 78.2°C. It burns in air with a pale blue flame. It is miscible in water and organic solvents.
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Chemical properties
1. Reaction with alkali metals - It liberates hydrogen by reacting with sodium or potassium metal.
2C2H5OH + 2Na → 2C2H5ONa + H2
sodium ethoxide
2. Reaction with acetic acid - It reacts with acetic acid to form ethyl acetate. This reaction takes place in the presence of a few drops of concentrated H2SO4 which acts as both a catalyst and a dehydrating agent.
concentrated H2SO4
CH3COOH + C2H5OH → CH3COOC2H5 + H2O
Like acetic acid, other carboxylic acids react with ethyl alcohol in a similar way. Compounds with common name esters are obtained and this reaction is called esterification.
3. Reaction with ammonia - It forms ethyl amine (C2H5NH2) on heating with ammonia under high pressure in the presence of copper chromite, alumina or other suitable catalyst.
C2H5OH + NH3 → C2H5NH2 + H2O
4. Reaction with halogen acids - It reacts with halogen acids to form ethyl halide. The reaction with HCl is carried out in the presence of anhydrous ZnCl2 and the reaction with HBr is carried out in the presence of concentrated H2SO4. The reaction with HI is reversible.
C2H5OH + HCl → C2H5Cl + H2O
anhydrous ZnCl2
C2H5OH + HBr → C2H5Br + H2O
C2H5OH + HI ⇌ C2H5I + H2O
5. Reaction with Phosphorus Pentachloride - It reacts with Phosphorous Pentachloride (PCIs) to form ethyl chloride.
C2H5OH+ PCI5 → C2H5Cl + POCI3 + HCL
6. Reaction with chlorine - The reaction of ethyl alcohol with chlorine is as follows-
CH3CH2OH + Cl2 → CH3CHO + 2HCl
ethyl alcohol acetaldehyde
CH3CHO + 3Cl2 → CCl3CHO + 3HCl
7. Oxidation - Acidified potassium dichromate (K2Cr2O7) solution is a major oxidizing agent. It provides nascent oxygen for oxidation as follows-
K2Cr2O7 + 4H2SO4 → K2SO4 + Cr2(SO4)3 + 4H2O + 3O
Acetaldehyde is obtained in the first step and acetic acid in the second step of oxidation by acidic potassium dichromate solution of ethyl alcohol.
CH3CH2OH + O → CH3CHO + H2O
CH3CHO + O → CH3COOH
acetic acid
Acetic acid is obtained as a result of this reaction but the reaction can be stopped after the first step by controlling the conditions of the reaction. Under these conditions the major product of the reaction would be acetaldehyde.
8. Action of hot copper - Acetaldehyde is obtained when vapors of ethyl alcohol are passed over hot copper at 300°C.
Cu
CH3 —CH2OH → CH3 —CHO + H2
300°C
CH3 —CH2OH → CH3 —CHO + H2
300°C
In this reaction, one molecule of hydrogen is separated from one molecule of ethyl alcohol. Hence this reaction is an example of dehydrogenation reaction.
9. Haloform reaction - On heating with chlorine and sodium hydroxide (or potassium hydroxide), it forms chloroform. On heating with iodine and sodium hydroxide (or potassium hydroxide), it forms iodoform.
C2H5OH + 4Cl2 + 6NaOH → CHCl3 + HCOONa + 5NaCl + 5H2O
C2H5OH + 4I2 + 6NaOH → CHI3 + HCOONa + 5NaCl + 5H2O
C2H5OH + 4I2 + 6NaOH → CHI3 + HCOONa + 5NaCl + 5H2O
Uses
100% pure ethyl alcohol is called absolute alcohol. The aqueous solution of ethyl alcohol (obtained by distillation) is called rectified spirit. Refined Sprint contains about 95% ethyl alcohol and 5% water. In industries and laboratories, ethyl alcohol is mainly used in the form of refined spirit.
The liquid obtained by adding methanol, pyridine or any other poisonous substance to refined spirit is called denatured spirit. Since refined spirit can be used to drink as an intoxicant, to prevent its misuse, denatured spirit is used as much as possible in place of refined spirit in laboratories and industries. To differentiate between denatured spirit and rectified spirit, methyl violet or any other suitable aniline dye is added to the denatured spirit, which turns its color blue.
Following are the main uses of ethyl alcohol-
- Ethyl alcohol is used as a solvent for many organic substances.
- Ethyl alcohol is used in the manufacture of ether, chloroform, dyes, perfumes and many other substances.
- Ethyl alcohol is also used as a reagent in the laboratory.
- The mixture of anhydrous ethyl alcohol and gasoline (petrol) is called power alcohol. It can be used as a fuel in place of petrol in automatic vehicles. The strength alcohol which contains about 10% ethyl alcohol is called gasohol. It does not require any modification to the engine when it is used as a fuel in automatic vehicles. If the proportion of ethyl alcohol in power alcohol is more than 10-15% then the engine has to be modified.
- Ethyl alcohol is also used for drinking as an intoxicant. The drugs in which ethyl alcohol is present are of two types— (i) spirit, and (ii) wine. If the alcoholic beverage is distilled, it is called spirit. If the alcoholic beverage is undistilled, it is called wine. Alcoholic beverages mainly contain ethyl alcohol from 3 to 40% and the rest is water. Proof spirit contains 49.3% ethyl alcohol by weight. x° proof sprint has x% proof sprint.
- It is also used in the preservation of biological specimens.
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