SOME COMMERCIALLY IMPORTANT ALCOHOLS
1. Methanol (CH3)
Methanol is the simplest alcohol present. It is also known as wood spirit or wood alcohol because it was originally prepared from wood. It is also called as methyl alcohol.
2. Ethanol (C2H5OH)
It is known as ethyl alcohol or simply alcohol.
Preparation of Ethanol
Ethanol can be prepared by following two methods-
- By hydration of ethene
- By fermentation of carbohydrates
a. Preparation of Ethanol by Hydration of Ethene
When ethene and steam are passed over catalyst phosphoric acid at 3000C temperature and 60 atmospheric pressure then ethanol is formed.
b. Preparation of Ethanol by Fermentation of Carbohydrates
Ethanol is also manufactured by fermentation of sugar or starch. Fermentation is a process in which complex organic compounds are broken down into simpler molecules by the action of enzymes.
The fermentation of sugar is done by adding yeast in sugar solution and keeping it for 2-3 days. The yeast plant produces enzymes invertase and zymase, which are necessary for fermentation. Enzymes are chemical compounds which help in breaking bigger molecules into smaller ones. Enzymes also act as catalysts. During fermentation the enzyme invertase hydrolyses sucrose present in sugar solution to glucose and fructose as given below :
The enzyme zymase then converts glucose and fructose to ethanol and carbon dioxide gas.
In this way during process of fermentation the complex molecules of sugar are converted into simple molecules of ethanol and carbon dioxide with the help of enzymes invertase and zymase.
During the process of fermentation fresh air is not allowed to enter the vessel in which fermentation is taking place because air can oxidize ethanol into vinegar.
The spirit containing 95.5% alcohol and 4.5% of water is called rectified spirit.
Test of Ethyl alcohol or Ethanol
Ethanol can be identified in a given sample of organic compound with the help of Lucas test.
When ethanol is heated by mixing with concentrated hydrochloric acid and anhydrous ZnCl2 then cloudiness appears in the test tube which shows the presence of ethyl alcohol in the given sample.
Effects of Ethyl alcohol on Health
Ethyl alcohol is highly soluble in water and is rapidly absorbed by our body when taken inside. So, it is used mainly as an alcoholic beverage in the form of beer, wine and whisky. These substances when taken internally can cause following harms to our body.
- It causes damage to liver by storage of fat in it.
- It causes damage to nervous system. It also damages stomach, blood vessels and kidneys.
- Alcohol lowers the resistance of body towards diseases.
- Alcohol reduces the judgment and mental control of our mind which result in loss of self-control and may even cause road accidents.
- Drinking of large quantities of alcohols effects the control and co-ordination mechanism of the body due to which the concerned person may become unconscious or may even die.
The mixture of ethanol and water is called antifreeze. Its freezing point is lower than the freezing point of water. So, a solution containing antifreeze cannot solidify even at very low temperature. So, antifreeze mixture is used in radiators of cars in very cold countries.
Ethyl alcohol is very important solvent which is used in industries for preparation of paints, lacquers, dyes, varnishes, cosmetics and perfumes etc. it is also used for drinking purpose in the form of beer, whisky, rum and gin. So, to avoid the misuse of ethyl alcohol meant for industrial processes, it is made unfit for drinking purpose by adding small amount of CuSO4, methanol and pyridine in it. This process is known as denaturation of alcohol and the alcohol thus obtained is called denatured alcohol.
Test for Identification of Alcohols
Alcohols can be identified in a given sample of organic compound with the help of following tests:
When carboxylic acids are added in alcohol in the presence of Conc. H2SO4 as catalyst then they form a sweet smelling substance called ester. This reaction is called esterification reaction.
When alcohols are treated with sodium metal they liberate hydrogen gas as given below:.