Carboxylic acids are the compounds containing the carboxyl functional group in their molecule. Their general formula is CnH2n+1COOH. The simplest carboxylic acid is methanoic acid (formic acid) having molecular formula HCOOH.
Fatty acids are the monocarboxylic acids which contain a long chain of carbon atoms. The minimum number of carbon atoms in fatty acids is 15. These are called as fatty acids because these are present mostly in fats and oils. For example, palmitic acid (C15H31COOH), oleic acid (C17H33COOH) and stearic acid (C17H35COOH).
Uses of Fatty Acids
Fatty acids are used in eatables, cold drinks, soaps and in medicines.
Nomenclature of carboxylic Acids
According to IUPAC system, the name of carboxylic acid is derived by replacing the terminal ‘e’ of the name of the corresponding alkane with ‘oic acid’.
|Common Name||IUPAC Name||Molecular Formula|
|Formic acid||Methanoic acid|
|Acetic acid||Ethanoic acid|
|Propanic acid||Propanoic acid|
|Butric acid||Butanoic acid|
Ethanoic Acid or Acetic Acid
Ethanoic acid can be prepared by following methods :
1. From Ethanol
Ethanoic acid can also be prepared by oxidation of ethanol in the presence of oxidizing agent K2Cr2O7 and H2SO4.
2. From Methyl Cyanide
When water is added into methyl cyanide then upon hydrolysis ethanoic acid is produced.
Properties of Ethanoic Acid
Following are the physical properties of ethanoic acid:
- It is a colourless liquid with pungent odour.
- It freezes below 16.50C.
- Its boiling point is 1180C.
- It is soluble in water.
Following are the important chemical reactions of acetic acid :
1. Reaction with Alcohols or Esterification
When acetic acid reacts with ethanol in the presence of conc. H2SO4 as catalyst sweet smelling esters are formed. This process is called esterification.
2. Reaction with Sodium Metal
Acetic acid reacts with sodium metal to produce sodium acetate and hydrogen gas.
3. Decarboxylation Reaction or Reaction with Soda Lime
Loss of carbon dioxide from molecule of sodium or potassium salt of carboxylic acid is called decarboxylation. In this reaction, when sodium or potassium salts of carboxylic acids are heated after mixing with soda lime (NaOH + CaO) then methane gas is produced.
Preparation of Soda Lime
Sodalime can be prepared for decarboxylation reaction by mixing 3 parts by volume of NaOH with 1 part by volume of CaO.
4. Reaction with Ammonia
Acetic acid reacts with ammonia to form acid amides.
Uses of Acetic Acid
Following are the uses of acetic acid:
- It is used as a solvent and chemical reagent in laboratories.
- It is used as a preservative.
- It is used in preparation of acetone and acetic anhydride.
- It is used in coagulation of latex of rubber.
- It is used as vinegar in cooking.
- It is used in manufacture of rayon and plastics.