Explain the following with an example.
Kolbe's reaction
Reimer-Tiemann reaction
Williamson ether synthesis
Unsymmetrical ether
Explain the following with an example.
Kolbe's reaction
Reimer-Tiemann reaction
Williamson ether synthesis
Unsymmetrical ether
Kolbe's reaction When phenol reacts with sodium hydroxide, reactive phenoxide ion is formed. So, electrophilic aromatic substitution takes place with CO2 under a pressure of 4-7 atm followed by acidification and ortho hydroxybenzoic acid (Salicylic acid) is formed. This is called Kolbe's reaction.
Reimer-Tiemann reaction When phenol is treated with chloroform in the presence of sodium hydroxide -CHO group is introduced at ortho position of benzene ring. This is called Reimer-Tiemann reaction.
Williamson ether synthesis Ethers (symmetrical and unsymmetrical) are prepared by this method. It involves the reaction of an alkyl halide with sodium alkoxide.
R−X+R′−ONa→R−O−R′+NaX
e.g., 1. (CH3)3−C−ONa+CH3Br→CH3O−C−(CH3)3+NaBr
2. C6H5OH+NaOH→C6H5ONaRX→C6H5−O−R
Unsymmetrical ether An ether in which alkyl or aryl groups attached to the oxygen atom are different is known as unsymmetrical ether. For example, ethyl methyl ether (C2H5OCH3) methyl phenyl ether (CH3−O−C6H5) etc.
Kolbe's reaction When phenol reacts with sodium hydroxide, reactive phenoxide ion is formed. So, electrophilic aromatic substitution takes place with CO2 under a pressure of 4-7 atm followed by acidification and ortho hydroxybenzoic acid (Salicylic acid) is formed. This is called Kolbe's reaction.
Reimer-Tiemann reaction When phenol is treated with chloroform in the presence of sodium hydroxide -CHO group is introduced at ortho position of benzene ring. This is called Reimer-Tiemann reaction.
Williamson ether synthesis Ethers (symmetrical and unsymmetrical) are prepared by this method. It involves the reaction of an alkyl halide with sodium alkoxide.
R−X+R′−ONa→R−O−R′+NaX
e.g., 1. (CH3)3−C−ONa+CH3Br→CH3O−C−(CH3)3+NaBr
2. C6H5OH+NaOH→C6H5ONaRX→C6H5−O−R
Unsymmetrical ether An ether in which alkyl or aryl groups attached to the oxygen atom are different is known as unsymmetrical ether. For example, ethyl methyl ether (C2H5OCH3) methyl phenyl ether (CH3−O−C6H5) etc.
