Why is bimolecular dehydration not appropriate for the preparation of ethyl methyl ether?
Bimolecular dehydration is best used for the synthesis of symmetrical dialkyl ethers from unhindered primary alcohols.
If two different alcohols are used, there is no way to control which -OH gets protonated (as obviously we are using primary alcohols and both primary alcohols would be almost equally basic towards protonation) and which -OH acts as a nucleophile, so a mixture of two different symmetrical and the desired asymmetrical ether is obtained.
Also, The dehydration of secondary and tertiary alcohols to get corresponding ethers is unsuccessful as alkenes are formed easily in these reactions. The yields of ethers with two 3° alkyl groups are particularly poor because of severe steric hindrance.]
IMP:::
1.It is a way of preparing diethyl ether from dehydrating action of conc sulphuric acid on ethanol.The dehydrating agent conc sulphuric acid abstracts a hydrogen from one ethanol and hydroxyl from neighbour.by this sulphuric acid grabs a mole of water
2. thsi method works only for symm ethers:di(alkyl)ethers
3.Methy ether is better prepared from sodium ethoxide and methanol
4.moreover,u get 3 ethers if u mix methanol+ethanol with sulphuric acid in bimolecular dehydration.so you will get all combinations incl ethyl methylether,di ethyl ether,di methyl ether.
cheers!
Bimolecular dehydration is best used for the synthesis of symmetrical dialkyl ethers from unhindered primary alcohols.
If two different alcohols are used, there is no way to control which -OH gets protonated (as obviously we are using primary alcohols and both primary alcohols would be almost equally basic towards protonation) and which -OH acts as a nucleophile, so a mixture of two different symmetrical and the desired asymmetrical ether is obtained.
Also, The dehydration of secondary and tertiary alcohols to get corresponding ethers is unsuccessful as alkenes are formed easily in these reactions. The yields of ethers with two 3° alkyl groups are particularly poor because of severe steric hindrance.]
IMP:::
1.It is a way of preparing diethyl ether from dehydrating action of conc sulphuric acid on ethanol.The dehydrating agent conc sulphuric acid abstracts a hydrogen from one ethanol and hydroxyl from neighbour.by this sulphuric acid grabs a mole of water
2. thsi method works only for symm ethers:di(alkyl)ethers
3.Methy ether is better prepared from sodium ethoxide and methanol
4.moreover,u get 3 ethers if u mix methanol+ethanol with sulphuric acid in bimolecular dehydration.so you will get all combinations incl ethyl methylether,di ethyl ether,di methyl ether.
cheers!
