NEET Chemistry Notes Alcohols,Phenols and ethers -Ethers
Ethers
Ethers
Organic compounds having —O— functional group are called ethers. Thus, ethers may look like
R’—O—R”
In other words, ethers are the derivatives of water as these are obtained when both the H-atoms of H20 are replaced by R groups. The R groups may be same or different. When both the R groups (alkyl groups) are same, the ethers are called simple or symmetrical ether and when both the groups are different, the ethers are called mixed or unsymmetrical ethers, e.g.
CH3— O — CH3 CH3OC2H5
(Simple or symmetrical ethers) (Mixed ether)
Structure of Ethers
In ethers, two bond pairs and two lone pairs of electrons on oxygen are arranged approximately in tetrahedral manner. The bond angle is slightly greater than tetrahedral angle due to the repulsive forces between the two bulky alkyl groups.
Preparation of Ethers
General methods used to synthesis ethers are as follows:
By Dehydration of Alcohols
Williamson’s Synthesis
Only primary alkyl halides when react with sodium alkoxide give ether while tertiary alkyl halide give alkene due to steric hindrance.
Physical Properties of Ethers
Ethers are polar but insoluble in H2O and have low boiling point than alcohols (having comparable molecular mass) because ethers do not form hydrogen bond with water.
Chemical Properties of Ethers
The reactions of ethers are mainly due to lone pair of ethereal oxygen, cleavage of C—O bond and —R group.
Reactions Involving Cleavage of C—O Bond
Addition Reactions
Electrophilic Substitution Reactions
—OR is ortho, para directing group and activates the aromatic ring towards electrophilic substitution reaction.
Uses
- Ethers are used asya solvent for oils, fats and Grignard reagent, etc.
- It is used as general anaesthetic. It provides inert and moisture free medium for various reactions.