-CH -O-CH +N HBF D XII U11-Hydroxy XII U11-Hydroxy - - - - Evaluate Yourself: . Which of the following reaction will give -methoxy- -nitrobenzene. a) -nitro- -bromobenzene + sodium methoxide. b) -nitrosodium phenoxide+bromomethane .
Arrange the following compounds in the increasing order of their acid strength. propan- -ol, , , -trinitrophenol, -nitrophenol, , -dinitrophenol, phenol, -methylphenol. Physical Properties: Ethers are polar in nature. The dipolemoment of ether is the vector sum of two polar C-O bonds with significant contribution from two lone pairs of electrons.
For example, the dipole moment of diethyl ether is .18D. Boiling point of ethers are slightly higher than that of alkanes and lower than that of alcohols of comparable masses. Compound Molar Mass Boiling point (CH ) n-heptane . 371K (CH ) -methoxypentane .
373K (CH ) hexan- -ol . 430K Oxygen of ether can also form Hydrogen bond with water and hence they are miscible with water. Ethers dissolve wide range of polar and non-polar substances. R R Chemical Properties of ethers: .
Nucleophilic substitution reactions of ethers. Ethers can undergo nucleophilic substitution reactions with HBr or HI . HI is more reactive than HBr . CH -O-CH -CH + HI CH I + CH -CH -OH me D → thoxy ethane iodo methane ethanol C H -O-CH + HI C H -OH + → CH I methoxy benzene Phenol iodomethane XII U11-Hydroxy XII U11-Hydroxy - - - - Mechanism: Ethers having primary alkyl group undergo SN reaction while tertiary alkyl ether undergo SN reaction.Protonation of ether is followed by the attack of halide ion.The halide ion preferentially attacks the less sterically hindered of the two alkyl groups which are attached to etherial oxygen.
CH + H I I - CH I + HO iodomethane ethanol When excess HBr or HI is used, the alcohol formed will further react with HBr or HI to form alkyl halides. CH -CH -OH CH -CH -Br ethanol excessHBr bromoethane Evaluate Yourself: 1mole of HI is allowed to react