Chemistry 2 Marks Questions

When mixed ether containing primary or secondary alkyl group reacts with HI, then the iodide ion goes to that alkyl group of the ether which is simpler and less steric hindrance. Due to the large size of iodide ion, it does not attached with larger or more substituted alkyl group.

Oxidation of cumene (iso propyl benzene) in the presence of air gives cumene hydro-peroxide. The reaction between cumene hydroxide and dilute acid gives phenol and acetone.

1-In aryl alkyl ethers the alkoxy group show + R effect and increases the electron density in the benzene ring. Hence, the alkoxy group activates the benzene ring towards electrophilic substitution.
(ii) Due to resonance ( + M effect) the electron density increases at ortho and para positions, hence, incoming electrophile attacks the ortho and para positions. This can be explained by the following resonance structures :

When HI is taken in small quantity,
1-iodopropane and propan-1-ol formed, whereas if HI is taken in excess two moles of 1-iodopropane are formed.

Ethers are obtained by reacting alkyl halide with sodium alkoxide, this is called Williamson's ether synthesis.

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In phenols, the reaction take place on benzene ring are electrophilic substitution reactions. The - OH group attached to benzene ring is an electron donating group, it increase the electron density (through resonance) in the benzene ring. Hence, - OH group activates benzene ring for electrophilic substitution reaction and directs the incoming electrophile to the ortho and para positions. The resonance structures of phenol are shown below :

When chlorobenezene is fused with NaOH at the 623 K temperature and 320 atm pressure sodium phenoxide is produced which on acidification (reaction with dil . acid) gives phenol.