Alcohols, Phenols and Ethers

Alcohols, Phenols and Ethers

Question

Explain the following behaviours:

(i) Alcohols are more soluble in water than the hydrocarbons of comparable molecular masses.

(ii) Ortho-nitro phenol is more acidic than ortho-methoxyphenol.

Answer

(i) As alcohol is a polar solvent .it form hydrogen bonding with water molecules while another hydrocarbon of comparable molecular masses does not form hydrogen bonding due to being non- polar i.e.

Alcohols undergo intermolecular H-bonding while hydrocarbons do not.

Hence, they are more soluble in water than the hydrocarbons of comparable molecular masses.

 

(ii)

The nitro-group is an electron-withdrawing group. The presence of this group in the ortho position decreases the electron density in the O-H bond. As a result, it is easier to lose a proton.

Also, the o-nitro phenoxide ion formed after the loss of protons is stabilised by resonance.

Hence, ortho-nitrophenol is a stronger acid.

On the other hand, a methoxy group is an electron-releasing group. Thus, it increases the electron density in the O-H bond and hence, the proton cannot be given out easily.

For this reason, ortho-nitrophenol is more acidic than ortho-methoxyphenol.

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