11.67 Give two reactions that show the acidic nature of phenol. Compare acidity of phenol with that of ethanol.

 

<p><strong>11.67</strong></p><p><strong>The acidic nature of phenol can be represented by the following two reactions:-</strong></p><p><strong> (a)</strong> Phenols react with sodium to give sodium phenoxide, liberating H₂.</p><p><strong> (b) </strong>Phenols react with sodium hydroxide to give sodium phenoxide and water as a by-product.</p><p>The acidity of phenol is more than that of ethanol. This is because phenol after losing a proton becomes phenoxide ion which undergoes resonance and is stabilized whereas ethoxide ion does not.</p><p>The resonating structures of phenoxide ion are shown as below:</p><p>The lone pair of electrons on oxygen delocalizes into the benzene (mesomeric effect) which reduces the electron density in the O-H bond. The O-H bonds are weaker and therefore breaks easily whereas in ethanol the electron releasing inductive effect of the alkyl group increases the electron density on the O-H bond. This strengthens the bond so the bond does not break easily. Therefore making ethanol less acidic than phenol.</p>

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