Question

What is the effect of:
a.Electron withdrawing groups on the acidity of phenols
b.Electron donating group on the acidity of alcohols
c.Boiling point of alcohols on increasing number of carbon atoms

Answer 1

Hint: This question follows the concepts of organic chemistry which include the effect of electron withdrawing and releasing groups on the acidity of compounds. The electron withdrawing groups generally increase the acidic strength. However, positional exceptions also occur while predicting the behavior of an organic compound.

Complete answer:
a.The acidic strength of phenol increases when an electron withdrawing group, such as the nitro group, is present on the benzene ring. Because delocalization of negative charge is more effective in the phenoxide ion, when these groups are present in ortho and para locations, their action is enhanced.

b.Electron donating groups increase the electron density on an alcohol compound. Due to this, the acidity of alcohol decreases.

c.When compared to other hydrocarbons with similar molecular weights, alcohols have greater boiling points. The presence of intermolecular hydrogen bonding between the hydroxyl groups of alcohol molecules accounts for this. The boiling point of alcohol generally rises as the number of carbon atoms in the aliphatic carbon chain rises. In aliphatic carbon chains, on the other hand, the boiling point decreases as the branching increases, and the Van der Waals forces diminish as the surface area reduces. As a result, primary alcohols have a greater boiling point than secondary alcohols.

Note:
For electrophilic aromatic replacements, electron donating groups are usually ortho/para directors, whereas electron withdrawing groups are usually meta directors, with the exception of halogens, which are also ortho/para directors since they have lone pairs of electrons that are shared with the aromatic ring.