Explanation: When electrophilic substitution reaction of pyridine is carried out in acidic conditions then pyridine ring will further get deactivated forming pyridinium ion. However, under more vigorous conditions the usual electrophilic substitution reaction can be possible but yield will be less.

Explanation: Common alkylations and acylations, such as Friedel–Crafts alkylation or acylation, usually fail for pyridine because they lead only to the addition at the nitrogen atom. Substitutions usually occur at the 3-position, which is the most electron-rich carbon atom in the ring and is, therefore, more susceptible to an electrophilic addition.

Explanation: Electrophilic substitution reaction at position the 3-position is preferred over attack at 2 and 4-position because the intermediate found by electrophilic addition at 3-position is more stable as it will have 3-resonating structure and none of will have positive charge on N.

Explanation: Electrophilic substitution reaction at position the 3-position is preferred over attack at 2 and 4-position because the intermediate found by electrophilic addition at 3-position is more stable as it will have 3-resonating structure and none of will have positive charge on N.

Explanation: Electrophilic substitution reaction at position the 3-position 5 position is preferred over attack at 2 and 4-position because the intermediate found by electrophilic addition at 3-position is more stable as it will have 3-resonating structure and none of will have positive charge on N.

Explanation: Electrophilic substitution reaction at position the 3-position is preferred over attack at 2 and 4-position because the intermediate found by electrophilic addition at 3-position is more stable as it will have 3-resonating structure and none of will have positive charge on N.

Explanation: Alkyl group activate the pyridine ring towards electrophilic substitution, however, directive influence of the ring predominates regardless of the position of alkylation i.e. attack at 3-position.

Explanation: Amino group dominates the ring orientation effect and direct the incoming electrophile to o- and p- position. 2-amino group directs the incoming electrophile predominantly to the 5-position.

Explanation: Amino group dominates the ring orientation effect and direct the incoming electrophile to o- and p- position. 3-amino group directs the incoming electrophile predominantly to the 2-position.

Explanation: Amino group dominates the ring orientation effect and direct the incoming electrophile to o– and p– position. 4-amino group directs the incoming electrophile predominantly to the 3-position.