REDOX Reaction Of Pyridine

Due to the low density of the electron cloud on the pyridine ring, it is generally not easy to be oxidized, especially under acidic conditions, after the salt of pyridine, the nitrogen atom has a positive charge, and the induction effect of electron absorption is strengthened, so that the electron cloud density on the ring is lower, and the stability of the oxidizer is increased. When the pyridine ring has a side chain, the side chain oxidation reaction occurs.
Under special oxidation conditions, pyridine can undergo an oxidation reaction similar to tertiary amine to produce N-oxide. For example, when pyridine interacts with peroxic acid or hydrogen peroxide, pyridine n-oxide is obtained.
Pyridine n-oxide can be reduced to deoxygenate. In the pyridine n-oxide, the unshared electron pair on the oxygen atom can be conjugated with the aromatic large π bond, which increases the electron cloud density on the ring, and the α and γ sites increase significantly, which makes the pyridine ring electrophilic substitution reaction easy to occur. Due to the positive charge on the nitrogen atom after the generation of pyridine n-oxide, the induced effect of electron absorption increases, so that the electron cloud density of the α position is reduced, so the electrophilic substitution reaction mainly occurs at 4(γ). At the same time, pyridine n-oxide is also prone to nucleophilic substitution reactions.
In contrast to oxidation reaction, pyridine is prone to hydrogenation reduction of benzene ring, which can be reduced by catalytic hydrogenation and chemical reagents.