Question

Why is pyridine a poor nucleophile $?$

Answer 1

First we have to know that nucleophiles are Lewis bases because they donate electrons. Nucleophilic describes the affinity of a nucleophile to bond with positively charged atomic nuclei. A nucleophile is a chemical species that forms bonds with electrophiles by donating an electron pair.

Complete Step By Step Answer:
Pyridine is a heterocyclic organic compound with a chemical formula ${C_5}{H_5}N$ . It is also known as Azine. It has a sour (acid taste like lemon), and fish like odour. It can be synthesized from ammonia, formaldehyde, acetaldehyde, and it can be made from crude coal tar. The structure of pyridine is similar to a benzene ring with one methine group replaced by a nitrogen atom.
Pyridine is a weaker base than saturated amines of similar structure because its electron pair is in $s{p^2}$ -hybridized orbital, and the electron pair is more tightly held by the atom. The lone pair on nitrogen is delocalized to some extent around the ring. Then the pyridine is not a strong base. Hence pyridine is a poor nucleophile.

Note:
Pyridine is miscible with water and is highly flammable. It is widely used as the precursor to agrochemicals and pharmaceuticals. Also, it is used as reagent and organic solvent. Pyridine and its simple derivatives are stable and relatively unreactive liquids, with strong penetrating odours that are unpleasant.