The heterocyclic compound among the given molecules is:a Pyridine C5H5N A heterocyclic compound is a cyclic compound that has atoms of at least two different elements as members of its ring. In the case of pyridine, it has a six-membered ring with five carbon atoms and one nitrogen atom.Structure:Pyridine has a planar hexagonal structure, similar to benzene. The nitrogen atom replaces one of the carbon atoms in the ring. It has alternating single and double bonds between the carbon atoms, and a single bond between the nitrogen and the adjacent carbon atom. The nitrogen atom has a lone pair of electrons that is not involved in the ring's conjugation.Properties:1. Basicity: Pyridine is a weak base due to the lone pair of electrons on the nitrogen atom, which can accept a proton. However, it is less basic than typical amines because the nitrogen's lone pair electrons are delocalized and participate in the aromatic system, making them less available for protonation.2. Aromaticity: Pyridine is an aromatic compound, as it follows the Hückel's rule 4n+2 electrons with six electrons in the ring, providing stability and resistance to reactions that would break the aromatic system.3. Electrophilic substitution: Pyridine undergoes electrophilic substitution reactions, but it is less reactive than benzene due to the electron-withdrawing effect of the nitrogen atom, which reduces the electron density in the ring.4. Nucleophilic substitution: Pyridine can undergo nucleophilic substitution reactions at the 2- and 4-positions adjacent to the nitrogen atom due to the electron-deficient nature of these carbon atoms.5. Solubility: Pyridine is polar and can form hydrogen bonds with water, making it soluble in water and other polar solvents.