The ring closure reaction of furan and pyrrole typically involves electrophilic aromatic substitution EAS reactions. In these reactions, an electrophile reacts with the electron-rich aromatic ring, leading to the formation of a new bond and the preservation of the aromaticity.Mechanism of the ring closure reaction:1. Generation of the electrophile: In the presence of a suitable catalyst or reagent, an electrophile is generated. Common electrophiles include halogens, nitronium ions NO2+ , and carbocations.2. Attack of the electrophile: The electron-rich furan or pyrrole ring attacks the electrophile, forming a new bond. This step results in the loss of aromaticity and the formation of a resonance-stabilized intermediate Wheland intermediate or arenium ion .3. Proton loss: A proton is lost from the intermediate, restoring the aromaticity of the ring. The reaction is completed with the formation of the substituted furan or pyrrole.Now, let's discuss the basicity of nitrogen in pyrrole and its effect on reactivity compared to furan.Pyrrole has a nitrogen atom in the ring, which has a lone pair of electrons. However, this lone pair is part of the aromatic -system, and it is delocalized over the entire ring. This means that the nitrogen in pyrrole is less basic compared to other nitrogen-containing compounds like amines, where the lone pair is localized on the nitrogen atom.Furan, on the other hand, has an oxygen atom in the ring, which also has a lone pair of electrons. However, the oxygen atom is more electronegative than nitrogen, and its lone pair is less available for donation.In terms of reactivity, pyrrole is generally more reactive than furan in electrophilic aromatic substitution reactions. The reason for this is that the nitrogen atom in pyrrole contributes more to the electron density of the ring, making it more nucleophilic and more susceptible to attack by electrophiles. Additionally, the lower basicity of nitrogen in pyrrole means that it is less likely to form a stable complex with the electrophile, which would inhibit the reaction.In summary, the mechanism of the ring closure reaction of furan and pyrrole involves electrophilic aromatic substitution. The basicity of nitrogen in pyrrole is lower than in other nitrogen-containing compounds due to the delocalization of its lone pair, but this contributes to its higher reactivity in EAS reactions compared to furan.