Synthesizing pyridine from benzene and ammonia is not a direct process, as these two reactants do not readily combine to form pyridine. However, you can synthesize pyridine from benzene through a series of reactions. One of the most common methods is the Chichibabin pyridine synthesis, which involves the following steps:1. Nitration of benzene:First, you need to nitrate the benzene ring. This is done by treating benzene with a mixture of concentrated nitric acid HNO3 and concentrated sulfuric acid H2SO4 at a low temperature. This reaction forms nitrobenzene.Benzene + HNO3 Nitrobenzene + H2O2. Reduction of nitrobenzene to aniline:Next, you need to reduce the nitro group in nitrobenzene to an amino group. This can be done using various reducing agents, such as hydrogen gas H2 in the presence of a catalyst like palladium on carbon Pd/C or iron Fe with hydrochloric acid HCl . This reaction forms aniline.Nitrobenzene + 3H2 Aniline + 2H2O3. Formation of the Schiff base:Aniline reacts with an aldehyde, such as formaldehyde HCHO , to form a Schiff base imine . This reaction is carried out in a basic medium, such as sodium hydroxide NaOH or potassium hydroxide KOH .Aniline + HCHO Schiff base + H2O4. Chichibabin pyridine synthesis:The Schiff base is then heated with sodium amide NaNH2 in liquid ammonia NH3 . This reaction leads to the formation of pyridine through a series of rearrangements and ring closures.Schiff base + 2NaNH2 Pyridine + 2NH3 + Na2OThe mechanism of the Chichibabin pyridine synthesis involves the following steps:1. Deprotonation of the Schiff base by sodium amide to form an anionic intermediate.2. Intramolecular nucleophilic attack of the nitrogen anion on the imine carbon, leading to a ring closure and the formation of a six-membered ring.3. Rearrangement of the six-membered ring to form a dihydropyridine intermediate.4. A second deprotonation by sodium amide, followed by an intramolecular nucleophilic attack to form a fully aromatic pyridine ring.After synthesizing pyridine, it can be purified by distillation or other purification techniques. Keep in mind that these reactions involve hazardous chemicals and should be performed in a well-equipped laboratory with proper safety precautions.