Question

Pyridine upon hydrogenation in presence of platinum at 25°C and 3 atm pressure yields

• A. Piperidine
• B. 2,3-Dihydropyridine
• C. Pyrazine
• D. 3,4-Dihydropyridine

Answer 1

The Correct Option is A

Pyridine is a six-membered aromatic heterocyclic compound with a nitrogen atom. It undergoes hydrogenation to produce different compounds depending on the conditions. In this case, we are examining what pyridine yields when hydrogenated in the presence of platinum at 25°C and 3 atm pressure.

Let's analyze the hydrogenation of pyridine:

1. In the presence of a catalyst like platinum and under standard conditions (low temperature and moderate pressure), pyridine undergoes complete hydrogenation.
2. Complete hydrogenation of pyridine involves the addition of five molecules of hydrogen (H₂) to the pyridine ring to saturate all the double bonds.
3. This results in the formation of piperidine, which is a saturated, cyclic secondary amine, with the molecular formula C₅H₁₁N.

Other options can be ruled out based on the following logic:

• 2,3-Dihydropyridine and 3,4-Dihydropyridine are partially hydrogenated products and are typically formed under milder conditions or by selective reduction methods, which are not indicated in this scenario.
• Pyrazine is a different heterocyclic compound altogether and is not formed from the hydrogenation of pyridine.

Therefore, pyridine upon hydrogenation with platinum catalyst at 25°C and 3 atm pressure yields piperidine.