Organic Chemistry Multiple Choice Questions on “Structure of Pyridine”.
1. Pyridine is a which type of heterocyclic compound from the following options?
a) Six membered heterocyclic compound
b) Seven membered heterocyclic compound
c) Four membered heterocyclic compound
d) Five membered heterocyclic compound
Answer: a
Clarification: Pyridine is a five membered heterocyclic compound. The chemical formula for pyridine is: C5H5N. The only way we can have five carbons, a nitrogen, and only five hydrogens is if the carbons and nitrogen form a ring with alternating double bonds.
2. Which element is present as hetero atom in pyridine?
a) Sulphur
b) Nitrogen
c) Oxygen
d) Sulphur and nitrogen
Answer: b
Clarification: Pyridine is an analogue of benzene in which one -CH unit is replaced by N. The chemical formula for pyridine is: C5H5N.
3. The electron of Nitrogen participating in the resonance in pyridine is present in which orbital?
a) p-orbital
b) sp2-orbital
c) sp3-orbital
d) sp -orbital
Answer: b
Clarification: In pyridine, from three sp2 orbital, one hybrid orbital is used for one electron which is utilized in the π-cloud.
4. Pyridine is a not a planner compound?
a) True
b) False
Answer: b
Clarification: Pyridine is planner monocyclic compound and contains 6 πe- the aromatic sextet. It fulfils the criteria for the Huckel’s rule.
5. How many number of resonating structure stabilises a pyridine molecule?
a) 4
b) 5
c) 6
d) 7
Answer: b
Clarification: Like benzene, pyridine also has 2 kekule structure (a and b) along with 3 more resonating structure (c, d and e) which contributes to a lesser extent to the stability of molecule.
6. Pyridine come under which category of heterocycle classification on the basis of chemical behavior?
a) -excessive heterocycle
b) -deficient heterocycle
c) -equivalent heterocycle
d) can’t say about the five membered rings
