The extent of π-electron conjugation in macrocyclic rings of (1) heme, (2) coenzyme B₁₂ and (3) chlorophyll follows the order

Q38 · CSIR-NET Chemistry, December 2014

Paper: CSIR-NET December 2014 · Subject: Inorganic Chemistry · Chapter: Bioinorganic Chemistry · Topic: Bioinorganic Chemistry – General · Marks: 2 · Difficulty: Medium

The extent of $\pi$-electron conjugation in macrocyclic rings of (1) heme, (2) coenzyme $\mathrm{B}_{12}$ and (3) chlorophyll follows the order

(a)$(1)>(3)>(2)$

(b)$(1)>(2)>(3)$

(c)$(3)>(1)>(2)$

(d)$(2)>(1)>(3)$

Answer

Answer: A ✓ checked by 4AB · confidence high

Explanation

Heme (porphyrin) is fully conjugated; chlorophyll (chlorin) has one reduced pyrrole ring; the corrin of B₁₂ is the least conjugated. Order 1 > 3 > 2.

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