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NEET CHEMISTRYOrganic Chemistry – Some Basic Principles and Techniques Medium

Question

Increasing order of bond length is:

A

NO−<NO<NO+<O2−NO^{-} < NO < NO^{+} < O_{2}^{-}

B

O2−<NO<NO−<NO+O_{2}^{-} < NO < NO^{-} < NO^{+}

C

O2−<NO−<NO<NO+O_{2}^{-} < NO^{-} < NO < NO^{+}

D

NO+<NO<NO−<O2−NO^{+} < NO < NO^{-} < O_{2}^{-}

Step-by-Step Solution

According to Molecular Orbital Theory, bond length is inversely proportional to bond order; as the bond order increases, the bond length decreases . To find the increasing order of bond length, we must determine the bond order (B.O.) for each species:

  1. NO+NO^{+}: This species has 14 electrons and is isoelectronic with N2N_{2}. Its bond order is 3.0 .
  2. NONO: This molecule has 15 electrons. Compared to N2N_{2}, the additional electron enters an antibonding π∗\pi^{*} orbital, reducing the bond order to 2.5 .
  3. NO−NO^{-}: This ion has 16 electrons and is isoelectronic with O2O_{2}. Following the molecular orbital configuration of O2O_{2}, it has a bond order of 2.0 .
  4. O2−O_{2}^{-} (superoxide ion): This species has 17 electrons. The extra electron further occupies antibonding π∗\pi^{*} orbitals, resulting in a bond order of 1.5 .

Comparing the bond orders: NO+(3.0)>NO(2.5)>NO−(2.0)>O2−(1.5)NO^{+} (3.0) > NO (2.5) > NO^{-} (2.0) > O_{2}^{-} (1.5). Therefore, the increasing order of bond length (the reverse of bond order) is NO+<NO<NO−<O2−NO^{+} < NO < NO^{-} < O_{2}^{-}.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Organic Chemistry – Some Basic Principles and Techniques . Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYOrganic Chemistry – Some Basic Principles and Techniques increasinglength

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