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The answer given is (3)but I am not quite sure about it. I feel it's (2) Can anyone please explain this ? Thank you in advance kind human.

  • 1
    $\begingroup$ why do you 'feel' it's 2? please state your reasoning/working as well in the question $\endgroup$ Oct 16 '20 at 13:08
  • $\begingroup$ Count the available orbitals and eventual electrons that can occupy them. All 3 kinds of atoms have the same orbital count, variably occupied. $\endgroup$
    – Poutnik
    Oct 16 '20 at 16:32
  • $\begingroup$ Feelings are worthless in science. Instead of "I feel", write "I think" followed by arguments. $\endgroup$
    – andselisk
    Oct 16 '20 at 23:25

Structures 1 and 2 can be draws in alternate forms, specifically, in 1, a double bond between the C and the N atoms is an accepted alternate configuration. In 2, similarly, a double bond between the C and B atoms gives a different configuration. In both cases, the electron charge distribution is now "dispersed" differently relative to the original structure as drawn. Remember, these are all constructs, or our way of understanding such molecules. In structure 3 however, aromatic stability of the six member ring can not be changed without creating a 5-valent carbon atom and and 5-valent nitrogen atom. So there are no alternate structures for 3 as there are for 1 and 2.


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