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According to my book the answer is given that structure III is the most stable because all the atoms have complete octets.

But I think it should be II because of,

(a) Structure III has positive charge on a highly electronegative atom and

(b) In structure II, the positive charge can be stabilized by the Indicutive effect of Oxygen as well as resonance.

Can anyone provide a more convincing explanation as to why III is more stable?canonical structures

RukshanJS
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student
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    The principle of resonance structures is that they are all equally stable, or rather that you cannot separate them from each other as only together do they show the character of the overall compound. There is no energy change between these, all three describe the same compound. That said, there is a most contributing structure which is III. – Jan Dec 16 '19 at 08:28
  • @Jan your comment is at least obscure. – Alchimista Dec 16 '19 at 10:52
  • Whoever wrote this oversimplified problem/answer deserves not to be killed but an even worse fate, showing up in Green Bay with Chicago Bears gear after the recent NFL football game. – Oscar Lanzi Dec 16 '19 at 19:31
  • Why this is off topic? – Alchimista Dec 17 '19 at 10:26

1 Answers1

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You're supposed to recognize that oxygen which has more valence electrons than carbon can take on the positive charge without giving up its octet, thus favoring Structure III.

Now, is it really true that the oxygen atom has more positive charge than the formally positive carbons in the other two structures, when oxygen is also more electronegative versus the octet rule? I suspect that is beyond the scope of your course material. You have to accept a higher priority for the octet rule in this situation whether that is real or not.

I hate oversimplified textbook problems :-( .

Oscar Lanzi
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  • "Now, is it really true that the oxygen atom has more positive charge than the formally positive carbons in the other two structures, when oxygen is also more electronegative versus the octet rule?"What does this statement mean? – student Dec 18 '19 at 08:30