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The name chlorobenzene represents the following molecule.

enter image description here

But the molecule shows resonance and its resonating structures are enter image description here

So does the same name represents all the resonance structures? Does it also represent the hybrid structure of these structures? When I used this service to find the name of the last structure I found its name to be Chloraniumbenzenide. See this image. But interestingly when I used the same service to get back the structure from the name it gave me an error. Google search also didn't give good results.

Osmium
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    Please note: The molecule shows resonance and therefore it has resonance structures. It has nothing to do with the classical concept of resonating, therefore the term you are using (while unfortunately get popular) conveys the wrong meaning. For more on resonance, I highly recommend https://chemistry.stackexchange.com/q/51632/4945 – Martin - マーチン Feb 06 '22 at 15:21
  • @Martin I know that. I know that only resonance hybrid is the correct lewis structure of a molecule and not the resonance structures, in the sense that it helps use explain observations. But that doesn't stop us from naming the resonance structures. Zeus is an imaginary character but it still has a name. In many places for example on wiki it can be seen that the name chlorobenzene is used for the first structure and resonance hybrid structure (3d model). My question was whether the same name represents all other resonance structures as well or do they have different names of their name. – Osmium Feb 07 '22 at 03:28
  • https://www.wikiwand.com/en/Chlorobenzene – Osmium Feb 07 '22 at 11:25
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    My comment was not about naming hypothetical structures, or even about whether or not they are correct (they are valid Lewis structures after all, a resonance hybrid technically is not as it is an extension to the original concept). These are concepts with limitations, and for nomenclature there are different rules or conventions that may or may not convey these technicalities. I was merely pointing out, that they are called resonance structures and not resonating structures. This might seem nitpicky, but I still think it's important. – Martin - マーチン Feb 08 '22 at 02:35

1 Answers1

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One should be careful with the structures to be submitted to a structure2name conversion.

The one you showed for chlorobenzene are formally correct

enter image description here

however the first one is the preferred one because it describes a structure lower in energy than the one with separated formal charges and charge separation costs energy. In addition to this, specific to this example, recall chlorine is more electronegative than carbon; in Pauling's scale (reference), EN(Cl) 3.16, EN(C) 2.55 - thus, it is not that likely chlorine would donate valence electrons to the more electropositive carbon.

Grossman condensed the (empiric) rules about resonance formulae to a set of four of decreasing order of importance. To quote (emphasis in the original):

  1. No first-row atom (B, C, N, O) can have more than eight electrons in its valence shell. (The octet rule is less sacred for heavier main group elements such as P and S, and it does not hold at all for transition metals.)

  2. Common error alert: Resonance structures in which all atoms are surrounded by an octet of electrons are almost always lower in energy than resonance structures in which one or more atoms are electron-deficient. However, if there are electron-deficient atoms, they should be electropositive (C, B), not electronegative (N, O, halogen).

  3. Resonance structures with charge separation are usually higher in energy than those in which charges can be neutralized.

  4. If charge is separated, then electronegative atoms should gain the formal negative charge and electropositive ones should gain the formal positive charge.

Now you may set the description of e.g., DMSO

enter image description here

into context, too.

Reference:

Robert B. Grossman. The Art of Writing Resonable Organic Reaction Mechanisms. Springer 2003 (second edition), p. 5. He moderates a companion web-site pointing to all (currently) three editions, supplementary material, and errata, too.

Buttonwood
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    I disagree with this answer. Resonance structures cannot be separated from each other, they cannot be measured, they do only formally exist. The notion that one structure is lower in energy than others of the same set implies a stability that doesn't exist. While I can guess I know what you are actually trying to say, is only my interpretation, and in that context, I think this is wrong. And in DMSO there are two electrons omitted, which are important. Arguably, the second structure is the main contributor, which contradicts the set of rules stated before. Details matter. – Martin - マーチン Feb 06 '22 at 15:34
  • @Buttonwood so the same name represents all the structures? – Osmium Feb 07 '22 at 03:21