OC Question - aromaticity

[CornHusker]

Anyone have a confident answer to this?

If you had a molecule like 1,4-dioxin (1,4-dioxane wit the double bonds), would you call that non-aromatic or anti-aromatic? I was taught that in molecules like these with heteroatoms, the lone pair's would not be incorporated into a the pie bond system because anti-aromatic is less stable than non-aromatic. However I came across a question in my ACS OC study book that claims it would be anti-aromatic with 8 pie electrons.

This is probably beyond the scope of the exam but I'm shooting for a 30 of my OC section and this question has been bothering me for some time now.

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[510586]

Always count one set of pi electrons OR one lone electron pair (as 2 electrons) at that given atom. This one I would count the 2 double bonds as 4 pi electrons total and then 2 lone electrons at each Oxygens so that would be 8 pi electrons for the whole compound. Thats how I always did it. Or you can resonate the O electrons down but I usually just do it like how I mentioned. Google actually says that this is a nonaromatic compound.

 

[CornHusker]

Haha ya pi, not pie...woops (I must be hungry)

I'm pretty sure it would be nonaromatic but I could see a question like "Which of the following are anti-aromatic?" and them assuming us to decide that it would be anti-aromatic based on a basic understanding of Huckel's rule, kinda like the ACS question asked. But in reality it is nonaromatic.

 

[510586]

Haha ya pi, not pie...woops (I must be hungry)

I'm pretty sure it would be nonaromatic but I could see a question like "Which of the following are anti-aromatic?" and them assuming us to decide that it would be anti-aromatic based on a basic understanding of Huckel's rule, kinda like the ACS question asked. But in reality it is nonaromatic.

This is situational though. At my school one of the teachers used to treat cyclooctatetraene as an antiaromatic compound even though it is nonaromatic (nonplanar). I hope the DAT is better about things and is more clear cut. Luckily we have orgoman, Chad, and people who scored very high to clear up a lot of these things. I think cyclooctatetraene being nonaromatic is the only exception to the rules that we should know right?.

 

[DAT Destroyer]

Anyone have a confident answer to this?

If you had a molecule like 1,4-dioxin (1,4-dioxane wit the double bonds), would you call that non-aromatic or anti-aromatic? I was taught that in molecules like these with heteroatoms, the lone pair's would not be incorporated into a the pie bond system because anti-aromatic is less stable than non-aromatic. However I came across a question in my ACS OC study book that claims it would be anti-aromatic with 8 pie electrons.

This is probably beyond the scope of the exam but I'm shooting for a 30 of my OC section and this question has been bothering me for some time now.

This is THE MOST DIFFICULT question ever posted on this forum ! I award you the PRIZE. I hope you are sitting down.

This molecule1,4-dioxin is the " darling " of Advanced Organic Chemistry. Usually, if you see 4 or 8 pi electrons the molecule is likely to be anti-aromatic. BUT...not here.
Why ?
Anti-aromatic molecules are very unstable. This molecule has been been studied with advanced molecular orbital techniques known as ab initio calculations. We have found that the molecule is NON-AROMATIC. The molecule seems to avoid being anti-aromatic by not allowing significant electron delocalization....a condition of anti-aromaticity. The pi electrons from the carbon bonds and the electron lone pair on the oxygen atoms do not overlap to a significant degree. This allows the molecule a way to " escape " being anti-aromatic.

There is no way you would know this by just simple inspection. Much research and study has been done on the specie. Thus the correct answer is NON AROMATIC.....even if some book authors call it anti-aromatic.

I hope this helps.

For the DAT.....spotting an aromatic specie should suffice !

Best wishes, Dr. Romano

 

[CornHusker]

Sweet! Gold star is going on the fridge today!

Thanks for helping clear that up. My mind can rest easy now haha.

 

[DAT Destroyer]

Sweet! Gold star is going on the fridge today!

Thanks for helping clear that up. My mind can rest easy now haha.

Make it double gold stars!