Sciencemadness Discussion Board

Is this an aromatic compound ?

red_heat_cat - 16-10-2006 at 01:57

Is this compound an aromatic? I don´t think so because there are 7 pi electrons in the ring. Is that right?

1.jpg - 46kB

woelen - 16-10-2006 at 02:16

No, this is not an aromatic compound. It is not derived from a benzene ring (or a benzene ring with a C replaced by N).

Nerro - 16-10-2006 at 03:06

Neither is THF woelen but that's aromatic :)

This molecule is not aromatic simply because it has no space for the third pi bond, the p orbital that is directed perpendicular to the plain is already full, if it has been empty (if there had been a B there) the ring would have been aromatic.

[Edited on Mon/Oct/2006 by Nerro]

garage chemist - 16-10-2006 at 04:01

THF is not aromatic.

Perhaps you meant Furan, Nerro?

[Edited on 16-10-2006 by garage chemist]

Nerro - 16-10-2006 at 04:55

yes I did. (5 ring with 4 carbons and 1 nitrogen. between the carbons there are two double bonds.)

woelen - 16-10-2006 at 06:43

Nerro, I indeed should have been more clear in my answer. I was referring to the benzene ring because of the six-membered ring in the molecule, presented by red_heat_cat.

But aromaticity is a more general concept, e.g. the ion C5H5(-) also is aromatic, while it is not a six-membered ring. No classical model of this ion can be written, 5 electrons are delocalized over the 5 C-atoms.

Nerro - 16-10-2006 at 07:01

not true, the ring has 4 + 2 electrons in its ring which complies with the rule.

C5H5- is a lot like pyrrole really, only nitrogen has a lone pair naturally while carbon only has it when its an anion.



[Edited on Mon/Oct/2006 by Nerro]

[Edited on Mon/Oct/2006 by Nerro]

solo - 16-10-2006 at 07:29

Reference Information



Introductory Organic and Biochemistry -What does "aromatic" really mean?


http://www.geocities.com/athens/thebes/5118/obc/arom.htm

woelen - 16-10-2006 at 09:18

Solo, thanks for that nice link. I again learnt something new and this is quite an interesting thing to learn and helps me understand things.

Pyrovus - 16-10-2006 at 16:26

That compound is aromatic. By redrawing it like this it should become apparent. Hopefully this image displays properly:




[Edited on 17-10-2006 by Pyrovus]

aromatic.gif - 2kB

chemoleo - 16-10-2006 at 16:39

Thanks for clarifying this Pyrovus. Precisely my thinking. This should make a nicely reactive species. The NO2 group acts as an electron acceptor (similar to picric acid) making this species more stable. Remember, styrene is also reactive, not only for polymerisation but also to form the seperate charge species which are stabilised by resonance/pibonding.

Thought first this might be for 'Beginnings' but due to the discussion it'd might be just right here in org chem :)

JohnWW - 21-10-2006 at 17:17

Separation of charges, in this instance to form a combined quaternary oxy-ammonium salt (two benzenoid resonance structures) and aliphatic carbanion, takes a fair amnount of energy. To contribute to the overall structure, the overall gain in stability through this would have to be significant compared to the other non-aromatic resonance structure shown at the start of this thread.

Nerro - 22-10-2006 at 00:59

Quote:
Originally posted by JohnWW
Separation of charges, in this instance to form a combined quaternary oxy-ammonium salt (two benzenoid resonance structures) and aliphatic carbanion, takes a fair amnount of energy. To contribute to the overall structure, the overall gain in stability through this would have to be significant compared to the other non-aromatic resonance structure shown at the start of this thread.
precisely my thinking.