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Topic: Quickie: Why is oxazole aromatic? It doesn't fit the reqs?  (Read 13107 times)

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Offline Fzang

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Quickie: Why is oxazole aromatic? It doesn't fit the reqs?
« on: December 14, 2010, 07:00:04 PM »


Two pairs of pi electrons from the ring itself, a pair from oxygen and a pair from nitrogen. That makes 4 pairs, which shouldn't be aromatic.

But why am I reading "aromatic" wherever I look?

Offline MissPhosgene

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Re: Quickie: Why is oxazole aromatic? It doesn't fit the reqs?
« Reply #1 on: December 14, 2010, 07:18:39 PM »
It is aromatic. 3 pi electrons from the carbons in the ring. Two from oxygen, one from nitrogen.
Stereograms of the 32 crystallographic point groups: little bike wheels of cold, hard, pure rationality.

Offline Hybrid

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Re: Quickie: Why is oxazole aromatic? It doesn't fit the reqs?
« Reply #2 on: December 14, 2010, 09:01:34 PM »
2 pi electron " c=c" & c=n" lone pair of N in sp2 orbital not p orbital + lone pair of O in p orbital. similar to imidazole see here





Offline Fzang

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Re: Quickie: Why is oxazole aromatic? It doesn't fit the reqs?
« Reply #3 on: December 15, 2010, 01:27:41 AM »
So nitrogen only provides an available lonepair if it has 3 bonds?

Offline Hybrid

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Re: Quickie: Why is oxazole aromatic? It doesn't fit the reqs?
« Reply #4 on: December 15, 2010, 01:57:43 AM »
as it "sp2 N" it has 3 sp2 and 1 p so if it make = it will consume the 1 p so every bond after that and its lone pair will be sp2 "not parallel to ring = " so it will be basic.

cupid.callin

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Re: Quickie: Why is oxazole aromatic? It doesn't fit the reqs?
« Reply #5 on: December 15, 2010, 09:10:08 AM »
Acc. to Huckel's rules, a molicule should be planar to be aromatic.
As you asked, N should have 3 bonds, it shoud have a pi bons. if the pi bond C=N is made C-N, it wont be aromatic anymore, you can check by making resonating structures.

If bond b/w C and N is single, due to tetrahedral shape, molicule wont be planar anymore.

Offline Telamond

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Re: Quickie: Why is oxazole aromatic? It doesn't fit the reqs?
« Reply #6 on: December 16, 2010, 11:47:21 AM »
Just want to mention this (since the op's question is already answered); a molecule doesn't have to be planar to be aromatic.
Barrelene is an example of this.

Offline jake.n

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Re: Quickie: Why is oxazole aromatic? It doesn't fit the reqs?
« Reply #7 on: December 16, 2010, 03:18:49 PM »
The hybridization arguments posted above are good.  Typically, if a molecule can be hybridized such that it is aromatic, it will be.  Aromaticity is a strong stabilizing force, and molecules tend to arrange themselves to minimize their energy.

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