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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Brook on July 23, 2013, 01:16:23 AM

Title: Pyran cation antiaromatic?
Post by: Brook on July 23, 2013, 01:16:23 AM

If I have a molecule like the one shown, is it antiaromatic because it does not satisfy Huckle's Rule; it only has 4 pi electrons?

Title: Re: Pyran cation antiaromatic?
Post by: Brook on July 23, 2013, 01:16:57 AM

My apologies for the extremely large picture.

Title: Re: Pyran cation antiaromatic?
Post by: limonade on July 23, 2013, 01:37:33 AM

It is actually going to be aromatic because the oxygen is sp2 hybridized. One of the lone pairs on oxygen is in a p orbital. So the number of pi electrons is actually 6. The molecule is planar , and has continous circle of p orbitals. So all conditions satisfied, it will be aromatic.

Title: Re: Pyran cation antiaromatic?
Post by: PhDoc on July 23, 2013, 08:29:31 PM

Yep, aromatic. I typically test student for both aromaticity and resonance at the same time via questions just like this. I would suggest getting more of these examples. If not available, ask your professor to assign "extra problems for the class."