[_cheers]

I think the size of this molecule is screwing me up a bit...is there two signals? One multi at 3 and one multi at 9.3?

relative to benzene..the inner hydrogens are more deshielded because of ? and outer less because of ??

Thanks for any hints!

[agrobert]

Your reasoning makes sense, you will have shielded and deshielded hydrogen given two different signals.  Where the peak arises is also temperature dependent because [18] annulene has several conformations.

Check this out, specifically in the Notes 22.

http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv6p0068

[_cheers]

Thanks muchly...and funny, I saw that article and will reread it

K, I did a quick read on note 22....is the annulene they are talking about a compound with tetrahydrafuran? or should I have 3 signals in my NMR? If so, I cant see where?? and should my shielded protons have a (-) sign? We havent used negative values for NMR....?

Does temperature cause the molecule to rapildy interchange resonance structures? Causing its protons to be more deshielded? and how? and why wouldnt this effect be as strong on benzene-(why is benzene less?) does the lack of bridging in Annulene have anything to do with it?

thanks