Thiophene rings

[dip12]

Are thiophene rings completely delocalised in a way similar to benzene i.e does it matter what location the sulfur atom is in?

I.e are there different versions of methiopropamine (MPA) that might be different? or would they in effect be identical.

 

[sekio]

Yes, there are different isomers of methiopropamine. And no, the sulfur is not delocalized.

 

[mad_scientist]

Yeah the two positional isomers of methiopropamine do have different activity, the thiophen-3-yl isomer is actually stronger by weight, but is also more difficult and expensive to make, hence why you only see the thiophen-2-yl isomer available for sale.

 

[dip12]

^Interesting.

Wonder if bk_thio's are possible? Probably not worth it for the bk_methiopropamine but maybe thioPV might be next. (Another post about future drug laws kind of gave away thiophene bk's as possibility)

 

[nuke]

Yes, there are different isomers of methiopropamine. And no, the sulfur is not delocalized.

A pair of electrons on the sulfur should be promoted and then thiophene satisfies Huckel's rule, I had thought. It certainly behaves like an aromatic with its electrophilic substitution patterns.
http://www.mymcat.com/wiki/Aromaticity_Introduction

 

[Transform]

I think what seiko is trying to say is that the sulphur does not move around the ring in as a delocalised atom. It certainly has a delocalised lone pair.