vimal - 31-1-2005 at 18:40
I am unable to predict this product!
The question (In Indian National Chemistry Olympiad 2005) says:
Benzene does not undergo D-Alder that easily, but when treated with hexafluoro 2-butyne, it reacts forming a compound (A). identify (A)
Have you seen this problem anywhere? If yes, please tell me 
and if possible, a
link to the PDF would be ok
I have read through Morrison and Boyd, and D-Alder with benzene wasnt discussed...
Thanks!
JohnWW - 31-1-2005 at 18:58
I have an idea that it would add across a double bond on the benzene to form a cyclobutene derivative, fused at the 2 and 3 positions to a 6-membered
4,6-cyclohexadiene ring having two conjugated double bonds. But because of the resonance stabilization of benzene which results in its C-C bonds all
having an effective bond order of 1½ rather than 1 and 2, such a reaction would not occur particxularly readily.
vimal - 31-1-2005 at 19:01
exactly what i had thought...
Synopsis - 31-1-2005 at 19:05
Indian olympiads aren't very hard in 2005 so it seems, they give you the answer within the question...
Consider benzene as a diene reacting with hexafluoro-2-butyne as dienophile. It yields a bicyclic adduct named
2,3-bis-trifluoromethyl-bicyclo[2.2.2]octa-2,5,7-triene...
[Edited on 1-2-2005 by Synopsis]
BromicAcid - 31-1-2005 at 19:09
Indeed it takes a very reactive dienophile to get a reaction with benzene with a Diels-Alder but I have seen it done. My nomnclature is pretty screwy
though so I can't describe the product in the correct terminology. But going from how benzene normally reacts in a Diels-Alder I would assume it
is a six membered ring, double bonds across from one another, attached at the 1 and 3 positions to a chain of two carbons (containing a double bond
between them) so you could turn it and it would look like the same six membered ring except they would have a CF3 group hanging off each. Jeeze, my
nomenclature sucks.
vimal - 1-2-2005 at 00:00
No!!
This was just a part of the question... the rest were pretty hard...which actually required a LOT of thinking!
ok. now, the dianion of cyclooctatetraene is aromatic. write the product of its reaction with acetone.
i would also like to know various other possible diels alder type reactions and their products.
if cyclooctatetraene reacts with a peracid to form an epoxide (1 eq only), what is the product when this epoxide is treated with a lewis acid?
i am asking these just to confirm my answers 
Thanks!
JohnWW - 1-2-2005 at 01:37
Actually, both the dianion and dication of cyclo-octatetraene are aromatic, with delocalization of the charges. The dianion can be formed by direct
reaction of alkali metals with cyclo-octatetraene. But because of the greater strain of the 135º angle, the resonance energy is less than for
benzene.
Even so, the reaction of acetone, if any, with the cyclo-octatetraene dianion would be slow or difficult to get started. I cannot find any reference
to it. Acetone does not react with benzene.