[Boo]

Hi there,

I reacted 1,3-cyclohexanedione with phenylhydrazine in the presence of acetic acid to produce 3-(Phenylhydrazono)-cyclohexanone.  This compound was refluxed for 4hr with 20% sulfuric acid to produce 1,2-dihydrocarbazol-4(3H)-one.



During the 4hr reflux,  black tar was formed on the sides of the reaction vessel (I decanted the liquid to remove this tar).  I was wondering what this tar could be?  Looking online I've found that indole is a main component in coal tar (which matches the physical description of the by-product), but coal tar contains other components not found in this reaction.  Could this tar be indole (or another derivative of indole) formed during this reaction? I've tried to come up with a mechanism for such a process, but every time I try I keep ending up with compound B (the product i was supposed to form, not a side-product!)

I also have a question about the polarity of the compounds formed. I did a reaction TLC during the 4hr reflux, in a 5:5, hexanes-DCM solvent system.  The starting material was compound A.  The TLC showed that the product being formed was more polar than compound A (the starting material had an Rf of 0.3 and the reaction spot remained on the baseline).  I thought the starting material would have been more polar because it has an extra nitrogen? The only explanation I can think of is an electron donating effect from the extra nitrogen to the aromatic ring (but I'm not sure if this makes sense).

Thank you for any direction you are able to provide!

[Vidya]

for the polarity I think in A Nitrogen is bonded to Nitrogen and hence the polarity is less .However in B -N is bonded to Carbon which may be the reason for high polarity.

[OC pro]

Your black tar consists of poorly soluble oligomeric and polymeric material.