[tachyneurogen51]

In my lab class we were making the product 4,4-diphenylbut-3-en-2-one via Grignard reagents.  I refluxed the ketal solution, placed it on the rotovap to remove the ether, and then placed a cap on my receiving flask.  When I went to measure out my product for NMR preparation ant  it turned into a viscous, tan solid inside of my pipet.  I used ether to dissolve the solid, and then prepared my NMR sample.  The experiment used HCl and acetone to remove the protective ketal, then I added water, ether, sodium bicarbonate, magnesium sulfide  prior to the rotovap.  If anyone has a clue what type of compound could have been formed I would appreciate the help.  The only thing I can guess is that there was some sort of radical reaction when exposed to the air.  None of my classmates experienced this problem though.  Go figure.  Thanks!