Good morning Steve and others,

 

     I'm writing to find out if anyone can explain a phenomena that I've observed while working on my research. I synthesized about 50 mg of 1-(3',5'-O-diacetyl-B-D-ribofuranosyl)-uracil. (This molecule is uridine with acetyl groups replacing the 3' and 5' hydroxyls). I was able to obtain this product as a white, crystalline solid.

     If I dissolve this compound in duterated chloroform, and then evaporate the solvent, the compound does not crystallize. I obtain it as an oil. If I dissolve the compound in dichloromethane, and then evaporate the solvent, the compound doesn't crystallize. Again, I obtain it as a transparent oil. Now, if I dissolve the compound in dichloromethane, and then add about twice the volume of petroleum ether, the compound precipitates as a white solid. I can evaporate the solvent and obtain beautiful, white crystals.

     Why on earth is the compound coming out as an oil from deuterated chloroform and straight dichloromethane? Why doesn't it precipitate out as a crystalline solid as the volume of the solvent decreases?

 

Thanks in advance for any help,

MikeKL5