Thursday, June 11, 2009

resolution

I was taking the products from the distillation and resolving them via their tartrate salts, and decided that was inefficient to do individually on a reaction by reaction basis. I saved up the products from all the remaining reactions I had, and started the resolution on a large scale today. On the left is all the product from the distillations of material in 7 volumes of solvent, and on the right is an equivalent of acid in about 7 volumes as well.



They are heated to boiling and then combined (adding the amine to the acid), and, when it works well, the salt starts to crystallize out immediately.



After cooling it is filtered and washed. One of the wonderful things about a good chiral resolution that is not often mentioned is that in addition to increasing diastereo purity, it increases chemical purity as well.


The product should be > 99.5% ee after one recrystallization, and I can take the dark mother liquor, free base the salt, and crystallize it with D-tartaric acid to get it with >99.5% ee.

2 comments:

Dr. Miller said...

why does it say 88% ee in the picture and 99.5% ee in the text? How many recrystallizations does it take to get 99.5%?

scientist 1 said...

The text says "The product should be > 99.5% ee after one recrystallization".