[wonka_vision]

Hello,
I'm currently working on the final step of a monomer synthesis. The reaction scheme of this step is shown here: http://i.imgur.com/56ymZ.png

In trying to develop a solvent system to separate the final product, I figured I would begin by doing silica TLC with 10%hexanes in 90% ethyl acetate and then stain with iodine to show the final product. I do get one spot that stains pretty nicely just below the solvent front, but when I irradiate with UV the same spot illuminates along with a spot just beneath it.
I can't think of any real chromophores present in this system or any potential side products.
Why would there be anything showing up on TLC after UV irradiation?

Thanks!

{MOD Edit -- embed image}

[Dan]

Could it be unreacted starting material? I've not worked with non-aromatic alkyl bromides, but C-I bonds can certainly result in a chromophore, so maybe C-Br can too?

I would also check the silica stability of your product - I would not be surprised is it's fairly unstable. Run a 2D TLC, it may be that the second spot is a product of silica promoted degradation.

[discodermolide]

What does the NMR look like? Does it show a relatively clean product?