[darkdevil]

Dear all,
I performed the following Grignard Reaction and obtained a TLC:




First of all, I assumed the reaction proceeded correctly (S = starting material, P = product). But I am not sure what is the difference between using long and short UV for TLC monitoring. I heard someone said the short and long UV irradiation have something related to fluorescence and phosphorescence (please correct me if I am incorrect), but doesnt the two fluorescence and phosphorescence event can only be distinguished by photoluminescence spectrophotometry (small and large stoke's shift)? 

Second question: If the glowing spot is really my product, Does anything related to the allyl group on pyrene do for such change in property under UV irradiation?

Finally, what are the common side products in Grignard reaction?

Thank you so much. I will have my product characterized soonly and update this post.

[Corribus]

It depends on where the molecules absorb. Some absorb better in long UV and some better in short UV. If you don't see anything in one, try the other. That is all.  Short wave vs. Long wave doesn't have much to do with fluorescence vs. phosphorescence. Due to Kasha's rule, you won't usually see much of a wavelength dependence on the way the excited state relaxes.

You'll notice your starting material doesn't really fluoresce. This is because the attached bromine quenches fluorescence by sensitizing efficient excited triplet state preparation. When you lose the bromine in the case of your product, you see that you get a nice blue pyrene fluorescence. This is usually an easy way to monitor whether halogenation reactions work on fluorescent substrates (or dehalogenation on halogenated conjugated substrates).

An organic chemist will have to address the Grignard question.  It's been too long since I did one of those.

[Eloquentia]

Be careful running your product on a silica gel at all. On silica the double bond may migrate to become conjugated to the pyrene system. If you are planning to run a column, try it on a small scale first. Also, avoid acidity. Under acidic conditions the double bond will surely isomerize. I would purify such a material by re-crystallization.