Sciencemadness Discussion Board

detecting alkyl halide in the pot

contrived - 10-3-2007 at 15:53

I'm alkylating something with an alkyl halide and have not found a suitable TLC scenario for monitoing it. Is there an easier way I haven't thought of, for simply detecting the presence, or not, of organo halide?

I'm sorry if this sounds stupid. Perhaps I am. In any case I have forgotten a lot and would appreciate, without going into the reaction details, any insights along this line.

XxDaTxX - 10-3-2007 at 16:21

Yes. (A vague answer for an equally vague question)

Honestly, what problems are you having with TLC? Even freshies in OCHEM1 can do it! I should have you washing my glassware instead of them. hehehhe

It sounds like you are having trouble detecting (visualizing?). If so, more details of your reactant and product would be in order. Do tell Mr. Alkylating With An Alkyl Halide.


[Edited on 10-3-2007 by XxDaTxX]

contrived - 10-3-2007 at 18:32

Here's the issue .. the slurry I made fell off the slides so I wnet back to filter paper. The solvent was hexane. It carried the halide to the top. It appeared as a pretty rose color in I2 vapor. The reaction mixture is colored however and I don't have an RF for the product. A brown spot showed up at the top of the solvent front that I think is my rose colored halide colored by the mixture but I'm not sure the solvent isn't carrying everything with it with no adsoprtive slowing. My terminology may need some work but I hope you get the picture. I'm hesitant to state the reagents as someone could make wrong assumptions about the ultimate products. If it would really help for you to know send me a u2u (?) ...u2u is interpersonal like email within the forum?

contrived - 10-3-2007 at 18:42

PS - I'm envious .. I don't trust my intern with my glassware .. guy never had any lab experience ... he thought my flash evaporator was a Van De Graff generator ... I suspect my TLC solvent system needs more work and I need some help making a (alumina) slurry that will stick to glass.

XxDaTxX - 10-3-2007 at 23:00

If your solvent is pulling reactant or product to the solvent front right away, then change solvent or your ratios. I don't know what your start and end products are so I can't make any suggestions. Try different ratios.

You are spotting both starting product and your reaction mix right? You don't always need RF values.

Having trouble making it stick? What are you using as a binder?

[Edited on 10-3-2007 by XxDaTxX]

contrived - 11-3-2007 at 11:54

I was mixing in a little maltose ... not sure what to try next .. I had maltose from some fermentations I was doing so it seemed worth a try. According to a lab manual I have I should be able to slurry alumina with DCM and have it stick but I don't see how. Anyway, tried it - no joy

XxDaTxX - 11-3-2007 at 20:46

Maltose?! Never heard of that. Alumina TLC binder is normally CaSO4.

contrived - 13-3-2007 at 21:21

You think Na2SO4 might work?

XxDaTxX - 14-3-2007 at 07:13

Starch has been used, although I have to admit I don't know off-hand the relative proportions. I always go with CaSO4 if I need to spread my own plates, there's a reason why its the main choice for binders.

chemrox - 14-3-2007 at 07:57

gypsum? in Me2Cl2/MeOH (trace)?

[Edited on 14-3-2007 by chemrox]