Problems with NBS in the response to penicillin bromide.

related topics . NBS brominated
reagents
and brominated reactionsone of my recent experiments was a reaction to bromination with NBS in the penicillin. Condition: NBS 1.05eq. Carbon tetrachloride solvents, reflow,
TLC
trace, trigger is AIBN, the addition is 1/10 of NBS (mass). Made a few times to find a few problems, please help:(1) TLC can not see a new point, it is possible that the product (a bromine replacement) points and raw materials run together, such a situation? Then I made a
mass spectrometrometromety
determined, it was a reaction.(2) It's a headache that I don't get a smooth reaction every time, and my system ends up with a bunch of white solids under carbon tetrachloride, even though the entire solution has turned dark red. In theory, it should be the reaction produced by butyl diamide floating on top of carbon tetrachloride, from this phenomenon can be inferred that the reaction did not take place, because TLC can not see, so I have been confirmed by mass spectrometry, indeed no reaction.a problem, why sometimes it triggers a reaction, sometimes it doesn't? What's wrong with that?.Isn't AIBN a trigger? I don't know if I need light to trigger it after I add AIBN? Is it aiBN that didn't trigger the reaction?how to determine whether the reaction is over, the reaction time, and whether chloromethane is feasible (most of the literature uses carbon tetrachloride, benzene, etc.), feeding ratio and sequence, post-treatment, etc.?problem analysis:nicotine bromide replacement and may run together with raw materials, do not see the new point, I have done, there is also the possibility that the expander has not been selected right, some are still very good to run away, as for the second question, the reaction generated by butylamide static will sink. AIBN is a trigger that, like benzoyl peroxide, does not require light (bromine). No response I do not know, there should be, just how much of the problem, the AIBN volume plus a little more, spin dry directly to the next reaction How to deal with after the reaction to remove these things? ( 1) Excess NBS (2) excess AIBN dissolved in carbon tetrachloride or the residual bromine of its decomposition product (3)this is important because it directly affects my next reaction, these things are best removed a little bit.recommendation: 1, AIBN is a heat trigger, 60 degrees is the production of free fundamentals, you can try to first
heating
to 60 degrees and then stop heating 2, be sure to no water anaerobic 3, avoid light 4, it is best not to use carbon tetrachloride as a solvent, too toxic, replaced with DMF and acetate, Or chloroform and acetic acid, this does not add AIBN triggered, because acid can also trigger NBS 5, solvent change time please note that if you want your product to be presumed, you have to choose some not very good soluble, solvent volume should also be as small as 6, this reaction I do when nitrogen protection is necessary raw materials and products or very close to the multiple start can be seen more clearly as if not so strict waterless bar. Carbon tetrachloride I was set up a distillation device re-steamed, neither intentionally to avoid light nor to light is to add things in the heating to the return flow, the reaction liquid will gradually change to orange-red 1 to 2h good, the reaction is complete directly
filtration
filter cake washed with carbon tetrachloride, and then concentrate it.
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