[foxfourfive]

Hi, I need to perform an Allylic Bromination without using pure Bromine. I've read about using NBS and potentially Copper Bromide.

Can anyone suggest the easiest route and amounts necessary? It looks like I'm going to go with the NBS route, but I'm unsure of what would happen to the Succinimide if its left behind, and how to separate if from the Brominated base product.

I know NBS contains around 44% Bromine, does that mean if the reaction required 100g Bromine to be added that I would use 250g of NBS? Does that also mean I'm left with 150g of Succinimide in the solution?

[Babcock_Hall]

Can you write a balanced chemical reaction for the intended process?

[Alwin Kristen]

Bromination with NBS is Wohl-Ziegler reaction. If you use carbon tetrachloride as a solvent, succinimide floats at the surface and you can easily collect it by filtration. You can easily produce more NBS from succinimide.. You need litlebit of Br2 for the reaction anyway. That's why NBS solutions normaly has that reddish color. Mechanically bromination happens like it would happen in Br2 solvent. Br radical reacts with allylgroup resulting allylic anion and HBr. HBr reacts with NBS resulting succinimide and Br2. Br2 reacts with allylic anion. Benefits of Wohl-Ziegler reaction is that you can mono-brominate doublebond. In pure Br2 solution you would have di-brominated doublebond as mainproduct, mostly.

To know how much you would need NBS and bromine, you should calculate amount of substance needed in moles, instead of grams. Bromination with NBS happens with quite good yield.

[foxfourfive]

Thanks Alwin,

The reaction requires 1.05 moles of Bromine, and I'm using NBS as a substitute. I calculated that NBS contains roughly 44% Bromine is that correct?

The problem I have is that the reaction of the base product is in Acetic Acid and I need a way to remove the Succinimide from the solution before evaporating off the volatiles by vacuum distillation.

[Babcock_Hall]

I usually calculate the mole ratio of compounds in a synthesis, then calculate their masses using their respective molecular weights.  In other words if I were using NBS, I would not use the value of 44% directly.  That does not necessarily mean your method is incorrect.

[discodermolide]

I agree with Babcock Hall.
Calculate in moles then convert to mass of the respective compounds.
The value of 44% Br is irrelevant.