Hi everyone, I have two questions about my master thesis:
1) Recently, I conducted a bromination reaction on a 3-alkylsubstituted thiophene with N-bromosuccinimide (NBS) in a lab synthetic chemistry (the solvent was DMF). The reaction work-up consisted of pouring 2.5 M NaOH solution into the reaction flask at 0°C, followed by washing the organic layer with 2.5 M NaOH, water and brine (saturated NaCl) respectively. I think that NaOH is used to quench the remaining NBS but I'm not sure how this happens:
- is it an SN-reaction between OH- and a C=O bond of NBS (resulting in opening of the NBS ring)?
- will OH- split the bond between N and Br? This seems not a logic option to me, however.
And I have absolutely no clue about this NaCl thing...
2) When performing a nickel catalyzed reaction to couple an organozinc compound (R-ZnBr) to 3-bromothiophene, why would one use LiBr as an additive? I've searched all over the internet --Wikipedia just says that 'it is useful as a reagent in organic synthesis'-- but I can't find a satisfying answer to my question.
Can someone help me with these topics? Your help is greatly appreciated!