[foxthreefour]

So I'm performing a halogenation reaction of a ketone with CuBr and EtAC to create the a-bromoketone. I've made an error in my calculations and used slightly wrong molar amounts, and a volume of solvent less than half of what was supposed to be used. During the reaction it is supposed to be a deep green colour, followed by amber once the HBr has been evolved from the solution, and the reaction is complete, this takes generally six hours. I've performed this with the correct ratios before and seen it progress properly, with a quantitative yield.

So the six hours is up and hardly any HBr has been seen evolving from the reaction vessel, normally there's quite a bit. The reaction mixture is a dark red/brown and there looks to be only Copper(i) Bromide recovered, so it seems as if the reaction has taken place. The mixture has a lacrymator effect which indicates the a-bromoketone is present, but in what quantity I'm not yet sure.

The ratios I used were:

1M Ketone
2M Copper(ii) Bromide
600ml EtAC

The ratios I was supposed to use were:

1M Ketone
1.6M Copper(ii) Bromide
1600ml EtAC

I'm wondering if the reaction was too concentrated in that volume of solvent to proceed properly. If perhaps another product has been formed because of the error. I've been told that a slight excess of ketone is advisable to avoid di-bromonation but not sure if that comes into play here, any insight would be appreciated.

[foxthreefour]

*UPDATE*

So I've realised that the recycled/distilled EtAC I've been using has formed an azeotrope and the reaction also had water in it to top it off. Would still love some insight if anyone has anything?

[mjc123]

You say the reaction involves CuBr, but you say you used copper(II) bromide. Was that just a typo, or did you use the wrong compound?

[foxthreefour]

Sorry, typo. It was Copper(ii) Bromide that was used.

[mjc123]

You mean CuBr was a typo and you used (and should have used) CuBr₂?