2-Bromo-2-methylpropionic acid can be left over in a workup after doing a reaction using a slight excess of α-bromoisobutyryl bromide, it is easily removed by liquid/liquid extraction with bicarbonate added to the aqueous phase. It can be ordered from Sigma Aldrich for a low price, but it I found it had a shorter shelf life than expected, after 1 year my NMR showed a second similar compound. C-NMR is better to analyze this compound as it gives three distinct peaks, whereas its H-NMR has one good peak but observing the hydroxyl is less reliable. However, I have discovered that it is remarkable easy to kugel rohr this reagent and it should be purified by kugel rohr before use. The compound looks very white and flakey when it is pure, like grated coconut, but after 1 year it has a slight yellow colour and instead of flakes it forms large crystalline shards. It has an acrid smell to it no matter how pure it is.