While the drop in consumption was small at an ArBr flow rate of 1.063 mL min -1 and the product distribution compared favourably with the faster flow rates studied, we elected not to continue with this flow rate for a a few reasons: The first being that use of an ArBr flow rate of 1.063 mL min -1 would force a lithiation residence time of 2 s due to the fixed internal volume of the HTM-ST. Although this is clearly appropriate for bromoanisole 1, it must be noted that this is a relatively unreactive substrate and so requires a longer residence time for complete lithiation. For the realisation of a general purpose reactor through which a variety of aryl halides may be metalated, with the resulting lithiates possessing varying degrees of stability, a residence time of 1 s represented to us the best compromise between enabling the metalation of a the widest range of substrates possible without keeping them in residence (and so at risk of decomposition) for an unnecessarily long time. This was a decision based on our historical experience of using a 1 s residence time across a number of substrates bearing many different functional groups. Our second concern was that any additional decreases in internal volume at an ArBr flow rate of 1.063 mL min -1 that could be realised via shortening the precooling (see next section) loops would result in an reactor that could not be practically mounted into our syringe pump and cooling bath setup. To address this issue, tubing with a narrower internal diameter could be utilised but this introduced the risk of pump stall due to excessive back pressure along with an increased risk of blockage.