Why must the alkyl halide product be dried carefully with anhydrous calcium chloride before distillation?

1 Answer
Mar 1, 2016

Because if it is not dried, you are likely to get some water vapour in your distillate.

Explanation:

Even if it is a volatile alkyl halide, distillation will always carry over some water vapour if water is present. Drying prevents this (and of course you don't want wet product, especially if you trying to make an organometallic reagent. Small quantities of alkyl halide can be dried simply by passing the NEAT liquid down a Pasteur pipette plugged with some glass wool and filled with basic alumina. I would always do this for a Grignard reaction.