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

Question

Skylar Alexander · Accepted Answer

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

Drying prevents this (and of course you don't want wet product, especially if you're trying to make an organometallic reagent). For a Grignard reaction, I would always pass the NEAT liquid down a Pasteur pipette plugged with some glass wool and filled with basic alumina to dry small quantities of alkyl halide. This is true even if the alkyl halide is volatile.

Nicholas Antonuccio · Answer

undefined The alkyl halide product must be dried carefully with anhydrous calcium chloride before distillation to remove any water present in the solution. Water can interfere with the distillation process by forming azeotropes with the alkyl halide, leading to impurities in the final product. Anhydrous calcium chloride is a desiccant that effectively absorbs water, ensuring that the alkyl halide is dry and pure before distillation.