Fortunately, all of the ones that overlap are never in the same preparation. The second distillation appears unnecessary in this experiment. After drying the product, don't let students forget to transfer it to a clean, preweighed vial, and reweigh it to determine the actual and percentage yields. We like to require the students to allow us to examine their final product before they are allowed to determine an infrared spectrum. In this way we can intercept any samples that are cloudy or otherwise show the presence of water.
Wet samples have to be redried.
See the comments on sample storage in one of the major sections above. Friedel Crafts Acylation Vacuum distillation is optional in this experiment. The crude products are sufficiently pure to yield spectra which are virtually identical to those of the products obtained after vacuum distillation. In the microscale experiment, an individual student may not have enough material to perform an effective vacuum distillation. We usually have 2-3 students work individually using the same starting material and then combine their crude products for distillation.