organic chemistry lab pre lab column chromatography
Pre-lab preparation: Refresh your memory by rereading the intro to TLC in Exp 7, then
read this write-up, carefully in its entirety.
(1) Briefly state the purpose of this experiment. (2) When applying a mixture of compounds to a chromatography column, should you (i) try to get the mixture completely onto the silica using as little solvent as possible, (ii) dissolve the sample in the first 10-mL portion of solvent, then add that solution to the silica, or (iii) add the sample to the column, then add the first portion of solvent to dissolve it inside the column. (3) Why is it always better to transfer 1 mL of a solution with a pipet instead of by pouring it? (hint: oink) (4) In Part A you will start with 30 mg of material. How many grams is this? (5) Near the end of the introduction, the TLC analysis of 20 5-mL fractions from a column is illustrated. Suppose we had instead collected everything that eluted from the column as just 4 fractions of 25 mL each. Sketch the TLC plate that we would have gotten from running those 4 column fractions. (Read carefully and think — that says four 25-mL fractions, not every 4th 5-mL fraction.) (6) You will be using ethyl acetate and hexane in this experiment. What are their boiling points? (7) Ask The Google what ailment is caused by inhalation of significant quantities of silica dust.
