A mixture containing three compounds (A-C, see below) will be purified by normal
ID: 712704 • Letter: A
Question
A mixture containing three compounds (A-C, see below) will be purified by normal- phase column chromatography, using silica gel as the stationary phase and hexanes:ethyl acetate as the eluent. Predict the order in which the compounds will elute from the column. YOH H2N Consider the following scenarios. For each case, indicate what effect (if any) would be seen in the separation of a fluorene-fluorenone mixture by column chromatography (as a. While packing your column, you forget to tap the sides, leading to several b. While loading your sample on the column, you mistakenly use methanol to c. Your sample was not completely dissolved when you loaded it on the column. performed in lab), and briefly explain your answer. large air bubbles. dissolve the sample instead of 50:50 ether:hexanes.Explanation / Answer
The compounds A-C are to be separated by normal phase column chromatography using silica as the stationary phase and a mixture of hexanes:ethyl acetate as the eluent. Silica is polar while the eluent is less polar.
A polar solute binds to the polar adsorbent (stationary phase material) more strongly than a less polar or non-polar solute. Consequently, less polar or non-polar solutes are more susceptible to interact with the less polar solvent (eluent) and hence, elutes out faster.
A is the most polar compound, having both a polar carboxyl (-COOH) group and a polar amine (-NH2) group. C is less polar than A, having only a polar ester (-COOR) group. B is the least polar (infact non-polar) compound, since B is a hydrocarbon.
Consequently, A will bind to the stationary phase (silica) strongly and will elute out the last. C will bind very poorly to the stationary phase and will elute out with the mobile phase quickly. Thus, the order of elution is C > B > A.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.