A chemist found that a mixture of four components (Compounds A-D) could be separ

Question

A chemist found that a mixture of four components (Compounds A-D) could be separated on a silica gel TLC plate using 10% diethyl ether in hexanes as the eluting solvent (see "original mixture" far left plate in the figure below). The mixture was then chromatographed on a silica gel column eluted with this same solvent mixture and 11 fractions of 15 mL each were collected. Thin-layer chromatographic analysis of the various fractions (1-11) under the conditions stated above gave the results shown in the figure below: According to these results which fractions should be combined to give pure samples of A, B, C, and D? Which fractions contain more than one component? Indicate for these 'mixed' fraction numbers what components of the original mixture are present.

Explanation / Answer

Looking at the above TLC data,

Compound A : Fraction 1 and 2

Compound B : Fraction 5 and 6

Compound C : Faction 8

Compound D : Fraction 10 and 11

Combination of these would give pure compounds A, B, C and D.

Fraction 3 and 4 has mixture of A and B

Fraction 7 has mixture of compound B and C.

Fraction 9 has mixture of compound C and D.

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