Question

How do you use TLC to determine the identity and purity of E-stilbene and stilbne dibromide. Also, refrecing intermolecular forces predict how stilbene dibromide would move on a TLC plate relative to E-stilbene

Answer 1

TLC or thin layer chromatography could be useful in the determination of identity and purity of E-stilbene and stilbene dibromide.

• It is useful in monitoring the progress of reaction, whether it is proceeding or has gone to completion. The disappearance of one spot of E-stilbene and the appearance of a different spot over time from the reaction mixture on the TLC indicates that the E-stilbene has been converted to stilbene dibromide. Further, when the compounds are spotted together with a pure sample on a TLC plate, the compound will show a single spot parallel to that of a pure E-stilbene and stilbene dibromide.

The intermolecular forces could be helpful in predicting how stilbene dibromide would move on a TLC plate relative to E-stilbene

• Trans-stilbene will have relatively high Rf value in any given condition and solvent as compared to the stilbene dibromide because it is a non-polar molecule and so does not interact with the polar molecules in the silica gel. Further, the bromination of E-Stilbene results in greater polarity in the stilbene dibromide. Thus, stilbene dibromide will bind to the polar stationary phase (low Rf), while the non-polar E-Stilbene will travel well with the non-polar mobile phase (high Rf).