Question

Using Thin Layer Chromotography to Analyze the components of analgesic drugs.

Acetaminophen, Aspirin, Caffeine, Ibuprofen

Can you put in order of polarity? (I have seen conflicting answers on the site and other sites)

I have Caffeine as most polar and Ibuprofen as least polar. (some people say aspirin is more polar than Ibuprofen)??

Analyze the structural formulas of Caffeine (most polar) and Ibuprofen (least polar) and discuss the differences in the two substances that account for the different adsorption characteristics.

Answer 1

Thin layer chromatography

Among the four compounds, caffeine is the most polar compound and thus would move slowest on the tlc plate

this is followed by acetaminophen which is second most polar compound.

Third would be aspirin and least polar of all is ibuprofen, which moves fastest on the tlc plate. Ibuprofen due to more hydrocarbon structure is least polar.

Caffeine is highly conjugated sysem and thus would have a high lambda-max value in the absorption spectrum as compared to less conjugated ibuprofen compound.