Why does iodine absorb organic molecules? This question is referring to the effect of the iodine chamber used in TLC.

Answer 1

Iodine has a high vapor pressure, for a solid, plus it is quite reactive to unsaturated compounds. The long and short of it is that iodine has a high affinity for organic compounds and because it vaporizes easily it can stain those spots on a TLC plate that are colorless thus making them visible. Care must be taken to circle the spots on the plate lightly (with a pencil) for the I2 often does not stay put when the compound is removed from the staining vessel.

Answer 2

Thank you!! =]