Hey,
I wasn't quite sure where to put this thread, feel free to move it to a more appropriate section if I got it wrong. So, I have 4 compounds and have to predict what would happen with different mobile phases on SiO
2 stationary phase (TLC).
1. Mobile phase consists of CH
2Cl
2:CH
3OH:H
2O (17:2:1). I think this is more or less a no brainer, compound 1 travels the shortest distance and Rfs increase in the order of 1
4, since MP is relatively non-polar.
2. But now instead of water, we have HCOOH (1 part). I'd reckon this means all of the basic centres in the compounds above get protonated and travel a shorter distance, proportional to the quantity of protonated N-atoms in the amide bond. Is it really this simple? I'd say that compound 1 is, relatively speaking, the least polar of the four after protonation. But, since the resonance structure of an amide bond clearly shows a partial positive charge on the nitrogen, does this perhaps mean it is hardly basic at all? But then, the TLC would look exactly the same or am I missing something here?
The task basically requires me to draw TLCs 1) and 2) parallel to one another for comparison of Rf.
Thanks for any and all clarification!