I have a question that I really hope someone can help me with, I need to answer some question about Environmental Analitical Chemistry and I'm having troubles with these two:
I need to incidcate the correct expected eluition order of four molecules analized HPLC with normal phase: the molecules are benzene (PhH), phenol (PhOH), chlorobenzene (PhCl) and acetophenone (C6H5-CO-CH3).
Now, I know that in normal phase I do expect to see exiting first the more neutral molecule, and last the more polar one, problem is that I haven't been given any tools to precisely evaluate and match the polarity of a molecule respect to others so similar.
I'm pretty sure the first one, the more neutral one, is for sure the benzene (PhH).
Then, trying to compare them considering polarity as charge/mass ratio, I'd go with acetophenone as the second molecule expected, since its low polarity is spreaded on a bigger surface.
Third I'd go with chlorobenzene (PhCl), since its charge is spreaded on a smaller surface.
Lastly I'd say phenol, since it's ability to from hydrogen bonds makes it the most polar of the group.
So my answer would be:
Is my reasoning correct? Can anyone provide me with a reliable tool/strategy to correctly evaluate the polarity of such similar molecules?
The second question is practically tha same, but in HPLC in reverse phase, so I expect first the most polar one. The molecules in this one are: Naphtalene, Nitrobenzene (PhNO2), Salicylic acid, Chloroform.
Iintially I've put them in this order:
1.Chloroform (since I thought that its small charge against such a small surface gave it a greater polarity)
2. Salicylic acid
But I've seen that the correct one is:
1. Salicylic acid
Because Chloroform is poorly soluble in water.
So it's clear that I have quite a bit of confusion about this topic, but I wasn't able to find any answer elsewhere.
Can someone help me out?
Thank you so much in advance!