This is totally something I should know for myself, and I think I have it figured out, but I want confirmation. If you were to run a TLC plate of 2-octanol and 2-octanone, which would have the greater Rf value? The ketone, because it’s more polar, is my assumption, but before I write it into my lab report, I’d kind of like to know. 
I forgot to include the little detail of which spot was which when I copied the TLC plate… Stupid, stupid, stupid! LOL
Thanks!
What kind of TLC plate? There are cellulose, silicon compounds, etc…, all varying in their polarity, charge, and half a dozen other things. Rf values will be vastly different among all of them.
Also, what solvent system were you running?
It breaks down to three things:
what was your stationary phase (i.e. the plate itself)
what was your mobile phase (i.e. the solvent system)
how many dimensions were you running? If more than one, were you using different solvent systems?
Clarify these points and I might be able to help you.
Good luck!
MM
sorry, i should have known to be more specific. I really just wanted to double check on which is more polar, an alcohol or a ketone.
The mobile phase is 20% ethyl acetate: 80% hexanes, and the stationary is…I dont know...the regular TLC plate from the labs... I think its silicon-based. I really dont know, since it doesnt seem to have been specified anywhere. And its only a single run, with iodine fumes to make the spots show up. I cant help you with more than that.
Its a polarity thing, so basically, which is more polar? I think its the ketone (those good old lone pairs) but I want to be sure. I’d hate to mess up on something that stupid for this report (I mean, we did this TLC plate JUST to see this result).
Thanks again!
Here’s some stuff straight out of my research notebook from a couple of years ago. Undecylenic acid (11 carbons with an alkene group at one end and carboxylic acid group at the other) has an Rf of about 0.7 using silica gel TLC and a 75%hexane/25% ethyl acetate mobile phase. The methyl ester of this acid is about 0.88 Rf.
Of note is the acid forms a comet shaped spot ( a central dark spot that streaks down to the origin). I’ve been told by a real organic chemist that this is characteristic of carboxylic acids.
The ester is not retained as well as the acid on the solid phase, I believe because of hydrogen bonding that occurs with the acid but not with the ester. I would think your alcohol would also be retained more (lower Rf value) because of hydrogen bonding.
I don’t know for sure but I don’t think the ketone is more polar than the alcohol. But I am pretty sure the alcohol will have the lower Rf because of hydrogen bonding.
I didn’t even think of hydrogen bonding!!! Grrr I think I’ll just leave blanks in my report (its in a notebook and not typed) and just fill them in later… My conclusions don’t change anyways, since there are only two spots, it’s one or the other at the top of the plate :). Hopefully I’ll be able to ask someone before I have to hand it in. I just don’t see anyone from that lab on Mondays, and I want to get it done asap.
Thanks anyways! (and if anyone else can tell me, fell free to! )