Polarity and Gas Chromatography

[fealomwen]

I'm supposed to put four compounds in the order of time they will spend on a polar and a non-polar stationary phase in a gas chromatograph. The compounds are a carbon ring with an oxygen, a benzene ring, a cyclohexane, and a compound with a tertiary amine and a ketone. The boiling points are also given, respectively 66, 138, 121, and 166. I can't figure out if I should use just the polarity or somehow also use the BPs. As I understand it, on a polar column, the non-polar compounds would move faster - so cyclohexane is fastest, then benzene, then the ring with an oxygen, and then the amine / ketone compound would be slowest. The reserve would be true on a non-polar stationary phase. Are the benzene and cyclohexane close enough in polarity that the boiling points should be used instead?

 

Thanks

[Kaeroll]

I'm guessing you're meant to use the boiling points as a guide to polarity, assuming the molecular weights are all within a tight range.

 

I would tentatively suggest that cyclohexane is more polar than benzene due to the symmetry of benzene, but I've not seen any data on this so it's merely speculation.

 

Edit- scrap the second half of that post. I'm wrong. Need coffee before posting here...

[hermanntrude]

benzene is more polarisable than cyclohexane i think, because of its delocalised electrons... i may be wrong...

[Kaeroll]

benzene is more polarisable than cyclohexane i think, because of its delocalised electrons... i may be wrong...

I came to that conclusion about thirty seconds after making that post. Apologies for any confusion to the OP...

[CharonY]

The non-polar column will essentially separate according to boiling point (as the latter correlates inversely with polarity). The reverse is true for the polar column.