[hippobrains]

Hi all. This is my first post. Hopefully instead of asking questions, i'll soon be able ot help answer some.

Down to business:

I did fractional distillation in my lab practical last week. I recorded IR spectra for the starting mixture (IR-A), the first component distilled out (IR B) and the second component distilled out (IR C). I am told to determine the efficiency of the seperation, using my IR spectra.

If IR-B and IR-C, the sprectra for distilled products, were superimposed upon one another, they would form IR-A, the spectra for the starting mixture. Would it be reasonable to say that since the spectra for the two products were clearly parts of that of the mixture that the seperation was very efficient? or are there other things I should be taking into consideration. Please and thanks!

[Yggdrasil]

It depends what you are separating.  Basically, in an efficient separation peaks characteristic of A but absent from B's spectra should show up in the fraction containing A but not in the fraction containing B.  For example, if you're separating a carbonyl compound (A) from a compound without a carbonyl (B), an efficient separation would show not C=O stretch in the fraction which should have pure B.