CHEM 2152 Lecture Notes - Lecture 6: Elution, Diethyl Ether, Miscibility
Discussion
In the results of this lab we are left with Benzoic Acid precipitate and
Acenaphthene that has been dried; if the remaining substance were to be analyzed
with GLC (in a polar column), you would see the Acenaphthene go through first
because it is neutral and will just be carried through the mobile phase. Then you
will see the Benzoic Acid as the second peak because the carboxylic acid group is
polar while the rest of the molecule is nonpolar. Furthermore, in terms of
efficiency of the GLC, which depends on the resolution of the peaks, if there were
extra peaks on the GLC analysis then that means that some contaminates must
have been present. Also, the peak heights, which correspond to the number of
particles that hit the detector, are a good indicator of efficiency of the separation as
well as the area under each peak (proportional to concentration).
In this experiment mistakes could have been made if water is added before
the addition of the KOH because H2O has the capability of acting as a base,
deprotonating the Benzoic acid because the KOH does. This addition of water
could have led to the low recovery of 54% because some may have been added by
accident. Although, when vacuum filtration is taking place, the water can be added.
The water will evaporate and the final Benzoic acid precipitate is insoluble in
water so it will have no effect. This leads into the discussion of extraction.
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Document Summary
In the results of this lab we are left with benzoic acid precipitate and. Then you will see the benzoic acid as the second peak because the carboxylic acid group is polar while the rest of the molecule is nonpolar. Furthermore, in terms of efficiency of the glc, which depends on the resolution of the peaks, if there were extra peaks on the glc analysis then that means that some contaminates must have been present. Also, the peak heights, which correspond to the number of particles that hit the detector, are a good indicator of efficiency of the separation as well as the area under each peak (proportional to concentration). In this experiment mistakes could have been made if water is added before the addition of the koh because h2o has the capability of acting as a base, deprotonating the benzoic acid because the koh does.
