Today: Exp.9,

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TodayExp.9, Separation and Identification of
an Unknown Mixture (3 lab periods)
Qualitative analysisThis experiment includes
liquid/liquid extraction, IR, recrystallization,
melting points, and other techniques you learnt
this semester
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Your unknown mixture (note its
number!) contains a carboxylic acid, a base
(aromatic amine), and a neutral organic compound
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Carboxylic acids
determined by their melting points Melting point
ranges
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Bases Aromatic Amines
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You will prepare a solid derivative and determine
its melting point to identify your amine. What
are desirable properties of a derivative?
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Neutral Compounds
determined by their IRWhat are we looking for in
an IR?
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Liquid-Liquid Extraction Partitioning between
aqueous and ether layer
Which one is the ether layer?
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Partition or Distribution Coefficient kp
Refer to pp. 58 60 in your lab text and to
todays class handout
solubility of compound A in solvent
2 solubility of compound A in solvent 1 or kp
(g/ml) organic layer / (g/ml) aqu. layer
Kp
Question to think about Assume that 100 ml of
an aqueous solution of compound A is extracted
twice with 100 ml of ether (using fresh ether
each time). If instead we extracted just once,
but with a volume of 200 ml of ether, would we
extract the same amount of A ? (Study handout!)
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Separation Scheme
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Begin of Separation
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Isolation of Carboxylic Acid
Do today
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Separation of Neutral
Do today
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Separation of Amine
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Amine Derivative Prepare only Benzanilide 2b)
Warning! Benzoyl chloride is an irritating liquid
with a sharp pungent odor. Exothermic reaction
with water. Wear safety glasses, gloves, use
hood!
Benzanilide m.p. 163 C
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IR Spectroscopy Your IR samples must be ready
for analysis today. Label the 50-mL E-flask
with your sample with your name and section.
Place a clean disposable glass pipette with a
rubber bulb in this flask. IR spectra will be
ready next time Next Lab Lecture IR