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Today: Exp.9, “Separation and Identification of an Unknown Mixture” (3 lab periods) “Qualitative analysis” This experiment includes: liquid/liquid extraction, IR, recrystallization, melting points, and other techniques you learnt this semester. Your unknown mixture (note its number!)

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Your unknown mixture note its number contains

Today:Exp.9, “Separation and Identification of an Unknown Mixture” (3 lab periods)“Qualitative analysis”This experiment includes: liquid/liquid extraction, IR, recrystallization, melting points, and other techniques you learnt this semester


Your unknown mixture note its number contains

Your unknown mixture

(note its number!)

contains:

a carboxylic acid, a base (aromatic amine), and a neutral organic compound


Your unknown mixture note its number contains

Carboxylic acids

determined by their melting points

Melting point ranges …


Your unknown mixture note its number contains

Bases: Aromatic Amines

..

..

..

..

..

..

You will prepare a solid derivative and determine its melting point to identify your amine.

What are desirable properties of a derivative?


Your unknown mixture note its number contains

Neutral Compounds

determined by their IRWhat are we looking for in an IR?


Your unknown mixture note its number contains

Liquid-Liquid Extraction

Partitioning between aqueous and ether layer

Which one is the ether layer?


Your unknown mixture note its number contains

Partition or Distribution Coefficient kp

Refer to pp. 58 – 60 in your lab text and to today’s 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!)







Your unknown mixture note its number contains

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


Your unknown mixture note its number contains

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