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:

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

Carboxylic acids

determined by their melting points

Melting point ranges …

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?

Neutral Compounds

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

Liquid-Liquid Extraction

Partitioning between aqueous and ether layer

Which one is the ether layer?

Partition or Distribution Coefficient kpRefer 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

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!)

Kp =

Separation Scheme

Begin of Separation

Isolation of Carboxylic Acid

Do today

Separation of Neutral

Do today

Separation of Amine

Benzanilidem.p. 163 C

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!

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