1.Once upon a time a student dumped out all the coffee cans into Tuperware, dut

Question

1.Once upon a time a student dumped out all the coffee cans into Tuperware, dut he didnt label the caffeinated and the decaffeinated. How might your determine which coffee is caffeinated and which is not? (Based on thin layer-chromatagraphy)

2. Melting point of an unknown X=112 C-115 C. Given:

Observed

Melting point Inference

A+X= 102-105, ?

B+X= 112-1115 , ?

C+X= 80-114 ?

Fill out the table and identify which out of A,B,C is X.(mixed melting point problem.)

3.If a substance has 20% enatiomeric excess of the dextrorotatory enatiomer what percentage of the mixture is the levorotatory enatiomers?

Explanation / Answer

Q1.

You will need to find the spot/mark for caffeine, which is pretty electronegative due to the Nitro and C=O groups

Those will remain low, since they are attached to the stationary phase.

If the Chromatograph used:

- nonpolar solvent ( such as hexane) caffeine will be low in the Rf layer

- polar solvent ( such as acetone) caffeine will be high in the Rf layer

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