9. After a rather lengthy organic chemistry synthesis procedure, a student ran t

Question

9. After a rather lengthy organic chemistry synthesis procedure, a student ran the product of the reaction on a TLC plate and obtained the result below. What might have been done wrong, if anything. with more Solvent than needed 10. A student spots an unknown sample on a TLC plate. After developing in petroleum ether/acetone 50:50, a single spot with an Rrof 0.55 is seen. Does this indicate that the unknown material is a pure compound? What can be done to verify the purity of the sample? re the valve

Explanation / Answer

1.

It seems three spots (merged)

Either you have spotted a too concentrated spot.

Or, you have developed the TLC with a more polar solvent system (mobile phase).

So, spot a low concentrated spot and decrease the polarity of the mobile phase.

2.

No, it can’t be claimed as the unknown material is pure. Try developing the TLC by decreasing the polarity of solvent system.

You performed TLC at

Petroleum ether:acetone = 50:50

Change the solvent system as

Petroleum ether:acetone = 40:60

Petroleum ether:acetone = 30:70

Petroleum ether:acetone = 20:80

Petroleum ether:acetone = 10:90

Or even at only Petroleum ether

Increasing the concentration of Petroleum ether, you are decreasing the poarity of the mobile phase.

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