Question

Which of these TLC solvent systems listed below is the most polar and explain why?

1:2 (v:v) Hexane:diethyl ether

2:1 (v:v) Hexane:diethyl ether

1:3 (v:v) Hexane:diethyl ether

3:1 (v:v) Hexane:diethyl ether

1:1(v:v) Hexane:diethyl ether            

(a) The Rf of compound B is? Circle the correct answer.

0.47
0.54
0.60
0.64
0.69
0.78
0.82
1.00

(b) Looking at the TLC plate in 4(a), which compound interacts least with the stationary phase? Explain (4 pts)

Would you need to use a more or less polar solvent system to get compound A to move further up the plate? (2 pt)

Circle all that apply when performing TLC analysis. (5 pts – no partial credit)

Spots should be below the solvent level
Spots should be above the solvent level
The TLC plate should be removed from the chamber before the solvent has reached the top of the plate
The TLC plate should be removed from the chamber after the solvent has reached the top of the plate
Spots should be small
Spots should be large
You should use pen to draw your line
You should use pencil to draw your line

Answer 1

The solvent system 1:3 (v:v) Hexane : Diethyl ether is most polar since among Hexane and Diethyl ether, diethyl ether is more polar, so when it's ratio is more, the solvent system becomes more polar.

a) unless you upload the pictures of your TLC we cannot tell what is Rf value.

To calculate tge Rf value divide the distance travelled by the spot from the point of spotting, with the distance traveled by the solvent from the point of spotting.

b) Whichever compound traveled highest on tlc plate interacts least with the stationary phase and therefore is carried yo a maximum distance by the solvent.

1) Spot should be above solvent level.

2) The tcl should be removed from the chamber before the solvent has reached the top of the plate.

3) spots should be small

4) you should use pencil to draw the line