How do boiling chips work Cem 255?
How do boiling chips work Cem 255?
How do boiling chips work? They create an uneven surface area in the flask to promote bubble formation and also prevents superheating/bumping in the solution and smooth bubbles.
Why is it not possible to isolate any benzophenone?
Why is it not possible to isolate any benzophenone, which is an intermediate in the Grignard reaction? Benzophenone is unstable and it reacts with Grignard reagents.
What is the purpose of using ether in this experiment Cem 255?
It is added to make the water layer more polar which forces cyclohexane out of the water layer and into the ether layer. It also removes some emulsified water from the organic layer.
What is the purpose of placing a piece of paper towel or filter paper inside the developing chamber?
What is the purpose of placing a piece of paper towel or filter paper inside the developing chamber? The paper towel or filter paper will absorb the evaporated solvent and allow the fluent solvent to completely saturate the chamber. The vapors eventually evaporate from the paper towel and saturate chamber.
What is the purpose of this Wick?
The purpose of a wick is to deliver fuel (wax) to the flame. Acting like a fuel pump, the wick draws the liquefied wax up into the flame to burn.
What problem can you run into if you allow the solvent front to go to the top of a TLC plate?
Chemicals move up a TLC plate along with the solvent being used to develop the plate. However, if the solvent reaches the top of the plate, the chemicals continue to move up.
What happens if the solvent line reaches the top of your TLC plate?
When the solvent has reached the top of the plate, the plate is removed from the developing chamber, dried, and the separated components of the mixture are visualized. If the compounds are colored, visualization is straightforward. Usually the compounds are not colored, so a UV lamp is used to visualize the plates.
Why should you not touch the TLC plate?
Never under any circumstances touch the face of a TLC plate with your fingers as contamination from skin oils or residues on gloves can obscure results. Also, alumina is more chemically reactive than silica gel and as a result, would require more care of compounds and compound classes.
What would happen if the solvent level is above the start line?
The solvent level has to be below the starting line of the TLC, otherwise the spots will dissolve away. Non-polar solvents will force non-polar compounds to the top of the plate, because the compounds dissolve well and do not interact with the polar stationary phase.
Why can’t the solvent touch the pencil line?
If your start line is inside the solvent or equal to level of solvent it can cause error. The solvent gives extra energy to pull up the sample and the sample will also dissolve in the solvent. That’s why as precautionary measure start line should stay above the solvent in chromatography!
Why don’t you use pen on the chromatogram?
You can’t use a pen because the ink will travel up the TLC plate with the TLC solvent, just like your chemical samples do. You can only spot/label/mark TLC plates using a pencil. The graphite in a pencil will not run up the plate!
Why does the spot have to be above the solvent level?
The baseline must be above the solvent level in the TLC chamber, so the solvent does not dilute to samples so much that they dissolve. More error would be present in our calculations if baseline is submerged below solvent level.
Why did you wait for the solvent to move almost to the top of the paper before removing it from the chamber?
It is important to stop the chromatograph before the solvent reaches the top of the paper because without knowing where the solvent reaches the top, you cannot calculate the Rf without measuring the distance from the origin to the solvent front.
When should the chromatogram be removed from the beaker?
– When the first solvent front reaches is about 1cm from the top of the chromatogram, all chromatograms are removed from their solvents. – When the first solvent front reaches is about 2cm from the top of the chromatogram, all chromatograms are removed from their solvents.
What is a high RF value?
A high Rf (Ie 0.92) would refer to a substance that is very non-polar. Ie that substance moved a 92% of the entire distance the solvent traveled. A low Rf value (0.10) would refer to a substance that is very polar. IE that substance was only able to move 10% of the entire distance the solvent traveled. Term.