Task 4 M2
Iman boukjija zamani
11053457
Task 4 Factors that influence purity
Aspirin TLC
● Raw materials, for this practical, it it ● Raw materials, like in Aspirin, raw
very important to have the right materials are very important, the
amount of raw materials, which will amount is not that important, since
be (2- hydroxybenzoic acid (silica we just need to juice very well the
acid), 11g and Ethanoic anhydride spinach and carrot leaves, which are
(CH3CO)2o, 4 cm3) the raw materials.
● Also having the right temperature for ● When doing chromatography, it is
hot filtration and crystallisation. We very important to keep in mind the
heat the mixture to get all the thickness of the TLC paper, silica
substances dissolved in the mixture coating it is where the pigments run
and we cool it because aspirin has a with the solvent, if it is thin it will run
very high cooling point, so this will faster than if it is thicke.
cool down and crystallize faster, to ● Regarding the size of the spot, we
get rid of the other materials. So we have to be very precise, because if
cool the aspirin to get cristas of the spot is too big, it can spring
aspirin with the least remaining through all over the paper, and mix
materials as possible, to purify it . with the other samples, so the spot
● When cooling the aspirin is very needs to be concentrated in the
important to know if it is cooling same place, in the experiment we
faster or slower, since that will lead were drying between spots, to
to bigger or smaller crystals, by prevent this from happening.
cooling it faster, crystals will form ● Rf value, can be affected, if the
very small, and if we cool it slowly it samples are carried out at different
will lead to bigger crystals, which is temperatures, since the samples will
better, since they will be more pure run at different rates, since the
and bigger in size, and we are also solubility is different one from the
preventing impurities from trapping. other.
● By products of aspirin are water ● Choosing the wrong solvent, will not
which is an eliminator from the dissolve the samples, so it will not
alcohol and acid, and in addition to run up the paper, polar samples are
water we also have 1 molecule of dissolved with polar solvent, and
acetic acid (CH3COOH) this by vice versa, the right solvent, needs
products, will cause impurities, and to be chosen, for the samples to
a good thing about them is that they move up the TLC paper.
are soluble in water, so if it is slightly ● Size of the TLC paper is important
heated up we can get rid of this by too, depending on how many
product. samples we have, and how long we
● To remove impurities from the will observing for, we will need a
aspirin, we use filtration, in this case bigger or smaller TLC paper.
acetic acid which is soluble in water
