Removing fluorescein from the organic phase. During the reaction an amide of fluorescein was made what doesn’t have a color and it does not fluoresces under these conditions. So hopefully, the transparency of the upper layer means something good.
The bottom layer is a dilute (1M) sodium hydroxide solution what reacts with the fluorescein to form the highly fluorescent fluoriescein sodium salt what produces this intense green color in the aqueous phase.
Interesting fact: the acid form of the fluorescein does not emit the characteristic intense green color under UV light, it only emits a yellowish-orange color in high concentrations.
9:30 pm • 1 September 2014 • 89 notes • View comments
1,4-Dioxane is a really useful solvent in the lab, since it dissolves most organics and it’s also miscible with water while most ethers are not. A bad point about it, that it is highly hygroscopic, forms peroxides upon standing and it is really toxic. Exposure may cause damage to the central nervous system, liver and kidneys.
If you would like to get out traces of water from it, than drop a large piece of sodium or potassium in it, add benzophenone and reflux the solution, till it turns deep blue, just as in this case: http://labphoto.tumblr.com/tagged/benzophenone
9:30 pm • 31 August 2014 • 59 notes • View comments
wuttipat-kiratipaisarl said: Did you have any ideas on qualitative test of monosodium glutamate? Someone has asked me few weeks ago to test for it in her food.
I would highly recommend to read CompoundChem's great infographic about MSG: http://compoundchem.tumblr.com/post/95758847506/the-second-graphic-in-the-undeserved-reputations . Every info what is important about this thing is wrote down over there.
If he/she still needs a qualitative test, than the best is to use a personal, built in bio-liquid-chromatograph (also called tongue).
6:56 pm • 31 August 2014 • 9 notes • View comments
A condensation under UV lamp. The reaction product is an aromatic, highly fluorescent compound what produces this nice blue-green fluorescense under the UV light.
9:30 pm • 30 August 2014 • 85 notes • View comments
When we do not have enough magnetic stirrers in the lab, but we would like to know that what would happen if we would use another catalyst for the same reaction on a smaller scale.
9:30 pm • 29 August 2014 • 18 notes • View comments
Column chromatography for beginners.
First, look after an immobile phase (usually silica or alumina) what was tested before with the correct eluent (mixture of 2 or more organic solvent). If the mixture of compounds separate with this mixture on a TLC (thin layer chromatography) what is made from the same immobile phase it will hopefully work on a larger scale also.
For every g of the purified material take at least 10-15 g of immobile phase, mix it with the eluent (1 pics) and load it in the column. Place your mixture of compounds on the top with a little celite or sand (3 pics) and let the eluent flow down the column (4 pics). Every time the top would dry, add more eluent to keep it always wet.
If you are lucky enough the main component will separate and it will form a nice layer on the column (last pics).
If anyone is interested in this chromatographic method I could write a step by step “how to do” from it. Anyone?
9:30 pm • 28 August 2014 • 56 notes • View comments
Cleaning capillary tubes with 35% H2O2 + muriatic acid mixture.
From time to time we often run out of clean capillary tubes what are important if we would like to check our reactions and products purity with TLC (thin layer chromatography).
The H2O2 and HCl mixture is a strongly oxidizing solution, what also dissolves gold (yes, not just aqua regia is suitable for this) and it also destroys everything what is organic, so it is perfect to clean glassware.
Important note: elemental chlorine (the yellow color is caused by this) is also generated from this reaction, so do not try it without at least a fume hood.
9:30 pm • 27 August 2014 • 46 notes • View comments
Fractional distillation on atmospheric pressure.
To keep the Vigreux column on permanent temperature on the full of its length, we often wrap it in glass wool or aluminium foil, or both. The glass keeps the heat inside, the aluminium foil acts as a heat mirror, so it also keeps most of the heat inside.
The brown thing what looks like as the fur of a bear is a piece of glass wool.
Why is this important? If the temperature is permanent, component A what has a boiling point 125 °C will distill till the whole glass apparatus is on a temperature 125 °C and component B which has a boiling point 142 °C will only start to distill after it. But if the surrounding air lets the heat escape, the distilling column will have places where it can cool down under 125 °C, while other parts are much hotter than 142 °C, so a mixture of the who compounds will distill to the receiving flask.
9:30 pm • 26 August 2014 • 19 notes • View comments
Flash column chromatography/filtration through silica. This method removes highly polar decomposition/side products in no time and gives a high purity product (that orange thing).
If there are compounds that have a high Rf (retention factor) difference on a TLC (thin layer chromatography), than it means that while compound A with high Rf could be easily separated with a short column with this method from compound B or C what has a low ~0-0,2 Rf.
9:30 pm • 25 August 2014 • 37 notes • View comments
Product of the distillation: a red colored, highly toxic, corrosive oil what was produced from a halogenation/chlorination.
Due the high molar weight of chlorine after the reaction while we changed the hydrogen atoms on the side chains of the molecule to chlorine atoms, the weight of the compound doubled. We started from 20g and got at least 45g of product what means a near 100% conversion, the only question what is left is the purity.
9:30 pm • 24 August 2014 • 48 notes • View comments