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General
Check for the concentration of common acids and bases.
Recommended reading prior to entering the lab: Extraction, TLC, Recrystallization (in SKR)
Step 2 (Work-up)
"36% HCl" refers to concentrated hydrochloric acid. There is nothing such as 100% hydrochloric acid. Why?
In some instances, the reaction turns green in color and a phase separation is observed upon standing. The green color is due to an oxidation reaction of the phenolate. The phase separation is most likely the result of the evaporation of some methanol or the absorption of additional moisture. Keep in mind that the majority of the formaldehyde solution is water already. Since the yield in these cases often is very low, the experiment has to be repeated :-(.
In order to perform the extraction in one batch in a 125 mL separatory funnel, the volume of the solution should be kept below 70 mL. If too much water was added, the suspension would have to be split into smaller batches. This means that more extractions have to be carried out, and ultimately more solvent is to be evaporated, which takes a lot of extra time. Please keep this in mind when you do the work-up of the mixture.
Other questions that you should ask yourself before going to the lab are (or how can I avoid "stupid" mistakes and make my life easier):
a. How much solvent is appropriate here to use for the extractions?
b. Which layer contains the desired product, top or bottom?
c. Why is dichloromethane used as solvent here? (Hint: see chapter about "Extraction Theory" in the Survival Kit Reader)
d. Afterwards the combined organic layers are extracted once with sodium bicarbonate solution and water. Can I skip these steps if I am running late?
e. The remaining organic layer is then treated with saturated sodium chloride solution and anhydrous sodium sulfate. Why?
f. The removal of the solvent should be aided by applying an air stream. Why?
The recrystallization step can require a significant amount of time in some cases (depending on the quality of the crude product). If the crystallization does not occur immediately, the solution of the crude product is stored over night in a sealed container. If the solution is too viscous, crystals generally form very slowly. The solution should not be placed in an ice-bath since there is a significant danger that the phenol precipitates as well if significant amounts are present. Often times more of the product crystallizes in the filter flask upon filtration. This compound should be redissolved and allowed to crystallize again to increase the yield.
The crude and the recrystallized (=pure ?) product have to be examined by TLC in order to evaluate their composition and purity.
Independent if the product was a solid or an oil, an IR spectrum should be acquired to get more information about the product to be discussed in the formal report.