Vanillin Recrystallization

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Experiment 1 and 2 Recrystallization: Purification of Solids and Melting points Purpose:

In the fist experiment, impure Vanillin was purified through the process of recrystallization. Desired solutes were recovered through the technique of vacuum filtration, and then dried to take percent recovery In the second experiment, a percent recovery of the recrystallized Vanillin from the first experiment was performed. The percent recovery of Vanillin was 77.18% A mixed melting point technique was used to discover the melting ranges of crude Vanillin, recrystallized Vanillin and to also reveal the identity of the Unknown (H:7). The percent recovery of the unknown sample proved to be 49.19%


For the Recrystallization:
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Then, we loaded samples of Crude Vanillin, a sample of my recrystallized Vanillin, my partners recrystallized Vanillin, and three samples that could be possible identities each with our Unknown (H:7) into capillary tubes and took the melting points of each sample, through the use of both a water bath and commercial heating apparatus.


Recrystallization: Purification of Solids

Test tube # Solvent Observations
1 Cyclohexane The liquid is clear
2 Ethanol The solution is a tinted yellow liquid at room temperature
3 Methanol Slight brown tint, unknown mostly dissolved
4 Hexanes The liquid is a very clear color
Figure 1: Table of possible solvents and their results

1. The solvent that seemed most appropriate to use was Methanol, and after confirming that it recrystallized in an ice bath, we decided that it was the solvent that we were going to use
2. We used 1.358 grams of the unknown (H:7) to perform the recrystallization process.

Vanillin 810C - 830C
Acenaphthene 900C -940C
Phenanthrene 980C - 1000C
Triphenylmethane 920C -940C
Figure 2: Melting Ranges of Possible Unknowns
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My lab partner and I successfully purified Vanillin and an unknown sample. By using Methanol as a solvent we were able to successfully determine the identity of our unknown (H:7).At the end of the experiment we obtained a more pure solute than what we first had. The last goal, percent recovery was successful, because although in recrystallization you will often recover less than the original sample, my partner and I recovered 77.18% of Vanillin, and 49.19% of the unknown (H:7), which is a reasonable percentage.
Whenever recrystallization takes place, there are some risk factors involved. One risk factor is that some of the sample will be lost due to the filtering of the impurities. By filtering out the impurities, only the pure sample remains. Another risk is that you could lose a little of the pure solute, because of the solvent that is used, which could lead to the loss of a 100% pure solute. Recrystallization is an appropriate technique for purification in a situation where the sample is not 100% pure.You would need this high percentage of purity to compensate for the possible loss of a pure solute. Smaller samples such as a gram or less would not be ideal for this technique because there would most likely be a very small recovery or none at all. Recrystallization may be ideal to use when there is a larger sample size. The ideal final purity that would be expected in a good recrystallization would be above

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