Suggest any limitations to the use of recrystallization as a purification method for a solid.
What does Cypress have to do with a chemistry question?
thought it asked for school, why does it matter anyways
Thank you for responding.
The subject matters because we have many experts who troll this board looking for questions they can answer. Since we're all volunteers who have limited time, some experts only look at the questions that are clearly in their field.
I'm sorry -- but I can't help you. My specialties are elementary and middle school subjects plus social sciences.
Crystallization as a means to purify a compound fails when the resulting crystal formed is a cocrystal made up off your compound and an impurity. This may occur if the impurities present depict shapes that are complementary to those of the molecules that compose the desired crystal compound. In other words, if the impurity has hydrogen bonds that are complementary to those of the molecules in the crystal lattice then both molecules are said to have complementary shapes to each other. This complementary shape to each other (the molecules) could then result in the formation of a new co-crystal with the impurity as one of the components, which would ultimately mean that the impurities would be incorporated within the the crystal lattice of the “purified” compound. Therefore, crystallization should not be used as a means of purification if the impurities present consist of complementary shapes to that of your desired compounds.
Recrystallization is a commonly used technique for purifying solids, but it does have some limitations. Here are a few limitations to consider:
1. Solubility: Recrystallization relies on the principle that the impurities in a solid have different solubilities compared to the desired compound. If the impurities have similar solubilities to the compound of interest, it becomes difficult to separate them effectively.
2. Complex mixtures: Recrystallization can be less effective when dealing with complex mixtures of compounds. If there are multiple compounds present with similar solubilities, they may co-crystallize or contaminate the purified crystals, making separation and purification challenging.
3. Loss of yield: During the recrystallization process, there is a possibility of losing some of the desired compound. For example, if the solubility of the compound is high at elevated temperatures, a significant amount of the compound may remain in the mother liquor after cooling and crystallization. This can lead to a lower overall yield of the purified substance.
4. Heat-sensitive compounds: Some compounds can decompose or degrade at high temperatures, especially during the evaporation step, which is often necessary to obtain crystals. This limits the applicability of recrystallization for purifying heat-sensitive compounds.
5. Time-consuming: Recrystallization can be a time-consuming process, especially if the compound has a very low solubility. It may require multiple recrystallization cycles to achieve the desired purity, which can be time-intensive.
6. Cost: If large quantities of solvents are required for the recrystallization process, it can become expensive, especially for industrial-scale purifications.
Despite these limitations, recrystallization remains a widely used purification method due to its effectiveness in many cases.