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Recrystallization is a method used to purify chemicals by dissolving a mixture of a compound and its impurities, in an appropriate solvent, prior to heating the solution. [1] Following the dissolution of crude product, the mixture will passively cool, yielding a crystallized compound and its impurities as separate entities.
Pure results of a successful purification process are termed isolate. The following list of chemical purification methods should not be considered exhaustive. Affinity purification purifies proteins by retaining them on a column through their affinity to antibodies, enzymes, or receptors that have been immobilised on the column.
purification by chromatography, distillation or recrystallization. The work-up steps required for a given chemical reaction may require one or more of these manipulations. Work-up steps are not always explicitly shown in reaction schemes.
Salting out (also known as salt-induced precipitation, salt fractionation, anti-solvent crystallization, precipitation crystallization, or drowning out) [1] is a purification technique that utilizes the reduced solubility of certain molecules in a solution of very high ionic strength.
This can be considered a crude form of recrystallization performed without changes in temperature. In pharmacy , trituration can also refer to the process of grinding one compound into another to dilute one of the ingredients, add volume for processing and handling, or to mask undesirable qualities.
Fractional crystallization has various advantages over other separation technologies. First of all, it makes the purification of close boilers possible. This allows for very high purities even for challenging components. Furthermore, because of the lower operating temperature, the thermal stress applied to the product is very low.
In the last case, an overall yield of 76% is produced following purification by recrystallization. [6] Microwave irradiation of phthalic anhydride and hydroxylamine hydrochloride in pyridine produces N-hydroxyphthalimide in 81% yield. [7]
It can also be synthesized in the laboratory. To do so, sodium hydroxide and bromine are added to an ice-water solution of succinimide. The NBS product precipitates and can be collected by filtration. [1] Crude NBS gives better yield in the Wohl–Ziegler reaction. In other cases, impure NBS (slightly yellow in color) may give unreliable results.