In chemistry, work-up refers to the series of manipulations required to isolate and purify the product(s) of a

chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and break ...

. Typically, these manipulations may include: * quenching a reaction to deactivate any unreacted reagents. * cooling the reaction mixture or adding an '' antisolvent'' to induce

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hai ...

, and collecting or removing the solids by

filtration Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filte ...

, decantation, or centrifugation * removal of solvents by evaporation * separating the reaction mixture into organic and aqueous layers by liquid-liquid extraction * purification by

chromatography In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system ( ...

distillation Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the he ...

or recrystallization For example, the Grignard reaction between

phenylmagnesium bromide Phenylmagnesium bromide, with the simplified formula , is a magnesium-containing organometallic compound. It is commercially available as a solution in diethyl ether or tetrahydrofuran (THF). Phenylmagnesium bromide is a Grignard reagent. It i ...

and

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

in the form of dry ice gives the conjugate base of benzoic acid. The desired product, benzoic acid, is obtained by the following work-up:{{cite book , title = Introduction to Organic Laboratory Techniques: A Small Scale Approach , author = Donald L. Pavia , year = 2004 , publisher = Thomson Brooks/Cole , isbn = 0-534-40833-8 , pages = 312–314 Benzoic acid synthesis

*The reaction mixture containing the Grignard reagent is allowed to warm to room temperature in a water bath to allow excess dry ice to evaporate *Any remaining Grignard reagent is quenched by the addition of water *Dilute

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the dig ...

is added to the reaction mixture to protonate the benzoate salts, as well as to dissolve the magnesium salts. White solids of impure benzoic acid are obtained. *The benzoic acid is decanted to remove the aqueous solution of impurities, more water is added, and the mixture is brought to a boil with more water added to give a homogeneous solution. *The solution is allowed to cool slowly to room temperature, then in an ice bath to recrystallize benzoic acid. *The recrystallized benzoic acid crystals are collected on a Buchner funnel and are allowed to air-dry to give pure benzoic acid.

References

Chemical reactions

See also

References