Ch. 12: Separations and Purifications Flashcards
Extraction
Combines 2 immiscible liquids, one of which easily dissolves the compound of interest. Carried our in a separatory funnel. One phase is collected and the solvent is then evaporated. Acid base properties can be used to increase solubility.
Extraction: aqueous phase
The polar (water) layer is called the aqueous phase and dissolves compound w hydrogen bonding or polarity.
Extraction: organic phase
The nonpolar layer is called the organic phase and dissolves nonpolar compounds.
Wash
Reverse of extraction: a small amount of solute that dissolves impurities is run over the compound of interest
Filtration
Isolates a solid (residue) from a liquid (filtrate)
Gravity filtration
Used when the product of interest is in the filtrate. Hot solvent is used to maintain solubility.
Vacuum filtration
Used when the product of interest is the solid. A vacuum is connected to the flask to pull the solvent through more quickly
Recrystallization
The product is dissolved in a minimum amt of hot solvent. If the impurities are more soluble the crystals will reform while the flask cools, excluding the impurities
Distillation
Separates liquids according to differences in their boiling points. The liquid w the lowest boiling point vaporizes first and is collected as the distillate.
Simple distillation
Can be used if the boiling points are under 150C and are at least 25 apart
Vacuum distillation
Should be used if the boiling point s are over 150*C to prevent degradation of the product
Fractional Distillation
Should be used if the boiling points are less than 25*C apart bc it allows for more refined separation of liquids by boiling point
Chromatography
Use two phases to separate compounds based on physical or chemical properties
Stationary phase or adsorbent
In chromatography, Usually a polar solid
Mobile phase
In chromatography, the mobile phase runs through the stationary phase and is usually a liquid or gas. This elutes the sample through the stationary phase
Retardation factors (chromatography)
Compounds w higher affinity for the stationary phase have smaller retardation factors and take longer to pass through, if at all; compounds w higher affinity for the mobile phase elute through more quickly. Compound therefore get separated from each other, called partitioning
Thin layer and paper chromatography
Used to identify a sample. The stationary phase is a polar material, such as silica, alumina, or paper. The mobile phase is a nonpolar solvent which climbs the card through capillary action. The card is spotted and developed; Rf values can be calculated and compared to reference values
Reverse phase chromatography
Uses a nonpolar card w a polar solvent
Column Chromatography
Utilizes polarity, size, or affinity to separate compounds based on their physical or chemical properties. The stationary phase is a column containing silica or alumina beads. The mobile phase s a nonpolar solvent, which travels through the column by gravity
Ion-exchange chromatography
The beads are coated w charged substances to bind compounds w opposite charge
Size exclusion chromatography
The beads have small pores which trap smaller compounds and allow larger compounds to travel through faster
Affinity chromatography
The column is made to have high affinity for a compound by coating the beads w a receptor or antibody to the compound
Gas chromatography
Separates vaporizable compounds according to how well they adhere to the adsorbent in the column. The stationary phase is a coil of crushed metal or a polymer. The mobile phase is a nonreactive gas. May be combined w mass spectrometry
Mass spectrometry
Ionizes and fragments molecules and passes these fragments through a magnetic field to determine molecular weight or structure
High performance liquid chromatography (HPLC)
Similar to column chromatography but uses sophisticated computer mediated solvent and temp gradients. It is used if the sample size is small or if forces such as capillary action will affect results. It was formerly called high pressure liquid chromatography
