Organic Chemistry Chapter 12: Separations and Purifications Flashcards
Extraction
combines two immiscible liquids, one of which easily dissolves the compound of interest.
What are the two phases of extraction?
Polar (water) layer = aqueous phase
Nonpolar layer = organic phase
Where is extraction carried out?
a separatory funnel. One phase is collected ant the solvent is then evaporated.
Wash
the reverse of extraction, in which a small amount of solute that dissolves impurities is un over the compound of interest.
Giltration
isolates a solid (residue) from a liquid (filtrate).
Gravity filtration
Used with the product of interest is the solid.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 amount 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 with the lowest boiling point vaporizes first and is collects as the distillate.
Simple distillation
can be used if the boiling points are over 150 degrees C. and are at least 25 degrees C apart.
Vacuum distillation
should be used if the boiling points are over 150 degrees C to prevent degradation of the product.
Fractional distillation
should be used if the boiling points are less than 25 degrees C apart because it allows more refined spearation of liquids by boiling point.
Chromatography
used two phases to separate compounds based on physical or chemical properties.
The stationary phase or adsorbent
usually a polar solid.
Mobile phase
Runs through the stationary stage and is usually a lipid or gas. This elutes the sample through the stationary phase.
Retardation factors
larger for compounds with higher affinity for the stationary phase & take longer to pass though, if at all. compounds with higher affinity for the mobile phase elute through more quickly.
Partioning
Separation of compounds.
Thin layer and paper chromatography
Used to identify a sample - stationary phase is a polar, material (silica, alumina, paper)
Mobile phase is a nonpolar solvent
Card is spotted and developed
Rf values calculated
Reverse phase chromatography
uses a nonpolar card with a polar solvent
Column chromatography
utilizes polarity, size or affinity to separate compounds based on their physical or chemical properties.
Stationary phase = column containing silica or alumina beads
Mobile phase = nonpolar solvent, which travels through the column by gravity
Ion-exchange chromatography
the beads are coated with charged substances to bind compounds with opposite charge
Size-exclusion chromatography
the beads have small pores which trap smaller compounds and allow larger compounds to travel through faster
Affinity chromatography
made to have high affinity for a compound by coating beads with a receptor or antibody to the compoud
Gas chromatography
separates vaporizable compounds according to how well they adhere to the adsorbent in the column.
Stationary = coil of crushed metal or a polymer
Mobile = nonreactive gas
High performance liquid chromatography
similar to chromatography but uses 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 formally called high pressure liquid chromatography.
