Separations and Purifications

combines two immiscible liquids, one of which easily dissolves the compound of interest; carried out in a separatory funnel; one phase is collected, and then the solvent is evaporated

extraction: the polar (water) layer; dissolves compounds with hydrogen bonding or polarity

extraction: the nonpolar layer; dissolves nonpolar compounds

a small amount of solvent that dissolves impurities is run over the compounds of interest; the reverse of extraction

isolates a solid (residue) from a liquid (filtrate)

filtration: is used when the product of interest is in the filtrate; hot solvent is used to maintain solubility

filtration: is used when the product of interest is the solid (residue); a vacuum is connected to the flask to pull the solvent through more quickly

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

separates liquids according to differences in their boiling points; the liquid with the lowest boiling point vaporizes first and is collected as the distillate

distillation: can be used if the boiling points are under 150ºC and are at least 25ºC apart

distillation: should be used if the boiling points are over 150ºC to prevent degradation of the product; pressure is decreased which allows the liquid to boil at a lower temperature

distillation: should be used if the boiling points are less than 25ºC apart because it allows more refined separation of liquids by boiling point; uses a fractionation column to increase surface area to allow more cycles of evaporation and condensation

uses two phases to separate compounds based on physical or chemical properties

chromatography: usually a polar solvent

chromatography: runs through the stationary phase and is usually a liquid or a gas; this elutes the sample through the stationary phase

chromatography: separation of compounds from each other due to differences in affinity for the stationary phase

chromatography: value used to identify unknown compounds; smaller in compounds with higher affinity for stationary phase, and larger in compounds with lower affinity for stationary phase

retardation factor (R(f))

chromatography technique: two similar techniques, that differ only in the medium used for the stationary phase; a card (stationary phase) is spotted and developed; R(f) values can be calculated and compared to reference values

thin-layer chromatography (TLC) and paper chromatography: is a polar material, such as silica (TLC), alumina (TLC), or paper (paper(cellulose))

thin-layer chromatography (TLC) and paper chromatography: is a nonpolar solvent, which climbs the card (stationary phase) through capillary action

thin-layer chromatography (TLC) and paper chromatography: same technique as TLC and paper, but the card (stationary phase) is nonpolar and the solvent is polar, so polar molecules move up quickly and nonpolar more slowly

chromatography technique: utilizes polarity, size, or affinity to separate compounds based on their physical or chemical properties; uses an entire column filled with silica or alumina beads as an absorbent, allowing for much greater separation

column chromatography: is a column containing silica or alumina beads