Separations and Purifications Flashcards
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
extraction: the polar (water) layer; dissolves compounds with hydrogen bonding or polarity
aqueous phase
extraction:
the nonpolar layer; dissolves nonpolar compounds
organic phase
a small amount of solvent that dissolves impurities is run over the compounds of interest; the reverse of extraction
wash
isolates a solid (residue) from a liquid (filtrate)
filtration
filtration:
is used when the product of interest is in the filtrate; hot solvent is used to maintain solubility
gravity filtration
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
vacuum filtration
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
recrystallization
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
distillation:
can be used if the boiling points are under 150ºC and are at least 25ºC apart
simple distillation
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
vacuum distillation
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
fractional distillation
uses two phases to separate compounds based on physical or chemical properties
chromatography
chromatography:
usually a polar solvent
stationary phase (absorbent)
chromatography:
runs through the stationary phase and is usually a liquid or a gas; this elutes the sample through the stationary phase
mobile phase
chromatography:
separation of compounds from each other due to differences in affinity for the stationary phase
partitioning
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))
retardation factor (R(f))
R(f) = distance spot moved / distance solvent front moved
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
thin-layer chromatography (TLC) and paper chromatography:
is a polar material, such as silica (TLC), alumina (TLC), or paper (paper(cellulose))
stationary phase
thin-layer chromatography (TLC) and paper chromatography:
is a nonpolar solvent, which climbs the card (stationary phase) through capillary action
mobile phase
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
reverse-phase chromatography
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
column chromatography:
is a column containing silica or alumina beads
stationary phase
column chromatography:
is a nonpolar solvent, which travels through the column by gravity
mobile phase
column chromatography:
the beads are coated with charged substances to bind compounds with opposite charge
ion-exchange chromatography
column chromatography:
the beads have small pores which trap smaller compounds and allow larger compounds to travel through faster
size-exclusion chromatography
column chromatography:
the column is made to have high affinity for a compound by coating the beads with a receptor or antibody to the compound
affinity chromatography
chromatography technique:
separates vaporizable compounds according to how well they adhere to the absorbent in the column
gas chromatography (GC)
gas chromatography (GC): is a coil of crushed metal or a polymer
stationary phase
gas chromatography (GC): is a nonreactive gas
mobile phase
gas chromatography (GC): often used in sequence with GC to determine molecular weight; ionizes and fragments molecules and passes them through a magnetic field to determine molecular weight or structure
mass spectrometry
is similar to column chromatography but uses sophisticated computer-mediated solvent and temperature gradients; it is used if the sample size is small or if forces such as capillary action will affect results
high-performance liquid chromatography (HPLC)