Separations and Purifications Flashcards
Chapter 12 (21 cards)
boiling point
The boiling point of a pure substance is the temperature at which the substance transitions from a liquid to the gaseous phase. At this point, the vapor pressure of the liquid is equal to the applied pressure on the liquid.
results from intramolecular interactions
distillation
uses boiling points to separate parts
mix, heat, boiling pts to vaporize which hit cold condensor, gas to liquid allows for isolation of one compound by using differences in boiling points
stronger the intramolecular force, higher the ——
boiling temperature
OH –> hydrogen –> strong
carbonyl –> dipoles –> less strong
simple distillation
requires boiling points to be low so compounds themselves dont degrade
and the differences within a compound have boiling points that differ by at least 25 degrees
fractionating column does what
helps isolate compounds when difference is less than 25 celcius in boiling point
with solid material increases surface area and promotes vapor and condensation cycles
volatile compounds have ___ boiling points
lower
liquid-liquid bases extraction
creates immiscible layers
aqeous (polar)
hydrophobic (non polar)
compounds sometimes have both properties and would be in both layers
how does charging a compound affect which layer
lone pair on N acts as base, accepts hydrogen, becomes + charged
which makes it more likely to be in aqueous solution (more polar than non polar)
adding vinegar to coffee extracts more out of it into aqueous layer
amines and carboxylic acids need what solutions
amines need acidic wash to protenate amine to make it + charged
carboxylic acids need base wash to make it - charged
both make a compound more aqueous bc more side chains that are charged means many ionizable side chains
chromatography
Chromatography is an important biophysical technique that enables the separation, identification, and purification of the components of a mixture for qualitative and quantitative analysis.
stationary and mobile phase of chromotography
stationary phase - solid support
mobile phase - solvent moving past stationary phase
the more the compound interacts with the mobile phase the ___ it moves
faster it moves
cellulose paper soaked in water (stationary phase)
solvent applied
organic layer as (mobile phase)
solvent travels UP due to capillaries
if the sample is more like the organic mobile phase, it migrates UP
if sample is more like the polar water on paper (stationary) it stays
TLC vis paper chromotgraphy
uses polar stationary silica phase instead of polar stationary phase (water absorbed on paper)
non polar mobile phase like paper chormography
better seperation
more support
TLC and paper chromotography both use Rf (retention factor)
What is Rf?
column chromotography
Column Chromatography is a preparative technique used to purify compounds depending on their polarity or hydrophobicity. In column chromatography, a mixture of molecules is separated based on their differentials partitioning between a mobile phase and a stationary phase.
gel fitration
seperation by size
affinity chromotography
uses antibodies to recognize shape of proteins
add 6 His residues to protein sequence with hi affinity to Nickel ions and you can isolate those proteins easily
ion exchange chromography
isolating compound based on net charge of molecule binding to column
anion (neg, de prot carboxylic)
cation (pos, prot amine)
isoelectric point or pI
ph at which the compound has a net charge of zero (zwitter ion form)
at pI - neutral
above pI - deprot, neg charged
below pI - prot, pos charged
we need to make sure pH is above pI to ensure binding to anion exchange column and vice versa
how to elute anion and cation exchange column solutions
increasing concentration of buffered salt solution like NaCl allows for ions to compete for binding sites
less charge compounds will elute in low salt solutions (vice versa)
elute - remove (an absorbed substance) by washing with a solvent, especially in chromatograph
