extraction
based on polarity, solubility, and miscibility
polarity
net dipole from polar bonds
solubility
like dissolves like (polar with polar)
intermolecular forces
more polar --> London > dipole-dipole > H bond > ion-dipole
miscibility
extent to which layers form based on solubility and density
immiscible
form layers (oil and water)
3 types of extraction
solid/liquid, liquid/liquid, chemically active
solid/liquid extraction
extracts soluble compounds from the solid (making coffee)
liquid/liquid extraction
compounds are separated between two immiscible solvents with opposing polarity; based on Kd
partition distribution coefficient
kd = [A]org/[A]aq; Kd>1 then in organic layer; Kd<1 then in aq layer
top layer
less dense always; usually organic
halogenated organic solvents
exception to which layer is on the top; more dense compared to water so will be on the bottom
chemically active
adding acid/base to change polarity of a compound
acid
loses a hydrogen atom
recrystallization
purifies non-volatile solids based on solubility and crystal lattice theory (thermodynamics)
solubility
how something dissolves; 3 stages of a solid (collision, dissociation, and solvation); increases with temperature
collision
undissolved solid
dissociation
more kinetic energy in the solid; more soluble
solvation
dissolved solid
crystal lattice theory
thermodynamics; G=H-TS
recrystallization process
impure solid + boiling hot solvent --> solution saturated with desired solid and unsaturated with impurities --> after cooled, pure solid recrystallizes
solvent used for recrystallization
insoluble at a low temp and soluble at a high temp
nucleation
seeding, glass seeding, and cool on ice
physical properties
can be observed/measured without changing substances identity
intrinsic/intensive properties
constant regardless of quantity; MP, BP, solubility, density
extrinsic/extensive properties
depends on the quantity; mass, volume, entropy
physical change
doesn't disturb covalent bonds or composition (usually referring to phase change)
melting point range
temperatures at which solid and liquid are in equilibrium, which isn't the amount, but the rate of exchange
1-2
pure melting point range within
lower
impure samples will melt at higher or lower temperatures
mixed melting point technique
when the melting point range matches more than one compound
boiling point
temperature at which vapor P of 1atm; vapor P of liquid = atmospheric pressure
<
if P<1atm then BP ___ literature BP
Raoult's Law
nonvolatile impurity increase experimental BP; VPa(impure) = VPa(pure)*X(mole fraction of A); if Xa<1, VPa<Vpa(pure) because Xa is not 100% so impure and increase T
distillation
can determine BP (identity/purity) and purify a volatile liquid
simple distillation
can separate volatile liquid from nonvolatile impurity, usually solid; separate two liquids with large difference in BP
simple distillation
can't separate two liquids with a BP within 50 degrees of one another
Dalton's Law of Partial Pressure
at constant volume and temperature, the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of the component gases
fractional distillation
uses columns that allow for multiple simple distillations in 1 experiment
less
the smaller the difference in BP, the ____ theoretical plates needed
height equivalent of theoretical plate
smaller height is better because takes less time to distill
reflux ratio
R ~ drops return to flask (into boiling flask)/drops collected (after condensed); large R is better because want slow distillation to get effective separation become some is coming back; should equal the number of TP
azeotropes
2 liquids in a specific mole fraction ratio act as a pure liquid; impossible to separate; composition of the vapor phase = composition of the liquid phase
chromatography
method used to separate components of a mixture based upon physical properties
types of chromatography
gas, column, thin layer, and high performance liquid
mixture partition
Kp(x) = [x]stationary/[x]mobile; Kp>1 then retained in the stationary phase longer; stationary is more polar
gas chromatography
analyzes heat stable volatile compounds by: checkin the sample purity, identifying components of a mixture, and purifying a substance (on a small scale)
mobile gas
inert (He, Ar)
injection port
vaporizes sample in gas phase in GS
thermal conductivity detector
keeps sample intact in GS
attentuator
weakens signal from detector to make readable in GS
Vernier hardware
generate readable chromatogram
coiled column
where the separation happens in GS; long metal tube containing silicone
larger surface area
elutes slower from column (more column interaction)
smaller surface area
elutes faster (fewer interactions); more in mobile phase
silica gel and alumina
two types of stationary solids (polar)
silica gel
SiO2; slightly acidic
alumina
Al2O3; slightly basic
eluatropic series
polar --> alkanes (pet ether, ligroin, hexanes) > acetone > methanol > acetic acid; compounds elute nonpolar to polar
ligroin
C7-C11; hydrocarbons saturated
mobile liquids
eluents that differ in their polarity; used in GS
column chromatography
separates based upon polarity; adsorption (stationary)/desorption (mobile)
thin layer chromatography
used to monitor the process of the reaction, test for impurity, see what is in the solvent
tension surface force and adhesive force
capillary action is based on
retention factor
A/B; less polar solvent (further from bottom) = larger Rf; range from 0-1
IR
determines the presence/absence of functional groups
mass and bond order
frequency absorved by bond depends on
mass
heavier then slower (smaller frequency absorbed)
bond order
stronger bonds are faster C=C>C-C
synthesis
overall transformation from one functional group to another