PRELIM 2 Flashcards
list 12 principles of green chemistry
catalysis
atom economy
reduce derivatives
degradation
safer solvents / chemicals
hazardous chemical syntheses
accident prevention
renewable feedstock
prevention, pollution prevention
energy efficiency
atom economy
MW of atoms in desired products / MW of atoms in all reactants * 100
what does an atom economy of 54% mean
46% wasted
prevention
better than remediation, avoid generating waste than dealing with it
solution to prevention
design syntheses to prevent waste
avoid waste treatment or clean up
minimize waste amount
what is E-factor (environmental factor)
total mass of waste from process / mass of product = all - product / product
ideal E-factor
0, no waste produced (crude oil refinement)
example of e-factor (bulky and pharmaceuticals)
bulky (solvents): 1-5
pharma: ~4000 (lots of steps and need to be pure)
what is NOT waste
water (not contaminated)
recyclable solvents
evaporable solvents
when is water considered waste
contaminated (i.e. with DCM or halogenated solvents)
process mass intensity
mass of all materials used / mass of product (includes silica, catalysts, solvents, magnesium sulfate, etc)
describe strong acid
lots of dissociation into H+ and A-, big Ka, small pKa
when pH = pKa…
[acid] = [conjugate base]
when pH solution > pKa molecule…
molecule is mostly de-protonated (mostly conjugate base)
negative if acid
neutral if base
when pH solution < pKa molecule…
molecule is mostly protonated (mostly acid)
neutral if acid
positive if base
Ka formula for acid and base
acid: [A-][H+] / [AH]
base: [B][H+] / [BH+]
relation between partition coefficient and pH
increase pH = strong acid de-protonates = partition coefficient decreases (moves to aqueous layer)
charged molecules are more soluble in water
why is DCM bad
goes through nitrile gloves
what is in anacin
caffeine + aspirin + starch
esterification formula
alcohol + COOH –(acid catalyst)–> ester + water
why is H2SO4 or sulfuric acid bad catalyst
thick, leaves mess, gives chemical burns
advantages of p-toluene sulfonic acid
crystal, solid
how to purify esters
use extraction
how to drive esterification to products
need to push towards products because equilibrium constant is small (by putting in excess of reactant, we did COOH)
OR remove H20 with sieve
why is catalyst needed in esterification
protonate the carbonyl oxygen of the carboxylic acid, which makes it more electrophilic and more susceptible to nucleophilic attack by the alcohol
if you start with achiral and add stereocenter, what will product be
racemic
what did walter do wrong in the show?
he started with achiral so that means he didnt make enantiomerically pure meth, he made racemic
sudafed and meth
sudafed is correct stereoisomer (SS) of meth but it has an additional OH
equation for specific optical rotation
specific optical rotation = observed angle of rotation / (c * l)
[alpha] = alpha_observed / (c * l)
EE
EE = (observed specific optical rotation )/(maximum specific rotation)
% isomer in excess
EE / 2 + 50%
chiral switch
switching drug from racemic to chiral (enantiomerically pure)
what does S proline do
enantiomerically pure catalyst; makes chiral transition state and therefore induces stereospecificity
how can we increase yield and decrease cost
reduce number of steps
thalidomide
racemic mixture marketed as safe anti-nausea drug for pregnant women but deformed babies were born because of (R)
distillation
used to separate liquids that ARE miscible in each other
fractional distillation
pure vapors condense on fractioning column then boil again to be even more pure
how are boiling point and vapor pressure related
lower boiling point = higher vapor pressure
vapor pressure of mixture
p_total = p_1 + p_2
mole fraction
x = mol x / mol total
when does boiling happen
P_vapor = P_atmosphere (on mountain, lower atm so lower bp so it takes longer to cook)
Raoult’s Law
vapor pressures can be calculated from mole fraction
(P_a = P_a* X x_A)
vapor pressure of A = vapor pressure of pure A * mol fraction A
bottom curve of distillation (bubble point)
BP of 2 component system; ends show BP of A and B
top curve of distillation (dew point curve)
BP of a liquid with that vapor composition; temperature at which vapor condenses
simple distillation
works well when BP different of solvents is big (>50 C)
refractive index
measures purity of liquids by measuring bending of light as it passes from one medium to another
refractive index equation
n_obs = n_A * x_A + n_B * x_B
measured RI = RI of A * mole fraction A + RI of B * mole fraction B
note x_A + x_B = 1
why did we use pyridinium tribromide instead of Br2 only
solid, easier to weigh; bromine is liquid BC polarization and vapors are dangerous
is it easier to synthesize racemic or enantiomerically pure
racemic
Sepracor scam
create 1 enantiomer of racemic mixture and sell back to company
positive deviation from Raoults law
- VP is greater than expected
- cannot separate components completely because you cannot change composition of the vapor (boils both at same temperature)
- BP azeotrope is less than both pure components
negative deviations from Raoults Law
- VP is lower than expected
- can separate components depending on compositions
- BP azeotrope is more than both pure components
azetrope
constant boiling temperature, vapor and liquid have same composition
do safer drugs have wider or narrower therapeutic windows
wider
danger of narrow window
small increase in dose may produce toxic effects, higher risk of overdose
lethal dose 50%
dose at which compound kills half the test animals
effective dose 50
dose required for 50% of subjects to experience given effect
toxic dose 50
dose where 50% experience toxic effect
therapeutic index
LD50 / ED50 for animals
TD50 / ED50 for humans
formaldehyde
carcinogen, causes cancers like leukemia, in vaccines (small amounts)
aspartame
artificial sweetener that breaks down into formaldehyde inside the body
are esters ionizable
no
large esters low VP (smell)
never reaches nose
purpose of bicarbonate wash
neutralize any remaining acidic components (carboxylic acid which was excess) in the organic layer
