PRELIM 2 Flashcards by Unknown Unknown

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

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atom economy

MW of atoms in desired products / MW of atoms in all reactants * 100

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what does an atom economy of 54% mean

46% wasted

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prevention

better than remediation, avoid generating waste than dealing with it

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solution to prevention

design syntheses to prevent waste
avoid waste treatment or clean up
minimize waste amount

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what is E-factor (environmental factor)

total mass of waste from process / mass of product = all - product / product

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ideal E-factor

0, no waste produced (crude oil refinement)

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example of e-factor (bulky and pharmaceuticals)

bulky (solvents): 1-5
pharma: ~4000 (lots of steps and need to be pure)

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what is NOT waste

water (not contaminated)
recyclable solvents
evaporable solvents

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when is water considered waste

contaminated (i.e. with DCM or halogenated solvents)

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process mass intensity

mass of all materials used / mass of product (includes silica, catalysts, solvents, magnesium sulfate, etc)

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describe strong acid

lots of dissociation into H+ and A-, big Ka, small pKa

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when pH = pKa…

[acid] = [conjugate base]

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when pH solution > pKa molecule…

molecule is mostly de-protonated (mostly conjugate base)
negative if acid
neutral if base

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when pH solution < pKa molecule…

molecule is mostly protonated (mostly acid)
neutral if acid
positive if base

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Ka formula for acid and base

acid: [A-][H+] / [AH]
base: [B][H+] / [BH+]

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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

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why is DCM bad

goes through nitrile gloves

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what is in anacin

caffeine + aspirin + starch

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esterification formula

alcohol + COOH –(acid catalyst)–> ester + water

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why is H2SO4 or sulfuric acid bad catalyst

thick, leaves mess, gives chemical burns

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advantages of p-toluene sulfonic acid

crystal, solid

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how to purify esters

use extraction

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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

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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 = (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

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