Organic Chemistry Flashcards
determining R/S
lowest in back, determine direction
Fischer – ignore #4, determine direciton, flip to its opposite (R>S, S>R)
polar protic solvent on nucleophiles
nucleophiles stronger DOWN periodic table
polar aprotic solvent on nucleophiles
nucleophiles stronger UP periodic table
phenols
OH groups on aromatic ring
H is very acidic due to resonance stabilization of O-
1° OH –> aldehyde
PCC ONLY
rare
1° OH –> COOH
most strong OA’s
2° OH –> ketone
PCC
or STRONG OA
mesylate/tosylates
make OH groups on alcohols better LG’s
protect OH groups because they don’t react
acetal vs hemiacetal
hemiacetal = RO-C-OH
acetal = RO-C-OR
make by adding 1 or 2 alcohols (-OR)
stabilization of C-
EWG stabilize -
EDG destabilize -
(opposite for C+?)
michael addition
form C-C bonds!
1. base deprotonates alpha carbon, enol–enolate ion
2. enolate ion (Nuc) attacks alpha-beta unsaturated C=C bond, bonds NEW C-C
claisen condensation
form new C-C bond
occurs between 2 esters or cabonyl-containing compounds
makes a beta-keto ester (ester + another C=O on B-carbon)
more stable conjugate base = stronger acid
EWG stabilize conjugate base and increase acidity
EDG destabilize conjugate base and lower acidity
reactivity: carbox acid derivatives
anhydrides > esters = carbox acid > amides
all derivatives formed by condensation rxn with COOH and nucleophile
amides
nuc. acyl sub with COOH + amine/ammonia
cannot occur with tertiary amines
cyclic amides = lactams
esters
nuc. acyl sub with COOH + alcohol (ROH)
esterification produces water (condensation)
fischer esterification (acidic cond.) – carbonyl attacked by alcohol
cyclic esters = lactones
no H-bonding, lower boiling point than alcohols
annhydrides
2x COOH’s – OH of one attacks C=O of other
cleavage: nuc attacks C=O of one, kicks other COOH off as a LOG
induction
distribution of charge across SIGMA bonds
polarity
conjugation and resonance
alternating single and multiple bonds
very stable compounds
stabilize + charge after nucleophilic attack = high reactivity
ring strain
lactams/lactones can be more reactive when there is ring strain
eg. antibiotics have B-lactams (high reactivity), some bacteria have enzymes that break these rings as a mechanism of resistance!
annhydride cleavage
nuc attacks one C=O, kicks other COOH off as LG
1. Nuc = NH3 = amide + COOH
2. Nuc = ROH = ester + COOH
3. nuce = H2O = 2x COOH
transesterification
new alcohol (nuc) attacks C=O of ester + replaces old ROH group in ester
AA’s
alpha carbon is chiral (except Gly)
ONLY L-isomers EXIST (NH2 on L side in fischer)
strecker synthesis of AAs
- aldehyde > protonate to OH+ > NH3 attacks carbonyl > lose H2O as LG > CN- nuc attacks C=N, bumps up bond to form Nitrile
- protonate nitrile > H2O attacks twice (2x OH), carbonyl reforms + kick off NH3 as LG
gabriel synthesis of AAs
begins with potassium pthalimide & diethyl bromomalonate
peaks on IR spectroscopy
OH (alcohol) = 3300 broad
OH (carbox acid) = 3000 broad
NH = 3300 SHARP
C=O = 1750 SHARP
IR spectroscopy
- measures molecular vibration
- determines FUNCTIONAL groups
- look at fingerprint region = 1400-4000 cm-1 (wavenumber = frequency = 1/wavelength)
UV-vis spectroscopy
- useful for studying systems with conjugated rings
- high conjugation = low energy gap = higher wavelength absoption (eg. red)
NMR spectroscpy
- measure allignment of nucelar spin with magnetic field
- determine connectivity
- spectrum is frequency VS absorption
- uses “chemical shift” in ppm
reading NMR spectroscopy
- hieght of peak proportional to # of H’s
- each peak group is a UNIQUE H group (different carbons) unless molecule symmetrical
- splitting: # of peak splits = n + 1 (n = # of other H’s surrounding on adjacent C’s)
- further LEFT = DESHIELDING by EWG or multiple bonds
- peak at 0ppm = TMS control (ignore)
- ORDER (L-R): COOH > aldehyde > aromatic > halide > alkane
SN1
The reactivity of an SN1 mechanism decreases as 3o > 2o > 1o
If dissociation of LG produces tertiary C+, EDG’s stabilize it more
