Organic Chemistry

Question 1

determining R/S

Answer 1

lowest in back, determine direction
Fischer – ignore #4, determine direciton, flip to its opposite (R>S, S>R)

Question 2

polar protic solvent on nucleophiles

Answer 2

nucleophiles stronger DOWN periodic table

Question 3

polar aprotic solvent on nucleophiles

Answer 3

nucleophiles stronger UP periodic table

Question 4

phenols

Answer 4

OH groups on aromatic ring
H is very acidic due to resonance stabilization of O-

Question 5

1° OH –> aldehyde

Answer 5

PCC ONLY
rare

Question 6

1° OH –> COOH

Answer 6

most strong OA’s

Question 7

2° OH –> ketone

Answer 7

PCC
or STRONG OA

Question 8

mesylate/tosylates

Answer 8

make OH groups on alcohols better LG’s
protect OH groups because they don’t react

Question 9

acetal vs hemiacetal

Answer 9

hemiacetal = RO-C-OH
acetal = RO-C-OR
make by adding 1 or 2 alcohols (-OR)

Question 10

stabilization of C-

Answer 10

EWG stabilize -
EDG destabilize -
(opposite for C+?)

Question 11

michael addition

Answer 11

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

Question 12

claisen condensation

Answer 12

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)

Question 13

more stable conjugate base = stronger acid

Answer 13

EWG stabilize conjugate base and increase acidity
EDG destabilize conjugate base and lower acidity

Question 14

reactivity: carbox acid derivatives

Answer 14

anhydrides > esters = carbox acid > amides
all derivatives formed by condensation rxn with COOH and nucleophile

Question 15

amides

Answer 15

nuc. acyl sub with COOH + amine/ammonia
cannot occur with tertiary amines
cyclic amides = lactams

Question 16

esters

Answer 16

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

Question 17

annhydrides

Answer 17

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

Question 18

induction

Answer 18

distribution of charge across SIGMA bonds
polarity

Question 19

conjugation and resonance

Answer 19

alternating single and multiple bonds
very stable compounds
stabilize + charge after nucleophilic attack = high reactivity

Question 20

ring strain

Answer 20

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!

Question 21

annhydride cleavage

Answer 21

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

Question 22

transesterification

Answer 22

new alcohol (nuc) attacks C=O of ester + replaces old ROH group in ester

Question 23

AA’s

Answer 23

alpha carbon is chiral (except Gly)
ONLY L-isomers EXIST (NH2 on L side in fischer)

Question 24

strecker synthesis of AAs

Answer 24

1. aldehyde > protonate to OH+ > NH3 attacks carbonyl > lose H2O as LG > CN- nuc attacks C=N, bumps up bond to form Nitrile
2. protonate nitrile > H2O attacks twice (2x OH), carbonyl reforms + kick off NH3 as LG

Question 25

gabriel synthesis of AAs

Answer 25

begins with potassium pthalimide & diethyl bromomalonate

Question 26

**peaks on IR spectroscopy**

Answer 26

OH (alcohol) = 3300 broad OH (carbox acid) = 3000 broad NH = 3300 SHARP C=O = 1750 SHARP

Question 27

IR spectroscopy

Answer 27

* measures molecular vibration * **determines FUNCTIONAL groups** * look at fingerprint region = 1400-4000 cm-1 (wavenumber = frequency = 1/wavelength)

Question 28

UV-vis spectroscopy

Answer 28

* useful for studying systems with **conjugated rings** * high conjugation = low energy gap = higher wavelength absoption (eg. red)

Question 29

NMR spectroscpy

Answer 29

* measure allignment of nucelar spin with magnetic field * **determine connectivity** * spectrum is frequency VS absorption * uses "chemical shift" in ppm

Question 30

reading NMR spectroscopy

Answer 30

* 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**

Question 31

SN1

Answer 31

The reactivity of an SN1 mechanism decreases as 3o > 2o > 1o If dissociation of LG produces tertiary C+, EDG's stabilize it more