Final Study Guide Flashcards by Catherine Anaya

Henderson Hasselbach Eq

pka = pH + log HA/A-

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Relationship between pH and pka

pH < pka = acidic form favored
pH > pka = basic form favored

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ARIO Priority

1) Atom
2) Resonance
3) Induction
4) Orbitals

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ARIO - atom

1) size (when comparing atoms in same group): larger atom, stronger acid, more stable base

2) electronegativity (when comparing atoms in same period): more eneg atom, stronger acid, more stable base

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ARIO - Resonance

atoms with possible resonance are more acidic, more stable base

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ARIO - induction

adding a substituent increases acidity
- greater effects for # of subs, eneg of sub, and proximity of sub

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ARIO - orbitals

the more S character, the more stable the base and more acidic the cmpd
- pka 25, 40, 60

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DoU formula

(2C + 2 + N - H - X) / 2

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Stereocenter

atom where swapping any 2 groups attached produces stereoisomer of original cmpd
- cis / trans
- enantiomers
- diastereomers

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Optical activity

cmpd containing a chiral center that is not meso

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Specific rotation formula

specific rotation = observed rotation / conc * path length (dl)

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regioselectivity

preferential formation of 1 constitutional isomer over all others

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most stable alkene has the ______ heat of hydrogenation

smallest

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stereoselective

preferential formation of one stereoisomer over another
- if its syn or anti

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stereospecific

if each stereoisomer of the reactant produces a different stereoisomer as a product

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Hydrogen halide

syn and anti addition
C+ intermediate

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water

syn and anti addition
C+ intermediate
uses H2SO4 as catalyst
- mechanism involves H3O+

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alcohols

syn and anti addition
C+ intermediate
uses H2SO4 as a catalyst
- mechanism involves ROH2

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Hydroboration Oxidation

syn addition
- always cis product
uses BH3/THF or 9-BBN and OH, H2O2, H20

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Halogenation

anti addition
-cis: same stereo
- trans: trans stereo
- cyclic : trans stereo
uses H2O or CH2Cl2 as solvent

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Peroxyacid (Epoxidation)

syn addition
- cis : cis stereo
- trans: trans stereo

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Hydrogenation

syn addition (using staggered conformation)
- cis: trans stereo
- trans: cis stereo
- cyclic: cis stereo

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Epoxide opening

uses LAH + H+

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Carbene addition

syn addition
- cis: cis stereo
- trans: trans stereo
uses reversible delta and tert O-

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Simmons Smith Reaction

uses CH2I2 with Zn (Cu) to form cyclopropane

Alkyne Hydrogen Halidess

- creates trans alkene - internal symmetric and terminal: form 1 P - internal asymmetric: form 2 P

Alkyne Halogenation

- creates trans alkene

Alkyne Water

- Markovnikov addition - uses H2SO4 - terminal: acid cat mech, use HgSO4 - internal symmetric: 1 P - internal asymmetric: 2 P

Alkyne Hydroboration Oxidation

- add syn to alkene - use OH- for base cat taut

Alkyne Hydrogenation

- to stop at cis alkene: use H2 and Lindlars cat - to stop at trans alkene: use Na or Li / NH2 at -78 degrees

To form acetylide

use NH2-

Alkylation reaction

uses chan of Br to elongate alkyne chain

Factors that decrease predicted resonance stability

1) incomplete octet atom 2) neg charge not on most eneg atom 3) pos charge on an eneg atom 4) separated charges

factors that increase delocalization energy (increase stability)

1) greater # stable contributors 2) more nearly equivalent contributors

Delocalization energy

stability gained by delocalizing e-'s

Conjugated dienes are more stable due to...

1) e- delocalization: ability for res 2) hybridization: more s character overlap

Stability of Alyllic and Benzylic C+

3 benz > 2 benz > 1 benz = allylic = 3 C+

Delocalization ____ acidity

increases

e- donation makes for a _____ acid and ______ base

weaker, less stable / stronger

e- withdrawal makes for a _____ acid and _____ base

stronger, more stable / weaker

e- donation by hyperconjugation

alkyl grp (methyl, ethyl, etc) donates e- to C

e- donation by resonance

sub. w/ L.P. atom donates to resonance

e- withdrawal by induction

e-neg atom sub. withdrawals e-'s

e- withdrawal by resonance

sub. w/ pi bond to e-neg atom withdrawals e-'s

EWG induction vs EDG resonance

EWG if sub is highly eneg EDG if sub has multiple L.P. or is not very eneg

kinetic product

forms faster, always 1,2

thermodynamic product

more stable, can be 1,2 or 1,4

proximity effect

1,2 product is always formed faster b/c Br is closer to 2 position than 4

to obtain kinetic control

use lower temps (forms 1,2)

to obtain thermodynamic control

use higher temps (forms 1,4)

aromaticity req.

1) planar, cyclic, uninterrupted p orbital 2) odd # pi e- pairs

antiaromaticity req.

1) planar, cyclic, uninterrupted p orbital 2) even # pi e- pairs

heterocyclic atom - when do LP count?

contains anything but C or H in cyclic cmpd - counts when atom w LP is not bound to a double bond

Sn2 rxn stereochem and attack style

flipped / inverted stereochem - due to backside attack (attacks at site of hashed wedge)

What impacts rate of Sn2 rxns

1) conc of both reactants 2) steric hinderance - bulkier sub = slower rxn 3) LG stability 4) a good nuc

Leaving group stability

the weaker the base, the better the leaving group - I- is best leaving group - F- is worst leaving group

Polar protic solvent

H attached directly to N or O

Polar aprotic solvent

H attached to anything except N or O

When is a strong base a better nucleophile?

In Sn2 reactions when: - atoms are same size - in polar aprotic solvent (diff sized atoms)

When is a weak base a better nucleophile?

In Sn2 reactions when: - in polar protic solvent (diff sized atoms)

Sn2 rxn rate trend

methyl bromide > 1 alk hal > 2 alk hal >>>> 3 alk hal

Sn1 rxn rate trend

only 3 alk hal undergoes Sn1 (unless indicated in problem)

Sn1 Rxn stereochem and attack style

Forms racemic mixture stereochem - due to carbocation formation

What substrates can undergo both Sn1 and Sn2 reactions

1 allylic 2 allylic 1 benzylic 2 benzylic

What dictates whether Sn1 or Sn2 is used when substrate can react using both pathways?

The nucleophile - good nucleophile = Sn2 - poor nucleophile = Sn1

What cannot undergo Sn1 or Sn2?

anything with a double bond connected to leaving group - Sn2: nucleophile cannot attack due to e- cloud - Sn1: carbocation formed is too unstable

Williamson Ether Synthesis

alkyl halide + alkoxide ion forming ether - follows Sn2 rules

Intermolecular rxns

2 mcls undergoing Williamson Ether synthesis

Intermolecular rxns

1 mcl undergoing Williamson Ether synthesis - forms cyclic cmpds from 3-6 membered rings

Final Study Guide Flashcards

(69 cards)