Organic Chemistry Exam 3 Sn1 SN2 E1 E2

DBN

Strong base, weak nucleophile

DBU

Strong base, weak nucleophile

t-BuO -

Strong base, weak nucleophile, bulky steric hinderance, cannot backside attack on SN2 so E2 and Hofmann

HO -

Strong base, strong nucleophile

CH3O - or MeO -

Strong base, strong nucleophile

CH3CH2 - or EtO -

Strong base, strong nucleophile

I -

Weak base, strong nucleophile

Br -

Weak base, strong nucleophile

Cl -

Weak base, strong nucleophile

RS -

Weak base, strong nucleophile

HS -

Weak base, strong nucleophile

RSH

Weak base, strong nucleophile

H2S

Weak base, strong nucleophile

H2O

Weak base, weak nucleophile

CH3OH or MeOH

Weak base, weak nucleophile

CH3CH2 or EtOH

Weak base, weak nucleophile

Strong reagent

high reactivity

Weak reagent

low reactivity

Bimolecular reactions

SN2: rate law = k [Nu][R-X], E2: rate law = k [base][R-X] and strong reagents

Unimolecular reactions

SN1 E1 and weak reagents: : rate law = k [R-X],

SN1 substrates

3° > 2° , NO METHYL OR 1° REQUIRES STABLE CARBOCATION

SN2 substrates

METHYL > 1° > 2°, NO TERTIARY, RATE DECREASES WITH STERIC HINDERANCE ONLY REACTION WITH METHYL

E1 substrates

3° > 2°, NO METHYL OR 1° REQUIRES STABLE CARBOCATION, NEEDS B-H

E2 substrates

1° = 2° = 3°, NO METHYL, NEEDS B-H

1° Strong Base Weak Nucleophile

E2 ONLY REACTION

1° Strong base Strong Nucleophile

SN2 MAJOR, E2 MINOR

Weak Base, Strong Nucleophile

SN2 ONLY REACTION

1° Weak Base Weak Nucleophile

NO REACTIONS

2° Strong Base Weak Nucleophile

E2 ONLY REACTION

2° Strong Base Strong Nucleophile

E2 MAJOR, SN2 MINOR

2° Weak Base, Strong Nucleophile

SN2 ONLY REACTION

2° Weak Base, Weak Nucleophile

BOTH SN1 AND E1 ARE MAJOR

3° Strong Base, Weak Nucleophile

E2 ONLY REACTION

3° Strong Base Strong Nucleophile

E2 ONLY REACTION

3° Weak Base Strong Nucleophile

SN1 ONLY REACTION

3° Weak Base Weak Nucleophile

BOTH SN1 AND E1 ARE MAJOR

Other substrates: 1° Strong Base Weak Nucleophile

SN2 ONLY

Other substrates: 1° Strong Base Strong Nucleophile

SN2 ONLY

Other substrates: 1° Weak Base Strong Nucleophile

SN2 ONLY

Other substrates: 1° Weak Base Weak Nucleophile

SN1 ONLY

Other substrates: 2° Strong Base Weak Nucleophile

E2 ONLY

Other substrates: 2° Strong Base Strong Nucleophile

E2 MAJOR SN2 MINOR

Other substrates: 2° Weak Base Strong Nucleophile

SN2 ONLY

Other substrates: 2° Weak Base Weak Nucleophile

EQUAL SN1 AND E1

Other substrates: 3° Strong Base Weak Nucleophile

E2 ONLY

Other substrates: 3° Strong Base Strong Nucleophile

E2 ONLY

Other substrates: 3° Weak Base Strong Nucleophile

SN1 ONLY

Other substrates: 3° Weak Base Weak Nucleophile

EQUAL SN1 AND E1

Differences Between Normal AND Other Substrates

SN1 NOW WITH 1° STABLE CARBOCATION, SN1/E1 NOW WITH 2°, NO E2 WITH 1° NO B-H

IF THERE IS HEAT

ELIMINATION

Primary Substrates

ONLY BIMOLECULAR SO SN2 AND E2, STRONG NU = SN2, E2 ONLY IF STRONG BASE WEAK NU

Tertiary Substrates

STERIC HINDERANCE = NO SN2, E2 ONLY WITH STRONG BASE, WEAK BASE = NU STRENGTH

Secondary Substrates

E2 WITH STRONG BASE, SN2 WITH STRONG NU WEAK BASE, SN1/E1 SLOW WITH SIMPLE ALKYL SUBSTRATES, CHIRAL SN2 INVERSION, SLOW RATES SO POLAR, APROTIC SOLVENTS INCREASE RATE OF SN2

Hyperconjugation

Overlap of sigma C-H and 2p orbitals, stabilizes the + charge and creates a very weak pi bond, increase alkyl groups and make it more substituted = increase hyperconjugation and Zaitsev, decrease alkyl groups and make it less substitued = decrease hyperconjugation and Hofmann.

Zaitsev Product

More substituted alkyl groups, hyperconjugation, small bases, HO-, CH3O - or MeO-, CH3CH2- or EtO-, less bulky

Hofmann Product

Less substituted alkyl groups, less hyperconjugation, bulky bases and steric hinderance.

Product of SN1

Racemic mixture of enantiomers, retention is the same R or S, inversion is different R or S, carbocation needs to be stable, resonance can do this in 1° with benzylic, allylic, or alpha atom with lone pair on O or N

Product of SN2

Inversion, stereospecific

Product of E1

Zaitsev product is major

Product of E2

Either one, based on number of substituted alkyl groups and hyperconjugation, needs to be antiperiplanar: H and LG must be anti/180° and axial

SN1 and SN2 occur at what type of hybridized carbons

Sp3, SN1 needs it for stable carbocation when lg leaves and when benzylic or allylic, enables to occur with 1° substrates, SN2 needs it for neighboring pi orbitals to interact for lower EA and faster backside attack

Strong Nu for SN2 as SN1 does not depend on Nu

negative charge, less EN, more polarizable so I - > Br - > Cl - > F - in polar protic so h-bond and THE OPPOSITE FOR polar aprotic, less steric hinderance, and rod shape

SN2 is faster in what solvent

Polar, aprotic no h-bond or resonance stabilization and F - > Cl - > Br - > I - THIS IS RARELY USED RELY ON THE OTHER ONE ALWAYS USE POLAR APROTIC WITH I- BEING THE BEST WHY IS THIS SO CONFUSING I AM LITERALLY GONNA SUE LOL