SN1 vs. SN2 reactions

kinetics SN1

rate= k[rx]

kinetics SN2

rate= k[rx][nuc]

substrate SN1

3>2»»1 (favors tertiary and secondary)

substrate SN2

Methyl>1>Rx»»>2Rx »»>3 (favors methyl and primary)

Nucleophile SN1

weak (usually neutral poor electron donor)

Nucleophile SN2

strong (strong bases w/ negative charge attached to a good leaving group)

solvent SN1

polar protic

solvent SN2

mostly polar aprotic (some polar protic though)

Stereochemistry SN1

inversion and retention

Stereochemistry SN2

inversion

mechanism SN1

3 steps: 1. loss of LG 2. Nucleophilic attack 3. Acid-Base reaction

mechanism SN2

1 step: nucleophile attacks electrophillic carbon and LG leaves

examples of strong nucleophiles

NaOH

NaCN

NaN3

NaOCH3

NaOEth

NaX (Halides)

NaSH

NaSR

SH2

SR2

PR3

examples of weak nucleophiles

H2O

ROH

NH3

R-COOH (carboxylic acid)

What is considered a good leaving group?

a weak base/ the conj base of a strong acid

examples of good leaving groups

Cl-

Br-

I-

OTS

OMS

OTF

examples of polar protic solvents

CH3OH (methanol)

H2O

CH3CH2OH (ethanol)

R-COOH (Acetic/Carboxylic acid)

examples of polar aprotic solvents

DMSO (Dimethylsulfoxide)

DMF (Dimethylfloramide)

CH3CN (acetonitrile)

acetone