SN1 Mechanism (tert-Butyl Chloride + Water)

Step 1 (Slow, RDS): Ionization
CC(C)(C)Cl  →  [CC(C)(C)+]  +  Cl-
tert-BuCl      tert-Butyl     Chloride
                carbocation    ion
                (planar, sp2)

Step 2a (Fast): Water attacks from top face
[CC(C)(C)+] + H2O → CC(C)(C)OH + H+   → gives (R)-product
Step 2b (Fast): Water attacks from bottom face
[CC(C)(C)+] + H2O → CC(C)(C)OH + H+   → gives (S)-product
Result: 50:50 mixture → RACEMIZATION

SN2 Mechanism ((R)-2-Bromobutane + OH-)

Transition State Geometry (180° attack):

HO-  ....C....  Br-
       /  |  \
     CH3  H  CH2CH3
     (three groups in equatorial plane,
      flipping from Br-side to HO-side)

Reactant: (R)-2-bromobutane  `SMILES: Br[C@@H](C)CC`
Product:  (S)-butan-2-ol     `SMILES: O[C@H](C)CC`

R → S: Complete Walden Inversion ✓

Finkelstein Reaction Scheme

CH3CH2Cl   +   NaI   ---[acetone]--->   CH3CH2I   +   NaCl↓
(chloroethane)  (soluble)              (iodoethane)  (precipitate)
SMILES: CCCl                                           SMILES: CCI

Driving force: NaCl is INSOLUBLE in acetone → precipitates → Le Chatelier drives forward

Swarts Reaction Scheme

CH3CH2Br   +   AgF   ---[neat]--->   CH3CH2F   +   AgBr↓
(bromoethane)                      (fluoroethane)  (precipitate)
SMILES: CCBr                        SMILES: CCF

Driving force: AgBr is INSOLUBLE → precipitates → Le Chatelier drives forward

Dow Process (Nucleophilic Aromatic Substitution)

Clc1ccccc1   +   NaOH   --[623 K, 300 atm]-->   Oc1ccccc1   +   NaCl
Chlorobenzene                                      Phenol

Meisenheimer Complex Intermediate:
Cl-
 \
[Ar-Cl-OH]- (anionic addition intermediate) → then Cl- departs → phenol

Label Table for Structures