CHE4803
ASSIGNMENT 2 2025
UNIQUE NO.
DUE DATE: 26 JUNE 2025
, Organic Chemistry IV
QUESTION 1 [25 MARKS]
1.1 Reagents, Conditions & Reaction Type (8 marks)
Transformation:
Involves substitution of OTs (tosylate) and OAc (acetate) under AcOH conditions.
Suggested Reaction Pathway:
Reagents: Acetic acid (AcOH), heat.
Reaction Type: SN1 substitution (since it's a tertiary carbon).
The tosylate (a good leaving group) departs, forming a carbocation, which is
then attacked by acetic acid or another nucleophile.
1.2 Mechanism, Orientation & Stereochemistry (7 marks)
Step 1: Loss of the tosylate group forms a stable tertiary carbocation.
Step 2: Depending on steric/electronic effects, the carbocation may rearrange
(hydride or methyl shift).
Step 3: Acetate ion (from AcOH) attacks the carbocation, leading to
substitution.
Stereochemistry:
SN1 mechanism → racemization (both retention and inversion possible).
Planar intermediate leads to non-stereoselective attack.
1.3 Definition & Mechanism of Ylides (9 marks)
ASSIGNMENT 2 2025
UNIQUE NO.
DUE DATE: 26 JUNE 2025
, Organic Chemistry IV
QUESTION 1 [25 MARKS]
1.1 Reagents, Conditions & Reaction Type (8 marks)
Transformation:
Involves substitution of OTs (tosylate) and OAc (acetate) under AcOH conditions.
Suggested Reaction Pathway:
Reagents: Acetic acid (AcOH), heat.
Reaction Type: SN1 substitution (since it's a tertiary carbon).
The tosylate (a good leaving group) departs, forming a carbocation, which is
then attacked by acetic acid or another nucleophile.
1.2 Mechanism, Orientation & Stereochemistry (7 marks)
Step 1: Loss of the tosylate group forms a stable tertiary carbocation.
Step 2: Depending on steric/electronic effects, the carbocation may rearrange
(hydride or methyl shift).
Step 3: Acetate ion (from AcOH) attacks the carbocation, leading to
substitution.
Stereochemistry:
SN1 mechanism → racemization (both retention and inversion possible).
Planar intermediate leads to non-stereoselective attack.
1.3 Definition & Mechanism of Ylides (9 marks)
