SN1 (hydrolysis): practice and mechanism
Tertiary haloalkanes form a stable carbocation in water (SN1); water traps it and the tertiary alcohol forms.
Example
Tertiary haloalkanes react via SN1: the halide leaves first and a stable tertiary carbocation forms. Water attacks it and a tertiary alcohol results. Polar protic water stabilises the carbocation.
Mechanism step by step
- 1
The halide leaves on its own (slow, rate-determining step), leaving a tertiary carbocation.
- 2
The planar carbocation is attacked by water from above or below (with stereocentres: racemate).
- 3
Another water molecule removes a proton: the tertiary alcohol forms.
Practice tasks
Which product forms, which reagent is needed? After each answer you see the explanation.
Which main product forms?
Typical mistakes
Often confused with: E2 (Zaitsev product) · SN1 (solvolysis in ethanol)
Frequently asked questions
Why is the tertiary carbocation so stable?
Three alkyl groups push electron density towards the positive carbon (inductive effect and hyperconjugation).
What does the rate depend on?
Only on the haloalkane concentration (rate = k·[RX]), because forming the carbocation is the slow step.