Advices For Studying Organic Chemistry

A Mechanism for the Reaction

Reaction of tert-Butyl Alcohol with Concentrated Aqueous HCl:

Step 1

HO

H

O H + H OH O

H

H

H

H 3 C C +

CH 3

CH 3

+

tert-Butyl alcohol acts as a base and

accepts a proton from the hydronium ion.

H 3 C C +

CH 3

CH 3

The product is a protonated alcohol and

water (the conjugate acid and base).

tert-Butyloxonium ion

Step 2

H 3 C C

CH 3

CH 3

OH

H

O

H

+ H 3 CC H

CH 3

CH 3

+ +

Carbocation

The bond between the carbon and oxygen of the tert-butyloxonium ion breaks

heterolytically, leading to the formation of a carbocation and a molecule of water.

Step 3

H 3 CC Cl −

CH 3

CH 3

+ + H 3 C C

CH 3

CH 3

Cl

tert-Butyl chloride

The carbocation, acting as a Lewis acid, accepts an electron

pair from a chloride ion to become the product.

2. Step 1 is a straightforward Brønsted acid-base reaction.


3. Step 2 is the reverse of a Lewis acid-base reaction. (The presence of a formal
   positive charge on the oxygen of the protonated alcohol weakens the