Chapter 14, Problem 14.71P

14-71 The mechanism of the acid-catalyzed dehydration of an alcohol to an alkene is the reverse of the acid- catalyzed hydration of an alkene. The dehydration mechanism occurs by the following three steps.

Step 1: Add a proton.

Step 2: Break a bond to form stable molecules or ions. Step 3: Take away a proton.

These three steps are illustrated here by the dehydration of 2-butanol to give 2-butene. Use curved arrows to show the flow of electrons in each step; that is, show how each bond-making or bond-breaking step occurs.

H

I +

Step 3: CH₃—CH—CH—CH₃

CH₃—CH=CH—CH₃ + H +

2-butene