Carbocations will rearrange to an adjacent, more stable position if possible. These have different names based on which atoms are rearranging.
Concept #1: Understanding why carbocations shift.
a. 1,2-Hydride Shift occurs when there is a hydrogen located on an adjacent, more stable carbon.
Concept #2: Carbocation Rearrangments
b. 1,2-Alkyl Shift occurs when only small alkyl groups are located on an adjacent, more stable carbon.
Concept #3: Carbocation Rearrangements
c. Ring Expansion occurs when a carbocation is adjacent to a 3, 4 or 5-membered ring.
Concept #4: Carbocation Rearrangements
I hope we didn't lose you with that last one! Just remember to label your carbons and you will do great. :)
NOW, we will move on to some practice questions. Let's see if we can apply what we just learned to different molecules who may or may not want to undergo a rearrangment.
Concept #5: Intro
Which of the following carbocations are likely to rearrange?
Practice: Which of the following carbocations would be likely to rearrange? Draw each rearranged structure below.
Molecule I
Practice: Which of the following carbocations would be likely to rearrange? Draw each rearranged structure below.
Molecule II
Practice: Which of the following carbocations would be likely to rearrange? Draw each rearranged structure below.
Molecule III
Practice: Which of the following carbocations would be likely to rearrange? Draw each rearranged structure below.
Molecule IV
So, how'd you do?
I know you guys rocked it. Let's move on.