Organic Chemistry

Learn the toughest concepts covered in Organic Chemistry with step-by-step video tutorials and practice problems by world-class tutors.

6. Thermodynamics and Kinetics

Carbocation Intermediate Rearrangements

Carbocations will rearrange to an adjacent, more stable position if possible. These have different names based on which atoms are rearranging.

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concept

Understanding why carbocations shift.

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a. 1,2-Hydride Shift occurs when there is a hydrogen located on an adjacent, more stable carbon.

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Hydride Shift

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b. 1,2-Alkyl Shift occurs when only small alkyl groups are located on an adjacent, more stable carbon.

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Alkyl Shift

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c. Ring Expansion occurs when a carbocation is adjacent to a 3, 4 or 5-membered ring.

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Ring Expansion

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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. 

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concept

Intro

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Which of the following carbocations are likely to rearrange?

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Problem

Which of the following carbocations would be likely to rearrange? Draw each rearranged structure below.

Molecule I

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Problem

Which of the following carbocations would be likely to rearrange? Draw each rearranged structure below.

Molecule II

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Problem

Which of the following carbocations would be likely to rearrange? Draw each rearranged structure below.

Molecule III

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Problem

Which of the following carbocations would be likely to rearrange? Draw each rearranged structure below.

Molecule IV

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So, how'd you do? 

 

I know you guys rocked it. Let's move on.