Chapter 8, Problem 8.19YT

Interpretation Introduction

Interpretation:

Free energy diagrams for the carbocation rearrangements shown in Equations 8-40 and 8-41 are to be drawn.

Concept introduction:

Carbocations are charged, high energy species. They are reactive species as a result of the high energy. They are also subject to rearrangements, particularly if it results in an alternate structure of lower energy. The carbocation may be stabilized by hyperconjugation or by resonance delocalization of the charge. The stability of a carbocation increases in the order ${\text{1}}^{\text{o}}{\text{ < 2}}^{\text{o}}{\text{ < 3}}^{\text{o}}$ as the extent of hyperconjugation increases. A primary carbocation can be converted to a more stable secondary or tertiary carbocation by the migration of a hydride ion or a methyl group from an adjacent carbon. This is known as $\text{1, 2-hydride}$ or $\text{1, 2-methyl}$ shift.

Another way in which a carbocation can reduce its energy is through resonance; this delocalizes the charge on more than one atom.