CHM 25500 Lecture Notes - Lecture 20: Hyperconjugation, Ion, Pi Bond
20 Jul 2015
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Chm 255 - lecture 20 - reaction intermediates: carbocations. Carbocations are molecules that contain an sp2 hybridized carbon with 3 groups attached and a positive charge. The groups attached to the charged carbon are all in the same plane. The remaining p orbital is perpendicular to the plane and contains no electrons. Carbocations are stabilized by groups that release electrons. The more carbons a carbocation is attached to, the more stable it is. I. e. methyl cation is less stable than a primary carbocation, which is less stable than a secondary carbocation, which is less stable than a tertiary carbocation (the most stable) There are two ways that adjacent carbons stabilize carbocations. Inductive effect - the positive charge is shared between adjacent carbons. Hyperconjugation - adjacent sigma bonds between neighboring carbons and other atoms overlap with the empty p orbital on the positively charged carbon. The relative stabilities of carbocations determine the products formed in electrophilic additions.
