Mechanism of addition of hx to alkenes mechanism

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Unformatted text preview: ddition of HX to Alkenes Mechanism Mechanism of Addition of HX to Alkenes Mechanism Step 1. Protonation. This step is slow and rate determining. Protonation gives the most stable cation. Therefore the proton adds to the alkene carbon that initially has the most protons. Mechanism of Addition of HX to Alkenes Mechanism Step 2. Combination of the anion and cation. In the rapid second step the bromide attaches to the carbocation. Potential Energy Graph for Addition of HBr Potential 6.5 Carbocation Rearrangements in Hydrogen Halide Addition to Alkenes Alkenes Carbocation Rearrangements Carbocations rearrange to form more stable cations. The fact that rearrangements occur on addition of HX to alkenes provides further support for the reaction mechanism. Carbocation Rearrangements The mechanism must explain the formation of both products. Here it involves a hydride shift. The final step has chloride attaching to either of the secondary or tertiary carbocations....
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