The Formation of Halohydrins Halolactonization and Haloetherification

Side Note 3.4. When cyclohexene is transformed into its bromohydrin, regiocontrol of the ring-opening of 

The Furst-Plattner Rule the onium ion may be exerted —in addition to the factors already discussed (factor 1 see Fig- 

However, essentially only one of them—namely, B—undergoes a nucleophilic backside attack by the hydroxy group. The brominated tetrahydrofuran D is produced via the oxonium ion C. An analogous intramolecular backside reaction by the alcoholic OH group in the bromonium ion iso-B is energetically disfavored and hardly observed. The result is that the bromonium ion iso-B can revert to the starting material A, whereby the overall reaction takes place almost exclusively via the more reactive bromonium ion B. 

3 Solvomercuration of Alkenes Hydration of C=C Double Bonds through Subsequent Reduction 

6 Additions that Take Place or Can Take Place without Stereocontrol Depending on the Mechanism 

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