Part A Bromonium Ion

Br—Br is called polarizable because electrons in the large orbitals that make up the Br—Br bond can slosh back and forth. This makes it easy for the bond to adopt a temporary dipole. Think of waves in a bathtub. At a given moment more water can be at one end of the tub than the other. 

CI2 and I2 also react with alkenes. We focus on Bv2 because Cf reacts too fast, and f reacts too slowly to be useful. 

If the reaction on the previous page is carried out in the presence of a large excess of another nucleophile (e.g., H2O), this other nucleophile will out-compete Br . Show a possible mechanism (via a carbocation intermediate) for formation of the halohydrin shown below, (halohydrin = a molecule with a halogen and an OH on adjacent carbons) 

Is the reaction above Markovnikov or anti-Markovnikov (circle one) Explain your reasoning. 

When Br2 is added to a double bond in a ring, the cis configurational stereoisomer is not observed. 

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