syn and anti addition

Addition of chlorine to ethene is syn addition or anti addition?

2 Answers

39
Pritish Chakraborty ·

Its anti addition. First Cl+ attaches to both C atoms, forming a chloronium ion. Then Cl- attacks a carbon atom by SN2, opening the 3 membered ring and since it attacks from the backside, an anti product is formed.

39
Pritish Chakraborty ·

If you want to add in a syn manner, you first add to the double bond OsO4/NaHSO3 which syn-dihydroxylates the bond, forming a cis diol. Then you use two eq of PCl5.

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