The Vespiary

The Hive => Chemistry Discourse => Topic started by: xxxxx on May 25, 2004, 06:54:00 PM

Title: solvent choice controls isomer produced?
Post by: xxxxx on May 25, 2004, 06:54:00 PM

i recall reading somewhere that when hcl is added to a double bond in ethyl ether the addition is 88% "syn" and in nitromethane the addition is 100% "anti". dichloromethane is somewhere intermediate between these two. what do these terms "syn" and "anti" mean? does it mean the sterochemistry of the product can be controlled by the solvent choice?

Title: syn/anti (cis/trans) addition
Post by: Rhodium on May 25, 2004, 07:25:00 PM

The stereochemistry will not be affected, but the regioselectivity will. Depending on the mechanism you may end up with different diastereomers but not different enantiomers.

Addition of a halogen (X₂) to an alkene to give a di-haloalkane can be either syn- (yielding the cis-dihaloalkane) or anti- (giving the trans-dihaloalkane).