A reaction between an alkene and a halogen with an alcohol or water as a solvent, results in the formation of a halohydrin such as chlorohydrin or bromohydrin.
Alkene is attacked by halogen forming an intermediate, bromonium/chloronium ion, and chlorine ion/bromine ion depending on halogen group used in the reaction. Intermediate is then attacked by lone pairs on alcohol/water. Water/alcohol is in abundance as compared to halogen ion thus lone pairs easily add to intermediate. Hydroxyl group from water or R-O- from alcohol, is added anti to chlorine atom as this would give the most stable, hence major product. Product is a racemic mixture of R and S enantiomers.
35. Draw the major product for the following reaction, showing the stereochemistry by using wedge bonds. The product will be racemic, but show only one enantiomer. (Remember that a hydrogen atom on a chirality center must be shown explicitly and with a wedge/hash bond.)
*enantiomers- nonsuperimposable mirror image molecules; have chiral centers
*chiral center/asymmetric center- atom bonded to four different groups
References
Paul Yurkanis Bruice Organic Chemistry Chapter 4: Isomers: The Arrangement of Atoms in Space Page 152-153, 163
Question was from Sapling learning
Very informative. Thanks for sharing.
ReplyDeleteHi Rina,
ReplyDeleteThis problem confused me the first time I did it and you explained it very well! The stereochemistry was the difficult part for me and your introduction was helpful as well. I like that you draw the lone pairs on the atoms because it makes it easier to see the electron flow. Showing the absolute configurations of the asymmetric centers was also helpful.
Thanks,
Rashmi Muthukkumar