Stereoselectivity refers to the formation of an unequal mixture of stereoisomers during a chemical reaction. It simply means that the reaction gives one stereoisomer over another as the final product of the reaction.
Also, this type of reactions occurs on two different occasions. One is during the non-stereospecific creation of a new stereocenter, and the other is during the non-stereospecific transformation of an existing stereocenter. This selectivity happens due to steric effects and electronic effects. Stereoselectivity may vary in different reactions but none of the reactions form one total stereoisomer; all these reactions give a mixture of stereoisomers with a major component and a minor component.
However, sometimes the minor product is not detectable because it is formed in a very little amount. Enantioselective — one enantiomer forms over other isomers; a chiral molecule forms from an achiral molecule, degree of selectivity is measured from enantiomeric excess.
Will this be anti elmimation similar to the case where the same reaction proceeds via E2.? Hi James, great article. How would i do that please? In my opinion, an interesting addition to the explanation above is how IUPAC defines the terms actually for me this is the only correct definition, even though it sometimes takes ages to really understand what it means.
Stereoselectivity has to do with the preferential formation of one stereoisomer over the other in a reaction. Here one could maybe prefer to use the terminology highly stereoselective probably also ill-defined or completely stereoselective depending on the case under investigation. This is illustrated in the following example: the reduction of 2-butyne with H2 in the presence of a Lindlar catalyst is a completely stereoselective reaction: the cis-alkene is exclusively formed.
This however is NOT a stereospecific reaction at least not in the IUPAC sense of the word as 2-butyne does not have a stereoisomer that could react differently. According to this definition, a stereospecific process is necessarily stereoselective but not all stereoselective processes are stereospecific. Let me explain. Take cisbutene and transbutene and epoxidize them.
After the Sharpless you might end up with a mixture of enantiomers. Why would you say hydroboration is regioselective? If the hydrogen has a partial negative charge with its bond with Boron, why would it add to the more highly substituted carbon instead? It was very helpful …. What do we call the reaction? If it were selectivity for an amine versus an alcohol i. I got it. Are elimination reactions favored at high temperatures? Are elimination reactions only organic reactions?
Do the numbers 1 and 2 in E1 and E2 reactions relate to the number of steps in the elimination What is reductive elimination in elimination reactions? See all questions in E1 and E2 Reactions. When an alkene undergoes addition, two new s bonds are formed. If we think of an alkene as having two faces, then the two new s bonds can either both form on the same face, which we call syn addition, or they can be formed on different faces which we call anti addition. Do you remember these terms from Chapter 3?
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