Stereoselectivity

In chemistry, stereoselectivity is the property of a chemical reaction that yields an unequal mixture of stereoisomers from a single reactant. Stereoselectivity may be partial, where the formation of one stereoisomer is favoured over the other, or it may be total where only one stereoisomer is formed. An example of partial stereoselectivity is dehydrohalogenation of 2-iodo-butane which yields 80% trans-2-butene and 20% cis-2-butene.