Chirality center inversion of configuration

Substitution at a chiral center Inversion of configuration. The nucleophile attacks the chiral center from the side opposite the leaving group. Racemization is favored. The carbocation intermediate is planar, and attack of the nucleophile occurs with equal probability from either side. There is often some net inversion of configuration. 

Notice the similarity among all of the S)si2 processes that we have seen in this section. All involve the conversion of the hydroxyl group into a better leaving group followed by nucleophUic attack. If any of these reactions occurs at a chirality center, inversion of configuration is to be expected. 

Stereochemistry. When the attack takes place at a chirality center, inversion of configuration is observed. 

Now let s turn our attention to the stereochemistry of ring-opening reactions under acid-catalyzed conditions. When the attack takes place at a chirality center, inversion of configuration is observed. This result is consistent with an Sj,j2-like process involving back-side attack of the nucleophile. 

This reaction can occur even at secondary substrates without competing E2 reactions, because the hydrosidfide ion (HS ) is an excellent nucleophile and a poor base. When this nucleophile attacks a chirality center, inversion of configuration is observed. 

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See also in sourсe #XX -- [ ]

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