Lesson20 - Stereochemistry of the [S N 2] Pathway The S N 2...

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Unformatted text preview: Stereochemistry of the [S N 2] Pathway The S N 2 reactions proceeds with _______ of configuration. Stereospecific or Stereoselective? inversion Stereospecific Reaction : A reaction in which the stereochemistry of the reactant completely determines the stereochemistry of the product without any other option. Stereoselective Reaction : A reaction in which there is a choice of pathway, but the product stereoisomer is formed preferentially because its reaction pathway is more favorable than the others available. Stereochemistry of the [S N 1] Pathway The nucleophile will attack both faces of the planar carbocation with equal probability resulting in a racemic mixture . planar carbocation (achiral) Starting with a single enantiomer http://www.chemtube3d.com/ The [E2] reaction pathway has very specific requirements: There must be ________________ among the orbitals in which σ bonds are made/broken and π bonds are made. continuous overlap Stereochemistry of the [E2] Pathway Conformational Requirements of [E2] Elimination (1) –X and –H oriented anti-periplanar (2) –X and –H oriented syn-periplanar For steric reasons, the preferred pathway for [E2] elimination is through (1). The double bond geometry depends on which pathway is followed. Consider the following example: The carbon atoms smoothly rehybridize from sp 3 to sp 2 http://www.chemtube3d.com/EliminationE2stereospecific.html Here’s another example: [E2] Pathway in Cyclic Compounds...
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This note was uploaded on 01/25/2012 for the course CHEM 232 taught by Professor Miller during the Spring '08 term at University of Illinois, Urbana Champaign.

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Lesson20 - Stereochemistry of the [S N 2] Pathway The S N 2...

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