Ch_322a_6.09

Ch_322a_6.09 - the formation of only the trans diastereomer...

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The Stereochemistry of the S N 2 Reaction The proposed mechanism of the S N 2 reaction is based on two different methodologies: (1) Kinetics: Rate = k[Nu:][substrate] (2) Stereochemistry : An inversion of configuration is observed at reacting stereocenters. HO - + C Cl H H H C H H H Cl HO !" !" C HO H H H + Cl - TS The stereochemistry of the S N 2 reaction was elucidated in studies on substrates with stereocenters .
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Stereochemical Studies Numerous studies on substrates with well-defined stereochemical features reveal that the S N 2 reaction proceeds with inversion at the reacting carbon center. CH 3 H H Cl + HO - CH 3 H H OH + Cl - cis -1-chloro-3-methylcyclopentane trans -3-methylcyclopentanol A backside attack by the nucleophile explains
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Unformatted text preview: the formation of only the trans diastereomer in this nucleophilic substitution reaction. via CH 3 H H Cl OH !" !" A Second Example Studies on chiral substrates where the absolute configurations and rotatory properties are known are also widely used as stereochemical probes of mechanisms. C C 6 H 13 CH 3 C C 6 H 13 CH 3 H Br (R)-(-)-2-bromooctane NaOH enantiomeric purity 100% H HO (S)-(+)-2-octanol enantiomeric purity 100% [ ! ] D 25 =-34.25 o [ ! ] D 25 = +9.90 o inversion The Hughes-Ingold mechanism explains the stereochemical outcome of 100% inversion . via C C 6 H 13 CH 3 H Br HO !" !"...
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Ch_322a_6.09 - the formation of only the trans diastereomer...

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