ORGANIC CHEMISTRY Chapter 5 5.8 The Origin of Optical Activity Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 5 5.8 The Origin of Optical Activity
ORGANIC CHEMISTRY Chapter 5 58 a Racemic form(外消旋体) g An equimolar mixture of two enantiomers is called a racemic form(either a racemate or a racemic mixture) o A racemic form shows no rotation of plane polarized light o It is often designated as being(+) CH CH 二 HO~c∠1+ H~二OH CH C CHOH HOcH CH2CH3 HOcH (R)-()-2-Butanol (S)-(+)-2-Butano (±)-2- Butanol 13.52 ab=+13.52 Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 5 5.8A Racemic Form (外消旋体) An equimolar mixture of two enantiomers is called a racemic form (either a racemate or a racemic mixture). A racemic form shows no rotation of planepolarized light. It is often designated as being (±). CH3 CHOH CH2CH3 (±)-2-Butanol [α]D25 = 0 C CH2CH3 CH3 HO H C CH2CH3 CH3 H OH (R)-(−)-2-Butanol (S)-(+)-2-Butanol [α]D25 = −13.52 [α]D25 = +13.52 + 1:1
ORGANIC CHEMISTRY Chapter 5 5.8b Racemic forms and enantiomeric Excess(外消旋体及对映体过量百分率) moles of one enantiomer-moles of other enantiomer 100% total moles of both enantiomers observed specific rotation 1009 specific rotation of the pure enantiomer R]_[S ×100% R]+[S] o ee= o enantiomeric excess Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 5 5.8B Racemic forms and Enantiomeric Excess (外消旋体及对映体过量百分率) moles of one enantiomer − moles of other enantiomer total moles of both enantiomers = observed specific rotation specific rotation of the pure enantiomer % ee = × 100% × 100% = [R]－[S] [R]＋[S] × 100% % ee = % enantiomeric excess
ORGANIC CHEMISTRY Chapter 5 5.9 The Synthesis of Chiral Molecules 手性分子的合成 Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 5 5.9 The Synthesis of Chiral Molecules 手性分子的合成
ORGANIC CHEMISTRY Chapter 5 5.9A Racemic forms OH Ch Cho CCh2 + h-h CH3CH2CHCH3(±) 2-butanone (±)-2- butanone (achiral achira Chiral molecules molecules) molecules but 50: 50 mixture()and(s)i Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 5 5.9A Racemic Forms CH3CH2CCH3 O + H H CH3CH2CHCH3 OH Ni (±) 2-butanone (±)-2-butanone (achiral molecules) (achiral molecules) [chiral molecules but 50:50 mixture (R) and (S)]
ORGANIC CHEMISTRY Chapter 5 o If a reaction that leads to the formation of enantiomers produces a preponderance of one enantiomer over its mirror image, the reaction is said to be enantioselective o for a reaction to be enantioselective. a chiral reagent, solvent, or catalyst must assert an influence on the course of the reaction Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 5 If a reaction that leads to the formation of enantiomers produces a preponderance of one enantiomer over its mirror image, the reaction is said to be enantioselective. For a reaction to be enantioselective, a chiral reagent, solvent, or catalyst must assert an influence on the course of the reaction
ORGANIC CHEMISTRY Chapter 5 5.9B Enantioselective Synthesis O C.IIIlCH2Ca3 HO CH C. III1CH2CH CH H H--H (R)-2-Butanol 50% H--H H I CH CH3 0-C C. IllICHbCH CH CH 50% (S)-2-Butanol Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 5 5.9B Enantioselective Synthesis HO C CH2CH3 H CH3 (R)-2-Butanol O C CH2CH3 CH3 H H 50% H H O C CH2CH3 CH3 H C CH2CH3 HO CH3 (S)-2-Butanol 50%
ORGANIC CHEMISTRY Chapter 5 o()LiAIHCH OH CH CH OH H H (2)H2O H H Ph CH(CH3h Ph CH(CH3h pI CH(CH3)2 5.0 H O (1LiAIH4 CH3)3C OH (CH33C (2)H2O 91% H More stable OH (CH3)3C H Less stable H Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 5 C Ph CH3 H CH(CH3)2 O (1) LiAlH4 (2) H2O C Ph CH3 H CH(CH3)2 OH H C Ph CH3 H CH(CH3)2 H OH + 5.0 1 O (CH3)3C H (1) LiAlH4 (2) H2O OH (CH3)3C H H OH (CH3)3C H H 91% 9% + More stable Less stable
ORGANIC CHEMISTRY Chapter 5 g many enzymes have also found use in the organic chemistry laboratory where organic chemists take advantage of their properties to bring about enantioselective reactions lease OEt OEt H-OH Ethyl(+)-2-fluorohexanoate ee>99 lan ester that is a racemate of (R)and(s) forms OH H-OEt ee>69 Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 5 Many enzymes have also found use in the organic chemistry laboratory, where organic chemists take advantage of their properties to bring about enantioselective reactions. C F O OEt H OH lipase C F O OEt C F O OH %ee > 99 %ee > 69 + + H OEt Ethyl (±)-2-fluorohexanoate [an ester that is a racemate of (R) and (S) forms]
ORGANIC CHEMISTRY Chapter 5 5.10 Chiral Drugs Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 5 5.10 Chiral Drugs
