有机化学教学课件：15-Stereochemistry

1、Chapter 7 Stereochemistry,7.1 Molecular Chirality and Enantiomers 7.1.1 Molecular Chirality and Enantiomers Characteristic of enantiomers Chiral molecules Chirality 7.1.2 Molecular Symmetry and Asymmetric Molecules Symmetric elements Achiral Molecules 7.1.3 Properties of Chiral Molecules: Optical Ac

2、tivity 7.1.4 Representation and Nomenclature of Chiral Molecules,A. Representation Fischer projections B. Naming enantiomers with one stereocenter by R-S notational system 7.2 Chiral Molecules With Two Stereocenters 7.2.1 Chiral Molecules With Two Different Stereocenter Diastereomers 7.2.2 Stereoiso

3、mers With Two Same Stereocenters Meso-form 7.2.3 Resolution of Enantiomers,Cis-, Trans,Molecular structure,Molecular constitution,Constitutional isomers: to have the same Molecular formula,Molecular configuration （构型,Stereoisomers,The same mole. constitution,The different spatial arrangement of atom

4、s or groups,Enantiomers (对映异构体,Diastereomers (非对映异构体,The former is unchang- ed by rota- tion of C-C Single bond,Configurational isomers,Molecular confor- mation(构象,Conformers,The same configuration,The different spatial arrangement of atoms or groups by rotation of C-C single bond,The atoms are bond

5、ed in different order: C skeleton isomers;isomers of the functional group site;isomers of functional group: Ex. CH3CH2OH, CH3OCH3,7.1 Molecular Chirality手(征)性 and Enantiomers,7.1.1 Molecular Chirality and Enantiomers,P183,A tetrahedron C is bonded to four different groups, its not superposable on it

6、s mirror image,Ex. Bromochlorofluoromethane,Enantiomers,Characteristic of enantiomers,The same mole. constitution. 2. The relationship of enantiomers,object and mirror image,3. Nonsuperposable,4. The same physical properties, the similar chemical properties,Chiral molecules,with its enantiomer,Chira

7、lity,Mole. isnt superposable with their mirror image,Stereocenter or stereogenic center, asymmetric center,1,2-Epoxypropane (1,2-环氧丙烷,Limonene (柠檬油精,The molecule that contains one chiral center have a pair of enantiomers,An isotope,Chiral center: the carbon with 4 different groups. Ex.2-butanol: C2,

8、)-Lactic acid (乳酸,Achiral center: a C atom is attached by 2 or more same groups,Achiral molecule(非手性分子,The molecule is achiral and is superposable with its mirror image,7.1.2 Molecular Symmetry and Asymmetric Molecules,Symmetric elements,A. A plane of symmetry(对称面)(,A plane bisects a molecule so tha

9、t one half of molecule is the mirror image of the other half,P185,6.2,Ex. 2-Chloropropane,2. All atomes in a molecule are on a plane,Ex. (E)-1,2-Dichloroethene,b. Center of symmetry(i,If any straight line passes a atom and molecular center, the same atom or group is encountered on the site at equal

10、distance but in the opposite direction,Ex.trans-2,4-dichloro-1,3-difluorocyclo- butane,Any molecule with a plane of symmetry or a center of symmetry-Achiral molecule,A symmetric molecule,Any chiral molecule is asymmetric one,Nonsuperposable with its mirror image and have a enantiomer,7.1.3 Propertie

11、s of Chiral Molecules: Optical Activity (旋光活性 or 光学活性,Optical activity,When a beam of plane-polarized light (平面偏振光) pass through an enatiomer, the planar polarization rotates,Separate enantiomers rotate the plane of plane-polarized light equal amounts and in opposite direction,Optically compounds,On

12、e enatiomer Levo-(左旋-) anticlockwise(,Other enantiomer Dextro- (右旋) clockwise(,)-2-Butanol, (+)-2-Butanol,The mixtures that contain equal amounts of enantiomers are Racemic(外消旋,2-Butanol,Polarimeter(旋光仪,To measure the effect of plane-polarized light on optically active compounds,Light source Polariz

13、er Sample tube Analyzer (起偏器) (检偏器,Specific rotation (比旋光度,The observed rotation, c: The concentration of the sample (g/mL) l: The length of the sample tube(dm) :wavelength(D,589nm) Na,)-2-Butanol,)-2-Butanol,D = -13.25,D = +13.25,Optical purity(光学纯度,Percent enantiomeric excess (对映体过量百分数,Ex. Specifi

14、c rotation: +6.76,50% pure (+)- 2-butanol + 50% ()- 2-butanol,Jean Baptiste Biot French Physicist b. 1774 d. 1862,Jean Baptiste Biot was born in Paris, France, and was educated there at the cole poly-technique. His work on determining the optical rotation of naturally occuring molecules included an

15、experiment on turpentine,7.1.4 Representation and Nomenclature of Chiral Molecules,A. Representation,1. Wedge and dash drawing(伞式,)-2-Butanol,2. Fischer projections,Ch.P113(二,Representation by,The longest carbon chain is on vertical position. The lowest numbered carbon is at the top,The rule for dra

16、wing,The intersection of vertical and horizontal lines: chiral C atom,Ex,)-2-Butanol,Vertical line represents the bond that project behind the plane of the paper; Horizontal line represents the bond that project out of the plane of the paper,南) P178,Hermann Emil Fischer Germany Berlin University Ber

17、lin, Germany b. 1852d. 1919,Generally considered the greatest organic chemist of his time, Fischer received the 1902 Nobel Prize in Chemistry for his work on carbohydrates and purines. His discovery that phenylhydrazine reacts with carbohydrates to form osazones enabled him to elucidate the stereoch

18、emistry of sugars. First to synthesize adenine and guanine, he made the first synthetic nucleotides. Among many other contributions was his work on protein structure and synthesis, the lock-and-key model for enzyme reactions, structure of triarylmethane dyes, and the design of laboratory hoods and s

19、afety equipment,Characteristics of Fischer projection,One group is fixed, the other three groups are rotated in turn, the configuration is not changed,To rotate the projection to 90, on the plane of the paper, the other enatiomer was got,)-2-Bromobutane,)- 2-Bromobutane,),To exchange any two groups,

20、 the configuration was changed, the other enantiomer was got,)-2-Bromobutane,),),),),),B. Naming enantiomers with one stereocenter by R-S notational system,P193, 6.6,Designation of absolute configuration,Rank the substituents according to Cahn-Ingold-Prelog rule(序列规则,2. Orient the molecule so that t

21、he lowest ranked substituent points away from you,)-2-Butanol,3. Draw the tree highest ranked substituent from the highest one to lowest one,The direction,Clockwise: ( R ),Anticlockwise: ( S ),R)-2-Butanol,7.2 Chiral Molecules With Two Stereocenter,7.2.1 Chiral Molecules With Two Different Stereocen

22、ter,The four stereoisomers of 2,3-dihydroxybutanoic acid,P194,)-Lactic acid,P196, 6.7,R)-甘油醛,S)-甘油醛,1) (2) (3) (4,2R,3R),2S,3S),2R,3S),2S,3R),2,3-Dihydroxybutanoic acid (2,3-二羟基丁酸,Normally n stereocenters 2n stereoisomers,Relationships of stereoisomers,Enantiomers,Diastereomers: (非对映异构体,1,3,4,2,The

23、relationship between diastereomers is not related as an object and its mirror imige,Nomenclature for diastereomers,Base on Fischer projection,The same groups are on the same sides of C chain: erythro-( 赤藓式),The same groups are on the opposite sides of C chain: threo-( 苏藓式),erythro- (赤型),2R,3R),threo

24、- (苏型),2S,3R),7.2.2 Stereoisomers With Two Same Stereocenters,Ex. Tartaric acid(酒石酸,2R,3R),2S,3S),2R,3S),5) (6) (7) (8,erythro,meso form (内消旋体,The meso form is achiral Mole,7.2.3 Resolution of Enantiomers （对映体的拆分,Pasteur,Sodium ammonium tartrate (酒石酸铵钠,Recrystallization (重结晶,Two kind crystals are mi

25、rror image,Louis Pasteur 1822-1895,The scientific contributions of Pasteur were among the most valuable in the history of science, and he is claimed equally by chemistry and microbiology. Best known to chemists for his work on the tartaric acids, he recognized the structural relationships (now calle

26、d chirality) responsible for optical isomerism, and that microorganisms can distinguish between enantiomers. Pasteur also showed that micro- organisms cause fermentation and various diseases, and he developed methods for pasteurization and for vaccination against anthrax and rabies. His work saved the wine, beer, and silkworm industries for France,Resolution of racemic lactic acid,6.25 (a),(d) 6.26 6.30 6.33 (a)(c,Problems to Chapter 6,P212,6.34 6.35 6.36 6.37 6.39 6.40 6.46(b) 6