Sterio Isomer

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  • (Stereochemistry) 6

    6.1

    (Stereochemistry) Sawhorse projections, Newman projections, Wedge projections 6.2

    Isomers structural isomers conformational Stereoisomers isomers enantiomers diastereoisomers

    geometrical isomers

    CM 328 57

  • 6.2.1 (Structural isomers) () Skeletal isomers

    CH3CH2CH2CH3 CH3 CH3CHCH3

    n-Butane Isobutene Positional isomers

    CH3CH2CH2Cl CH3 CH3CH

    Cl 1-Chloropropane 2-chloropropane Functional isomers

    CH2CH2OH CH3 O CH3

    Ethanol Dimethyl ether

    6.2.2 (Conformational isomers)

    Acyclic compounds Ethane

    H

    H

    H

    H

    HH

    H

    H H

    H

    HH

    HH

    H

    H H

    H

    HH H

    H HH

    sawhorse Newman Sawhorse Newman Eclipsed staggered

    CM 328 58

  • n-Butane

    H

    H H

    CH3H

    H3C

    H

    CH3

    H

    H3C

    HH

    HCH3

    H

    H H

    CH3CH3H H

    H HCH3

    HCH3

    CH3

    HH CH3

    H

    CH3H

    H

    HCH3

    HH

    CH3H

    CH3

    H3C

    HH

    H

    HHH

    (sp) (ac) (sc) (ap)

    Cyclic compounds

    Cyclopropane Cyclobutane

    Envelope half-chair Cyclopentane

    Twist-boatChair Boat Cyclohexane

    CM 328 59

  • 6.3 (Stereoisomers)

    (space)

    X

    C

    YA

    B

    X YA B

    4 (chiral center) asymmetric carbon atom 2

    1 1 2

    2 (Enantiomers)

    CHOCHO

    CH3

    CHOC

    CH3

    OHHCHO

    ClCCl

    CH3

    CHOC

    CH3

    ClClH

    ( 1 ) ( )

    CM 328 60

  • 2 ( ) (non-superimposable) 2 ( ) (super-imposable) ( ) (mesomer) 1

    1 2 () 2n n

    CHO CHO

    C H

    C C

    H HO

    CH2OH

    OHC

    HHOOHHCHO CHO

    H

    C C

    HO H

    CH2OHCH2OH

    CHHOOH

    H

    CH2OH

    COH

    : 4 2

    () < 2n

    CM 328 61

  • COOHC

    H

    COOH

    OHCOHH

    COOH COOH

    OH

    C C

    HO CH

    COOH COOH

    HCHHOOHH

    : 3 1 1

    (mesomer) 6.4

    2 (optically active compounds) (optical activity)

    2 2 1. dextrorotatory d + levorotatory l (Lactic acid)

    CM 328 62

  • COOH

    HO C H

    CH3

    COOH

    H C O

    CH3

    H

    d -lactic acid (+)-lactic acid l -lactic acid (-)-lactic acid 2. 2 (reagent) (optically active) 2 R

    NH2

    CH COOH

    R

    NH2

    CH COOH

    D-enantiomer

    R

    D-aminooxidase

    L- enantiomerO2 , H2O2

    C OHD-aminooxidase

    O2 , H2O2H2O

    ONH3+ +

    6.5 (Fisher projection)

    Emil Fisher(1891) () ()

    CH3

    COOH

    CHO H C

    CH3HO H

    COOH

    CH3

    HO H

    COOH Wedge projection Fisher projection

    CM 328 63

  • CH3

    COOH

    CH C

    CH3H OH

    COOH

    H

    CH3

    OH

    COOHOH

    Wedge projection Fisher projection

    180o

    1.

    1800

    CH3CHCOOH

    OHCH3

    C H

    COOH

    HO

    2.

    CH3

    OH

    COOH

    H CH3

    OH

    COOH

    H

    CH3

    OH

    COOHH

    CH3

    HO

    COOH

    H

    6.6 (Absolute configuration) 6.6.1 RS R S (Absolute configuration)

    sequence rule priority sequence rule

    CM 328 64

  • (atomic number) R S

    R-2-Butanol S-2-Butanol Priority : - OH > -CH2CH3 > -CH3 > H

    CHO CHO

    H

    C C

    HO H

    CH3 CH3

    CHHOOH

    HC

    OH

    (2R , 3S)-Butanol (2S , 3R)-Butanol sequence rule : I > Br > Cl > S > P > F > O > N > C > D(deuterium) > H C(CH3)3 > CCH(CH3)2 > CH2CH3 > CH3

    CO

    CO

    NH2CO

    RCO

    HCO

    > > > >OR OHC N > C C CH CH2>H

    CM 328 65

  • 6.6.2 DL

    R1 CHX R2 X (, X = OH; , X = NH2) D X L

    CHO

    CH

    CH2OH

    OHCHO

    C H

    CH2OHHO

    D-(+)-glyceraldehyde L-()-glyceraldehyde

    HO

    CHOOHHHHOOHHOHH

    CH2OHD-(+)-Glucose

    COOHHNH2 OHH

    CH3

    COOHH

    CH3

    L-(+)-ThreonineL-(+)-Lactic acid

    2

    5

    ( NH2 C2 ( OH C5

    ) ) 6.7 Cis-trans isomers

    6.7.1 EZ (geometrical isomers) -

    - (cis - trans isomers) priority sequence rule 2 priority

    CM 328 66

  • C CBr Cl

    CH3 I Br priority CH3 E-1-bromo-2-chloro-2-iodo-propene I priority Cl Br I

    HH3C

    H

    CH3H

    CCH3C

    HCC

    CH3 Z - 2 -Butene E - 2 Butene Cis -2 Butene trans 2 - Butene

    H H H CH3 H3C CH3 H3C H Z- Cis- E- trans- 1,2 Dimethylcyclopropane

    6.7.2. re-si (faces)

    () sequence rule

    CM 328 67

  • XY

    ZC

    C

    X

    ZCX

    Y ZY

    si re

    C=C re-si ( 1 2)

    re-si si-si

    C CHOOC COOH

    H HC C

    H COO

    HOOC H

    H1 2 1 2

    si - re re-re

    maleic acid fumaric acid

    CM 328 68

  • 6.8 steroid [ (steroid) axial ()] [(steroid) equatorial () ]

    O

    H

    OH

    H

    OH

    H

    OHOHH

    H

    OH

    O

    H

    OH

    H

    OH

    H

    HOHH

    OH

    OH

    - D-(+)- glucopyranose - D-(+)- glucopyranose

    CH3

    CH3

    HO

    H

    H

    COOH

    H

    H

    OH

    steroid ()

    6.9 Symmetry elements Chirality symmetry elements

    (chirality) symmetry elements

    1. (A plane of symmetry plane) 2

    CM 328 69

  • COOHC

    H

    COOH

    OHC

    OHH

    2. (A center of symmetry i)

    i

    HO CL

    OH

    i

    Cl

    3. - (rotation-reflection axis Sn)

    n

    0360

    H

    Cl

    Cl

    H

    Cl

    H

    Cl

    HC S4

    CM 328 70

  • 4. (axis of symmetry Cn , n > 1)

    (n > 1)

    n

    0360

    CHCH3

    C2H5HC

    C2H5

    CH3

    C2

    (achiral molecule) symmetry elements 1. () 2. ( i ) 3. (Sn)

    (chiral molecule) 1. symmetry element (Cn , n > 1 ) 2. symmetry elements point group C1 6.10 (Optical activity)

    (optically active compound) (optical activity)

    CM 328 71

  • 1. chiral center

    CH3CH

    CH3CHO

    C6H5 C6H5

    OH H

    [] = +42.9o (neat) [] = - 42.9o (neat) 27D 27D 1-Phenylethanol