ESTEREOQUÍMICA<br />
enantiomers<br />diastereomers<br />Isomers<br />constitutional<br />isomers<br />stereoisomers<br />
Molecular Chirality:  Enantiomers<br />
Chirality<br />	A molecule is chiral if its two mirror image forms are not superposable upon one another. <br />	A molecul...
Bromochlorofluoromethane is chiral<br />Cl<br />	It cannot be superimposed point for point on its mirror image.<br />Br<br...
Bromochlorofluoromethane is chiral<br />Cl<br />Cl<br />Br<br />Br<br />H<br />H<br />F<br />F<br />	To show nonsuperimpos...
Bromochlorofluoromethane is chiral<br />Cl<br />Br<br />Cl<br />Br<br />H<br />H<br />F<br />F<br />
Another look<br />
Enantiomers<br />nonsuperimposable mirror images are called enantiomers<br />and<br />are enantiomers with respect to each...
Chlorodifluoromethaneis achiral<br />
Chlorodifluoromethaneis achiral<br />	The two structures are mirror images, but are not enantiomers, because they can be s...
The Chirality Center<br />
w<br />x<br />y<br />C<br />z<br />The Chirality Center<br />a carbon atom with fourdifferent groups attached to it<br />a...
H<br />F<br />Cl<br />C<br />Br<br />Chirality and chirality centers<br />A molecule with a single chirality center is chi...
H<br />CH3<br />CH2CH3<br />C<br />OH<br />Chirality and chirality centers<br />A molecule with a single chirality center ...
CH3<br />CH2CH2CH2CH3<br />CH3CH2CH2<br />C<br />CH2CH3<br />Examples of molecules with 1 chirality center<br />a chiral a...
OH<br />Examples of molecules with 1 chirality center<br />Linalool, a naturally occurring chiral alcohol<br />
H2C<br />CHCH3<br />O<br />Examples of molecules with 1 chirality center<br />1,2-Epoxypropane:  a chirality center<br />c...
CH3<br />H<br />C<br />CH2<br />CH3<br />Examples of molecules with 1 chirality center<br />Limonene:  a chirality center ...
H<br />CH3<br />D<br />C<br />T<br />Examples of molecules with 1 chirality center<br />Chiral as a result of isotopic sub...
A molecule with a single chirality centermust be chiral.<br />But, a molecule with two or more chirality centers may be ch...
Properties of Chiral Molecules:Optical Activity<br />
Optical Activity<br />A substance is optically active if it rotates the plane of polarized light.<br />In order for a subs...
Light<br />	has wave properties<br />	periodic increase and decrease in amplitude of wave<br />
Light<br />	optical activity is usually measured using light having a wavelength of 589 nm<br />	this is the wavelength of...
Polarized light<br />ordinary (nonpolarized) light consists of many beams vibrating in different planes<br />plane-polariz...
Nicol prism<br />Polarization of light<br />
<br />Rotation of plane-polarized light<br />
AbsoluteandRelative Configuration<br />
Configuration<br />Relative configuration compares the arrangement of atoms in space of one compound with those of another...
Configuration<br />Relative configuration compares the arrangement of atoms in space of one compound with those of another...
CH3CHCH2CH3<br />CH3CHCH<br />CH2<br />OH<br />OH<br />Relative configuration<br />Pd<br />[] + 33.2°<br />[] + 13.5°<br...
H<br />HO<br />H<br />HO<br />OH<br />OH<br />H<br />H<br />Two possibilities<br />H2, Pd<br />H2, Pd<br />	But in the abs...
H<br />HO<br />H<br />HO<br />OH<br />OH<br />H<br />H<br />Two possibilities<br />H2, Pd<br />H2, Pd<br />	Nor can we tel...
H<br />HO<br />H<br />HO<br />OH<br />OH<br />H<br />H<br />Absolute configurations<br />H2, Pd<br />[] +33.2°<br />[] +...
CH3CH2CHCH2Br<br />CH3CH2CHCH2OH<br />CH3<br />CH3<br />Relative configuration<br />HBr<br />[] -5.8°<br />[] + 4.0°<br ...
The Cahn Ingold PrelogR-S Notational System<br />
Two requirements for a systemfor specifying absolute configuration<br />1.  	need rules for ranking substituents at chiral...
The Cahn-Ingold-Prelog Rules<br />1.  Rank the substituents at the chirality center according to same rules used in E-Z no...
1<br />1<br />4<br />3<br />3<br />4<br />2<br />2<br />Example<br />Order of decreasing rank:4 > 3 > 2  > 1<br />
The Cahn-Ingold-Prelog Rules<br />1.  Rank the substituents at the chirality center according to same rules used in E-Z no...
1<br />1<br />4<br />3<br />3<br />4<br />2<br />2<br />counterclockwise<br />clockwise<br />R<br />S<br />Example<br />Or...
H<br />H<br />CH2CH3<br />CH3CH2<br />C<br />HO<br />C<br />OH<br />CH3<br />H3C<br />(S)-2-Butanol<br />(R)-2-Butanol<br ...
Very important!  Two different compounds with the same sign of rotation need not have the same configuration.<br />	Verify...
H<br />H3C<br />R<br />H<br />H<br />Chirality center in a ring<br />—CH2C=C   >   —CH2CH2   >  —CH3   >   —H<br />
Fischer Projections<br />	Purpose of Fischer projections is to show configuration at chirality center without necessity of...
Rules for Fischer projections<br />H<br />Cl<br />Br<br />F<br />	Arrange the molecule so that horizontal bonds at chirali...
Rules for Fischer projections<br />H<br />Br<br />Cl<br />F<br />	Projection of molecule on page is a cross.  When represe...
Rules for Fischer projections<br />H<br />Br<br />Cl<br />F<br />	Projection of molecule on page is a cross.  When represe...
Physical Properties of Enantiomers<br />
Physical properties of enantiomers<br />Same: 	melting point, boiling point, density, etc<br />Different: 	properties that...
Odor<br />CH3<br />CH3<br />O<br />O<br />H3C<br />H3C<br />CH2<br />CH2<br />(–)-Carvonespearmint oil<br />(+)-Carvonecar...
H<br />H3C<br />CH2CH(CH3)2<br />C<br />C<br />HO<br />O<br />Chiral drugs<br />Ibuprofen is chiral, but normally sold asa...
Chiral MoleculeswithTwo Chirality Centers<br />	How many stereoisomers when a particular molecule contains two chirality c...
O<br />CH3CHCHCOH<br />HO<br />OH<br />2,3-Dihydroxybutanoic acid<br />2<br />3<br />	What are all the possible R and S co...
O<br />CH3CHCHCOH<br />HO<br />OH<br />2,3-Dihydroxybutanoic acid<br />2<br />3<br />	4 Combinations = 4 Stereoisomers<br ...
O<br />CH3CHCHCOH<br />HO<br />OH<br />2,3-Dihydroxybutanoic acid<br />2<br />3<br />	4 Combinations = 4 Stereoisomers<br ...
O<br />CH3CHCHCOH<br />HO<br />OH<br />2,3-Dihydroxybutanoic acid<br />2<br />3<br />enantiomers:	2R,3R and 2S,3S<br />2R,...
CO2H<br />CO2H<br />[] = -9.5°<br />[] = +9.5°<br />R<br />S<br />HO<br />OH<br />H<br />H<br />enantiomers<br />OH<br /...
O<br />CH3CHCHCOH<br />HO<br />OH<br />2,3-Dihydroxybutanoic acid<br />2<br />3<br />but not all relationships are enantio...
Isomers<br />constitutional<br />isomers<br />stereoisomers<br />enantiomers<br />diastereomers<br />
CO2H<br />CO2H<br />R<br />S<br />HO<br />OH<br />H<br />H<br />OH<br />HO<br />H<br />H<br />R<br />S<br />CH3<br />CH3<b...
Fischer Projections<br />	recall for Fischer projection:  horizontal bonds point toward you;  vertical bonds point away <b...
Fischer projections <br />	transform molecule to eclipsed conformation in order to construct Fischer projection<br />
CO2H<br />OH<br />H<br />H<br />OH<br />CH3<br />Fischer projections <br />
Two chirality centers in a ring<br />S<br />R<br />S<br />R<br />trans-1-Bromo-1-chlorocyclopropane<br />nonsuperposable m...
Two chirality centers in a ring<br />S<br />S<br />R<br />R<br />cis-1-Bromo-1-chlorocyclopropane<br />nonsuperposable mir...
Two chirality centers in a ring<br />S<br />S<br />R<br />R<br />cis-1-Bromo-1-chloro-cyclopropane<br />trans-1-Bromo-1-ch...
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Estereoq

  1. 1. ESTEREOQUÍMICA<br />
  2. 2. enantiomers<br />diastereomers<br />Isomers<br />constitutional<br />isomers<br />stereoisomers<br />
  3. 3.
  4. 4. Molecular Chirality: Enantiomers<br />
  5. 5. Chirality<br /> A molecule is chiral if its two mirror image forms are not superposable upon one another. <br /> A molecule is achiral if its two mirror image forms are superposable.<br />
  6. 6. Bromochlorofluoromethane is chiral<br />Cl<br /> It cannot be superimposed point for point on its mirror image.<br />Br<br />H<br />F<br />
  7. 7. Bromochlorofluoromethane is chiral<br />Cl<br />Cl<br />Br<br />Br<br />H<br />H<br />F<br />F<br /> To show nonsuperimposability, rotate this model 180° around a vertical axis.<br />
  8. 8. Bromochlorofluoromethane is chiral<br />Cl<br />Br<br />Cl<br />Br<br />H<br />H<br />F<br />F<br />
  9. 9. Another look<br />
  10. 10. Enantiomers<br />nonsuperimposable mirror images are called enantiomers<br />and<br />are enantiomers with respect to each other<br />
  11. 11. Chlorodifluoromethaneis achiral<br />
  12. 12. Chlorodifluoromethaneis achiral<br /> The two structures are mirror images, but are not enantiomers, because they can be superimposed on each other.<br />
  13. 13. The Chirality Center<br />
  14. 14. w<br />x<br />y<br />C<br />z<br />The Chirality Center<br />a carbon atom with fourdifferent groups attached to it<br />also called:<br />chiral centerasymmetric centerstereocenter<br />stereogenic center<br />
  15. 15. H<br />F<br />Cl<br />C<br />Br<br />Chirality and chirality centers<br />A molecule with a single chirality center is chiral.<br />Bromochlorofluoromethane is an example.<br />
  16. 16. H<br />CH3<br />CH2CH3<br />C<br />OH<br />Chirality and chirality centers<br />A molecule with a single chirality center is chiral.<br />2-Butanol is another example.<br />
  17. 17. CH3<br />CH2CH2CH2CH3<br />CH3CH2CH2<br />C<br />CH2CH3<br />Examples of molecules with 1 chirality center<br />a chiral alkane<br />
  18. 18. OH<br />Examples of molecules with 1 chirality center<br />Linalool, a naturally occurring chiral alcohol<br />
  19. 19. H2C<br />CHCH3<br />O<br />Examples of molecules with 1 chirality center<br />1,2-Epoxypropane: a chirality center<br />can be part of a ring<br />attached to the chirality center are:<br />—H<br /> —CH3<br />—OCH2<br />—CH2O<br />
  20. 20. CH3<br />H<br />C<br />CH2<br />CH3<br />Examples of molecules with 1 chirality center<br />Limonene: a chirality center can be part of a ring<br /> attached to thechirality center are:<br />—H<br /> —CH2CH2<br />—CH2CH=<br />—C=<br />
  21. 21. H<br />CH3<br />D<br />C<br />T<br />Examples of molecules with 1 chirality center<br />Chiral as a result of isotopic substitution<br />
  22. 22. A molecule with a single chirality centermust be chiral.<br />But, a molecule with two or more chirality centers may be chiral or it may not.<br />
  23. 23. Properties of Chiral Molecules:Optical Activity<br />
  24. 24. Optical Activity<br />A substance is optically active if it rotates the plane of polarized light.<br />In order for a substance to exhibit opticalactivity, it must be chiral and one enantiomer must be present in excess of the other.<br />
  25. 25. Light<br /> has wave properties<br /> periodic increase and decrease in amplitude of wave<br />
  26. 26. Light<br /> optical activity is usually measured using light having a wavelength of 589 nm<br /> this is the wavelength of the yellow light from a sodium lamp and is called the D line of sodium<br />
  27. 27. Polarized light<br />ordinary (nonpolarized) light consists of many beams vibrating in different planes<br />plane-polarized light consists of only those beams that vibrate in the same plane<br />
  28. 28. Nicol prism<br />Polarization of light<br />
  29. 29. <br />Rotation of plane-polarized light<br />
  30. 30. AbsoluteandRelative Configuration<br />
  31. 31. Configuration<br />Relative configuration compares the arrangement of atoms in space of one compound with those of another.<br />Absolute configuration is the precise arrangement of atoms in space.<br />
  32. 32. Configuration<br />Relative configuration compares the arrangement of atoms in space of one compound with those of another.until the 1950s, all configurations were relative<br />Absolute configuration is the precise arrangement of atoms in space. we can now determine the absolute configuration of almost any compound<br />
  33. 33. CH3CHCH2CH3<br />CH3CHCH<br />CH2<br />OH<br />OH<br />Relative configuration<br />Pd<br />[] + 33.2°<br />[] + 13.5°<br />No bonds are made or broken at the chirality centerin this experiment. Therefore, when (+)-3-buten-2-ol and (+)-2-butanol have the same sign of rotation, the arrangement of atoms in space is analogous. The twohave the same relative configuration.<br />
  34. 34. H<br />HO<br />H<br />HO<br />OH<br />OH<br />H<br />H<br />Two possibilities<br />H2, Pd<br />H2, Pd<br /> But in the absence of additional information, we can't tell which structure corresponds to(+)-3-buten-2-ol, and which one to (–)-3-buten-2-ol.<br />
  35. 35. H<br />HO<br />H<br />HO<br />OH<br />OH<br />H<br />H<br />Two possibilities<br />H2, Pd<br />H2, Pd<br /> Nor can we tell which structure corresponds to(+)-2-butanol, and which one to (–)-2-butanol.<br />
  36. 36. H<br />HO<br />H<br />HO<br />OH<br />OH<br />H<br />H<br />Absolute configurations<br />H2, Pd<br />[] +33.2°<br />[] +13.5°<br />H2, Pd<br />[] –13.5°<br />[] –33.2°<br />
  37. 37. CH3CH2CHCH2Br<br />CH3CH2CHCH2OH<br />CH3<br />CH3<br />Relative configuration<br />HBr<br />[] -5.8°<br />[] + 4.0°<br />Not all compounds that have the same relativeconfiguration have the same sign of rotation. No bondsare made or broken at the chirality center in thereaction shown, so the relative positions of the atoms are the same. Yet the sign of rotation changes.<br />
  38. 38. The Cahn Ingold PrelogR-S Notational System<br />
  39. 39. Two requirements for a systemfor specifying absolute configuration<br />1. need rules for ranking substituents at chirality center in order of decreasing precedence<br />2. need convention for orienting molecule so that order of appearance of substituents can be compared with rank <br />The system that is used was devised by R. S. Cahn, Sir Christopher Ingold, and V. Prelog.<br />
  40. 40. The Cahn-Ingold-Prelog Rules<br />1. Rank the substituents at the chirality center according to same rules used in E-Z notation.<br />2. Orient the molecule so that lowest-ranked substituent points away from you. <br />
  41. 41. 1<br />1<br />4<br />3<br />3<br />4<br />2<br />2<br />Example<br />Order of decreasing rank:4 > 3 > 2 > 1<br />
  42. 42. The Cahn-Ingold-Prelog Rules<br />1. Rank the substituents at the chirality center according to same rules used in E-Z notation.<br />2. Orient the molecule so that lowest-ranked substituent points away from you. <br />3. If the order of decreasing precedence traces a clockwise path, the absolute configuration is R. If the path is counterclockwise, the configuration is S.<br />
  43. 43. 1<br />1<br />4<br />3<br />3<br />4<br />2<br />2<br />counterclockwise<br />clockwise<br />R<br />S<br />Example<br />Order of decreasing rank:43 2 <br />
  44. 44. H<br />H<br />CH2CH3<br />CH3CH2<br />C<br />HO<br />C<br />OH<br />CH3<br />H3C<br />(S)-2-Butanol<br />(R)-2-Butanol<br />Enantiomers of 2-butanol<br />
  45. 45. Very important! Two different compounds with the same sign of rotation need not have the same configuration.<br /> Verify this statement by doing Problem. All four compounds have positive rotations. What are their configurations according to the Cahn-Ingold-Prelog rules?<br />
  46. 46. H<br />H3C<br />R<br />H<br />H<br />Chirality center in a ring<br />—CH2C=C > —CH2CH2 > —CH3 > —H<br />
  47. 47. Fischer Projections<br /> Purpose of Fischer projections is to show configuration at chirality center without necessity of drawing wedges and dashes or using models. <br />
  48. 48. Rules for Fischer projections<br />H<br />Cl<br />Br<br />F<br /> Arrange the molecule so that horizontal bonds at chirality center point toward you and vertical bonds point away from you.<br />
  49. 49. Rules for Fischer projections<br />H<br />Br<br />Cl<br />F<br /> Projection of molecule on page is a cross. When represented this way it is understood that horizontal bonds project outward, vertical bonds are back.<br />
  50. 50. Rules for Fischer projections<br />H<br />Br<br />Cl<br />F<br /> Projection of molecule on page is a cross. When represented this way it is understood that horizontal bonds project outward, vertical bonds are back.<br />
  51. 51. Physical Properties of Enantiomers<br />
  52. 52. Physical properties of enantiomers<br />Same: melting point, boiling point, density, etc<br />Different: properties that depend on shape of molecule (biological-physiological properties) can be different <br />
  53. 53. Odor<br />CH3<br />CH3<br />O<br />O<br />H3C<br />H3C<br />CH2<br />CH2<br />(–)-Carvonespearmint oil<br />(+)-Carvonecaraway seed oil<br />
  54. 54. H<br />H3C<br />CH2CH(CH3)2<br />C<br />C<br />HO<br />O<br />Chiral drugs<br />Ibuprofen is chiral, but normally sold asa racemic mixture. The S enantiomer is the one responsible for its analgesic and antiinflammatory properties. <br />
  55. 55. Chiral MoleculeswithTwo Chirality Centers<br /> How many stereoisomers when a particular molecule contains two chirality centers?<br />
  56. 56. O<br />CH3CHCHCOH<br />HO<br />OH<br />2,3-Dihydroxybutanoic acid<br />2<br />3<br /> What are all the possible R and S combinations of the two chirality centers in this molecule?<br />Carbon-2 R R S S<br />Carbon-3 R S R S<br />
  57. 57. O<br />CH3CHCHCOH<br />HO<br />OH<br />2,3-Dihydroxybutanoic acid<br />2<br />3<br /> 4 Combinations = 4 Stereoisomers<br />Carbon-2 R R S S<br />Carbon-3 R S R S<br />
  58. 58. O<br />CH3CHCHCOH<br />HO<br />OH<br />2,3-Dihydroxybutanoic acid<br />2<br />3<br /> 4 Combinations = 4 Stereoisomers<br />What is the relationship between these stereoisomers?<br />Carbon-2 R R S S<br />Carbon-3 R S R S<br />
  59. 59. O<br />CH3CHCHCOH<br />HO<br />OH<br />2,3-Dihydroxybutanoic acid<br />2<br />3<br />enantiomers: 2R,3R and 2S,3S<br />2R,3S and 2S,3R<br />Carbon-2 R R S S<br />Carbon-3 R S R S<br />
  60. 60. CO2H<br />CO2H<br />[] = -9.5°<br />[] = +9.5°<br />R<br />S<br />HO<br />OH<br />H<br />H<br />enantiomers<br />OH<br />HO<br />H<br />H<br />R<br />S<br />CH3<br />CH3<br />CO2H<br />CO2H<br />S<br />R<br />OH<br />HO<br />H<br />H<br />enantiomers<br />OH<br />H<br />HO<br />H<br />R<br />S<br />[] = -17.8°<br />[] = +17.8°<br />CH3<br />CH3<br />
  61. 61. O<br />CH3CHCHCOH<br />HO<br />OH<br />2,3-Dihydroxybutanoic acid<br />2<br />3<br />but not all relationships are enantiomeric<br /> stereoisomers that are not enantiomers are diastereomers<br />Carbon-2 R R S S<br />Carbon-3 R S R S<br />
  62. 62. Isomers<br />constitutional<br />isomers<br />stereoisomers<br />enantiomers<br />diastereomers<br />
  63. 63. CO2H<br />CO2H<br />R<br />S<br />HO<br />OH<br />H<br />H<br />OH<br />HO<br />H<br />H<br />R<br />S<br />CH3<br />CH3<br />diastereomers<br />CO2H<br />CO2H<br />S<br />R<br />OH<br />HO<br />H<br />H<br />OH<br />H<br />HO<br />H<br />R<br />S<br />CH3<br />CH3<br />[] = -9.5°<br />[] = +9.5°<br />enantiomers<br />enantiomers<br />[] = -17.8°<br />[] = +17.8°<br />
  64. 64. Fischer Projections<br /> recall for Fischer projection: horizontal bonds point toward you; vertical bonds point away <br />staggered conformation does not have correct orientation of bonds for Fischer projection<br />CO2H<br />CH3<br />
  65. 65. Fischer projections <br /> transform molecule to eclipsed conformation in order to construct Fischer projection<br />
  66. 66. CO2H<br />OH<br />H<br />H<br />OH<br />CH3<br />Fischer projections <br />
  67. 67. Two chirality centers in a ring<br />S<br />R<br />S<br />R<br />trans-1-Bromo-1-chlorocyclopropane<br />nonsuperposable mirror images; enantiomers<br />
  68. 68. Two chirality centers in a ring<br />S<br />S<br />R<br />R<br />cis-1-Bromo-1-chlorocyclopropane<br />nonsuperposable mirror images; enantiomers<br />
  69. 69. Two chirality centers in a ring<br />S<br />S<br />R<br />R<br />cis-1-Bromo-1-chloro-cyclopropane<br />trans-1-Bromo-1-chloro-cyclopropane<br />stereoisomers that are notenantiomers; diastereomers<br />

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