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Chapter 51 Stereochemistry: Chapter 5 The Arrangement of Atoms in Space; The Stereochemistry of Addition Reactions

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Chapter 52 Contents of Chapter 5 Conformational and Configurational Isomers Chirality Centers, Enantiomers Optical Rotation, Optical Purity Isomers with More Than One Chirality Center Separation of Enantiomers Reactions of Chiral Compounds Absolute Configurations Stereochemistry of Reactions

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Chapter 53 Kinds of Isomers

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Chapter 54 Conformational Isomers

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Chapter 55 Configurational Isomers: Cis-Trans Diastereomers

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Chapter 56 Isomers with One Chirality Center A chirality center arises when four different substituents are bonded to a carbon Only two isomers are possible, an R isomer and an S isomer.

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Chapter 57 Chirality R and S enantiomers are mirror images of each other, just as your right hand is the mirror image of your left hand

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Chapter 58 Chirality Any object that has a plane or point of symmetry is achiral (not chiral).

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Chapter 59 Examples chiral achiral

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Chapter 510 Mirror Trick Whenever two structures can be positioned around a symmetry plane if they aren’t identical they’re enantiomers.

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Chapter 511 Drawing Enantiomers Fischer Projections N and S are down into plane, E and W are up out of plane of page or screen.

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Chapter 512 Naming Enantiomers: The R,S System of Nomenclature Rank groups by atomic number of the atom bonded to the chirality center. Use the same system that was used for the E and Z isomers of alkenes

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Chapter 513 2.Orient molecule so that group (or atom) of lowest priority is directed into plane. 3.Draw a curve from group of highest priority through the group of second priority to group of third priority Naming Enantiomers: The R,S System of Nomenclature

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Chapter 514 Naming Enantiomers: The R,S System of Nomenclature R (Latin rectus) = right turn S (Latin sinister) = left turn 1 2 3 4 (S)-2-bromobutane

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Chapter 515 If for any reason you ever wish a group were in a different position simply swap it with another group. Swap simply reverses the chirality. R for switched compound implies S for actual compound Swap Trick

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Chapter 516 If the low priority group in figure points up rather than down simply draw circular arrow and reverse chirality. Low Priority Group Up Trick R for reversed chirality implies S for actual chirality

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Chapter 517 If low priority group on vertical line (into plane) draw normal rotating arrow. If low priority group on horizontal line draw rotating arrow and reverse the R or S result. Rule of thumb: If group 4 is Vertical, Very true. If group 4 is Horizontal, Horribly wrong. (R)-2-bromobutane Fischer Tricks (S)-2-bromobutane

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Chapter 518 90º rotation reverses all chiralities. 180º rotation maintains all chiralities. Fischer Tricks

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Chapter 519 Can rotate 3 groups either CW or CCW without changing configuration If 3 grps have same rel CW or CCW sequence C’s same Multi-Carbon Fischer Trick

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Chapter 520 For front C swap low priority group to back C If swap was necessary curved arrow now gives reversed chirality; otherwise correct Newman Projections

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Chapter 521 For back C swap low priority group to front C If swap was necessary curved arrow now gives correct chirality; otherwise reversed Newman Projections

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Chapter 522 Compounds with More Than One Chirality Center Two Pairs of Similar Groups

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Chapter 523 Compounds with More Than One Chirality Center Three Pairs of Similar Groups

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Chapter 524 Meso Compounds

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Chapter 525 Drill on Meso Compounds Problem 27 Does the following compound have a stereoisomer that is a meso compound? Plane of symmetry Meso form possible

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Chapter 526 Topology of Stereoisomers With Two Chiral Centers

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Chapter 527 R,S System for Isomers with More Than One Chirality Center Compound is (2S,3R)-3-bromo-2-butanol

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Chapter 528 R,S System for isomers with more than one Chirality Center Compound is (2S,3R)-3-bromo-2-butanol

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Chapter 529 Relative and Absolute Configurations (–) amphetamine is known to have the R- configuration Therefore the (+) form has S configuration

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Chapter 530 Separation of Enantiomers Racemic lactic acid can be reacted with a naturally occurring chiral base, such as morphine or strychnine The product is a pair of diastereomers Properties of diastereomers are sufficiently different from each other to allow separation After separation, each diastereomer can be reacted with hydrochloric acid, yielding an optically pure R or S acid

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Chapter 531 Enantiotopic, Diastereotopic, and Homotopic Hydrogens

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Chapter 532 Enantiotopic, Diastereotopic, and Homotopic Hydrogens

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Chapter 533 Regioselective, Stereoselective, and Stereospecific Reactions A regioselective reaction is one in which multiple constitutional isomers possible, but more of some formed than others.

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Chapter 534 Regioselective, Stereoselective, and Stereospecific Reactions A stereoselective reaction can produce multiple stereoisomers theoretically, but more of some produced than others.

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Chapter 535 Regioselective, Stereoselective, and Stereospecific Reactions A stereospecific reaction produces different stereoisomer products from different stereoisomer reactants.

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Chapter 536 Syn Addition When the two substituents add to the same side Addition of H 2 is a syn addition

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Chapter 537 Anti Addition When the two substituents add to opposite sides

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Chapter 538 Stereochemistry of Addition Unmodified only works for addition of X 2 For addition of XY use to calculate X eclipses Y or X opposite to Y in Fischer projection. CIS-SYN-ERYTHRO RULE

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Chapter 539 Stereochemistry of Addition Cis-Syn-Erythro Example

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Chapter 540 Stereochemistry of Addition Pro-Fischer Analysis

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Chapter 541 Stereochemistry of Addition Pro-Fischer Analysis Example

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© 2016 Pearson Education, Inc. Isomers: The Arrangement of Atoms in Space Paula Yurkanis Bruice University of California, Santa Barbara Chapter 4.

© 2016 Pearson Education, Inc. Isomers: The Arrangement of Atoms in Space Paula Yurkanis Bruice University of California, Santa Barbara Chapter 4.

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