Chapter 5 - Wade(1)

Chapter 5 Wade(1) - Introduction to General and Organic Chemistry II Chapter 5 Stereochemistry Dr David P Brown Department of Chemistry

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Chapter 5 Stereochemistry Stereochemistry Dr. David P. Brown Department of Chemistry Introduction to General and Organic Chemistry II
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2 Introduction ISOMERS Constitutional Isomers Stereoisomers These are structural Isomers. Ex: C 2 H 6 O CH 3 -CH 2 -OH CH 3 -O-CH 3 Same connectivity Between the atoms Different spatial arrangements
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3 Chirality Chirality - “Handedness”: Refers to the non-superimposability of an object and its mirror image. Molecules will either be chiral or achiral .
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4 Stereoisomers The non-superimposable mirror images of chiral molecules are called enantiomers . Any compound that is chiral MUST have an enantiomer. cis -1,2-dichlorocyclopentane trans - 1,2-dichlorocyclopentane H Cl H H H H H H H
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5 Stereoisomers The presence of a chirality center is usually the most distinguishing feature of a chiral molecule. The chirality center is also known as the stereocenter Usually, this is a carbon atom with four Different groups bonded to it.
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6 Stereogenic Carbons Tetrahedral carbons with 4 different attached groups are stereogenic and may render the molecule chiral.
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7 General Principles If a cpd. has no stereocenter it is usually achiral. If a cpd. has just one stereocenter, it is chiral. If a cpd. has more than one stereocenters, it may or may not be chiral Any molecule that has an internal plane of symmetry will not be chiral.
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8 Mirror Planes of Symmetry A molecule with an internal mirror plane cannot be chiral. This isomer is achiral. The trans isomer is chiral!
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9 ( R ), ( S ) Stereochemical Designations Gives the Absolute Stereochemistry at a given stereocenter. Members of an enantiomeric pair are thus distinguishable. The Cahn-Ingold-Prelog convention is applied is designating a stereocenter ( R ) or ( S ).
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10 Cahn-Ingold-Prelog Rules Assign a priority number to each group attached to the chiral carbon. Atom with the highest atomic number assigned the highest priority #1 .
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This note was uploaded on 04/10/2008 for the course CHE 1120 taught by Professor Brown during the Spring '08 term at St. Johns Duplicate.

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Chapter 5 Wade(1) - Introduction to General and Organic Chemistry II Chapter 5 Stereochemistry Dr David P Brown Department of Chemistry

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