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38 Cards in this Set
- Front
- Back
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What are Isomers?
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Isomers are different compounds with the same molecular formula
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How are Stereoisomers different?
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Stereoisomers ONLY differ in the way the atoms are oriented in space (cis or trans, etc.)
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What is Chirality?
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Chirality is when a molecule cannot be superimposed on its mirror image
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What is Achirality?
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Achirality is when a molecule can be superimposed on its mirror image.
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What are Enantiomers?
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Enantiomers are mirror images that are NOT superimposable.
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What is a Stereogenic Center?
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A carbon atom bonded to four DIFFERENT groups.
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What is a plane of symmetry?
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It is a mirror plane that cuts a molecule in half so that one half is the mirror image of the other half.
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Which usually contains a plane of symmetry: achiral molecules or chiral molecules?
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ACHIRAL Molecules!
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Any molecule with one tetrahedral stereogenic center is WHAT? (chiral or achiral? and enantiomers or different molecules?)
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A Chiral Compound and exists as a pair of enantiomers!
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The stereogenic center Carbon atom must be WHAT?
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An sp3 hybridized carbon atom
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Counter Clockwise: (+) or (-)? D or L?
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- and L!
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Clockwise: (+) or (-)? D or L?
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+ and D!
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The +/D and -/L mean what?
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The direction of optical rotation when light is passed through the molecule.
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Are +/D/-/L related to R and S?
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NO NO NO NO NO!
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What is the Absolute Configuration?
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Relative orientation of groups about the chiral center in space.
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In regards to Absolute Configuration, what is the notation for clockwise?
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R
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In regards to Absolute Configuration, what is the notation for counter clockwise?
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S
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In regards to Absolute Configuration, substituents are prioritized by what?
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Atomic Weight! Larger AW = higher priority!
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What always has 4th priority?
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Hydrogen!
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Where is the lowest priority always put when trying to figure out the absolute configuration?
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In the back!
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For n stereogenic centers, the MAXIMUM number of stereoisomers is what?
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2^n
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What are Diastereomers?
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Stereoisomers that are NOT mirror images of each other.
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If one enantiomer has the absolute configuration RSR, what is its enantiomer's absolute configuration?
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SRS
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What are Meso Compounds?
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Meso compounds are achiral compounds that contain tetrahedral stereogenic centers.
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Enantiomers share what 3 things?
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1. same mp
2. same bp 3 same chemical properties unless reacting w/ other optical active compounds |
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Diastereomers share what?
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Nothing. Everything is different except atomic mass.
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What is Asymmetric Synthesis?
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Specific synthesis of ONE enantiomer (tis a very difficult process).
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What is Enantiomeric Excess?
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% of enantiomer desired
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What is the formula for Enantiomeric Excess?
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ee=[alpha mixture]/[alpha pure enantiomer](100)
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What is Alpha?
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Alpha is the optical rotation observed.
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What is the formula for Alpha?
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Alpha = Alpha'/(lxc)
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What is l and c in the formula for Alpha?
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l = length of cuvette and c = concentration
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Identical compounds have the same or different R,S designations at every stereogenic center?
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SAME!
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Diasteriomers have the same R,S designations for at least what?
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Has the same designation for at least ONE stereogenic center and the opposite for at least one of the other stereogenic centers.
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Do enantiomers have exactly the same or exactly the opposite R,S designations?
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Exactly OPPOSITE.
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An equal amount of two enantiomers is called what?
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A racemic mixture
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Is a racemic mixture optically active? Why or why not?
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NO. Because with equal amounts of each enantiomer, the optical activity in each is counteracted by the other.
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What is another formula for ee?
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% of one enantiomer - % of the other enantiomer
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