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xijunzhu
on FreezingBlue Flashcards.
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structural isomers/constitutional isomers
same molecular formula
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stereoisomers
share the same atomic connectivity
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conformational isomers
differ in rotation around single bonds
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configurational isomers
interconverted only by breaking bonds
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anti-conformation
two largest groups are antiperiplanar (opposite sides)
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staggered conformation
no overlap of atoms along the line of sight, opposite of eclipsed
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what is the most stable conformation of cyclohexane?
chair conformation where two equatorial methyl groups are trans to each other.
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does enantiomers have identical physical and chemical properties
yes except for optical acitivity and reactions in chiral environments
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optical activity
refers to the rotation of plane-polarized light by a chiral molecule.
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specific rotation
- standardized units for comparison purposes
- equals observed rotation in degrees divided by concentration (g/ml) and path length
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racemic mixture
equal amounts of both enantiomers, no optical activity.
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diastereomers
- non-mirror images
- molecule has two or more stereogenic centers and differs at some, but not all of these centers.
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for molecule with n stereocenters, how many possible stereoisomers?
2^n
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differences between diastereomers and enantiomers
- diastereomers have diff chem properties
- rotate plane-polarized light but the magnitude is not equal and opposite to another diastereomer
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cis-trans/geometric isomers
substituents differ in position around an immovable bond
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E and Z forms
used for compounds with polysubstituted double bond
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cahn ingold prelog priority rules
- based on atom bound to double bond (E/Z)
- higher the atomic number, more priority
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what does horizontal and vertical lines represent in Fischer projection
- horizontal lines (pointing out)
- vertical lines (bonds going into the page)
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assigning R and S
any time two groups are switched on a chiral carbon, the stereochemistry is inverted.
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what changes the absolute conformation?
when reactant and product has different stereochemistry (R to S)
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relative configuration
stays the same when bonds of stereocenter are not broken, when positions of chiral carbons are maintained.
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can E and Z be diastereomers?
yes b/c they have the same connectivity
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