CHEM 261: CHAPTER 5 IMPORTANT TERMS
31 Cards in this Set
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absolute configuration
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the three-dimensional structure of a chiral compound. the configuration is designated by R or S. the configuration is called absolute to distinguish it from a relative configuration
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achiral
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a molecule or object that contains an element (a plane or point) of symmetry
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cis-trans isomers
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result from not being able to rotate about a carbon-carbon bond. they are also called geometric isomers or E,Z isomers
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cis isomer
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the isomer with substituents on the same side of a cyclic structure, or the isomer with the hydrogens on the same side of a double bond
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trans isomer
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the isomer with substituents on the opposite sides of a cyclic structure or the isomer with the hydrogens on the opposite sides of a bond
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chiral
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has a nonsuperimposable mirror image
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asymmetric center
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an atom that is bonded to four different substituents
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enantiomers
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nonsuperimposable mirror-image molecules
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stereocenter (stereogenic center)
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an atom at which the interchange of two groups produces a stereoisomer
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perspective formula
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method of representing the spatial arrangement of groups bonded to an asymmetric center. two bonds are drawn in the plane of the paper; a solid wedge is used to depict a bond that projects out of the plane of the paper toward the viewer, and a hatched wedge is used to represent a bond tha…
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fischer projection
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a method of representing the spatial arrangement of groups bonded to an asymmetric center. the asymmetric center is the point of intersection of two perpendicular lines; the horizontal lines represent bonds that project out of the plane of the paper toward the viewer, and the vertical lin…
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R configuration
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after assigning relative priorities to the four groups bonded to an asymmetric center, if the lowest-priority group is on a vertical axis in a fischer projection (or pointing away from the viewer in a perspective formula), an arrow drawn from the highest priority group to the next highest…
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S configuration
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after assigning relative priorities to the four groups bonded to an asymmetric center, if the lowest-priority group is on a vertical axis in a fischer projection (or pointing away from the viewer in a perspective formula), an arrow drawn from the highest priority group to the next highest…
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plane-polarized light
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light that oscillates in a single plane passing through the direction the light travels
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polarized light
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light that oscillates in only one plane
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optically active
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rotates the plane of polarization of plane-polarized light
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optically inactive
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does not rotate the plane of polarization of plane-polarized light
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dextrorotatory
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the enantiomer that rotates the plane of polarization of plane-polarized light in a clockwise direction (+)
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levorotatory
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the enantiomer that rotates the plane of polarization of plane-polarized light in a counterclockwise direction (-)
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polarimeter
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an instrument that measures the rotation of the plane of polarization of plane-polarized light
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observed rotation
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the amount of rotation observed in a polarimeter
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specific rotation
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the amount of rotation that will be observed for a compound with a concentration of 1.0g/mL in a sample tube 1.0 decimeter long
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racemix mixture (raemate)
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a mixture of equal amount of a pair of enantiomers
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enantiomerically pure
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only one enantiomer is present in the sample
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diastereomer
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stereoisomers that are not enantiomers
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meso compound
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a compound that possesses asymmetric centers and a plane of symmetry; it is achiral, because it has a plane of symmetry
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plane of symmetry
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an imaginary plane that bisects a molecule into pieces that are a pair of mirror images
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amine inversion
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results when a compound containing an sp3 hybridized nitrogen with a nonbonding pair of electrons rapidly inverts
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configuration
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three-dimensional structure of a chiral compound, designated by R or S
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configurational isomers
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stereoisomers that cannot interconvert unless a covalent bond is broken, cis trans isomers and isomers with asymmetric centers are examples
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stereoisomers
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isomers that differ in the way the atoms are arranged in space
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CHEM 261: CHAPTER 1