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35 Cards in this Set
- Front
- Back
stereochemistry
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is the study of the structure and chemistry of stereoisomers.
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constitutional isomers (structural isomers)
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are connected differently; they differ in their bonding sequence.
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stereoisomers
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differ only in how their atoms are oriented in space.
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chiral
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Different from its mirror image.
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achiral
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Not chiral
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superimposable
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Identical in all respects. The three-dimensional positions of all atoms coincide when the molecules are placed on top of each other.
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enantiomers
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A pair of nonsuperimposable mirror-image molecules: mirror-image isomers.
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asymmetric carbon atom (chiral carbon atom)
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A carbon atom that is bonded to four different groups.
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chirality center
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The IUPAC term for an atom holding a set of ligands in a spatial arrangement that is not superimposable on its mirror image. Asymmetric carbon atoms are the most common chirality centers.
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stereocenter
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An atom that gives rise to stereoisomers when its groups are interchanged. Asymmetric carbon atoms and double-bonded carbons in cis-trans alkenes are the most common stereocenters.
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stereocenter (stereogenic atom)
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An atom that gives rise to stereoisomers when its groups are interchanged. Asymmetric carbon atoms and double-bonded carbons in cis-trans alkenes are the most common stereocenters.
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internal mirror plane
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A plane of symmetry through the middle of a molecule, dividing the molecule into two mirror-image halves. A molecule with an internal mirror plane of symmetry cannot be chiral.
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configurations
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The two possible spatial arrangements around a chirality center or other stereo-center.
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Cahn–Ingold–Prelog convention
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The accepted method for designating the absolute configuration of a chirality center (usually an asymmetric carbon) as either (R) or (S).
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polarimeter
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An instrument that measures the rotation of plane-polarized light by an optically active compound.
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plane-polarized light
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Light composed of waves that vibrate in only one plane.
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optical activity
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Rotation of the plane of polarized light.
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optically active
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Capable of rotating the plane of polarized light.
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optical isomers
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Compounds with identical properties except for the direction in which they rotate polarized light. (
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polarimeter
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An instrument that measures the rotation of plane-polarized light by an optically active compound.
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dextrorotatory, or (d)
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Rotating the plane of polarized light clockwise.
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levorotatory
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(l) Rotating the plane of polarized light counterclockwise.
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specific rotation
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A measure of a compound's ability to rotate the plane of polarized light, given by where c is concentration in g mL and l is length of sample cell (path length) in decimeters.
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chiral probe
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A molecule or an object that is chiral and can use its own chirality to differentiate between mirror images. (
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racemic mixture
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A mixture of equal quantities of enantiomers, such that the mixture is optically inactive.
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optical purity (o.p.)
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The specific rotation of a mixture of two enantiomers, expressed as a percentage of the specific rotation of one of the pure enantiomers. Similar to enantiomeric excess.
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enantiomeric excess (e.e.)
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The excess of one enantiomer in a mixture of enantiomers expressed as a percentage of the mixture. Similar to optical purity.
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Fischer projection
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A method for drawing an asymmetric carbon atom as a cross. The carbon chain is kept along the vertical, with the IUPAC numbering from top to bottom. Vertical bonds project away from the viewer, and horizontal bonds project toward the viewer.
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diastereomers
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Stereoisomers that are not mirror images.
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cis-trans isomers
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Isomers that differ in their cis-trans arrangement on a ring or double bond. Cis-trans isomers are a subclass of diastereomers. (p. 287) cis: Having similar groups on the same side of a double bond or a ring. trans: Having similar groups on opposite sides of a double bond or a ring. Z: Having the higher-priority groups on the same side of a double bond. E: Having the higher-priority groups on opposite sides of a double bond.
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meso compound
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An achiral compound that contains chirality centers (usually asymmetric carbon atoms). Originally, an achiral compound that has chiral diastereomers.
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absolute configuration
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The detailed stereochemical picture of a molecule, including how the atoms are arranged in space. Alternatively, the (R) or (S) configuration at each asymmetric carbon atom. (
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relative configuration
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The experimentally determined relationship between the configurations of two molecules, even though the absolute configuration of either may not be known.
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resolution
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The process of separating a racemic mixture into the pure enantiomers. Resolution requires a chiral resolving agent.
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resolving agent
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A chiral compound (or chiral material on a chromatographic column) used for separating enantiomers.
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