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__ is the study of the 3D structure of molecules.
Biological systems are __, and they often discriminate between molecuels with subtle __.
- stereochemistry
- exquisitely selective
- stereochemical differences
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What are the two broad classes.
- constitutional (structural): differ in their bonding sequence; their atoms connect differently
- stereoisomers: same bonding sequence, but differ in the orientation of their atoms in space
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Stereoisomers have different __ (4)__.
physical, chemical and biological propertie
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Objects that have left-handed and right- handed forms are called __. Explain it.
- chiral
- chiral objects have mirror images that are different from the original object
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What is an object that looks the same in the mirror?
achiral
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Two objects are said t be __ if they can be placed on top of each other and the 3D position of each atom of one molecule coincides with the equivalent atom of the other molecule.
superimposable
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Nonsuperimposable mirror-image molecules are called __.
enantiomers
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A chiral compound always has an __. An achiral compound always has a mirror image that is the same as the original molecuel.
enantiomer (a nonsuperimposable mirror image)
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Summary:
enantiomers
chiral
achiral
- mirror-images; pairs of compounds that are nonsuperimposable mirror images
- chiral: different from its mirror image; having an enantiomer
- achiral: identical with its mirror image; not chiral
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What makes a molecule chiral?
the most common feature is a carbon atom that is bonded to four different groups= asymmteric carbon (or chiral carbon atom)
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An asymmetric carbon atom is the most common example of a __, the IUPAC term for any atom holding a set of ligands in a spatial arrangement that is not superimposable on its mirror image.
chirality center (chiral center)
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__ belong to an even broader group called __, which is what?
- chirality centers
- stereocenters
- any atoms at which the interchange of tow groups gives a stereoisomer
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__ and the __ in __ are the most common types of __.
- asymmetric carbons
- double-bonded carbon atoms
- cis-trans isomers
- stereocenters
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If two of the four groups on a carbon atom are the same, the arrangement is __.
not chiral
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Generalize chirality, but keep in mind what.
- that the ultimate test for chirality is always whether the molecule's mirror image is the same or diferent
- 1) if a compound has no asymmetric carbon atom, it's usually achiral.
- 2) if a compound has just one asymmetric carbon atom, it must be chiral
- 3) If a compound has more than one asymmetric carbon, it may or may not be chiral
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internal mirror plane
bisecting a carbon atom and its two hydrogen atoms, the part of the molecule that appears to the right of the line is the mirror image of hte part on the left
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Any molecule that has an __ cannot be __, even though it may contain asymmetric carbon atoms.
- internal mirror plane of symmetry
- chiral
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If a carbon atom has only three different kinds of substituents, it has an __. Therefore, it cannot contribute to __ in a molecule.
- internal mirror plane of symmetry
- chirality
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An asymmetric carbon has __ possible (mirror-image) spatial arrangments, which we call __.
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The __ is the most widely accepted system for naming the configurations of chirality centers. Each asymmetric carbon atom is assigned a letter (R) or (S) based on its __.
- Cahn-Ingold-Prelog convention
- 3D configuration
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To determine the name, we follow a two-step procedure that assigns "__" to the four __and then assigns the name based on the __.
- priorities
- substituents
- relative positions of these substituents
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What is the procedure? 1.
1a.
- assign a relative "priority" to each group bonded to the asymmetric carbon.
- - Look at the first atom of the group--the atom bonded to the asymmetric carbon. Atoms with higher atomic numbers receive higher priorities
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With different isotopes of the same element, what?
the heavier isotopes have higher priorities
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What is the procedure? 1b.
in case of ties, use the next atoms along thechain of each group as tiebreakers.
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What is the procedure? 1c.
Treat = adn triple bonds as if each were a bond to a separate atom. When you break a bond, you always add two imaginary atoms
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What is the procedure? 2.
using a 3D drawing or model, put the fourth priority group away from you and view the molecule with the first, second , and third priority groups radiating toward you like the spokes of a sterring whell. Draw an arrow from the first priority group, through the second, to the third.
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Explain what the arrows indicate.
If the arrow points clockwise, the asymmetric carbon atom is called R. If it points counterclockwise, it is called S.
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