Chapter 5 Flashcards
Having the property of handiness, i.e., the case where mirror images of an object are not superposable
Chiral
Two objects are superposable if, when one object is placed on top of the other, all parts of each coincide
Superposable
Different molecules that have the same molecular formula
Isomers
Compounds that have the same molecular formula but that differ in their connectivity (i.e., molecules that have the same molecular formula but have their atoms connected in different ways)
Constitutional isomers
Compounds with the same molecular formula that differ only in the arrangement of their atoms in space
Stereoisomers
Chemical studies that take into account the spatial aspects of molecules
Stereochemistry
Stereoisomers that are mirror images of each other
Enantiomers
Stereoisomers that are not mirror images of each other
Diastereomers
A molecule that is not super possible on its mirror image; have handedness and are capable of existing as a pair of enantiomers
Chiral molecule
A molecule that is superposable on its mirror image; lacks handedness and are incapable of existing as a pair of enantiomers
Achiral molecule
An atom bearing groups of such nature that an interchange of any two groups will produce a stereoisomer
Chiral center
When the exchange of two groups bonded to the same atom produces stereoisomers, the atom is said to be a stereogenic atom, or stereogenic center
Stereogenic center
A single tetrahedral carbon with four different groups attached to it; also called an asymmetric carbon, a stereocenter, or a chirality center
Stereogenic carbon
An imaginary plane that bisects a molecule in a way such that the two halves of the molecule are mirror images of each other. Any molecule with a plane of symmetry will be achiral
Plane of symmetry
A method for designating the configuration of a tetrahedral chiral centers
R, S-system
The particular arrangement of atoms (or groups) in space that is characteristic of a given stereoisomer
Configuration
A compound that rotates the plane of polarization of plane-polarized light
Optically active compound
Light in which the oscillations of the electrical field occur in one plane
Plane-polarized light
A device used for measuring optical activity
Polarimeter
A compound that rotates plane-polarized light clockwise
Dextorotatory
A compound that rotates plane-polarized light in a counterclockwise direction
Levorotatory
A physical constant calculated from the observed rotation of a compound using the following equation: [a]D = ac^xl where a is the observed rotation using the D line of a sodium lamp, c is the concentration of the solution or the density of a neat liquid in grams per milliliter, and l is the length of the tube in decimeters
Specific rotation
An equimolar mixture of enantiomers; is optically inactive
Racemic mixture (racemate or racemic form)
A percentage calculated for a mixture of enantiomers by dividing the moles of one enantiomers by the moles of both enantiomers and multiplying by 100; equals the percentage optical purity
Enantiomers excess (enantiomeric purity)
A percentage calculated for a mixture of enantiomers by dividing the observed specific rotation for the mixture by the specific rotation of the pure enantiomers and multiplying by 100; equals the enantiomeric purity or enantiomeric excess
Optical purity
I’m reactions where chiral centers are altered or created, a stereoselective rotation produces a preponderance of one stereoisomer; this type of reaction can either be enantioselective, in which case the reaction produces a preponderance of one enantiomer, or diastereoselective, in which case the reaction produces a preponderance of one diastereomer
Stereoselective reaction
A process in which the rate of a reaction with one enantiomer is different than the other, leading to a preponderance of one produce stereoisomer. This process is said to be “stereoselective” in that is leads to the preferential formation of one stereoisomer over other stereoisomers that could possibly be formed
Kinetic resolution
An optically inactive compound whose molecules are achiral even though they contain tetrahedral atoms with four different attached groups
Meso compound
A two-dimensional formula for representing the three-dimensional configuration of a chiral molecule. They are written with the main carbon chain extending from top to bottom with all groups eclipsed. Vertical lines represent bonds that project behind the plane of the page (or that lie in it). Horizontal lines represent bonds that project out of the page
Fischer projection
The relationship between the configurations of two chiral molecules. Molecules are said to have the same relative configuration when similar or identical groups in each occupy the same position in space. The configurations of molecules can be related to each other through reactions of known stereochemistry, for example, through reactions that cause no bonds to a stereogenic center to be broken
Relative configuration
The actual arrangement of groups in a molecule; can be determined by X-ray analysis or by relating the configuration of a molecule, using reactions of known stereochemistry, to another molecule whose absolute configuration is known
Absolute configuration
The process by which the enantiomers of a racemic form are separated
Resolution
Conformational isomers that are stable, isolable compounds
Atropisomers
