Organic Chemistry Chapter 5: Chirality, Enantiomers and Diastereomers

Configurational Isomer

Molecular species that have the same connectivity but differ in a way other than by rotations about a single bond

Stereoisomer

Molecular series that have the same connectivity but are not superimposable.

Enantiomers

Configurational isomers that are mirror images of eachother

Diastereoisomers

Constitutional isomers that are not mirror images of eachother

Nonsuperimposable

Describes two molecules for which there is no orientation such that all atoms of both molecules can be superimposable 

Chiral 

Describes a moelcule that has an enantiomer 

Achiral

Describes a molecule that does not have an enantiomer 

Plane of symmetry

A plane that bisects a molecule in such a way that one half of the molecule is the mirror image of the other half 

Chiral Center

A tetrahedral atom bonded to four different groups

Stereochemical Configuration

The classification of the three dimensional arrangement of substituents attached to a chiral center or a double bond. 

Meso

Describes a molecule that contains at least two ciral centers but has a plane of symmetry that makes it achiral overall 

R configuration 

A chiral center where the substituents having priorities 1-3 are arranged clockwise when priority 4 substituent points away

S Configuration

A chiral center where the substituents having priorities 1-3 are arranged counterclockwise when priority 4 substituent points away

Nitrogen Inversion

The process by which the configuration about Nitrogen inconvert in the species NR,R’’R’’’

Z configuration

Describes a double bond in which the higher priority substituents attached to the ends of the double bond appear on the same side of double bond

E configuration

describes a double bond in whcih the highest priority substituents attached to the ends of the double bond appear on opposite sides of double bonds

Fischer Projection

2D representation of configuration about chiral center in a given molecule. Horizontal bond point toward viewer and vertical away 

Chiral environment

An environment that is non superimposable onits mirror image, in which enantiomers must have different physical chemical properties

Achiral environment

An environment that is superimposable on its mirror image, in which the enantiomers have exactly same physical and chemical properties. 

Plane Polarized

describe light whose photons have their electric field oscillating in the same plane

Polarizer

A device that generates plane polarized light by allowing through only photons whose electric field is osciilating in a specified plane, effectively filtering out light whose electric field oscillates in any other plane

Dextrorotatory

Describes chiral compounds that rotate plane polarized light clockwise

Levorotatory

Describes chiral compounds that rotate plane polarized light counterclockwis

Measured Angle of rotation

The angle by which plane polarized light is rotated on passign through a sample of chiral compound

Specific rotation

A constant term that is unique for a given chiral compound and describes the compounds propensity for rotating plane polarized light

Racemic mixture

A mixture that contains equal amounts of the + and - enantiomers of a chiral molecule

Enantiomeric excess

The fraction of a mixture of enantiomers that is not racemic and contributes to the rotation of plane polarized light