Stereochemistry

thumb|right|400px|The different types of isomers. Stereochemistry focuses on [[stereoisomers.]]

mixing (superposition) of atomic orbitals in chemistry

distinct arrangements of substituents around double bonds in chemistry

geometric property of some molecules and ions

thumb|(S)-(+)-lactic acid (left) and (R)-(–)-lactic acid (right) are non-superposable mirror images of each other.

theoretical model used in chemistry

mixture with equal amounts of left- and right-handed enantiomers of a chiral molecule

thumb|300px|Rotation about single bond of butane to interconvert one conformation to another. The gauche conformation on the right is a conformer, while the eclipsed conformation on the left is a transition state between conformers. Above: Newman projection; below: depiction of spatial orientation.

number of atoms, molecules or ions bonded to in a molecule or crystal

the full linear sequence of amino acids of a peptide or protein

angle between two planes in space

general three-dimensional form of local segments of proteins

projection formula in which vertically drawn bonds are considered to lie below the projection plane and horizontal bonds to lie above that plane

molecule composed of only two atoms of the same or different chemical elements

projection formula in which the ring is drawn as if planar and the substituents points straight up or straight down perpendicular to the ring

rotation of the plane of linearly polarized light as it travels through a chiral material

{| align="right" class="wikitable" |- !colspan="2"|Diastereomers that are also epimers |- |bgcolor="#FFFFFF"| 150px |bgcolor="#FFFFFF"| 150px |- |bgcolor="#FFFFFF"| 166px |bgcolor="#FFFFFF"| 144px |- | D-threose | D-erythrose |}

In stereochemistry, an epimer is one of a pair of diastereomers. The two epimers have opposite configuration at only one stereogenic center out of at least two. All other stereogenic centers in the molecules are the same in each. Epimerization is the interconversion of one epimer to the other epimer.

geometric aspects of ions and molecules affecting their shape and reactivity

In stereochemistry, mutarotation is the change in optical rotation of a chiral material in a solution due to a change in proportion of the two constituent anomers (i.e. the interconversion of their respective stereocenters) until equilibrium is reached. Cyclic sugars show mutarotation as α and β anomeric forms interconvert. The optical rotation of the solution depends on the optical rotation of each anomer and their ratio in the solution.

In carbohydrate chemistry, anomers () are specific types of stereoisomers found in sugars.

number and arrangement of multiple folded protein subunits in a multi-subunit complex

projection formula representing the spatial arrangement of bonds on two adjacent atoms in a molecular entity

thumb|right|Two kinds of stereoisomers|200px

In organic chemistry, regioselectivity is the preference of chemical bonding or breaking in one direction over all other possible directions. It can often apply to which of many possible positions a reagent will affect, such as which proton a strong base will abstract from an organic molecule, or where on a substituted benzene ring a further substituent will be added.

form of chemical synthesis

an optically inactive isomer that has two or more stereocenters

upright=1.3|thumb|Two enantiomers of a generic [[amino acid at the stereocenter]]

rules for ordering substituents when assigning descriptors to identify stereoisomers in organic chemistry nomeclature

In chemistry, stereoselectivity is the property of a chemical reaction in which a single reactant forms an unequal mixture of stereoisomers during a non-stereospecific creation of a new stereocenter or during a non-stereospecific transformation of a pre-existing one. The selectivity arises from differences in steric and electronic effects in the mechanistic pathways leading to the different products. Stereoselectivity can vary in degree but it can never be total since the activation energy difference between the two pathways is finite: both products are at least possible and merely differ in a

thumb|right|A ball-and-stick model of syndiotactic polypropylene.

difference between the abundance of enantiomers in a chiral substance

carbon atom attached to four different atoms or groups

In chemistry, racemization is a conversion, by heat or by chemical reaction, of an optically active compound into a racemic (optically inactive) form. This creates a 1:1 molar ratio of enantiomers and is referred to as a racemic mixture (i.e. contain equal amount of (+) and (−) forms). Plus and minus forms are called dextrorotation and levorotation. The D and L enantiomers are present in equal quantities, the resulting sample is described as a racemic mixture or a racemate. Racemization can proceed through a number of different mechanisms, and it has particular significance in pharmacology in

In chemistry, stereospecificity is the property of a reaction mechanism that leads to different stereoisomeric reaction products from different stereoisomeric reactants, or which operates on only one (or a subset) of the stereoisomers.

molecular geometry

thumb|Two enantiomers of a generic amino acid that is chiral

permanent geometry that results from the spatial arrangement of molecular bonds

optical property of chiral chemical compounds

guidelines outlining the relative favorabilities of ring closure reactions in alicyclic compounds

Empirical observation that states that a double bond cannot be placed at the bridgehead of a bridged ring system

Structures of cyclohexane

stereogenic group or unit that is temporarily incorporated into an organic compound in order to control the stereochemical outcome of the synthesis

chemical nomenclature describing absolute stereochemistry of double bonds, generalizing cis–trans notation

stereochemical projection for an acyclic molecule (or portion of a molecule) where the main chain is represented by a zig-zag line in the plane and the substituents are shown above or below the plane

right|300px|thumb|Atropisomers of 6,6'-dinitro-2,2'-diphenic acid were first experimentally described case, by Christie and Kenner (1922).

chemistry

Molecular geometry with 5 atoms bonded to a central atom and no lone pair.

thumb|An sp2-hybridized carbon atom, with re and si faces

group of stereoisomers

type of chemical isomerism

racemic mixture of tartaric acid

preferential formation of chemical reaction

Homochirality is a uniformity of chirality, or handedness. Objects are chiral when they cannot be superposed on their mirror images. For example, the left and right hands of a human are approximately mirror images of each other but are not their own mirror images, so they are chiral. In chemistry, chirality is a geometric property of some compounds and ions. These compounds exist in two different chiral conformations, enantiomers, often described as the left-handed and right-handed isomers of a compound (denoted by L- (levorotatory to the left) and D- (dextrorotatory to the right), respectivel

chemical conformation of an ethane-like moiety

stereochemistry term

measure of the steric bulk of a ligand in a transition metal complex

atypical situation where groups separated by a torsion angle of approximately 60°, is more stable than 180°

type of strain energy in organic chemistry