Search results
Results from the WOW.Com Content Network
In stereochemistry, prochiral molecules are those that can be converted from achiral to chiral in a single step. [1] [2] An achiral species which can be converted to a chiral in two steps is called proprochiral. [2] If two identical substituents are attached to an sp 3-hybridized atom, the descriptors pro-R and pro-S are used to distinguish ...
An achiral molecule having chiral conformations could theoretically form a mixture of right-handed and left-handed crystals, as often happens with racemic mixtures of chiral molecules (see Chiral resolution#Spontaneous resolution and related specialized techniques), or as when achiral liquid silicon dioxide is cooled to the point of becoming ...
Instead, both effects can also occur when the propagation direction of the electromagnetic wave together with the structure of an (achiral) material form a chiral experimental arrangement. [10] [11] This case, where the mutual arrangement of achiral components forms a chiral (experimental) arrangement, is known as extrinsic chirality. [12] [13]
In nature, only one enantiomer of most chiral biological compounds, such as amino acids (except glycine, which is achiral), is present. Enantiomers differ by the direction they rotate polarized light: the amount of a chiral compound's optical rotation in the (+) direction is equal to the amount of its enantiomer's rotation in the (–) direction.
are arranged around the chiral center carbon atom. With the hydrogen atom away from the viewer, if the arrangement of the CO→R→N groups around the carbon atom as center is counter-clockwise, then it is the L form. [14] If the arrangement is clockwise, it is the D form. As usual, if the molecule itself is oriented differently, for example ...
Extrinsic means that the chirality is a consequence of the arrangement of different components, rather than an intrinsic property of the components themself. For example, the propagation direction of a beam of light through an achiral crystal (or metamaterial) can form an experimental arrangement that is different from its mirror image.
Chiral auxiliaries are incorporated into synthetic routes to control the absolute configuration of stereogenic centers. David A. Evans' synthesis of the macrolide cytovaricin, considered a classic, utilizes oxazolidinone chiral auxiliaries for one asymmetric alkylation reaction and four asymmetric aldol reactions, setting the absolute stereochemistry of nine stereocenters.
Indirect enantiomer separation involves the interaction between the chiral analyte (CA) of interest and the suitable reactive CS (in this case it is an enantiopure chiral derivatizing agent, CDA) leading to the formation of a covalent diastereomeric complex that can be separated with an achiral chromatographic technique.