The nadir (UK: /ËnÃ¦dÉªÉr/), (US: /ËneÉªdÉªÉr/) (from Arabic: ÙØ¸ÙØ±ââ / ALA-LC: naáºÄ«r, meaning counterpart) is the direction pointing directly below a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface there.
Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen preferentially to one of two faces of an unsaturated substrate molecule, such as an alkene or ketone.ne of these is in the asymmetric hydrogenation of N-unfunctionalized imines to give primary amines. Such species can be difficult to selectively reduce because they tend to exist in complex equilibria of imine and enamine tautomers, as well as (E) and (Z) isomers.
Optical isomerism is an example of stereo-isomerism. It occurs when substances have the same molecular and structural formulae, but one cannot be superimposed on the other. Put simply, they are mirror images of each other (see the diagram on the right).ptical isomers can occur when there is an asymmetric carbon atom. An asymmetric carbon atom is one which is bonded to four different groups. The groups can be something hideously complex, or something comfortably simple like a hydrogen or chlorine atom.