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.
Molecules, which have the same molecular formula, and the same structural formula, and same shape, can still exist in two different forms if they are asymmetric. The simplest form of molecular asymmetry is when four different groups are attached to a carbon atom as shown below.he two forms are called enantiomers, and exhibit a form of isomerism known as optical isomerism. When alanine is produced in a laboratory under normal conditions a mixture is obtained, half of which is (S)-alanine and the other (R)-alanine.