Axial chirality

( S)- BINOL

(R) - (-) - trans-cyclooctene Other Names: (P ) - (- )-trans- cyclooctene and ( -) - ( E)- cyclooctene

( S) - ( ) - trans-cyclooctene Other Names: (M ) - ( )-trans- cyclooctene and ( ) - ( E)- cyclooctene

(P) - helicity

(M) - helicity

(P) - helicity of a spiral staircase in the Vatican Museum

(M) - helicity of a mirror image of the original spiral staircase in the Vatican Museum

Axial chirality is a special case of chirality, in which the molecule has no chiral center, but a chiral axis.

Occurrence

Axial chirality occurs at atropisomeric biaryl before, its rotation is prevented by the aryl-aryl bond, and at Dihydroanthracenon compounds. The appearance in 1922 was first detected in the 6,6 '- Dinitrodiphensäure.

In addition, have all connections and cumulenes with an even number of cumulative double bonds with unsymmetrical substitution axial chirality (eg propadiene derivatives). Spiro compounds may also exhibit axial chirality.

Also, some trans - cycloalkenes can be axially chiral, for example, there are two enantiomers of trans -cyclooctene. However, the classification as axially chiral at trans- cycloalkenes is controversial.

Helical molecules such as the helicenes are axialchiral.

The enantiomers of axially chiral compounds the stereochemical descriptors ( R) and ( S), characterized and Ra and Sa in more complicated cases, the index "a" is "axial". The Plus ( P) - / minus (M ) notation is in use.

Application

Axially chiral ligands with C2 symmetry as BINAP [2,2 '-bis ( diphenylphosphino ) -1,1' -binaphthyl ] are used in the enantioselective homogeneous catalysis. By using suitable ring substituents, the steric and electronic effects can vary.