Diastereomeric excess

The diastereomeric excess, or just de - value (from English: diastereomeric excess), is the excess of one diastereomer in a mixture of diastereomers at.

It is defined as

With: mass of the diastereomer in excess,: mass of the diastereomer in deficit. The definition of the diastereomeric excess de is thus similar to that of the enantiomeric excess ee. The characterization of stereoisomer with ee and de values ​​is now largely obsolete, as it is enantiomeric and diastereomeric ratio dr he clean the defined terms.

When a 1:1 mixture of two diastereomers thus is de = 0 %, with a diastereomerically pure compound is de = 100 %

Nowadays, the term is increasingly de diastereomeric excess by the term diastereomer ( diastereomeric ratio english, dr) replaced, while a mixture of diastereomers is characterized by the ratio [ m1 ] [ m2] or [ m2] [ m1 ].

For example, resulted in mass fractions of the diastereomers of 70 % to 30% of a 40% strength diastereomeric excess (40 % de) for the mixture of diastereomers. The diastereomeric ratio would be in this example, dr = 7:3.