Racemization and Configurational Stability

The study of configurational stability is of prime importance since, for example, it allows us to know the timescale during which a reaction must occur in order for the configuration of a chiral reactant to be maintained. Taking, for example, the coordination compound [Cr° C204)3]K3 (2.10) K3, obtained as an enantiomer with a negative sense of rotation ([a] p = —1800 (c = 0.02, the value of the rotation diminishes 

The thermodynamic constants have been measured and they show that it is a complex process, including the solvent (in this case water) and possibly ammonium salts (i.e. the counter ion plays a part in the racemization). In organometallic and coordination chemistry, because of the numerous dative bonds involved, the question of racemization must be studied to ensure that the product obtained as an enantiomer does not racemize over time. This can happen in solution, where the solvent can act as a ligand and thereby participate in the process, but it is also true of the solid state in the presence of an external agent, such as temperature or exposure to light. We say that an enantiomer has configurational stability if it does not racemize under given conditions. 

We will see later that, while in most cases racemization is an inconvenience that destroys what the chemist has spent much time in achieving, it can be put to use in the resolution of a racemic compound to obtain one enantiomer in a yield close to one. 

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