**Gérard Coquerel \* and Marine Hoquante**

SMS EA3233, Place Emile Blondel, University of Rouen Normandy, CEDEX, F-76821 Mont-Saint-Aignan, France; marine.hoquante@univ-rouen.fr

**\*** Correspondence: gerard.coquerel@univ-rouen.fr

Received: 21 September 2020; Accepted: 26 October 2020; Published: 30 October 2020

**Abstract:** In this paper, macroscopic chiral symmetry breaking refers to as the process in which a mixture of enantiomers departs from 50–50 symmetry to favor one chirality, resulting in either a scalemic mixture or a pure enantiomer. In this domain, crystallization offers various possibilities, from the classical Viedma ripening or Temperature Cycle-Induced Deracemization to the famous Kondepudi experiment and then to so-called Preferential Enrichment. These processes, together with some variants, will be depicted in terms of thermodynamic pathways, departure from equilibrium and operating conditions. Influential parameters on the final state will be reviewed as well as the impact of kinetics of the R ⇔ S equilibrium in solution on chiral symmetry breaking. How one can control the outcome of symmetry breaking is examined. Several open questions are detailed and different interpretations are discussed.

**Keywords:** chirality; deracemization; preferential enrichment; thermodynamics; phase diagrams; kinetics
