Grinding-induced homochirality in crystal growth

It has been recently observed that coupling Viedma ripening with a seeded in-situ metastable racemic crystal to conglomerate transformation leads to accelerated and complete deracemization: crystal transformation-enhanced deracemization. By means of a simple kinetic model, we show that the mechanistic pathway of this new process depends profoundly on the interplay between the crystal transformation and racemization processes, which in turn influence the nucleation process of the counter enantiomer. If the nucleation of the counter enantiomer is suppressed (e.g. by sufficiently fast racemization, low amount of racemic compound or gradual feed, low relative solubility between racemic compound and conglomerate), deracemization proceeds via a second order asymmetric transformation (SOAT) and is limited primarily by the dissolution rate of the racemic crystals and the growth rate of the preferred enantiomer crystals. Breakage and agglomeration accelerate the process, but contrary to conventional Viedma ripening, they are not essential ingredients to explain the observed enantiomeric enrichment. If the nucleation process of the counter enantiomer is not sufficiently suppressed, deracemization is initially controlled by the dissolution rate of the racemic crystals, but Viedma ripening is subsequently required to convert the conglomerate crystals of the counter enantiomer formed by nucleation, resulting in slower deracemization kinetics. In both cases, the combined process leads to faster deracemization kinetics compared to conventional Viedma ripening, while it autocorrects for the main disadvantage of SOAT, i.e. the accidental nucleation of the counter enantiomer. In addition, crystal transformation-enhanced deracemization extends the range of applicability of solid-state deracemization processes to compounds that form metastable racemic crystals. interplay between the crystal transformation and racemization processes, which in turn influence the nucleation process of the counter enantiomer. If the nucleation of the counter enantiomer is 3 suppressed (e.g. by sufficiently fast racemization, low amount of racemic compound or gradual feed, low relative solubility between racemic compound and conglomerate), deracemization proceeds via a second order asymmetric transformation (SOAT) and is limited primarily by the dissolution rate of the racemic crystals and the growth rate of the preferred enantiomer crystals.Breakage and agglomeration accelerate the process, but contrary to conventional Viedma ripening, they are not essential ingredients to explain the observed enantiomeric enrichment. If the nucleation process of the counter enantiomer is not sufficiently suppressed, deracemization is initially controlled by the dissolution rate of the racemic crystals, but Viedma ripening is subsequently required to convert the conglomerate crystals of the counter enantiomer formed by nucleation, resulting in slower deracemization kinetics. In both cases, the combined process leads to faster deracemization kinetics compared ...

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“…Monte Carlo simulations 35,[42][43][44] , dispersive kinetic models 45 and population balance models [46][47][48][49] .…”

Section: Introductionmentioning

confidence: 99%

Coupling Viedma Ripening with Racemic Crystal Transformations: Mechanism of Deracemization

Xiouras

Horst

Gerven

et al. 2017

Crystal Growth & Design

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“…27,28 Other studies have stochastically considered homochirality to determine the final probability distribution of levo-or dextro-rotatory crystals. [29][30][31] There are still several questions associated with our understanding of autocatalytic reactions in ARD systems. First, many numerical simulations approach this problem from a Lagrangian framework in the limit of infinitely fast reactions, an assumption that makes it difficult to study autocatalytic reactions across a broad range of physical parameters, including dependence on the diffusion coefficient and the reaction rate.…”

Section: Introductionmentioning

confidence: 99%

Competitive autocatalytic reactions in chaotic flows with diffusion: Prediction using finite-time Lyapunov exponents

Schlick

Umbanhowar

Ottino

et al. 2014

Chaos: An Interdisciplinary Journal of Nonlinear Science

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We investigate chaotic advection and diffusion in autocatalytic reactions for time-periodic sine flow computationally using a mapping method with operator splitting. We specifically consider three different autocatalytic reaction schemes: a single autocatalytic reaction, competitive autocatalytic reactions, which can provide insight into problems of chiral symmetry breaking and homochirality, and competitive autocatalytic reactions with recycling. In competitive autocatalytic reactions, species B and C both undergo an autocatalytic reaction with species A such that [Formula: see text] and [Formula: see text]. Small amounts of initially spatially localized B and C and a large amount of spatially homogeneous A are advected by the velocity field, diffuse, and react until A is completely consumed and only B and C remain. We find that local finite-time Lyapunov exponents (FTLEs) can accurately predict the final average concentrations of B and C after the reaction completes. The species that starts in the region with the larger FTLE has, with high probability, the larger average concentration at the end of the reaction. If B and C start in regions with similar FTLEs, their average concentrations at the end of the reaction will also be similar. When a recycling reaction is added, the system evolves towards a single species state, with the FTLE often being useful in predicting which species fills the entire domain and which is depleted. The FTLE approach is also demonstrated for competitive autocatalytic reactions in journal bearing flow, an experimentally realizable flow that generates chaotic dynamics.

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“…We introduced the simple rate equation model of crystallization with grinding of chiral crystals. Our model does not include any effects of convection [10,11] and nonlinearity [21,22,24,29]. The analytical solution shows that the ratio of crystal X and Y does not change.…”

Section: Discussionmentioning

confidence: 99%

“…Such phenomena have been observed in other organic systems [16][17][18], and the resultant chirality can be controlled with the use of additives [14,19,20]. In order to understand the mechanism of the appearance of the homochiral state (such a process may be called Viedma ripening [15]), several other theoretical models have been proposed [11,[21][22][23][24][25][26][27][28][29][30]. Some of these models, which include nonlinear effect, reproduce the experimentally observed exponential increase of the enantiomeric excess (EE).…”

Section: Introductionmentioning

confidence: 96%

Appearance of a homochiral state of crystals induced by random fluctuation in grinding

Katsuno

Uwaha

2012

Phys. Rev. E

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We study crystallization of chiral crystals from achiral molecules using a master equation based on a simple reaction model. Although there is no chiral symmetry breaking in the reaction model, random fluctuations drive the system to a homochiral state. The time necessary for the appearance of the homochiral state is proportional to the total number of molecules in the system. This behavior is described by a diffusion equation in a size space with a position-dependent diffusion coefficient. We also study the effect of chiral impurities, which affect the crystal growth. Depending on the type of impurities, the chiral symmetry breaking occurs either deterministically or with the help of random fluctuations.

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Grinding-induced homochirality in crystal growth

Cited by 29 publications

References 23 publications

Coupling Viedma Ripening with Racemic Crystal Transformations: Mechanism of Deracemization

Coupling Viedma Ripening with Racemic Crystal Transformations: Mechanism of Deracemization

Competitive autocatalytic reactions in chaotic flows with diffusion: Prediction using finite-time Lyapunov exponents

Appearance of a homochiral state of crystals induced by random fluctuation in grinding

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