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Diffusion and kinetics of solvent-free reaction between molecular crystals by time-resolved powder UV-vis reflection spectrum

Journal Article


Abstract


  • Traditionally, chemical reaction between solids has been considered to typically occur on a geological time scale without the benefit of high temperature, due to diffusion block in the solids. However, recent advancements have revealed that many solvent-free reactions between molecular crystals can quickly occur at room or near-room temperature. These reactions have raised a novel scientific question as to how the reactive species can overcome the diffusion-controlled kinetic limitations under such moderate conditions. From time-resolved powder UV-vis reflection spectra and optical micrographs with the reaction between dimethylglyoxime and Ni(Ac)2 · 4H 2O and the reaction between hexamethylenetetramine and CoCl 2 · 6H2O as models, we found that the solvent-free reaction really occurs at an intermediate state between the solid state and the liquid state. Formation of the liquid phase provides a convenient approach to diffusion of reactive species, whereas formation of a solid product layer hampered the transfer of reactive species. Both factors led to a broad reactive rate band in the long reaction region. The results have explained the diffusion mechanism of the fast reaction between the molecular crystals under moderate conditions. © 2008 American Chemical Society.

Publication Date


  • 2008

Citation


  • Tang, X. C., Jia, D. Z., Jiang, C. K., Jiang, L. H., & Guo, Z. P. (2008). Diffusion and kinetics of solvent-free reaction between molecular crystals by time-resolved powder UV-vis reflection spectrum. Journal of Physical Chemistry A, 112(24), 5390-5394. doi:10.1021/jp801835h

Scopus Eid


  • 2-s2.0-53349101801

Web Of Science Accession Number


Start Page


  • 5390

End Page


  • 5394

Volume


  • 112

Issue


  • 24

Abstract


  • Traditionally, chemical reaction between solids has been considered to typically occur on a geological time scale without the benefit of high temperature, due to diffusion block in the solids. However, recent advancements have revealed that many solvent-free reactions between molecular crystals can quickly occur at room or near-room temperature. These reactions have raised a novel scientific question as to how the reactive species can overcome the diffusion-controlled kinetic limitations under such moderate conditions. From time-resolved powder UV-vis reflection spectra and optical micrographs with the reaction between dimethylglyoxime and Ni(Ac)2 · 4H 2O and the reaction between hexamethylenetetramine and CoCl 2 · 6H2O as models, we found that the solvent-free reaction really occurs at an intermediate state between the solid state and the liquid state. Formation of the liquid phase provides a convenient approach to diffusion of reactive species, whereas formation of a solid product layer hampered the transfer of reactive species. Both factors led to a broad reactive rate band in the long reaction region. The results have explained the diffusion mechanism of the fast reaction between the molecular crystals under moderate conditions. © 2008 American Chemical Society.

Publication Date


  • 2008

Citation


  • Tang, X. C., Jia, D. Z., Jiang, C. K., Jiang, L. H., & Guo, Z. P. (2008). Diffusion and kinetics of solvent-free reaction between molecular crystals by time-resolved powder UV-vis reflection spectrum. Journal of Physical Chemistry A, 112(24), 5390-5394. doi:10.1021/jp801835h

Scopus Eid


  • 2-s2.0-53349101801

Web Of Science Accession Number


Start Page


  • 5390

End Page


  • 5394

Volume


  • 112

Issue


  • 24