nfluence of solvent choice and operating conditions on Chlorzoxazone crystal shape and size


  • Dhayananth Natarajan Department of Chemical Engineering, National Institute of Technology, Tamilnadu, India
  • Kalaichelvi Ponnusamy Department of Chemical Engineering
  • Radhakrishnan Thota Karunakaran Department of Chemical Engineering
  • Karthika Shanmugam School of Chemical Engineering, Vellore Institute of Technology, Tamilnadu, India



Chlorzoxazone, Solubility, Cooling crystallization, Solvent choice, Crystal shape, Size distribution


Solubility of pharmaceutical drugs in organic solvents is one of the important parameters to understand the equilibrium concentration of solute-solvent, which helps optimize and design crystallization conditions to obtain the desired product crystals. In the present study, Chlorzoxazone (CHZ) is used as a model pharmaceutical compound to investigate the equilibrium solubility, the influence of solvent and the operating conditions on the shape, and the size distribution. The solubility of CHZ is determined in organic solvents like Isopropanol, Ethanol, and 2-Ethoxyethylacetate, Ethylacetate and Ethyllactate using shake flask method from -5ºC to 60ºC. The solubility of CHZ in these solvents shows an increasing trend as the temperature increases in the following order: ethyllactate + water (0.5+0.5) < ethylacetate < isopropanol < ethanol < 2-ethoxyethylacetate < ethyllactate + water (0.75+0.25). The solvents, isopropanol, ethanol, and ethyl lactate, produce needle-shaped crystals, while 2-ethoxyethylacetate and ethyl acetate tend to produce plate shaped crystals. CHZ crystals obtained from 2-ethoxyethylacetate tend to have plate shaped crystals with a lower aspect ratio and are selected for batch cooling crystallization experiments performed at different cooling rates, and agitation. It is found that the agitation at 300 rpm and the cooling rate 0.2ºC/min produce more uniform crystal size distribution.


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How to Cite

Dhayananth Natarajan, Kalaichelvi Ponnusamy, Radhakrishnan Thota Karunakaran, & Karthika Shanmugam. (2023). nfluence of solvent choice and operating conditions on Chlorzoxazone crystal shape and size. Brazilian Journal of Pharmaceutical Sciences, 59, e20918.



Original Article