Purifying 1-(4-chlorophenyl)pyrazol-3-ol via Solvent Extraction
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Solution Overview
Problem
Current methods for producing crystalline 1-(4-chlorophenyl)pyrazol-3-ol result in moderate purity, which is insufficient for technical fungicide synthesis, and require multiple steps leading to yield losses, with the additional challenge of producing specific polymorphs like polymorph I without contamination from other forms.
Innovation Solution
Contacting an aqueous solution of metal 1-(4-chlorophenyl)pyrazol-3-olate with solvents like anisole or cyclopentyl methyl ether, adjusting the pH to ≤8, removing the aqueous phase, and crystallizing 1-(4-chlorophenyl)pyrazol-3-ol within the resulting solution, achieving high purity and selective polymorph production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acidification with suitable inorganic or organic acids, precipitation and solid-liquid separation is used to isolate 1-(4-chlorophenyl)pyrazol-3-ol from metal salts, then the compound can be obtained, but the purity is only moderate and often insufficient for technical fungicide synthesis
Solution Approach 1:
The patent introduces an organic solvent (ethyl acetate, n-butyl acetate, or isopropyl acetate) as an intermediary substance to facilitate the separation and purification of 1-(4-chlorophenyl)pyrazol-3-ol. The solvent mediates between the aqueous phase containing the compound and the solid phase, enabling selective dissolution and subsequent purification through controlled crystallization, thereby achieving high purity without complex multi-step procedures
Solution Approach 2:
The patent utilizes parameter changes in the form of pH adjustment (to ≤8) and temperature control during crystallization to optimize the purification process. By controlling these parameters, the compound crystallizes in high purity form directly from the solvent system, eliminating the need for multiple purification steps while maintaining simplicity of operation
2Manufacturing precision
If crystallization via multiple steps is used to achieve high degree of purity at large technical scales, then purity of at least 98% by weight can be achieved, but considerable yield losses occur
Solution Approach 1:
The patent segments the purification process into a single optimized crystallization step rather than multiple sequential steps. By dividing the purification task into distinct phases (dissolution in organic solvent, pH adjustment, and controlled crystallization), the process achieves high purity in one operation, minimizing material losses that would occur during repeated handling and transfer in multi-step procedures
Solution Approach 2:
The patent maintains continuity of useful action by implementing a streamlined process where the compound transitions directly from the aqueous metal salt solution through solvent extraction and crystallization to the final pure product. This continuous process eliminates interruptions and repeated processing steps that cause yield losses, while maintaining purity of at least 98% through controlled crystallization conditions
3Productivity
If standard isolation methods are used, then 1-(4-chlorophenyl)pyrazol-3-ol can be obtained, but by-products remain present which are not sufficient for use as synthesis intermediate in technical fungicide synthesis
Solution Approach 1:
The organic solvent acts as an intermediary that selectively interacts with 1-(4-chlorophenyl)pyrazol-3-ol, dissolving it while leaving by-products behind in the aqueous phase or as separate solids. This selective solvation enables the removal of by-products in a single operation, achieving the required 98% purity while maintaining high productivity through large-scale applicability
Solution Approach 2:
The patent employs parameter changes including pH adjustment to ≤8 and controlled temperature during crystallization to maximize purity. These parameter optimizations ensure that the crystallization process selectively forms pure 1-(4-chlorophenyl)pyrazol-3-ol crystals while excluding by-products, thereby meeting the stringent purity requirements for technical fungicide synthesis intermediates at large production scales
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method achieves crystalline 1-(4-chlorophenyl)pyrazol-3-ol with a purity of at least 98% and selectively produces polymorph I without other polymorphs, enhancing yield and purity for use in commercial pesticide synthesis.
Implementation Method 1
contacting an aqueous solution of a metal 1-(4-chlorophenyl)pyrazol-3-olate with a solvent, wherein i. the solvent is selected from anisole or cyclopentyl methyl ether
Implementation Method 2
crystallizing 1-(4-chlorophenyl)pyrazol-3-ol in the solution resulting from step b). Furthermore, surprisingly, it has been found that using the method of the present invention, polymorph I of 1-(4-chlorophenyl)pyrazol-3-ol is obtained without presence of further polymorphs
Data Source
AI summary
The present invention relates to a process to produce highly purified crystalline 1-(4-chlorophenyl)pyrazol-3-ol (I).