A novel crystalline form of oxamyl, a process for its preparation and use of the same
A technology of killing lines and crystallization, which is applied in the field of agricultural chemical preparations
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Embodiment 1
[0106] Example 1: According to the No. 5,284,962 U.S. Patent, the disclosure of Example 2 prepares amorphous Xanthicarb
[0107] A two-stage, co-feed continuous reactor system was used to make MIC (methyl isocyanate) and the oxime (2-(dimethylamino)-N-hydroxy-2-oxoethyliminothioic acid methyl ester) to produce 2-(dimethylamino)-N-[[(methylamino)carbonyl]oxy]-2-oxoethyliminothioic acid methyl ester (xamyl). The reactor was maintained at approximately 42°C. During steady state operation, methyl isocyanate (MIC) was fed at a rate of 1.2 g / min and evaporated and mixed with nitrogen (which was fed at approximately 2200 mL / min). The oxime was fed at a rate of 7.9 g / min as a 40% slurry in water containing 0.2% TEA. The conversion of oxime in the first reactor was about 93%. The composition of the product solution from the second reactor was approximately 47% title product, 0.9% oxime and 0.8% DMU (dimethyl urea). This composition corresponds to 97% conversion of the oxime and 8% ...
Embodiment 2
[0110] Example 2: Preparation of Shaxiancarb Crystalline Modification I
[0111] Crystallized from ethyl acetate
[0112] 10 g of the amorphous thixacarb sample prepared in Example 1 was put into a 3-neck round bottom flask together with 50 mL of ethyl acetate, and the resulting slurry was heated to 65° C. to obtain a homogeneous solution. Undissolved particles (if any) were filtered and the solution was slowly cooled to 20°C-25°C. After cooling, fine crystals formed and the resulting heterogeneous mixture was stirred at 20°C for 2 hours. Then, the slurry was filtered and washed with 3 mL of ethyl acetate at 20 °C. The filtered crystals were dried under vacuum at 40°C. The purity of the resulting crystalline product was >98%, and the yield of product recovered as crystals was found to be about 90%.
[0113] The obtained crystals were analyzed by IR spectroscopy, X-RPD and DSC, and found to be as figure 1 , figure 2 and image 3 Crystallization modification I of Xanth...
Embodiment 3
[0119] Example 3: Preparation of Shaxiancarb Crystalline Modification I
[0120] Crystallized from nitrobenzene
[0121] A 5 g sample of the amorphous thixacarb prepared in Example 1 was put into a 3-neck round bottom flask together with 30 mL of nitrobenzene, and the resulting slurry was heated to 83° C. to obtain a homogeneous solution. Insoluble particles (if any) were filtered and the solution was cooled slowly to 20°C. After cooling, fine crystals formed and the resulting heterogeneous mixture was stirred at 20°C for 2 hours. Then, the slurry was filtered, washed with 3 mL of nitrobenzene at 20°C, and dried under vacuum at 45°C. The purity of the crystalline product thus obtained was >98% and the recovered yield was found to be about 90% yield.
[0122] Using IR spectroscopy, X-ray powder diffraction and DSC as described in Example 2, the crystals were characterized as crystalline modification I of siloxan.
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