SU1470181A3 - Method of producing 2,3,5,6-tetrachloropyridine - Google Patents

Abstract

The invention relates to pyridine derivatives, in particular, a method for producing 2,3,5,6-tetrachloropyridine intermediate in the synthesis of herbicides. The goal is to simplify the process. The latter is carried out by the reaction of pentachloropyridine with powdered zinc (preferably with a particle size of 7-15 μm) in an aqueous medium at 90-145 ° C (preferably at 100-145 s) and mo-. The relative ratio of zinc and pentachloropyridine (, 0): 1. Moreover, it is desirable to disperse pentachloropyridine in water at a mass ratio of 1: (5.3-19.3). The method allows to exclude the use of "1 of inorganic acids. 3 hp f-ly, - 7 tab.

Description

one

The invention relates to the field of production of pyridine halo derivatives, in particular, to a process for the preparation of 2,3 5,6-tetrachloropyridine, which is a valuable intermediate in the synthesis of herbicides.

The aim of the invention is to simplify the process of obtaining 2,3,5,6-tetrachloropyridine by reacting pentachloropyridine with powdered zinc in water when heated from 90 to 145 ° C and the molar ratio of zinc and pentachloropyridine (0.5-1.0): 1 .

Example 1. In a 2 liter Parr system reactor equipped with a turbine paddle stirrer, thermocouple sleeve, electric heating jacket, condenser to separate heavy components from the vapor mixture and a pressure and temperature regulator, 377 g (1.5 mol) are placed pentachloropyridine (PCP), 98 g (1.5 mol) of metallic zinc in the form of a fine powder having a nominal average particle diameter of 7 μm and 420 g (23 mol) of water. The reactor is hermetically sealed, start stirring at 600 rpm and heat the mixture to 130 ° C for 25 minutes.

The pressure regulator is adjusted to maintain a pressure that spontaneously sets at about 266.8 kPa (24 pounds per square inch). During the period of heat supply, this pressure is controlled by a thermostat, removing the reactor system at 130 C. After 2 hours, 1000 g of cooled water is supplied to the reactor under a nitrogen layer. The mixture is left under stirring for 2 minutes, the excess pressure is released, the reactor is opened and its contents are poured onto 1200 g of toluene. Organic compounds are extracted with stirring to

00

 Oj

luolnoy phase, the whole mixture is filtered and the resulting dense mass, pressed on the filter, washed with about 500 water and 300 g of toluene. The toluene and aqueous phases in the filtrate are weighed and analyzed. The dense mass pressed by the filter is dried, weighed and analyzed.

Chromatographic analyzes of the only fraction showed a 74% conversion of PCP with about 94% selectivity to 2,3,5,6-tetrachloropyridine (symmetric tetrachlorpyridine), 2% to 2,3,4, 5- and 2,3,4,6-tetrachloropyridine, 3% - to trichloropyridines and 1% - to dichloropyridines. Analyzes of the aqueous phase and the dried dense mass pressed on the filter, carried out according to standard technology, show complete (Conversion of zinc into a mixture of chloride | zinc in zinc hydroxide, I EXAMPLE 2. Mixture 190 g PCP (0.75 mol) 50 g (0.75 mol) of zinc plaster (average particle diameter 7 μm), 210 g (12 mol) of water and 1 g of toluene are heated with a reverse holocellar with vigorous stirring in a round bottom flask with a capacity of 500 ml, equipped with reverse chol | ks11kom. After 5 hours of holding at 100 i, the content of the product is mixed into 600 g-toluene, extracted t, as in example 1, the mixture was filtered in general and the solid mass pressed on the filter was washed with 250 g of water and 150 g of toluene. The phases were separated and anaed as described above. approximately 96% election with respect to the symmetric Yoma tetrachloropyridine, 2% with other tetrachloropyridines, 1 ,, 5% With trichloropyridines and O, 5% with Yichloropyridines. entered into the reaction, it turned out rto essentially complete.

Examples 3-6. The table shows the results of liio examples 3-6. The nominal size of the zinc particles is 12 µm, the molar ratio ZnsnxnjHiO is 1: 1: 15.

about 1 POV

five

0

five

0

Examples 7-10. In tab. 2 shows the results of the experiments according to Example 7–10 s, the nominal particle size is 7 µm zinc, the molar resp. wearing Zn snXHsHjO 1: 1: 15.

Examples 11-15. In tab. 3 shows the results of experiments in examples 11-15. The particle size of the zinc dust and the molar ratio of the reactants are the same as in examples 7-10.

Examples 16-19. In tab. 4 shows the results of experiments corresponding to examples 16-19. The nominal 15 particle size of the zinc particle is 15 μm; the molar ratio of the reactants is the same as in Examples 11-T5.

Examples 20-23. In tab. 5 shows the results of experiments corresponding to examples 20-23. The nominal particle size of the zinc plut is 7 μm, .. the molar ratio of Zn: E. the same as in the examples

Example 24-26. In tab. 6 shows the results of experiments corresponding to examples 24-26.

Example 27-31, In table. 7 shows the results of experiments corresponding to examples 27-31.

Claims (2)

1. A method of producing 2,3,5,6-tetrachloropyridine from pentachloropyridine using zinc when heated in an aqueous medium, revealing that, in order to simplify the process, pentachloropyridine is reacted with powdered zinc in water when heated from 90 up to 145 C and molar ratio of zinc and pentachloropyridine (0.5-1.0): 1. 2. The method according to claim 1, 1, and t-l and h ay - y and so that the process is carried out at 100-145 ° C. 3, The way that.1, the difference is that 1dank use five u and with that. in the form of particles with a size of 7-15 microns. 4, the method according to claim 1, which differs from the fact that pentachloropyridine is dispersed in water at a ratio of 5.3-19.3 parts by weight of water per part by weight. pentachloropyridine, Table 1 Table4 Nominal particle size of zinc dust, µm Molar ratio water: PCP Reaction temperature, with Reaction time, h Conversion PCP,% Conversion Zn,% Selectivity, mol.%, With respect to Cl, Pyr Cl Rug symmetric Cl.Pyr 12 12 12 12