General Description
A colorless liquid. Insoluble in water and denser than water. Hence sinks in water. Contact may irritate skin, eyes, and mucous membranes. Very toxic by ingestion, inhalation and skin absorption. Used to make other chemicals.
Reactivity Profile
3,5-DICHLORO-2,4,6-TRI-FLUOROPYRIDINE is a halogenated amine. Behaves as a weak chemical base, neutralizing acids in exothermic reactions. May be incompatible with isocyanates, halogenated organics, peroxides, phenols (acidic), epoxides, anhydrides, and acid halides. Flammable gaseous hydrogen may be generated in combination with strong reducing agents, such as hydrides.
Air & Water Reactions
Insoluble in water.
Health Hazard
Highly toxic, may be fatal if inhaled, swallowed or absorbed through skin. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.
Fire Hazard
Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Containers may explode when heated. Runoff may pollute waterways.
Chemical Properties
Clear colorless to pale yellow liquid
Uses
3,5-Dichloro-2,4,6-trifluoropyridine serves as a base for agrochemicals[3]. The compound acts as a precursor in Suzuki–Miyaura reactions with arylboronic acids to prepare 3,5-diaryl-2,4,6-trifluoropyridines and 5-aryl-3-chloro-2,4,6-trifluoropyridines, and reacts with sodium methoxide to yield 3,5-dichloro-2-methoxy-4,6-difluoropyridine[1][2]. A 2% formulation of the substance is applied to skin samples[3].
Synthesis
The general procedure for the synthesis of 3,5-dichloro-2,4,6-trifluoropyridine from pentachloropyridine (2,3,4,5,6-pentachloropyridine) was as follows: in a 1000mL three-necked flask, 600mL of DMI (1,3-dimethyl-2-imidazolidinone) and 146.72g of anhydrous KF (potassium fluoride) (purity of 99%, particle size of 20-50 μm) were added. 60 g of solvent was removed by stirring distillation under reduced pressure (130-135 °C/60 mmHg), and the system was heated to 90 °C after the moisture content was determined to be less than 1000 ppm by water evaporation. Subsequently, 129.40 g of pentachloropyridine of 97% purity was added, the reaction temperature was maintained at 90 °C and stirred for 1.5 hours. Upon completion of the reaction, the heating was stopped and the reaction mixture was cooled to room temperature. The reaction mixture was filtered and the filtrate and solid residue were obtained by separation. The solid residue was washed with 100 mL of DMI and diafiltrated to obtain the wash solution. The wash solution and initial filtrate were combined and a distillation operation was carried out to collect the fractions at a pressure of 65-70.5 KPa to obtain the target product 3,5-dichloro-2,4,6-trifluoropyridine.
References
[1] Patent: CN106008331, 2016, A. Location in patent: Paragraph 0059; 0063
[2] Patent: CN108017574, 2018, A. Location in patent: Paragraph 0040-0043; 0052
[3] Journal of the Chemical Society - Perkin Transactions 1, 1997, # 24, p. 3623 - 3627
[4] Russian Chemical Bulletin, 2007, vol. 56, # 11, p. 2239 - 2246
[5] Patent: CN106187872, 2016, A. Location in patent: Paragraph 0027; 0028; 0029
