Overview[1][2]
Methophos, whose common English name is ethoprophos, is a highly effective insecticide that can be used to control a variety of pests in crops such as rice, peanuts, and cotton. It is especially effective against rice gall mosquitoes and underground nematodes. The original drug is a light yellow transparent liquid. Dimitriphos is a non-systemic, non-fumigating nematicide and soil pesticide. It has a contact killing effect on pests and can be used to control root-knot nematodes, short-bodied nematodes, stinging nematodes, baseline nematodes, sword nematodes, and burr nematodes. Nematodes and other nematodes. Applicable crops include: tobacco, peanuts, sugar beets, soybeans, citrus, bananas, pineapples, strawberries, various vegetables and other economic crops, fruit and vegetable crops and ornamental plants. For some Lepidoptera that inhabit the soil. , Coleoptera, and Diptera pest larvae also have control effects.
Methophos has no teratogenic, mutagenic or carcinogenic effects on animals, but its acute toxicity is high. Demiphos was registered in my country by the French company Aventis Crop Science in 1992. In recent years, dimiphos has been effective in controlling rice gall mosquitoes. Now it is mainly used to control rice gall mosquitoes in my country. In recent years, Farmers generally use w (miphos) = 10% granules to control rice gall mosquitoes and other pests, and the control effects are good.
Character[3]
This product is a light yellow transparent liquid, boiling point 86~91℃/26.6 Pa (0.2mmHg), solubility: water 750mg/L, acetone, cyclohexane, 1,2-dichloroethane, ether, ethanol, Ethyl acetate, xylene >300g/kg. This product is stable in water up to 100℃ (pH=7); but it hydrolyzes rapidly in alkaline medium (pH=9) at 25℃.
Toxicology[3]
Acute toxicity oral LD50: rat 62mg/kg, rabbit 55mg/kg.
Synthetic route [1][3][4]
Route 1:
1) The reaction between thiophosphoric acid and sodium hydroxide produces the intermediate sodium thiophosphate;
2) Then an alkylation reaction occurs with propyl bromide to form the intermediate propylthioester;
3) Aminolysis rearrangement and esterification reaction between propylthioester and dimethylamine;
4) It then reacts with propane bromide to form phosphonium, with an average yield of 88% and an average content of more than 93%. The specific reaction process is as follows:
Route 2:
1) Using O,O`-diethylthiophosphate as the starting material, react with bromopropane to generate O,O`-diethylthiophosphate: add anhydrous potassium carbonate and acetone into the reaction kettle , add O,O-diethyl thiophosphoric acid dropwise with stirring, a large number of bubbles will be released, cool appropriately to avoid flushing. After the dropwise addition is completed, stir for another 10 minutes and add propane bromide.
React under reflux and the reaction will be complete in two hours. Cool, filter, and evaporate the acetone under reduced pressure. The residue is extracted with ether, dried over anhydrous sodium sulfate, and distilled under reduced pressure to obtain a colorless transparent liquid, which is O,O-diethyl-S-propylthiophosphate, melting point 99～100℃/240Pa, yield 88%.
2) Then react with potassium thiocyanide ethanol solution to generate O-ethyl-S-propylthiophosphate potassium salt: add absolute ethanol and potassium hydroxide into the reaction kettle, and add H2S gas under stirring ( Generated by the reaction of FeS and dilute hydrochloric acid) to obtain a saturated ethanol solution of potassium hydrogen sulfide, add O,O-diethyl-S-propylthiophosphate to this solution, and react at reflux temperature for 5 hours to complete the reaction, which is An ethanolic solution of O-ethyl-S-propylthiophosphate potassium salt.
3) Then react with n-bromopropane to generate phosphonium: Add the ethanol solution of O-ethyl-S-propylthiophosphate potassium salt and n-bromopropane into the reaction kettle, and react at reflux temperature for 5.5 hours. completely. Cool, filter, and distill under reduced pressure to obtain phosphorus, with a boiling point of 104~108°C/13~133Pa, a purity of 96.05%, and a yield of 80%. , the specific reaction process is as follows:
Process flow chart[3]
Notes[5]
Dimitriphos is very effective in controlling peanut root-knot nematode disease. Its shortcoming is that it is too sensitive to peanuts and is prone to phytotoxicity. The obvious symptoms of phytotoxicity are: small and dark green leaves that do not stretch. In mild cases, the main root rots or twists, the root system is underdeveloped, and in severe cases, the plant dies. In order to improve the efficacy and reduce the harm of the medicine, on the one hand, the dosage of medicine must be strictly used, and on the other hand, direct contact between the medicine and the seeds must be avoided. Use deep spraying, isolation of medicinal seeds or mixing of medicinal and soil before sowing.
Residue standards[2]
The maximum residue limit (MRL) of methotrexate in rice, peanuts and potatoes set by our country is 0.02mg/kg; my country’s European Food Safety Authority FAO/WHO stipulates the allowable daily intake of metfenphos per kilogram of body weight ( ADI) are 0.005, 0.005, 0.003mg/kg respectively; my country’s maximum residue limit for agricultural products is 0.02mg/kg for peanuts, 0.02g/kg for potatoes, and 0.02mg/kg for rice; Japan’s maximum residue limit for oranges is 0.005mg /kg, apple 0.01mg/kg, rice 0.005mg/kg; the United States stipulates a maximum residue limit of 0.02mg/kg for potatoes; the European Food Safety Authority (EFSA) stipulates that ADI is 0.0004mg/(kg/d); FAO/WHO stipulates that 0.0003mg/(kg/d).
Microbial degradation[6]
Difenfosin has been registered on dozens of crops for the control of various nematode diseases and underground pests due to its good control effect and low residue. Since phosphorus is rarely transmitted to the above-ground parts, and the residual amount in the above-ground parts is small or even non-existent, it is becoming more and more popular among people. Therefore, the use of phosphorus has a tendency to expand. But at the same time��, the solubility of phosphatide in water is 700 mg·L-1 (20℃), the water solubility is high, and the adsorption effect of phosphatide on the soil is weak, so it remains in the soil. The phosphorus in it is easy to move in the soil, making it potentially harmful to groundwater and thus harmful to human health. On the other hand, methotrexate is very toxic to aquatic organisms. Studies have proven that it is teratogenic and lethal to the early embryonic development of Chinese giant toads and eels. Studies have shown that microorganisms have a great influence on the degradation of phosphorus in soil, and the presence of microorganisms accelerates the degradation of phosphatide.
The degradation of fenfoside by Bacillus cereus is mainly affected by its concentration, pH value and temperature. It has a good degradation effect on 10-200 mg·L-1 of methotrexate, and the degradation rate decreases with the increase of the concentration of the agent. Among them, at 10 mg·L-1, the degradation rate of fenfoside is maximum 77.1%, and the degradation amount is 7.8 mg·L-1, while 50 mg·L The highest degradation amount of -1 is 26.8 mg·L-1, so it is more convenient to choose the latter to study the degradation characteristics. Bacillus cereus has the highest relative degradation rate of fenfoside when the pH value is 7 as a cosmetic raw material, and the optimal degradation temperature of fenfenfos is 30°C; it has a good degradation effect on fenfoside in inorganic salt culture media.
Introduction to related drugs[7]
Chlorazofos: Chlorazofos is an organophosphorus insecticide and nematicide developed by the Swiss Ciba-Jiakin Company (now Novartis) in 1973. Its common name is isazofos in English and its trade name is rice. Leer has contact, stomach poisoning and systemic effects. Used on corn, cotton, rice, sugar beets, lawns and vegetables to control various above- and below-ground pests such as nematodes, borers, leaf beetles, and beetles.
It can be used as a soil treatment agent, seed treatment or foliar application. Acute poisoning with chlorzophos usually occurs within 12 hours, and symptoms occur immediately after oral administration. Mild cases can cause headache, dizziness, nausea, vomiting, etc.; moderate cases can cause mild difficulty breathing, muscle tremors, pupil constriction, confusion, etc. in addition to the above symptoms; severe cases can also cause coma, convulsions, and difficulty breathing. , foaming at the mouth, incontinence of urine and feces, convulsions, respiratory paralysis, etc. At this time, 1 to 5 mg of atropine can be injected subcutaneously or intravenously (depending on the severity of the poisoning); or 0.4-1.2 g of pralidoxime can be injected intravenously (depending on the severity of the poisoning). Morphine, theophylline, phenothiazines, and diuretics are prohibited. flat.
Main reference materials
[1] Li Lixin. Synthesis test of phosphorus. Anhui Chemical Industry. 2000, 5: 29-30.
[2] Chen Xiaojun et al. Degradation dynamics and residue analysis of amiphos on rice. Journal of Jiangxi Agricultural University 2010, 32(1):0067-0072.
[3] Wang Daquan, editor-in-chief. Illustration of Fine Chemical Production Flow Part 2. Beijing: Chemical Industry Press. 1999.
[4] Wang Min. Research on a new synthesis route of phosphorus. RESTICIOES.1995,34(10):12-14.
[5] Wang Nianping. Effect of instant death of mites on eggplant two-spotted spider mite. Pesticides. 2000, 39(7):37-38.
[6] Li Yanfang et al. Isolation, identification and degradation characteristics of dimiphos-degrading bacterium DS-1. Chinese Agricultural Sciences 2010, 43(8): 1594-1600.
[7] Li Yanjuan et al. High performance liquid chromatography analysis of chlorzophos. Pesticides. 2006, 45(10): 685.
