Background and overview[1][2]
Research on the residual degradation of fenitrothion is also called “fenitrothion”. Chemical name: O,O-dimethyl-O-(3-methyl-4-nitrophenyl)phosphorothioate. An organophosphorus pesticide first developed by Japan’s Sumitomo Chemical Co. in 1959. It is made from raw materials such as phosphorus trichloride, methanol, m-cresol, sodium nitrite, nitric acid and sulfuric acid, and is generally processed into emulsifiable concentrate and powder. Fenitrothion has contact and stomach poisoning effects and has a short residual effect. Used to control rice borers, pink bollworms, aphids, soybean heartworms, cabbage caterpillars, etc. Phytotoxicity sometimes occurs in cruciferous vegetables.
Lowly toxic to humans and animals. The maximum residue limit (MRL) value of fenitrothion in cabbage set by my country is 0.5 mg/kg, and the MRL value of fenitrothion in cabbage set by FAO/WHO is 1 mg/kgt. While it is widely used as an efficient pesticide, the problem of residues has become increasingly prominent. It has stomach poisoning and contact killing effects on pests and mites. With the increase in the use of pesticides such as fenitrothion, especially on crops and vegetables, it has caused many harms to human health, which has aroused widespread concern.
Physical and chemical properties[3]
Fenitrothion pure product is a light yellow oily liquid that decomposes at the boiling point. It is relatively stable under neutral and acidic conditions and easy to decompose under alkaline conditions. Certain metals such as iron, tin, aluminum, copper, etc. can promote decomposition. Stable to light. Can be stored for a long time at room temperature. Insoluble in water, solubility 14 mg/L at 30°C, soluble in most organic solvents, but low solubility in aliphatic hydrocarbons.
Apply[3]
Fenitrothion has a good effect on sucking mouthparts, chewing mouthparts pests and borer pests. It is mainly used for water spray or powder spraying of emulsifiable concentrate on rice, soybeans, cotton, vegetables, Yaba fruit trees, tea trees, oil crops and forest trees. It has special effects on rice borer and can also control other lepidopteran larvae and leafhoppers. , planthoppers, thrips, aphids, scale insects, sweet potato weevils and other pests and spider mites, but the efficacy against mite eggs is poor. It can also control flies, mosquitoes, cockroaches and other hygiene pests and warehouse pests. It is generally not harmful to crops, but sorghum and cruciferous vegetables are more sensitive. The ban period before harvest is generally 10 to 15 days.
Poisoning diagnosis[4]
1. A series of manifestations of cholinergic nerve overexcitability.
2. A few patients develop intermediate myasthenic syndrome during the course of the disease.
3. Some poisoned patients may develop delayed peripheral neuropathy.
4. Blood cholinesterase activity is reduced.
5. Increased levels of p-nitrophenol in urine.
Principles of poisoning treatment
1. People with oral poisoning should induce vomiting quickly and perform gastric lavage repeatedly and thoroughly. Use alkaline solution or water for gastric lavage. Avoid using potassium permanganate solution.
2. People with contaminated skin should wash thoroughly and repeatedly with soapy water as soon as possible, especially hair and nails.
3. Both atropine and oxime cholinesterase reactivating agents have good curative effects, and the two drugs should be used together in patients with moderate or severe poisoning.
4. Symptomatic treatment.
Preparation [5][6]
Method 1: Use m-cresol as raw material, nitrate it in mixed acid to generate p-nitro m-cresol, and then use it as a copper chloride catalyst and in the presence of sodium carbonate, in a toluene solution at 90 It reacts with O,O-dimethylthiophosphoryl chloride at ℃ to generate fenitrothion [1]. After recovering toluene by distillation under reduced pressure, the organic layer is taken out, washed with water, and then distilled and refined to obtain fenitrothion [1].
Method 2: A new process for synthesizing fenitrothion, including:
1) Condensation reaction: React m-cresol (compound 1) with a base to form m-cresol. The base is one or more combinations of sodium hydroxide, sodium carbonate, potassium hydroxide and potassium carbonate. Cresolate and methyl chloride generate a condensation product in the presence of a catalyst. The catalyst is a monovalent copper salt, including but not limited to cuprous chloride, cuprous bromide, and cuprous oxide;
2) Nitrification reaction: react the condensate obtained in step (1) with nitric acid to generate the target product fenitrothion. The temperature of the nitrification reaction is 10-50°C.
Method 3: Obtained from the condensation of O,O-dimethylphosphorothioate chloride and 4-nitro-m-cresol ([2581-34-2]) under alkaline conditions. Add toluene to the condensation reaction pot, add 4-nitro-m-cresol, sodium carbonate and cuprous chloride under stirring, add O,O-dimethylphosphorothioate chloride at 95-97°C, and react above 90°C 3h, then filter, take the toluene layer and wash it with sodium hydroxide solution and water in sequence. After distilling under reduced pressure to recover the toluene, fenitrothionine crude oil is obtained, with a content of 90%.
When using the molar ratio of 4-pin-m-cresol: O,O-dimethylthiophosphoryl chloride: sodium carbonate = 1:1.1:1, the amount of toluene is about 3 times that of 4-nitro-m-cresol times (weight), when cuprous chloride is about 2% (weight) of 4-nitro-m-cresol, the yield of fenitrothion is over 95%. The obtained crude oil has an effective ingredient content of not less than 93.0% for high-quality products and ≥85.0% for first-class products. Raw material consumption quota: m-cresol 550kg/t, nitric acid (100%) 860kg/t, phosphorus trichloride (100%) 1240kg/ t, methanol 600kg/t.
Main reference materials
[1] Health Dictionary
[2] Zhang Hongjun. Fenitrothion is banned in Australia[J]. Pesticide Science and Management, 2004, 25(7): 39-39.
[3]Encyclopedia of Chinese Agriculture·Pesticide Volume
[4] Practical Poisoning First Aid Digital Manual
[5] Practical Fine Chemical Dictionary
[6] Liu Wei; Li Huiyue; Zhang Yanxiang; Wang Hongdong. A new process for synthesizing fenitrothion. CN201710505541.3, application date 201706 Antioxidant 101028
