Background and Overview
Dipyrothion has a strong contact killing effect on pests and has a long lasting effect in the soil. It is a good agent for controlling underground pests. This pesticide is prohibited from being used on vegetables, melons, fruit trees, tea and Chinese herbal medicines.
Toxicity
Acute oral LD50: male rats 24.5 mg/kg (racemate), female rats 10.8 mg/kg. Acute dermal LD50: 278 mg/kg in guinea pigs and 159 mg/kg in rabbits. No irritation to rabbit skin and eyes. The acute oral LD50 of quail is 133 mg/kg. Rainbow trout LC50 (96 hours) 215 mg/L. Toxic to bees.
Dosage forms: 3%, 5%, 10%, 15%, 20% granules, 48% emulsifiable concentrate.
Mechanism of action and prevention and treatment targets
It is an acetylcholinesterase inhibitor that has a strong contact killing effect on pests and quickly enters the insect body. Long lasting in soil. It is suitable for controlling underground pests in crops such as wheat, soybeans, peanuts, corn, and sugarcane.
Features
Difenthion is a contact-killing dithiophosphonate insecticide. It is an inhibitor of cholinesterase. This drug is highly toxic and is mainly used to control underground pests in a variety of crops. Since thiophosphonate has a structure that is easier to penetrate the cuticle of insects than phosphonate esters, it is more effective in controlling pests. The drug lasts for a long time in the soil and is suitable for controlling underground pests in long-growing crops such as wheat, peanuts, corn, and sugar cane.
How to use
1． To control peanut grubs, use 1.5 to 2 kilograms of 5% difenthion granules per acre (75 to 100 grams of active ingredient), add 1 to 2 kilograms of fine sand, mix evenly, and spread it in the seed trench. , and then use a two-tooth hook to retain the soil in the ditch, so that the pesticide, fertilizer, and soil are fully mixed before sowing peanut seeds. Do not let the seeds come into direct contact with pesticides. Cover the soil with soil after sowing, and the effect of insect control and seedling preservation is good.
2. Prevention and Control of Pests in Dry Grain Crops
(1). During the sowing period, use 1.5 to 2.5 kilograms of 5% difenthion granules per acre (active ingredients 75 to 125 g), mix 1 to 2 kilograms of fine sandy soil, then spread it in the sowing trench, and cover it with soil after sowing.
(2). For corn and soybean field grubs, use 1 to 1.5 kilograms of 5% difenthion granules per acre, and the application method is the same as above.
3． Precautions for controlling sugarcane pests
(1). During the initial stage of damage to newly planted sugarcane and light-backed sugarcane turtles when the adults emerge, use 3 to 4 kilograms of 5% sulfur rubber antioxidant phosphorus granules per acre (150 to 200 grams of active ingredient). Spread the granules on the rhizosphere at the base of the sugarcane seedlings, cover with a thin layer of soil or drizzle with mud. When burying ratoon sugarcane in ridges, apply 4 to 5 kilograms of 5% diplothion granules per acre (200 to 250 grams of active ingredient) in furrows and then bury the ridges.
(2). When newly planted sugarcane is being cultivated from late June to early July, 3 to 4 kilograms of 5% difenthion granules (active ingredients 150 to 200 mg) should be used per acre. Gram), open a shallow ditch next to the sugarcane bed, and build up the soil immediately after applying the pesticide.
(3). When sowing newly planted sugar cane, use 3 to 5 kilograms of 5% difenthion granules (150 to 200 grams of active ingredient) per acre. After sowing the sugar cane, That is to apply pesticides and cover with soil.
Synthesis【2】
1. Method 1
Preparation of ethoxyethylphosphonic acid chloride: Under the catalysis of iodine, triethyl phosphite is isomerized to form diethoxyphosphonate, and then the diethoxyphosphonate is exposed to light in DMF solvent gas reaction. Obtain ethoxyethylphosphonic acid chloride. The yield is 99%.
Preparation of thiophenol The reaction between benzene and chlorosulfonic acid produces benzenesulfonyl chloride. Then benzene sulfonyl chloride is reduced in the presence of zinc powder and concentrated sulfuric acid to obtain thiophenol. The yield is 76%. The reaction formula is as follows:
Or produced by the reaction of sodium benzenesulfonate and phosphorus pentachloride.
Synthesis of difenthionate: Ethoxyethylphosphonochloride reacts with thiophenol or sodium thiophenol to obtain O-ethyl-S-phenylthiophosphonate ethyl ester, which is then reacted with P2S5 , synthesized difenthion. The yield is 90%.
2. Dichloroethylthiochloride method (EPTD):
This method is based on the acetification of dichloroethyl thiophene acid and sodium ethoxide to obtain the monoester, which is then condensed with sodium thiophenolate to obtain the product. The yield is 84%. The reaction is as follows:
Example: Add 203g (1.25mol) into a 1L reaction bottle, cool to 0-5°C, add the prepared 500 ml sodium ethoxide in batches, react for about 3 hours, and obtain 93% of the monoester. Add ( Sister) 108.8g of thiophenol (dissolved in 170g of 25% NaOH) was added, and the mixture was refluxed at 95°C for 45 minutes. After layering, washing with water, and desolvation, 206.79g of the product (purity 97.5%) was obtained, with a yield of 91.1%.
3. Diethyl chloride thiochloride method:
Add thiophenol (miscible with part of ethanol) to the sodium and ethanol solution, heat to 60 ℃, then cool to 30 ℃, add diethyl monochlorothiophenic acid (thiophenic acid) dropwise, and stir for a certain period of time After a certain time, a large amount of ice water was added, extracted with toluene, dried and desolvated to obtain the product (process) with a yield of 73%. The yield of this method is low, and the reaction is as follows:
Notes【3】【4】
1. It may cause some phytotoxicity when used near seeds.
2. If symptoms of poisoning occur, the patient should be kept away from the scene and lie quietly in a ventilated place as soon as possible, and seek medical treatment.
3. This medicine should be stored in a dry and dark place, away from fire sources, seeds and grains.
4. Symptoms of difenthion poisoning include headache, feeling depressed, vomiting,The opening and closing of the hole are out of control. Once this happens, the patient should be kept away from the scene and lie quietly in a ventilated place. And drink plenty of water to increase metabolism and expel decomposition products from the body. You can take atropine and ask a doctor for treatment immediately.
5. Avoid mixing with alkaline substances to avoid decomposition and failure.
References
[1] Pesticide Control Institute of the Ministry of Agriculture, compiled by the Secretariat of the National Pesticide Residue Standards Review Committee, Application Guidelines for Maximum Residue Limits of Pesticides in Food (GB2763-2012), China Agricultural Press, 2013.02, page 19
[2] Editor-in-Chief Zhu Liangtian, Fine Chemical Products Handbook Pesticides, Chemical Industry Press, 1st Edition, September 2004, Page 59
[3] Compiled by Shanghai Agricultural Technology Extension Service Center, Pesticide Safety Manual, Shanghai Science and Technology Press, 2009.09, page 240
[4] Editor-in-Chief Yang Pinghua, Commonly Used Pesticide Application Technologies in Farmland, Sichuan Science and Technology Press, 2009.01, page 70
