[Background and Overview][1][2][3]
With the increasing awareness of environmental protection in our country and the successive promulgation of national environmental protection policies, our country’s pesticide and chemical industry will enter an important transition period. Over the years, highly toxic organophosphorus pesticides have been used extensively in crop production in my country, which can easily cause poisoning in humans and animals. It causes harm to human health and food safety, while destroying wildlife resources. Due to the extensive use of highly toxic organic phosphorus in crops, the organic phosphorus content of food and cash crops exceeds the standard and cannot meet international trade indicators. This makes my country’s agricultural products lack competitiveness and has a major impact on the sustainable development of my country’s agricultural economy.
According to an announcement from the Ministry of Agriculture of my country, the use of five highly toxic pesticides including methamidophos has been completely banned since January 1, 2007. In addition, policies have been introduced to gradually restrict or prohibit the use of various other highly toxic organophosphorus pesticides, causing my country’s pesticide market to enter an unprecedented “revolutionary” stage. From low-toxicity to high-toxicity, from environment-friendly dosage forms to backward traditional dosage forms, from pesticides at the expense of the environment to green products that comply with ecological environmental protection and food safety, my country’s pesticide chemical companies and the pesticide market are facing major challenges , and also usher in new business opportunities. Many companies and merchants have launched acephate as a flagship product to replace highly toxic pesticides. Acephate will also become a best-selling pesticide product due to its outstanding performance.
Acephate is a low-toxic broad-spectrum phosphorothioate pesticide. It is a low-toxic variety developed on the basis of research on methamidophos. It is an amino acetylated derivative of methamidophos, hence its name. It was first developed by Chevron Chemical Co. in the United States in 1969. Rat acute oral LD50, industrial pure product (♀) 866 mg/kg, (♂) 945 mg/kg, mouse 361 mg/kg, chicken 852 mg/kg; rabbit transdermal LD 50>2 000 mg/kg, two-year feeding test, 100 mg/(kg·d) for puppies and 30 mg/kg for rats, no lesions were found, only cholinesterase showed Inhibited, no teratogenic, carcinogenic or mutagenic effects; toxicity to fish (96 h) LC50rainbow trout>1 0 inorganic pigment 00 mg/L, goldfish 9 550mg/L. Its aqueous solution is easily absorbed by human skin, so care should be taken when using it. Relatively non-toxic to fish and toxic to bees. It has contact killing, systemic and gastric poisoning effects on pests, as well as certain egg-killing and fumigation effects. It is highly efficient, low-toxic, low-residue, and has broad-spectrum insecticide.
[Physical and chemical properties][1]
Pure acetylmethylamide is a white needle-shaped crystal with a melting point of 91 to 92°C. Its chemical properties are relatively stable, but it is easy to decompose under alkaline conditions. Easily soluble in water, with a solubility of about 650 g/L at room temperature, and soluble in general organic solvents. Industrial pure product (80%~90%) is a colorless solid with a melting point of 82~89°C, a vapor pressure of 226μPa at 24°C, and a density of 1.35. Solubility in room temperature water is 650 g/L, acetone and ethanol are 100 g/L, and aromatic solvents are 50 g/L.
[Application][2]
The insecticidal spectrum of acephate is basically the same as that of methamidophos, and its use can be expanded to vegetables, fruit trees and other recently harvested crops. Mainly use emulsifiable concentrate or wettable powder mixed with water as a foliar spray to control aphids, thrips, leafhoppers, planthoppers, spider mites, leaf mites and other crops on cotton, rice, corn, soybeans, tobacco, vegetables, fruit trees, forest trees and other crops. Bees, scale insects, stink bugs and lepidopteran larvae. Treating wheat seeds can prevent underground pests. It can also prevent and control cockroaches, which are sanitary pests. It is generally harmless under normal use, but crops such as sunflowers and certain varieties of apples are more sensitive.
[Specifications][4]
Emulsifiable concentrate: 30%, 40%; wettable powder: 25%; soluble powder: 25%, 50%, 75%.
【Usage and Dosage】[4]
Spray: Approximately one week after the peak of adult egg-laying, spray the larvae at the 2nd to 3rd instar stage. Use 80-120ml of 30% EC (effective ingredient is 24-36g) per 667m2, mix it with 40-50kg of water and spray evenly.
[Notes][4]
Do not mix with alkaline drugs. Not suitable for use on tea trees and mulberry trees. The safe interval for pesticide application on vegetables shall not be less than 7 days. The symptoms of poisoning are typical of organophosphorus poisoning, but the course of the disease lasts longer, cholinesterase recovery is slower, and care should be taken to prevent cerebral edema.
【Preparation】[5][6]
Method 1: Using dimethylphosphorothioate chloride as raw material, ammonia is used for amination under stirring, and then acetylation is performed with acetic anhydride. Acetylation is carried out in the presence of sulfuric acid. Acetylation During the process, acetic anhydride is partially converted into acetic acid, which is then neutralized with ammonia. Acetyl chloride can also be used as the acylating agent. After the acylation is completed, the solution is left to stand, and the organic phase is in the lower layer. After separation, dimethyl sulfate is used for isomerization, and then distillation under reduced pressure is performed to purify the product. , concentrated under reduced pressure and crystallized to prepare acephate [1].
Method 2: A method for preparing acephate with a simple process, high yield, low cost and high purity; it can overcome the neutralization process required for the separation of acetic acid and reduce the risk of acephate caused by neutralization The score��Loss, while not requiring a large amount of organic solvent extraction process and generating a large amount of waste water. The technical solution includes the following synthesis reaction process:
(1) Using ketene and O,O-dimethylthiophosphoramide as raw materials, under the conditions of acylation catalyst and organic solvent, ketene and O,O-dimethylthiophosphoramide An acetylation reaction occurs to obtain acetylated O,O-dimethylthiophosphoramide; among which, the mass ratio of ketene to O,O-dimethylthiophosphoramide is (0.15-0.40): 1;
Hydroxybutyl acrylate
(2) Prepare acephate solution by reacting acetylated O,O-dimethylthiophosphoramide under the conditions of isomerization catalyst;
(3) The acephate solution is crystallized, solid-liquid separated, and dried to prepare acephate raw powder.
The chemical reaction equation is as follows:
[Main reference materials]
[1] Agricultural Dictionary
[2] Encyclopedia of Chinese Agriculture·Pesticides Volume
[3] Zhang Zhijie. Application prospects of acephate, a substitute for highly toxic organophosphorus pesticides [J]. Guangdong Agricultural Sciences, 2007 (6): 66-6
[4] New Practical Drug Handbook
