Application and preparation of bromoxynil_Kain Industrial Additive

Background and overview^[1]

Bromoxynil, also known as Bandi Nong, is a selective post-emergence contact herbicide. The chemical name is 3,5-dibromo-4-hydroxy-1-cyanobenzene. The original drug is a brown solid with a melting point of 188~192℃ and a vapor pressure of 6.7×10^-3Pa at 25℃. The pure product is a white solid. , melting point 194~195℃, slightly soluble in water, soluble in acetone. It can be absorbed by leaves, inhibit photosynthesis, and cause weed tissue necrosis. It is suitable for crop fields such as wheat, barley, rye, corn, sorghum, flax, etc., and controls annual dicotyledonous weeds such as quinoa, amaranth, amaranth, and sage. It is moderately toxic to humans and livestock. The acute oral LD₅₀ in rats is 190mg/kg, the acute dermal LD₅₀>2000mg/kg, and the acute inhalation LC₅₀ is 0.38mg/L. Irritation to skin and eyes, low toxicity to fish, moderate toxicity to birds.

Apply^[2-4]

Bromoxynil, in the form of its caprylic acid ester, sodium salt, and potassium salt, is widely used as a contact herbicide for selective post-emergence stem and leaf treatment abroad. Mainly absorbed by leaves, it quickly causes tissue necrosis by inhibiting various processes of photosynthesis. This agent is mainly used in the fields of wheat, barley, rye, corn, sorghum, flax and other crops to control anthrax, amaranth, wheat pitcher, nightshade, cocklebur, Salsola spp., field bindweed, and buckwheat vines. and other broadleaf weeds. The dosage of wheat is 22.5-35g (active ingredient) per mu; the dosage of sorghum and corn is 18.7-30g per mu; the dosage of flax is no more than 18.7g per mu. Bromoxynil is stable in storage and generally does not react with other herbicides. In addition to being used alone, it can also be mixed with a variety of herbicides to expand the herbicidal spectrum.

Bromoxynil is usually used in combination with other ingredients, such as a compound herbicidal composition containing clodinyl and bromoxynil. The herbicidal composition contains clodinyl and bromoxynil as the main active ingredients. The mass ratio to bromoxynil is 1 to 99: 1 to 99, and the total mass percentage of the two in the herbicidal composition is 10 to 80%. The herbicidal composition of the present invention can be used for post-emergence weeding in wheat fields, and is particularly effective in controlling gramineous weeds and broadleaf weeds in wheat fields. Compared with a single agent, the herbicidal composition of the present invention delays weed resistance, has a wide herbicidal spectrum, has a long duration of effect, and is safe for wheat and subsequent crops on the premise of improving the efficacy. Or a herbicidal composition containing trifluorosulfuron-methyl and bromoxynil, the herbicidal composition uses trifluorosulfuron-methyl and bromoxynil as active ingredients, and the mass ratio of trifluorosulfuron-methyl and bromoxynil is 1 ~60: 1~60. The herbicidal composition of the present invention can be used for post-emergence weeding in sugarcane fields, and is particularly effective in controlling broadleaf weeds in sugarcane fields. Compared with a single agent, the herbicidal composition of the present invention delays weed resistance, has a wide herbicidal spectrum, has a long duration of effect, and is safe for sugar cane and subsequent crops on the premise of improving the efficacy.

Key points in poisoning diagnosis^[5]

1. The incubation period ranges from several hours to 1 to 2 days.

2. Skin contact may cause local irritation symptoms.

3. Oral administration may cause dizziness, headache, upper abdominal discomfort, nausea, vomiting, numbness of hands and feet, etc. Severe cases may cause difficulty breathing, cyanosis, and coma.

Principles of poisoning treatment^[5]

1. When skin is contaminated, wash it with water or soap as soon as possible.

2. For oral administration, gastric lavage and catharsis.

3. For mild poisoning, give 20-25ml of 25% sodium thiosulfate solution by slow intravenous injection.

4. For severe poisoning, sodium nitrite-sodium thiosulfate combined therapy can be used.

Preparation^[6]

A production process for the synthesis of bromoxynil, which is characterized by: including the following process steps,

(1) Synthesis of p-hydroxybenzonitrile

a. Select a 250ml three-necked flask. The three-necked flask is equipped with a stirrer, a thermometer, and a set of reflux condenser tubes.

b. Weigh 13-14g of p-hydroxybenzoic acid, 8-10g of urea, 19-20g of sulfamic acid and 40-60ml of p-cresol and add them to the three-necked flask in step a in sequence, and start stirring.

c. Heat the mixture in the flask in step b, slowly raise the temperature to 140-160°C and then keep the reaction for 35-45 minutes.

d. After the insulation reaction in step c is completed, raise the temperature to 180-200℃ again, and add 2-4g againUrea, continue the incubation reaction for 55-65 minutes.

e. Filter the reaction mixture in step d, wash the filter residue with a hot melt agent, then combine the filtrate and conduct distillation under reduced pressure to obtain p-hydroxybenzonitrile.

(2) Bromination reaction of p-hydroxybenzonitrile

a. Select a 250ml four-necked flask. The four-necked flask is equipped with a stirrer, a thermometer, a reflux condenser and a dropping funnel.

b. Weigh 11-12g of p-hydroxybenzonitrile, 35-45ml of 95% ethanol, 10-20ml of water, and 0.05-0.15g of concentrated hydrochloric acid and add them to the flask in step a in sequence, and start stirring until Parahydroxybenzonitrile is fully dissolved.

c. Heat the mixture in the flask in step b, slowly raise the temperature to 30-40℃, then add 16-17g of bromine dropwise, the dropping time is 55-65min, and continue reaction.

d. After the reaction solution in step c fades, add dropwise the solution prepared by 3.5-4.5g of sodium chlorate and 5-7ml of water into the flask, and then continue the reaction for 180 minutes.

e. Filter the reaction mixture in step d, then wash with water until the solution is neutral, and then dry the product, which is the finished product of bromoxynil, and package it for storage.