SU1177299A1 - Method of producing 5-chlor-2-methylbenzimidazole - Google Patents

Description

The invention relates to methods for producing 5-chloro-2-methylbenzimidazole of the formula _m

used in agriculture as a herbicide.

The purpose of the invention is to increase the yield of the target product, simplifying the process technology.

Example. The reductive cyclization of 4-chloro-2-nitroaniline is carried out in a reactor with a capacity of 1200 l, 5 equipped with a low-speed mechanical stirrer, a heating and cooling jacket and a reflux condenser, which are cooled with running water. The reactor vessel is lined with acid-resistant ceramic plate. The starting materials are loaded into the reactor in the following order: the first batch of iron chips 9 kg, 4-chloro-2-nitroaniline in the amount of 60.4 kg from the self-unloading bunker, acetic acid 103.5 kg from the mernik, hydrochloric acid 303.6 kg of the measuring device. Total amount of chips loaded

55.2 kg. After pre-heating; at 60-70 ° C, the steam supply is turned off ^ as the process then proceeds spontaneously with heating with a hydrogen release. Iron loading of 6 kg is carried out every 30-45 minutes. 35 After adding the last portion of iron chips to the reaction mass, boil for 1 hour. After that, a sample is taken from the reactor for analysis

the reaction mixture. If initial 4-chloro-2-nitroanilini is detected in the sample, then 1 kg of iron shavings is again added to the reactor.

Then the heating is turned off, the reaction mixture is transferred by way of slipping into an enameled reactor with a capacity of 1200 l, equipped with a mechanical stirrer, cooling jacket and reflux condenser. The reaction mixture with stirring and cooling is treated with warm (45-50 ° C) saturated aqueous solution of 340.4 kg of sodium pyrophosphate Na ₂ H ₂ P _g 0 ₇ ⁴ 6H ₂ O in 500 l of water from the measuring device. The resulting reaction mixture should have a pH of 5-5.5 (if pH / 5, then adjusted to pH = 5.0-5.5 by adding a 5% aqueous solution of KOH or NaOH). The mixture is squeezed onto a filter for filtering, the filter cake is washed with 20-30 liters of water (2030 ° C).

The filtrate, together with the washing water, is sent to a 1200-liter reactor alkalinized to pH = 8-9 with 5% aqueous alkali solution from a measuring device. The mixture is squeezed out onto the filter; the filter cake is washed with 50 liters of warm water. The product is sent to a vacuum oven, where it exists at 60-70 * C in vacuum. The yield per operation 52.5 kg (90%), the content of the basic substance is 95%.

The proposed method allows to increase the yield of the target product (90% instead of 75%), reduce the number of stages (7 instead of 9), and also simplify the process technology.

Claims (1)

METHOD FOR OBTAINING 5-CHLOR-2-METHIPBENZIMDAZOLA formula reducing cyclization of 4-chloro-2-nitroaniline with iron shavings in a mixture of acetic and hydrochloric acids, followed by treatment of the reaction mixture with sodium hydroxide to pH 8-9 and isolation of the target product, characterized in that the reaction mixture is first treated with an equivalent amount of _β sodium pyrophosphate to pH 5-5.5, for - ® the filtrate is treated with a dilute sodium hydroxide solution. 51) „1177299 1177299