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0LABORATORY AND INDUSTRIAL TECHNOLOGY FOR THE PRODUCTION OF BIS-CARBAMATES BASED ON HEXAMETHYLENE DIISOCYANATE
1Mashayev E., 2Makhsumov A., 3Absalyamova G., 4Khakimova G.
1 Philosophy Doctor on Chemical Sciences, PhD, Tashkent Institute of Chemical Technology 2Doctor of Chemical Sciences, professor of Tashkent Institute of Chemical Technology
3Associate Professor, PhD, Tashkent Institute of Chemical Technology 4Senior lecturer of the Department of General Chemistry, Tashkent Institute of Chemical
Technology https://doi.org/10.5281/zenodo.14024365
Abstract. This research paper discusses the method for synthesizing the first synthesized bis-carbamate based on cresols and diisocyanatos. First, a laboratory method and a setup for synthesizing the bis-carbamate N, N'-hexamethylene bis-[(o-cresol)-carbamate] (MEE-1) by nucleophilic addition of reagents are presented. Based on the laboratory setup, a small, waste-free, environmentally friendly, energy-saving industrial setup for obtaining the bis-carbamate MEE-1 with a high yield was designed. The initial input data of the setup are given. Based on this scheme and data, this bis-carbamate MEE-1 can be used as a plant biostimulant.
Keywords: bis-carbamate, synthesis, equipment, product, nucleophile, laboratory, reactor.
Introduction. Urethanes or carbamates are compounds of the general formula R'R''NCOOR, where R' and R'' are H, Alk, Ar; R is Alk, Ar. Urethanes are esters of unstable carbamic acid H2NCOOH and its N-substituted derivatives; urethanes were originally called ethyl carbamates, but the terms are currently synonymous. Carbamates are widely used in various industries. Representatives of this class of chemical compounds exhibit biological activity, which is why they are used as medicines and plant protection products (herbicides, acaricides, pesticides, and insecticides) [1]. Herbicides that move in the plant mainly through the xylem include triazines, carbamates, pyridazinones, triazinones, etc [2]. Some carbamates are also found in medicines. They act by inhibiting enzymes in the nervous system of pests. When working with them, safety precautions must be followed. Carbamate-bearing molecules play an important role in modern drug discovery and medicinal chemistry. Organic carbamates (or urethanes) are structural elements of many approved therapeutic agents. Structurally, the carbamate functionality is related to amide-ester hybrid features and, in general, displays very good chemical and proteolytic stabilities. Carbamates are widely utilized as peptide bond surrogates in medicinal chemistry. This is mainly due to their chemical stability and capability to permeate cell membranes. Another unique feature of carbamates is their ability to modulate inter- and intramolecular interactions with the target enzymes or receptors. The carbamate functionality imposes a degree of conformational restriction due to the delocalization of nonbonded electrons on nitrogen into the carboxyl moiety. In addition, the carbamate functionality participates in hydrogen bonding through the carboxyl group and the backbone NH. Therefore, substitution on the O- and N-termini of a carbamate offers opportunities for modulation of biological properties and improvement in stability and pharmacokinetic properties [3]. The main method for synthesizing urethanes of the general formula R'HNCOOR is the reaction of isocyanates with the corresponding alcohols or phenols: R'NCO + ROH ^
R'HNCOOR. The authors of this article synthesized about 20 bis-carbamates and their derivatives by the method of nucleophilic addition of diisocyanates with cresols [4,5]. This work aims to develop a process flow chart for obtaining bis-carbamate based on a laboratory synthesis setup.
Materials and Methods. Preparation of N,N'-hexamethylene bis-[(o-cresol)-carbamate] (MEE-1): Add 10 ml of triethylamine, 35 ml of DMF to 8.40 g (0.1 mol) of ortho-cresol, add dropwise with stirring at room temperature 8.42 ml (0.05 mol) of hexamethylene diisocyanate dissolved in 20 ml of DMF. The reaction mixture is stirred for 3.0-4.0 hours at a temperature of 35-45 °C; after the time has elapsed, the contents of the flask are transferred to a glass, and water is added. The resulting precipitate is washed with TLC. After drying, a snow-white powder is obtained, the product yield is 18.74 g (97.6% of theoretical).
Results and Discussions. The technology for the synthesis of MEE-1 in laboratory conditions was developed and assembled in the laboratory of the department "Chemical Technology of Oil and Gas Refining" of Tashkent Institute of Chemical Technology (Fig. 1.).
Note: 1- Reactor; 2- electric mixer; 3- separating funnel; 4- Buchner's funnel; 5.13- Bunsen flask; 6.14- vacuum pump; 7- drying cabinet; 8- scales; 9-Wurtz flask; 10- electric plate; 11-
The synthesis process is carried out as follows: 10.8 g (0.1 mol) of ortho-cresol, 10 ml of triethylamine catalyst, and 35 ml of DMFA solvent are loaded into reactor 1, and mixed in mixer 2, 8.40 g of ortho-cresol is dissolved in 20 ml of DMFA from separator funnel, 3 g (0.05mol) of GMDI was added dropwise and stirred at 35-40 °C for 4.0 hours. After the stirring is stopped, the mixture is cooled and precipitated. We filter the resulting precipitate (mixture of components) in a notch filter equipped with a 4-Buchner funnel and 5-Bunzen flask for receiving filtrate. To do this, soak the filter paper in methanol alcohol and place it in the funnel. To create a vacuum during the filtration process, we connect the Bunsen flask to the 6th water flow pump. The liquid part of the filtrate is collected in the 5th Bunsen flask. We wash the precipitate remaining in the filter 3-4 times with methanol. The washed wet precipitate is dried in the 7th drying cabinet at a temperature of 5-10 °C higher than room temperature until the moisture content of the precipitate does not exceed 2%. The liquid part of the filtrate from the 5th Bunsen flask is loaded into the 9th Wurtz flask. The Wurtz flask is heated in an oil bath to a temperature of 100-150 °C on a 10-electric plate.
Figure 1. A device for synthesizing MEE-1 in a laboratory
thermometer; 12- cooler.
In this case, after the TEA triethylamine catalyst with a boiling point of 89.5 °C is distilled, a vacuum is created through the 14th water flow pump 35 mm s.u. At residual pressure and temperature, the solvent dimethylformamide (DMFA) is distilled using a condenser 12 at 150 °C. At the end of the work, the finished product in the form of a white powder was measured on the 8th scale, in which 18.74 g (97.6% of theory) was obtained.
A technology for industrial production of MEE-1 was developed based on a laboratory synthesis device. Environmentally clean and safe technology was developed to obtain MEE-1 as a new highly effective biostimulant that replaces imports for poly crops, including tomatoes, cucumbers, cotton, and other crops. To achieve this goal, we built a pilot-test equipment consisting of one technological line with a periodic process (see Figure 2).
The MEE-1 waste-free production method we designed is simple, light, environmentally friendly, and highly efficient, and does not require extra additional costs, because no gaseous or solid waste is generated. The solvent and main catalyst are produced as liquid waste, which is used in further operations after regeneration.
Y-6~~|
Figure 2. Production technology of N,N'-hexamethylene bis-[(ortho-cresolyl)-carbamate] i.e.
MEE-1 drug
Note: Y1-Y6 - containers, D1-D4 - dispensers, N1-N3 - pumps, Rl-reactor mixer, Fl-nutch filter, Bl-drum dryer, El-elevator, Ml-crusher, Tl-oscillating sieve, K1 -drive cube.
Description of the technological process: o-cresol in Y1-vessel, DMFA solvent in Y2-vessel, and TEA catalyst in Y3-vessel are sent to R1-reactor with mechanical stirrer using dispensers D1-D3. The GMDI in the Y4-vessel is fed in a small amount to R1-reactor through D1-doser and the substances are mixed. The reactions take place at atmospheric pressure, at a temperature of 30-40 °C. The reactor can be supplied with hot or cold water to control the temperature. The duration of the reaction is 3.5-4 hours. The reaction process is carried out based on the mechanism of nucleophilic coupling. After the end of the reaction, the resulting mixture is sent to the F1-nutch filter using the N5 pump. The part of the mixture separated from the solvent
and catalyst in the filter is sent to the B1 drum dryer. Drying is carried out at room temperature for 2 hours. The dried product passes through the E1-elevator to the M1-crusher, where it is crushed and passed through the T1-oscillating sieve. The finished product is packed in Y6 containers with a capacity of 50-200 dm3, that is, in polyethylene barrels. The reaction product is MEE-1 in the form of a white powder with a yield of 187.4 g (97.6% theoretical). The mixture of solvent DMFA and catalyst TEA in filter F1 is sent to tank Y5 using pump N6. The mixture collected in the tank is sent to the K1-drive cube using the N7 pump. When the filtrate is heated at 90-95 °C, TEA (B.p=89 °C) is isolated, when we increase the temperature to 157-160 °C, DMFA (B.p=155 °C) is expelled. The separated solvent and catalyst are used in the re-process after regeneration. Initial data for calculating the material input and output of MEE-1 production (table 1.):
Table 1.
Initial data for calculating material income
Initial information Unit of measure Value
Production capacity tn/year 100
The number of working days during the production year day 120
Technological and mechanical losses % 5
Duration of one process for the synthesis of MEE-1 hour 12
Moisture content of finished bis-carbamates % 2
Average device performance per hour kg/hour 50
Conclusion. Based on the laboratory setup, a small, waste-free, environmentally friendly, energy-saving industrial setup for producing bis-carbamate MEE-1 with a high yield was designed. Due to the exothermicity of the reaction, the process is more cost-effective. The initial setup data provided can help in the following developments or improvements of the setup for producing bis-carbamate MEE-1.
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