DEVELOPMENT OF TECHNOLOGY FOR THE PRODUCTION OF ACETYLENE DIOLS AND THEIR VINYL ETHERS

ABSTRACT

The research work aims to elaborate on the technology of obtaining acetylene diols and their vinyl ethers. The reaction of formation mono-, divinyl ethers as a result of vinyl butyn-2-diol-1,4, by acetylene and the influence of solvents, the catalyst and its quantity, duration of reaction, temperatures were investigated. Reaction velocity was defined. Recommended vinyl-3-butyn-2-diol-1,4, acetylene in the presence of highly basic systems at atmospheric pressure.

АННОТАЦИЯ

Целью исследований является разработка технологии получения ацетилендиолов и их виниловых эфиров. Исследована реакция образования моно-, дивиниловых эфиров ацетиленом в результате образования винилбутин-2-диола-1,4, а также влияние растворителей, катализатора и его количества, продолжительности реакции, температуры. Определена скорость реакции. Рекомендуется винил-3-бутин-2-диол-1,4-ацетилен в присутствии высокоосновных систем при атмосферном давлении.

Keywords: butyn-2-diol-1,4, vinyl ethers, homogeneous catalysis, acetylenic diol, КОН-DMSO.

Ключевые слова: бутин-2-диол-1,4, виниловые эфиры, гомогенный катализ, ацетиленовый диол, КОН-ДМСО.

At present, acetylene-based products are used in chemical production and engineering, medicine, to obtain the growth of regulatory drugs and pesticides, light industry, perfumery, food and other fields [1,2,5,8]. Particular attention is paid to the technology for the production of vinyl ethers and, on their basis, new drugs, unique polymeric materials, high-quality solvents for radio engineering, as well as reagents for directed organic synthesis [3,4,10].

Butyne-2-diol-1,4, a valuable chemical compound, enters into many organic reactions, forming many promising materials. Undoubtedly, in this aspect, the study of the vinylation reaction of butyn-2-diol-1,4 is of increased interest, since it has not yet been studied.

For the synthesis of various vinyl ethers for research purposes, Watanabe's transvinylation method of available vinyl ethers of alcohols and acids with other alcohols and diols in the presence of mercury, palladium, or iridium salts is widely used.

The second most important method for the synthesis of vinyl alkyl ethers is the acetal dealkoxylation reaction [2], which is usually accelerated by using various acid catalysts:

1,2-Divinyloxy-1- and 1,2-divinyloxy-2-propenes (I), (II) were first obtained with a total yield of 68% upon heating (100-110 °C) glycerol and acetylene in the super-basic KOH- DMS, successfully proven in vinylation reactions. The synthesis of propenes (I) and (II) was carried out in an autoclave under acetylene pressure using a significant excess (90-130 mol %) of KOH to glycerol. Under these conditions, 4-vinyloxymethyl-2-methyl-1,3-dioxolane is also formed with a yield of up to 9% [14].

β-substituted vinyl ethers can also be obtained by isomerization of allyl ethers under the action of strong bases [9] or metal complex catalysts [9,11]. According to this method, in the presence of ruthenium complexes, monoalkyl ethers of diols are easily isomerized to the corresponding monovinyl (1-propenyl) ethers of diols [12]:

For the synthesis of various vinyl ethers for research purposes, Watanabe's method of transvinylation of available vinyl ethers of alcohols and acids with other alcohols and diols in the presence of mercury, palladium, or iridium salts is widely used [6,7].

It is known that the vinylation of saturated alcohols has been well studied, while that of acetylenic alcohols and diols has been insufficiently studied. Our research goal is to develop a technology for producing acetylene diols and their vinyl ethers.

Research and methodology

0.215 g of KOH and 40 ml of DMSO were placed in a flask equipped with a reflux condenser, a stirrer and a tube for supplying acetylene, then the mixture was heated with constant stirring to 97-100 °C, after which it was slowly cooled to 35 °C, 4.3 g (0,05 mol) butyn-2-diol-1,4 and acetylene was passed through the reaction mixture at a temperature of 110 °C.

After 8 hours, the process was stopped and, after cooling, the reaction mixture was extracted with ether and dried with MgSO4. Then the solvent was distilled off and the distillation was carried out in the presence of the hydroquinone inhibitor. After that, a fraction with a boiling point of 177-178 °C was obtained (at 10 mm Hg) corresponding to 2.69 g of monovinyl ether of butyn-2-diol-1,4 with Bp = 92-93 °C (at 10 13 mm Hg).

Product yield - 2.69 g, 48.1% (of theory), d=0,870 g/cm³,

Similarly to the above procedure, vinylation was carried out at various reaction times, temperatures and amounts of catalysts, which were also used as LiOH and NaOH.

Results and discussion

In this part of the study, an attempt was made to carry out the vinylation of butyn-2-diol-1,4 with acetylene in a super basic medium. It was found that in the reaction mono- and divinyl ethers of diol were formed. Reaction scheme:

The role of the KOH-DMSO system in the implementation of the vinylation reaction is reduced to the formation of a highly basic low-solvated dimsil anion:

However, the role of DMSO is not limited to this. In the general case, changes in such factors as the dielectric constant of the medium, the degree of hydrogen bonding, and others can play a significant role in the implementation of reactions.

The conditions and yields of the reaction products were presented in Table 1 on the example of vinylation of butyn-2-diol-1,4. As follows from the data obtained, the dependence of the yield of mono and divinyl ethers on temperature was significant: at 100-120 °C it is 49.4% and 70%, respectively.

The kinetics of the synthesis of vinyl ethers of butyn-2-diol-1,4 were studied. The main factors were determined - the nature of the solvents, the temperature, and the amount of catalyst that affect the course of the process. Benzene, dioxane, DMSO, and DMF were used as a solvent, and LiOH, NaOH, and KOH served as catalysts. It was revealed that the optimal solvent is DMSO, and the catalyst is KOH. The results obtained under these conditions are shown in Table 1.

Table 1.

Synthesis conditions and yield of vinylation products of butyn-2-diol-1,4

The influence of the nature of the catalysts on the yield of vinyl ethers was also investigated (Table 2). In this case, the amount of catalyst was 5% by weight of alcohol.

Table 2.

Effect of the nature of the catalyst on vinylation of butyn-2-diol-1,4

It can be seen from the results obtained that the nature of the alkaline catalyst affects the yields of butyn-2-diol-1,4 ethers. In the order of the used catalysts LiOH, NaOH, and KOH, their yields increase. The values for monovinyl ether were respectively: 24.2; 35.3 and 27.1%, and for divinyl ether 36.8; 38.4 and 43.4%. Thus, in the synthesis of vinyl ethers, KOH was the most active catalyst in synergy with dimethyl sulfoxide.

The amount of catalyst also affects the product yield. To determine this factor, the influence of the amount of KOH in the range of 2-10% of the mass of butyn-2-diol-1,4 was investigated. The data obtained are shown in Table 3.

Table 3.

Effect of the amount of KOH catalyst on the product yield vinyl

It follows from Table 3 that with an increase in the content of the catalyst in the studied interval, the yield of monovinyl ether of butyn-2-diol-1,4 noticeably decreases from 34.0 to 24.0%, respectively. A further increase in the amount of catalyst does not significantly affect the product yields.

With an increase in the amount of catalyst, the yield of divinyl ether increases symbiotically. This fact is explained by the fact that in the process, monovinyl ether was first formed. An increase in the yield of divinyl ether always leads to a decrease in the yield of butyn-2-diol-1,4 monovinyl ether.

When the reaction was carried out under homogeneous conditions, the product yield and the selectivity of catalytic systems were significantly affected by the nature of the solvent. Data on the study of the effect of the nature of solvents (benzene, dioxane, DMSO, DMF) on the yield of the reaction product were given in Table 4.

Table 4.

Influence of the nature of solvents on the yield of monovinyl ether of butyn-2-diol-1,4. (The reaction time is 8 hours, the temperature is 130 ° C, the catalyst is KOH (5%)).

Of the solvents used, DMSO was found to be the most suitable. In its presence, the yields of mono- and divinyl ethers are, respectively, 27.1 and 43.4%.

The role of DMSO boils down to the fact that, firstly, acetylene dissolves well in it, and secondly, it forms a super-basic system with KOH. In this case, the basicity of KOH increases due to the separation of ion pairs. Vinyl ethers were formed by nucleophilic addition of diol mono- and di-potassium alcoholate.

It is known that the reaction time and temperature have a great influence on the product yield. In this regard, the effect of temperature (in the range of 100-150 °C) and reaction time (4-10 hours) on vinylation of butyn-2-diol-1,4 in the presence of KOH was also studied (Table 5).

Table 5.

Influence of the reaction time and temperature on the yield of butyn-2-diol-1,4 divinyl ether (DMSO solvent, KOH catalyst in an amount of 5% by weight of alcohol)

To identify the dynamics of the process and improve its preparative characteristics, kinetic experiments were carried out. Fig. 4 shows the curves reflecting the change in the concentration of mono - (2) and divinyl (1) ethers of butyn-2-diol-1,4. The appearance of the obtained kinetic curves corresponds to a simple sequential reaction: the initially formed monovinyl ether easily binds to the second acetylene molecule to form divinyl ether, the concentration of which gradually increases and after 5-6 hours reaches a plateau (Curve 1).

The maximum on the kinetic curve of monovinyl ether was reached after 2 hours (curve 2). At elevated temperatures (110-140 °C), favourable conditions were created for the detected elimination of acetylene from the divinyl ether.

Figure 4. Kinetic curves of the accumulation of divinyl (1) and monovinyl (2) ethers during the vinylation of butyn-2-diol-1,4 in the KOH-DMSO system at a temperature of 95 °C and a ratio of diol: KOH = 1:1

It follows from the table that with an increase in the duration of the reaction at all temperatures studied, the yield of vinyl ether passes through a maximum.

It should be noted that with an increase in the process temperature, the optimal value of the reaction time decreases. For example, at a temperature of 100 °C with an increase in the reaction time from 4 to 6 hours, the yield of the product increases from 25.6 to 33.2%, and at 150 °C in the range of 4-8 hours, the yield of ether increases from 30 to 47.0%.

The study of the effect of temperature in the range of 100-150 °C showed that the product yield passes through a maximum. The maximum yield (49.2%) of butyne-2-diol-1,4 divinyl ether was observed at 130 °C and its partial polymerization occurs.

Thus, the optimal conditions for vinylation of butyn-2-diol-1,4 are the reaction time of 10 hours and the temperature of 130 ^oС.

The effect of the nature of the catalyst on the yield of butyn-2-diol-1,4 divinyl ether (temperature 130 °C, solvent DMSO) was also studied. LiOH, NaOH, and KOH were used as catalysts. The results were shown in Table 6.

Table 6.

Influence of the nature of the catalyst on the yield of vinyl ether butyn-2-diol-1,4 (temperature 130 °С, solvent DMSO)

It was found that with an increase in the duration of the reaction in the range of 4-10 hours in all cases, the product yield increases.

Among the catalysts used, the highest yield was achieved with the use of KOH. It follows from this that the greater the basicity of the catalyst, the higher the likelihood of its positive effect on the product yield.

The yield of the products and their purity were determined by gas-liquid chromatography. In fig. 1 shows the gas-liquid chromatogram of the catalyzate formed upon vinylation of butyn-2-diol-1,4 with acetylene. It was shown that the catalyzate contains vinyl ether of butyn-2-diol-1,4 (1,2), unreacted butyn-2-diol-1,4 (3), solvent DMSO (4), and a small amount of a substance of an unknown structure.

In fig. 2 shows the chromatogram of the synthesized vinyl ether of butyn-2-diol-1,4. The kinetics of the synthesis of the vinyl ether of butyn-2-diol-1,4 has been studied (Table 7).

Table 7.

Kinetic data for the synthesis of the  vinyl ether of butyn-2-diol-1,4 (catalyst KOH, 5% by weight of alcohol, solvent DMSO)

Based on the results obtained, the dependence of lgW on 1/T was constructed (Fig. 3) and, according to the Arrhenius equation, the value of the activation energy for the formation of the divinyl ether of butyn-2-diol-1,4 was calculated, which is 51.7 kJ/mol.

Figure 4. Dependence of lgW on 1 / T in the formation of divinyl ether of butyn-2-diol-1,4

Conclusion

The optimal conditions for vinylation of butyn-2-diol-1,4 providing the maximum yield of butyn-2-diol-1,4 divinyl ether were determined. The best effect as a solvent among the investigated benzene, dimethyl sulfoxide, has dimethyl sulfoxide. With an increase in the reaction time, the yield of divinyl ether increases, reaching a maximum after 8 hours. The relatively low value of the calculated activation energy, equal to 51.7 kJ / mol, indicates a fairly high rate of the vinylation reaction of butyn-2-diol-1,4.

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