CS259391B1 - A method of preparing acetylene monoaddition with isopropyl alcohol by photochemical synthesis - Google Patents

Abstract

The method for preparing the monoadduct of acetylene with isopropyl alcohol by photochemically initiated radical addition in the presence of 0.1 to 10% mol is addressed. acetone as a UV sensitizer, pressure 0 to 1 MPa acetylene carried out by exposure of a homogeneous reaction mixture circulating in a thin layer around the source of UV radiation during the reaction time, allowing a non-liquid increase in the selectivity of monoadduct formation. The procedure can be used as a new way of producing dimethyl vinyl carbonyl.

Description

259391

The present invention relates to a process for the preparation of an acetylene mono-isopropyl alcohol mono-chemically initiated reaction of acetylene with isopropyl alcohol in the presence of 0.1 to 10% mol. acetone as the UV radiation absorbent, an acetylene pressure of 1 to 1 MPa by irradiating a homogeneous thin-film circulating reaction mixture around a UV radiation source of suitable intensity and spectral character. The preparation of said acetylene adducts with isopropylalcohol was published in the patent literature in 1967 in Pat. U.S. Pat. No. 3,304,277, and only a few authors in the specialist literature deal with the subject matter. All published processes for the preparation of a new C-C bond by photochemical and free radical-initiated addition of alcohols to acetylene are characterized by inactivity and very low product yields.

The reactions take place in a phase-heterogeneous gas-liquid dispersion system, causing undefined chemical reaction mechanisms. The preparation of the reaction mixtures is based on a large excess of UV absorbent, which results in a variety of free-radical reactions already in the initiation period or in the absence of the UV sensitizer, resulting in insufficient use of UV radiation and slowing down the rate of reaction. the effect of the intensity of the radiation absorbed in the reaction system on the selectivity of the monoadduct formation by the aquant yield of the photochemical synthesis of the acetylene mono- and polyadducts with isopropanol. Said process for the preparation of adduct ethylene with alcohols leads to the substitution of the classical two-stage process of the prepared adducts by the ethynylation of the carbonyl compounds followed by the selective hydrogenation of the alkyne alcohols to the alkaloalkols already industrially mastered.

The process for the preparation of the addition products (¾) of IPA (U.S. Pat. No. 3,304,247) discloses the reaction of PIA with C2H2 and ω2 compounds at a temperature of 30 DEG to 80 DEG C. and a reaction time of 1 to 5 hours in the presence of a UV sensitizer. in a pyrex immersion typereactor tempered by an external duplicator, a 450 W mercury vapor lamp was used as the source of UV radiation, and 963 ml (12.5 µl) of isopropanol (IPA) and 88 ml (1.2 mol) of acetone were charged to the reactor. Acetylene was fed to the reactor at a rate of 0.5 l.min-1 and was efficiently dispersed, and the reaction mixture was heated at 28 DEG C. for 3 hours to give 21 g of 2-methyl-3-buten-2-ol (DVK). (2.5 wt.%) And 30 g (3.6 wt.%) Of 2,5-dimethyl-2,5-hexanediol. The amount of UV sensitizer is not considered critical, although 0 , 08 part of acetone per 1 part of isopropyl alcohol.

However, a similar process for the preparation of acetylene adducts (U.S. Pat. No. 3,352,929), however, by the use of peroxydic peroxide initiation utilizes higher acetylene temperatures and pressures. This is due to yields equivalent to UV radiation of the target system. As byproducts of DVK and dimethylhexanediol, acetylene molecular telomeres are formed, which is also initiated by isopropyl-cobol radicals. The formation of DVK is preferred by lower pressures. Higher acetylene pressures favor diol formation. The products are obtained by sequentially distilling off unreacted feedstocks.

The kinetic study of acetone-sensitized photoacid of selected solvents naacetylene is (Cand. J. of Chem. 45,3 209, 1967). The solvents used were cyclohexane, ethanol, diethyl and acetone, 2-methyltetrahydrofuran. Acetylene solubilities, quantum product yields, and rate constants of vinyl adducts were measured. The work points out that the main product vinyl derivative solvent increases during the initiation period, but tends to decrease if the reaction is more than a few percent of the product. The residue is due to the secondary reaction of the free radical product. The addition proceeded at atmospheric pressure at 25 ° C in an external source of reactor.

The direct photoaddition of acetylene and its derivatives to isopropyl alcohol is the subject of study (Jur. Org. Chimii 9, 1606, 1973). The work is compared by both direct and acetone-sterilized photochemically initiated addition of acetylene and its derivatives to isopropyl alcohol against both direct and sensitized additive olefins such as ethylene and 1-hexene. The reaction was carried out in a cylindrical glass reactor with effective scattering of ethylene. Inside the reactor was a 375 W high pressure mercury lamp, protected by a high quality creme casing, cooled by circulating water. The thickness of the reaction layer in the working part of the device was 8 mm. The temperature was maintained at 18-20 ° C. The bubbling rate of acetetylene was 200 ml / min. 3.8 g (0.96% by weight) of Z-methyl-3-buten-2-ol and 0.5 g (0.13%) of isopropyl alcohol were obtained by exposure to 500 ml of isopropyl alcohol for 3 hours under direct exposure to isopropyl alcohol. % by weight of 2,5-dimethyl-2,5-hexanediol. In an acetone-sensitized photoaddition, exposure of a mixture of 500 ml of isopropyl alcohol and 50 ml of acetone for 3 hours while still bubbling acetylene yielded 11.8 g (2.6% by weight) of 2-methyl-3-buten-2-ol and 31% by weight. g (7.2 wt.%) of 2,5-dimethyl-2,5-hexanediol.

At an exposure delay of up to 8 hours, the yield of carbinol was stabilized at 14.4 g (3.3%) of adiol, increasing to 55 g (12.7% by weight). The acetylene was freed from acetone by freeze-drying and washed in conc. H2.SO4 aluhu. It was found that at 5 to 7 hours the conc. carbinol peak and gradually decreases at the expense of the secondary reaction. 2 5 9 3 91 5 β

The forming olefin does not cause UV-inactivation of the extracted molecules. The process mechanism of the process has been proposed. The process of acetone sensitized reaction is considered to be non-selective due to the high concentration of 2-hydroxyisopropyl radicals during exposure because large amounts of diol are formed during the induction period. In the direct photo-acetylation of acetylene naisopropanol due to the low extinction of the acetylene in the UV region, even the tert-butyl radicals and the subsequent forming diol are low. This method of preparation indicates that the technique is technically appropriate.

The disadvantages of these processes are avoided by the process of the present invention, whereby a photochemical initiated reaction of acetylene with isopropanol is carried out by reacting acetylene with isopropanol in the presence of 0.1 to 10% moles. acetone as the UV absorbent, acetylene pressure of 0 to 1 MPa by exposing the homogeneous reaction mixture circulating in a thin layer around the UV radiation source of appropriate intensity and spectral characteristics to the radiation by passing the reaction through the reaction mixture to the reaction mixture. the time at which DVKXsdvk selectivity is 90% and DVKO'VVK quantum yield 10. The advantage of the process of the invention is that by defining the critical UVabsorbent concentration and the maximum irradiation ridge, the UV radiation absorption becomes uniform throughout the reactor volume. This does not result in the local absorption of the thin-layer radiation on the reactor walls closer to the UV sources and hence the overall excess of 2-hydroxyisopropyl radicals over the dissolved acetylene. Another advantage with substantial significance is the definition of the radiation intensity absorbed in the unit volume of the reaction mixture between 1 1017 and 1 1019 quan / sdm3 in the wavelength range of 253.7 to 320nm from the known participation of the quartz chemistry of the excitation and photoreduction process. carbonyl compound. Significant influence of the radiation intensity absorbed in the system confirms the chain mechanism of addition of the 2-hydroxyisopropyl radical to acetylenene. The chain nature results in a high quantum yield of 10, which has a positive effect on the energy costs of the initiating allergy.

The selected reaction temperature critical values do not affect the primary photochemical deterioration between the UV radiation and the radiation absorber, but the optimum range when the rate of hydrogen removal from the isopropyl alcohol already excited by the sensitizer is already high. Another significant advantage of the preparation of acetylene adducts with isopropyl alcohol is that it allows the pressures of 0 to 1 MPaC2H2 to increase the concentration of acetylene in the reaction mixture. Since the present addition is a first order reaction with respect to acetylene, a higher concentration of acetylene increases the selectivity of the formation of dimethylvinylcarbinol and the rate of monoadduct formation in the first hours of the process in the first hours of the process. The advantage is also the separation of acetylene absorption in a self-contained functional device from the reaction space. The reaction mixture entering the UV radiation exposure area is a homogeneous liquid reactant mixture as opposed to dispersions in known processes. This allows for the definition of the process of photoreduction of the carbonyl sensitizer in the liquid phase and removes the variety of primary gas photochemical processes.

The technological process illuminating the essence of the invention is shown schematically on the figure.

The apparatus is charged with a reaction mixture of isopropyl alcohol and a sensitizer through the valve 1 such that the reactor 2 is filled and assembled from the reactor and the absorber 3 allows circulation through the pump 4 with variable output. The reactor consists of a reaction exposition zone S, a tempering and filtering zone 6 and a source of UV radiation of sufficient output 7, which are mercury suitable UV intensity and spectral characterization.

The acetylene pressure selection is enabled by the reduction valve 8 on the acetylene pressure bottle from the safety supply and from the need for inertization before and after the process, the nitrogen is fed with the reduction valve 9. The temperature zone only connected to the thermostat 10.

The circulation system is supplemented by one additional pressure pump 11 for the supply of reactants during the process. After the system has been filled with the reactants, the soluble oxygen is removed by acetylene for 1 hour. The acetylene is purified from the acetone by freezing in a washing machine 12 followed by adsorption of the alumina layer 13. The acetylene from the apparatus is discharged through the freezer 14 and the valve 15 from the hood exhaust. By selecting the reaction conditions, the process is modulated to the desired adducts. Example 1

650 g of isopropanol and 13.4 g of acetone were introduced into the apparatus shown schematically. Under continuous circulation, the mixture was saturated for 1 hour with ethylene. Reaction mixture after 1 h irradiation with MPa and reaction temperature 20 ° C. After saturation, the source of UV radiation with the radiation intensity absorbed in a unit volume of 4 x 10 4 quart / s dm 3 in the area of 253.7 to 320 nm was switched on. Consumed acetylene was charged with the reducing valve under steady circulation. The reaction mixture after irradiation for 1 h contained 2.15 wt. 2-methyl-2-butene-3

Claims (4)

A process for the preparation of an acetylene monoaduct with isopropyl alcohol by photochemical synthesis of acetylene with isopropyl alcohol, characterized in that the reaction is carried out in the presence of 0.1-10 mol% acetone as UV absorber, at a pressure of 0 to 1 MPa of acetylene, a source of UV radiation of an intensity of 1.10 ¹⁷ to 1.10 ¹⁹ kv / s dm ³ in the wavelength range 253.7 to 320 nm in a reaction time at which the selectivity of DVK formation is greater than 90% and the quantitative yield of DVK is greater than 10.