Radical Formation in Sugar-Derived Acetals under Solvent-Free Conditions

The degradation of acetal derivatives of the diethylester of galactarate (GalX) was investigated by electron paramagnetic resonance (EPR) spectroscopy in the context of solvent-free, high-temperature reactions like polycondensations. It was demonstrated that less substituted cyclic acetals are prone to undergo radical degradation at higher temperatures as a result of hydrogen abstraction. The EPR observations were supported by the synthesis of GalX based polyamides via ester-amide exchange-type polycondensations in solvent-free conditions at high temperatures in the presence and in the absence of radical inhibitors. The radical degradation can be offset by the addition of a radical inhibitor. The radical is probably formed on the methylene unit between the oxygen atoms and subsequently undergoes a rearrangement.

Chemically recyclable thermoplastics from reversible-deactivation polymerization of cyclic acetals

Identifying plastics capable of chemical recycling to monomer (CRM) is the foremost challenge in creating a sustainable circular plastic economy. Polyacetals are promising candidates for CRM but lack useful tensile strengths owing to the low molecular weights produced using current uncontrolled cationic ring-opening polymerization (CROP) methods. Here, we present reversible-deactivation CROP of cyclic acetals using a commercial halomethyl ether initiator and an indium(III) bromide catalyst. Using this method, we synthesize poly(1,3-dioxolane) (PDXL), which demonstrates tensile strength comparable to some commodity polyolefins. Depolymerization of PDXL using strong acid catalysts returns monomer in near-quantitative yield and even proceeds from a commodity plastic waste mixture. Our efficient polymerization method affords a tough thermoplastic that can undergo selective depolymerization to monomer.

Preparation of cyclic acetals and gem-dichlorocyclopropanes based on 1,2-dichloromethylbenzol

Using 2,2-dimethyl-4-hydroxymethyl-1,3-dioxolane (sol-ketal) and 1,2-dichlomethylbenzene under the conditions of phase transfer catalysis, mono- and diesters containing cycloacetal fragments were synthesized. Also, with the help of dichloride, in the presence of benzene, mono- and diesters of allyl alcohol were obtained. Dichlorocyclopropanation of unsaturated ethers using chloroform, alkali and catamine AB catalyst made it possible to obtain compounds containing gem-dichlorocyclopropane fragments. O-alkylation of the sol-ketal with 1-[(alloxy)methyl]-2-(chloromethyl)benzene (mono-derivative of allyl alcohol) was used to synthesize an ether combining in its structure 1,3-dioxolane and gem-dichlorocyclopropane fragments simultaneously. The obtained substances were analyzed and confirmed by mass spectrometry («Chromatek-Kristall» instrument with Nist research database) and NMR spectroscopy («Bruker instrument»). It was found that among a number of compounds obtained, only 4-{[(2-{[(2,2-dichlorocyclopropyl) methoxy]methyl}-benzyl)oxy] methyl}-2,2-dimethyl-1,3-dioxolane exhibits cytological activity against the cell lines HEK293, SH-SY5Y, MCF-7 and A549.

Advances and achievements of Academician D.L. Rakhmankulov’s scientific school in the field of applied and oilfield chemistry

This paper reviews the achievements of the scientific school of Academician of the Academy of Sciences of the Republic of Bashkortostan, Professor of the Ufa State Petroleum Technological University (USPTU) D.L. Rakhmankulov in the field of applied and oilfield chemistry. Having achieved fundamental results during theoretical and experimental research into the structure, properties and mechanisms of transformations of substituted cyclic acetals and heteroanalogues, D.L. Rakhmankulov and his colleagues proposed to apply this knowledge in various sectors of the national economy, in particular, in the oilfield chemistry. An analysis of copyright certificates obtained by the researchers from the 1970s to the 1990s, which were related to the development of reagents of the class of cyclic acetals intended for use in the oilfield chemistry, showed that the obtained reagents can be effectively used as components of drilling fluids, inhibitors of hydrogen sulphide corrosion of oilfield equipment, bactericidal reagents that inhibit the growth of sulphate-reducing bacteria. The efficiency of such reagents significantly exceeded that of well-known industrial reagents. It was noted that aqueous compositions containing 1,3-dioxacycloalkanes dissolve and keep in volume particles of resins and asphaltenes in the form of microemulsions, which makes it possible to increase oil recovery and use cyclic acetals as reagents-solvents of asphalt-resin-paraffin deposits. It was found that the use of cyclic acetals, e.g. 4,4-dimethyl-1,3-dioxane, in the composition of drilling fluids can significantly improve their lubricating, antiwear and anticorrosive properties. By-products of petrochemical industries were often used as a raw material for the production of compounds of the class of cyclic acetals, which at the same time solved the problem of their recycling. It was found that the bottom residue of industrial production of 4,4-dimethyl-1,3-dioxane, containing oxymethyl-1,3-dioxanes, can be successfully used for dissolving gypsum hydrocarbon fuels deposited in oil wells. In order to expand the range of reagents that inhibit the growth of sulphate-reducing bacteria, D.L. Rakhmankulov and his colleagues proposed to use aqueous solutions of 1,3-dioxacycloalkanes as bactericides.

Acetalization of glycerine at presence of acid-modified clinoptilolite, bentonite and tripolite from the domestic deposits

In recent years, the situation with glycerol (Gl) has changed dramatically due to rapid development of biodiesel industry, in production of which Gl is formed in large quantities. Cyclic acetals of Gl are used as additives to motor fuels, as well as intermediates in the synthesis of various mono derivatives of Gl, which are widely used in food and pharmaceutical industries, cosmetics, etc. On the examples of Gl interaction with acetone (Ac), benzaldehyde (BA) and formaldehyde (FA), authors revealed the prospects of nitric acid-modified samples of natural clinoptilolite (H-СPT), bentonite (H-BNT) and trepel (H-TRP) from Sokirnytsky, Dashukivsky and Konoplyansky deposits of Ukraine (respectively) as catalysts for Gl transformation into cyclic acetals. Factors that determine the optimal conditions for acid modification of raw material, providing maximum conversion of Gl and catalytic activity of obtained samples, have been identified. A characteristic feature of studied processes is need to change the reaction conditions when changing the carbonyl compound-partner of Gl. It was found that number of catalyst samples obtained on H-BNT basis, their activity is superior (or comparable) with cation exchange resin KU-2.

One-pot synthesis of short-chain cyclic acetals via tandem hydroformylation-acetalization under biphasic conditions

A novel method for the synthesis of 2-ethyl-1,3-dioxolane and related short-chain acetals by tandem hydroformylation-acetalization of ethylene is described. The reaction processes in biphasic system. Polar phase contains the catalytic...