Radiolysis of tetrachloromethane-water two-phase systems

The radiolysis of two-phase systems CCl₄-water proceeds in kinetical regime up to dose 12 kGy. Groos radiation yields of chloride ions are the same as the radiolysis of saturated solutions in this period. A two-phase rule of additivity is valid and the partial yields for both phases were calculated; G_CCl4(Cl^- = 5.61 ± 0.10 and G_H2O(Cl^-) = 8.29 ± 0.51 molecules/100 eV, respectively.The radiolysis proceeds in diffusional regime at the absorbed dose of more than 50 kGy. The gross radiation yield of chloride ions is determined by hydrolysis of molecular chlorine which is produced with G(Cl₂) = 0.68 ± 0.14 molecules/100 eV. An additional part of chloride ions is produced by radiolysis of substrates which diffuse into both phases with value G_dif(Cl^-) = 2.38 ± 0.31 molecules/eV. This value is approximately three times less than the gross radiation yields in kinetical regime of radiolysis of two-phase systems in saturated solutions of these substrates.     

Determination of radiation yields of ionogenic products of two-phase water-dibutylphosphate systems by capillary isotachophoresis

The main ionogenic radiolytical degradation products are monobutylphosphate, phosphoric acid, formic, acetic, propionic and butyric acids as the result of gamma-irradiation of two-phase water-dibutylphosphate system. The products were determined using capillary isotachophoresis. According two-phase theory the total (_T G(X)) and partial (G_I(X) for aqueous phase and G_II(X) for organic phase) radiation yields of products and decomposition of DBP in the radiolysis of two phase water-dibutylphosphate systems were calculated from the results.Dedicated to 65th birthday of prof. L. T. Bugaenko     

Mass spectrometric study of the radiolysis of di-(2-ethylhexyl)phosphoric acid

A mass spectrometric study on DEHPA was carried out and compared with radiolysis data on DEHPA for γ-irradiation in the liquid phase. The mass spectra of DEHPA show an extremely low intensity of parent ion and the presence of double rearrangement ions of (RO)P(OH) ₃ ⁺ and P(OH) ₄ ⁺ , where R is the 2-ethylhexyl group. The appearance potentials of the principal ions in the mass spectrum were determined and the dissociation processes of DEHPA in the phase discussed. The fragment ions show good agreement with the results in the liquid phase where the mono-ester, orthophosphoric acid, octane and heptane were formed by the dealkylation, however, the peak intensities of some fragment ions in the mass spectrum differ from the radiolytic yields of the corresponding products. These differences imply the significant role of neutralization and recombination reactions in the liquid phase radiolysis.     

Radiation decomposition of Co(acac)3 in alcohol-water matrices

The reduction yields of Co(acac)₃ in methanol-water (11) solutions and also the formation yields of the radiolysis products Co(acac)₃Co(acac)₂ + acac have been determined. These yields were found to depend considerably on the acidity and also on the initial complex concentration. Solvated electrons, transformed in acidic solutions into atomic hydrogen, less effective in reducing acetyloacetonate, are of basic significance in the reduction process of Co(acac)₃. Studies of the methanol-glycol Co(acac)₃ solutions showed that the type of radiolytic products formed depends on the composition of the matrix.     

A study of changes in the yields of radiolytic products in two-phase systems with tributyl phosphate

With the aim of studying the effects of volume ratios and composition of the organic phase on the total yields of the main degradation products of tributyl phosphate (TBP) radiolysis, the following two-phase systems were used: water-TBP-carbon tetrachloride and water-TBP-n-alkane with various ratio of TBP in the organic phase and various volume ratios of organic-aqueous phases. We examined the influence of the distribution of two-phase systems components-precursors of radiolytic products on the total yields of the main radiolytic products and mechanism involved.     

Stable products and radicals in the radiolysis of dichloromethane and 1,1,-dichloroethane gamma-irradiated in an oxygen-free atmosphere

Stable and transient products of the -radiolysis of dichloromethane (DCM) and 1,1-dichloroethane (11 DCE) have been investigated in an oxygen-free atmosphere. The stable products were separated by preparative gas chromatography and identified by NMR and mass spectroscopy. The quantitative determinations were performed by potentiometric and gas chromatographic analysis. The main products of radiolysis of DCM are dimers (11DCE, 12DCE, 112TCE, 1122TetraCE) and the product of dechlorination CM; in the case of 11DCE-dimers (133TCB, 2233TetraCB) and the product of dechlorination CE as well as products of isomerization and chlorination of the parent compound (12DCE, 112TCE). The gas products of both chlorides are HCl and H₂. The ESR investigations at 77 K indicate the formation of at least two kinds of radicals in both chlorides: CH₂Cl/CHCl₂=1/3 in DCM and CH₃CCl₂/CH₃CHCl=2.5/1 in 11DCE. An outline of the mechanism of radiolysis is proposed.     

Radiolysis of iodotyrosines in aqueous-ethanol solutions

⁶⁰Co-gamma radiolysis of 3-iodotyrosine and 3,5-diiodotyrosine in aqueous-ethanol solutions has shown that the chemical effects are mainly determined by the interaction of radicals from the radiolysis of solvent and controlled by the composition of the solution. The influence of varying solvent composition and radiation dose on the amount of iodoamino acid converted and on the yields of the radiolysis products (I₂, I^–, IO ₃ ^– and H₂O₂) formed in aerated solutions at room termperature were investigated. The formation of I₂ is dependent upon the acidity of the solution and is mainly produced as an after-effect due to the interaction of H₂O₂ with I^– ions, both being radiolysis products. The variation of radiation-chemical yields with the solute and solvent composition, and the probable mechanisms for formation of the radiolysis products are discussed.     

Nuclear Versus Side-Chain Bromination of 4-Methoxy Toluene by an Electrochemical Method

The electrochemical bromination of 4-methoxy toluene by two-phase electrolysis yields 3-bromo 4-methoxy toluene at first, which subsequently undergoes side-chain bromination to give 3-bromo 4-methoxy benzyl bromide as a final product in 86% yield. The two-phase electrolysis consists of 25–50% NaBr as aqueous electrolyte and CHCl₃ containing aromatic compound as organic phase. The reaction temperature is maintained at 10–25 °C. The probable orientation of bromine atom in an alkyl aromatic compound (nuclear versus side chain) is explained from the experimental result.     

Calculated and measured transient product yields in pulse radiolysis of aqueous solutions: Concentration dependence

Pulse radiolysis of aqueous solutions was modeled by using 54 equations for the reaction of water radiolysis intermediates with carefully selected rate coefficients. Yields of products formed in the hydrated electron+solute and hydroxyl radical+solute reactions were calculated and compared with the measured yields in wide concentration range. These reactions are in competition with the reactions of the water radiolysis intermediates with each other and with H₂O, H⁺ and H₂O₂. An empirical equation was developed for the calculation of scavenged product yields that can be used in cases when due to low rate coefficient, low solubility or very high absorbance, low solute concentrations are applied and a considerable fraction of the water radiolysis intermediates does not react with the solute.     

A facile and convenient one-pot synthesis of polysubstituted thiophenes from 1,3-dicarbonyl compounds in water

A facile and convenient one-pot synthesis of polysubstituted thiophenes 2 and polysubstituted thieno[2,3-b]thiophenes 3 from 1,3-dicarbonyl compounds 1 has been achieved in high yields catalyzed by tetrabutylammonium bromide (TBAB) in the presence of K₂CO₃ in water. TBAB in the aqueous phase can be recycled after the separation of organic products.     

Formation of 5-Hydroxy-5,6-Dihydrothymidine and cis-5,6-Dihydroxy-5,6-Dihydrothymidine in the Radiolysis of N2O-Saturated Aqueous Solutions of Thymidine, Thymidine 5"-Monophosphate, and DNA

The yields of formation of 5-hydroxy-5,6-dihydrothymidine and cis-5,6-dihydroxy-5,6-dihydrothymidine in the radiolysis of thymidine, thymidine 5"-monophosphate, and DNA in N₂O-saturated aqueous solutions were measured in order to study the mechanism of nucleic acid radiolysis. The above compounds were found to be main radiolysis products upon irradiation of thymidine and thymidine 5"-monophosphate. However, these compounds were formed in very low yields upon irradiation of DNA, and they amounted to less than 2% of the degradation yield of DNA thymine. The yield of the 5-hydroxythymidin-6-yl radical was evaluated by determining the amount of 5-hydroxy-5,6-dihydrothymidine formed in the radiolysis of the above compounds in the presence of cysteamine.     

The reaction of O(3P) with C2HCl3

The reaction of O(³P), prepared from the Hg photosensitization of N₂O, with C₂HCl₃ was studied at 25°C. The products of the reaction in the absence of O₂ were CO, CHCl₃, and polymer (as well as N₂ from the N₂O). The quantum yields of CO and CHCl₃ were 0.23 ± 0.01 and 0.14 ± 0.05, is respectively independent of reaction conditions. The reaction mechanism is with k_14a/k₁₄ = 0.23, where k_14a + k_14b. Most of the HCl and CCl₂ combine to form CHCl₃, but some other products must also be formed to account for the difference in the CO and CHCl₃ quantum yields. The C₂HCl₃O* adduct polymerizes without involving additional C₂HCl₃ molecules, since the quantum yield of C₂HCl₃ disappearance, ? Φ{C₂HCl₃}, was about 1.0 at high values of [N₂O]/[C₂HCl₃]. The rate coefficient for the reaction of O(³P) with C₂HCl₃ is 0.10 that for the reaction of O(³P) with C₂F₄. In the presence of O₂ the free radical chain oxidation occurs because of the reaction The main product is CHCl₂CCl(O) with smaller amounts of CO and CCl₂O, and some CO₂. The chain lengths were long and values of ? Φ {C₂HCl₃} up to 90 were observed.     

Radiation-chemical processes in methanolic solutions of rhodium acetylacetonates

The processes of radiation decomposition of Rh/acac/₃ and Rh/acac//CO/₂ in liquid and frozen methanol-water systems have been studied. The rate constants of electron scavenging by these complexes have been measured using the pulse radiolysis and the yields of the decomposition of the complexes in liquids have been determined as the effect of -radiolysis. In frozen glassy systems the efficiency of electron scavenging by Rh/acac/₃ has been measured by both optical and ESR methods. In the last method the yields of Rh/II/ complex occurred as the transient product have also been determined.     

Photochemical and photocatalytic reactions of carbon tetrachloride with alcohols

The photo-initiated oxidation of alcohols by carbon tetrachloride was studied. The main reaction products formed during the irradiation of CCl₄ solutions in ethanol with light of = 254 nm are chloroform, acetaldehyde, and hexachloroethane. With increase in concentration of CCl₄ in the mixture with ethanol from 0.5 to 5 mole/liter, the quantum yields of the formation of CHCl₃ and CH₃CHO decrease from 9.2 to 4.4 and from 4.3 to 1.4, respectively, while the quantum yield of formation of C₂Cl₆ increases from 0.38 to 0.68. By using semiconductor photocatalysts (TiO₂, TiO₂/Pd, CdS), the oxidation of alcohols can be carried by the action of light of the near-UV and visible regions of the spectrum (320 < < 520 nm). When the reaction is carried out photocatalytically, the maximum quantum yields of the formation of CHCl₃ and CH₃CHO were attained with a palladized TiO₂ (0.77 and 0.36, respectively). The initial stage of the mechanism of the photochemical process involves the cleavage of the C-Cl bond with absorption of a quantum of light by the CCl₄ molecule, and this is followed by reactions of free radicals. When semiconductor photocatalysts are used, the cleavage of the C-Cl bond occurs either by the action of hydroxyethyl radicals, formed by the reaction of ethanol molecules with valence zone holes of the semiconductor (in the case of TiO₂), or electrons of the semiconductor conductivity zone (in the case of CdS).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 6, pp. 682–688, November–December, 1989.     

The chemical composition of mixed wastes: Analysis of the photolysis products of organic ligands

A survey of the literature regarding the composition of mixed wastes originating from the clean ups of spills of radioactive solutions shows that (1) the mixtures obtained in studies of the X-ray and -ray radiolysis, and of the UV-photolysis of organics in aqueous solutions have very similar composition provided the photolysis is carried out with UV beams with wavelengths below 242 nm; (2) the composition of the organic fraction of mixed wastes containing initially EDTA, NTA, and/or citric acid is complex. The mass recoveries are between 20 and 60%; and (3) the UV-photolysis of complexing agents gives much more complex mixtures at high pH than at low pH, because carbonyl compounds are formed, and these compounds undergo complex series of reactions in strongly alkaline solutions. The mixed wastes considered have a high pH due to the necessity of complexing strongly the heavy metals involved in spills. These results are confirmed by an investigation of the properties of the products of the UV-irradiation of EDTA, citric acid and some of their binary mixtures. The products of the esterification by BF₃/BuOH are only partly soluble in methylene chloride. Much better yields are obtained by using BF₃/BuOH as the reagent.¹³C NMR illustrates the composition of the mixture, without requiring a separation and is useful to follow the fate of compounds during their methylene chloride extraction after esterification.     

Si-C coupling reaction of polychloromethanes with HSiCl3 in the presence of Bu4PCl: Convenient synthetic method for bis(chlorosilyl)methanes

Coupling reaction of polychloromethanes CH_4−nCl_n (n = 2-4) with HSiCl₃ in the presence of tetrabutylphosphonium chloride (Bu₄PCl) as a catalyst occurred at temperatures ranging from 30 °C to 150 °C. The reactivity of polychloromethanes increases as the number of chlorine-substituents on the carbon increases. In the reactions of CCl₄ with HSiCl₃, a variety of coupling products such as bis(chlorosilyl)methanes CH₂(SiCl₃)(SiXCl₂) [X = Cl (1a), H (1b)], (chlorosilyl)trichloromthanes Cl₃CSiXCl₂ [X = Cl (2a), H (2b)], and (chlorosilyl)dichloromthanes Cl₂HCSiXCl₂ [X = Cl (3a), H (3b)] were obtained along with reductive dechlorination products such as CHCl₃ and CH₂Cl₂ depending on the reaction temperature. In the reaction of CCl₄, 2a is formed at the initial stage of the coupling reaction and converted to give CHCl₃ at low temperature of 30 °C, to give 1a, 3a, and CHCl₃ at 60 °C, and to afford 1a as major product and CH₂Cl₂ in competition above 100 °C. Si-H bond containing silylmethanes can be formed by the H-Cl exchange reaction with HSiCl₃. Reaction of CHCl₃ with HSiCl₃ took placed at 80 °C to give three compounds 1a, 3a, and CH₂Cl₂, and finally 3a was converted to give 1a and CH₂Cl₂ at longer reaction time. While the condition for the reaction of CH₂Cl₂ with HSiCl₃ required a much higher temperature of 150 °C. Under the optimized conditions for synthesizing bis(chlorosilyl)methanes 1a,b, a mixture of 1a and 1b were obtained as major products in 65% (1a:1b = 64:1) and 47% (42:5) yields from the reaction of CCl₄ and CHCl₃ at 100 °C for 8 h, respectively, and in 41% (34:7) yield from that of CH₂Cl₂ at 170 °C for 12 h. In the Si-C coupling reaction of polychloromethanes with HSiCl₃, it seems likely that a trichlorosilyl anion generated from the reaction of HSiCl₃ with Bu₄PCl is an important key intermediate.     

Unexpected reactions of dichloro(ethyl)silane with DMSO in organic solvents

The effect of the solvent nature on the composition of the products formed upon the reaction between EtSi(H)Cl₂ and DMSO (molar ratio 1: 1, 0 °C) was revealed. This reaction in non-polar and low polar solvents (toluene, chloroform) gives oligoethyl(hydro)cyclo-siloxanes ((EtSi(H)O) _n , n = 3—8) as the major products in the yields up to 77%. In MeCN, oligoethyl(hydro)cyclosiloxanes are formed along with cyclic monochlorinated siloxanes ((EtSi(H)O) _n (EtSi(Cl)O), n = 2—7) in a ratio of ~7: 3 (68: 29 wt.%). In excess diethyl ether, the overall yield of oligoethyl(hydro)cyclosiloxanes does not exceed 25% and the major products are linear α,ω-diethoxyoligoethyl(hydro)siloxanes (EtO(EtSi(H)O) _n Et, n = 2—7) formed in 70—75% yields. A plausible reaction mechanism leading to the final products was suggested. Apparently, the reaction proceeds via ethyl(hydro)-and chloro(ethyl)silanones as intermediates.     

The effect of chain length of bonded organic phases in reversed phase high performance liquid chromatography

Summary Bonded hydrocarbon phases have been prepared by the reaction of organotrichlorosilanes with silica (Lichrosorb Si-100, 10 m, Merck) using conditions for maximum coverage. Alkyl phases, CH₃ (CH₂)_n-With n=7, 10, 12, 14, 17 and 20 and arylakyl phases, Ph (CH₂)_n—with n=0,2,4,6 were investigated. In reverse phase chromatography using water/methanol phases a linear relationship was between the capacity ratios k and the amount of coverage, independent of chain length. The selectivity, however, depends on the chain length of the bonded phase and molecular structure of the solute, whereas for halogenated benzene derivatives the selectivity is constant, and changing the mobile phase composition shows only a minor effect. The selectivity of 4,4-dibromodiphenyl in relation to the benzene derivatives is strongly influenced by the chain length and solvent composition. The utilization of chemically bonded organic long chain phases with maximum coverage makes it possible to reduce the water content in the water/methanol phase increasing the efficiency and loading capacity. The extent of maximum coverage was slightly dependent on the chain length and showed only a 10% decrease from n-octyl-to heneicosyl phase. Treatment of the bonded organic phase with TMCS was not effective with long chain materials, but further reaction occurred with bonded phenyl phase, which could be shown by IR-analysis.     

Donor number estimation for oxygen- and nitrogen-containing solvents via proton NMR shift of chloroform

A linear correlation was determined for oxygen- and nitrogen-containing solvents between the proton NMR shift of chloroform, dilute in a solvent, and the donor number (DN) of that solvent. Results are given for water and for 13 organic solvents. The best straight line is given by DN=7.4–16.6 (CHCl ₃ ) where (CHCl ₃ ) is the shift of pure chloroform relative to that of chloroform in dilute solution. Donor numbers of several solvents were estimated from the correlation.     

Interaction of fluorine-containing 1,3-dicarbonyl compounds with polyamines

In the reaction of fluorinated copper(II) 1,3-diketonates with diethylenetriamine (or triethylenetetramine) in CHCl₃, N,N-bis(1,3-aminovinylketones) are formed in 21–35% yields. Fluorine-containing 1,3-diketones and 1,3-ketoesters, upon interaction with polyamines without solvent, undergo acid cleavage, forming the corresponding amides. The copper(II) 1,3-ketoesterates are readily cleaved in CHCl₃ at 25°C in excess triethylenetetramine or ethylenediamine.Department of Fine Organic Synthesis, Institute of Organic Chemistry, Ural Branch, Russian Academy of Sciences, 620219 Ekaterinburg. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2591–2596, November, 1992.