Phase and miscibility behavior of binary lipid systems

Differential scanning calorimetry was applied to study the phase diagrams of the following binary lipid systems: myristic acid (C₁₃COOH) / pentadecanoic acid (C₁₄COOH); palmitic acid methyl ester (C₁₅COOMe) / heptadecanoic acid methyl ester (C₁₆COOMe); palmitic acid methyl ester (C₁₅COOMe) / stearic acid methyl ester (C₁₇COOMe); palmitic acid methyl ester (C₁₅COOMe) / arachidic acid methyl ester (C₁₉COOMe). A distinct succession in the phase diagram types and phase regions was observed, according to the chemical structure of the mixing components.In the systems C₁₃COOH/C₁₄COOH; C₁₅COOMe/C₁₆COOMe and C₁₆COOMe/ C₁₇COOMe, both components are completely miscible in the low- and high-temperature phase. Contrasting with these three binary lipid systems, the system C₁₅COOMe/ C₁₄COOMe shows complete miscibility only in the high-temperature phase, but almost complete demixing in the solid state. In the phase diagram an incongruent melting 11 complex is built up. This complex forms an eutectic mixture with the phase of C₁₅COOMe and a peritectic system with C₁₉COOMe.     

Hydrolysis of α-amino acid esters in mixed ligand complexes with bis(piperidine)palladium(II)

Summary -Amino acid esters, NH₂CH(R)CO₂R, interact withcis- [Pd(pip)₂(OH₂)2]²⁺ (pip = piperidine) in aqueous solution according to the equilibrium (1). The kinetics of hydrolysis of the ester group in the complexes [Pd(pip)₂(NH₂CH(R)CO₂R°)]²⁺ have been studied by pH-stat methods and rate constants for the kinetic processes (2) and (3) determined for methyl glycinate, ethyl glycinate, ethyl L--alaninate, methyl L--phenylalaninate, ethyl picolinate, methyl L-cysteinate and methyl L-histidinate. For the first five esters, substantial rate enhancements are observed for base hydrolysis (factors of 2.8 × 10⁵ fold for methyl glycinate to 4.9 × 10⁷-fold for ethyl picolinate). The effects with methyl L-cysteinate and methyl L-histidinate are much less marked as the mixed ligand complexes do not involve alkoxycarbonyl donors. Thus with methyl cysteinate donation occursvia the primary amino group and the thiolate group. Activation parameters have been determined for reactions (2) and (3) with methyl glycinate. Possible mechanisms for these hydrolytic reactions are considered. Nucleophilic attack by water or hydroxide ion on a chelate ester species satisfactorily accounts for the experimental observations.     

Reaction of the N,N-dimethylamide and methyl ester of 3-phenyl-3-chloro-2-ketopropionic acid with triphenylphosphine

Conclusions The dimethylamide of 3-phenyl-3-chloro-2-ketopropionic acid reacts with Ph₃P to give -(N,N-dimethyloxamoyl)benzyltriphenylphosphonium chloride. In the presence of methanol, this reaction gives dimethyl(phenylpyruvoyl)amide and Ph₃PO.2. The methyl ester of 3-phenyl-3-chloro-2-ketopropionic acid reacts with Ph₃P to give methoxycarbonylstyryloxytriphenylphosphonium chloride, which, upon heating in benzene at reflux, gives methyl -chlorocinnamate and Ph₃PO.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1395–1396, June, 1989.     

Investigations in the field of complex lipids

Summary 1. The methyl ester of N-(N-carbobenzoyglycyl)-methoxyneuraminic acid has been synthesized by the carbodiimide method.2. Hydrogenation of the methyl ester of N-(N-carbobenzoxyglycyl)-methoxyneuraminic acid over Pb/BaSO₄ has given the methyl ester of N-glycyl-methoxyneuraminic acid.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 4, pp. 241–244, 1965     

The effect of water on the rate and direction of the oxidation of organic substances

The effect of the polarity of the medium on the rate and direction of oxidation processes has been studied. It has been shown that the rate of oxidation of methyl ethyl ketone in aqueous solutions diminishes with increase in the water concentration. A considerably greater reduction in the rate of decomposition of the RO ₂ ^. radical is observed than in the rate of the interaction of this radical with methyl ethyl ketone, which results in an increase in the selectivity of the oxidation process. When methyl ethyl ketone is diluted with water in the molar ratio C₄H₈O H₂O=120, the quantity of acetic acid in the reaction products amounts to 98–99% of the methyl ethyl ketone consumed. The suggestion is made that the high selectivity of the oxidation of methyl ethyl ketone in aqueous solutions is due to the effect of the dielectric constant of the medium on the ratio between the two parallel reactions of the peroxide radical RO ₂ ^. .     

Decomposition of benzenediazonium fluoborate in esters of α,β-unsaturated acids

Summary It was shown that In contrast to the Meerwein-Koelsch reaction, the decomposition of benzenediazonlum fluoborate In esters of ,-unsaturated acids proceeds by a heterolytlc mechanism with the phenyl attacking the -carbon and the carbalkoxyl group of these esters. The reaction with ethyl crotonate gave -methylatropic acid (after hydrolysis) and a small amount of a dibasic acid, C₁₄H₁₆O₄ (or C₁₄H₁₄O₄). With methyl acrylate it gave atropic acid, phenyl acrylate, and a smaller amount of -methyl--phenylglutaric acid. With methyl methacrylate It formed benzylacrylic acid and the product of further conversions of phenyl methacrylate, namely the keto phenol 2-methyl-5-hydroxyindan-1-one.     

Photolysis of methyl ester of 1β,2β-epoxy-3-keto derivative of gibberellin A1

Conclusion A study was made of the photolytic opening of the epoxide ring in the methyl ester of the 1,2-epoxy-3-keto derivative of gibberellin A₁, which led to the formation of the methyl ester of 1,3-dihydroxyepial-logibberic acid and the methyl ester of the 1-hydroxy-3-keto derivative of gibberellin A₁.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 459–461, February, 1972.     

Homogeneous Rhodium–Copper–Halide Catalytic Systems for the Oxidation and Oxidative Carbonylation of Methane

Homogeneous catalytic systems for the oxidation and oxidative carbonylation of methane in aqueous trifluoroacetic acid solutions were developed. The system included rhodium compounds and copper compounds as cocatalysts. Methanol, methyl trifluoroacetate, formic acid, and acetic acid were the reaction products. The process was accompanied by the intense oxidation of CO to CO₂. Regularities of the process were studied, optimum process parameters were determined, and conditions at which methyl trifluoroacetate was formed with 90% selectivity were found. Kinetic isotope effects with respect to the solvent were determined. For the formation of organic products, k _H/k _D was 1, whereas it was 1.6 for the oxidation of CO. Studies were also performed with the use of compounds containing the ¹⁸O isotope. Conceivable mechanistic models of this process are discussed.     

Significance of solvation in the effectiveness of inhibitor action

It is shown that the effectiveness of inhibitors in the oxidation of methyl ethyl ketone is significantly less than in a hydrocarbon medium; this is due to the formation of hydrogen bonds between ketone and inhibitor. The elementary rate constants of the interaction of the RO ₂ ^. radical of methyl ethyl ketone with -naphthol and phenol derivatives were measured. In aqueous solutions of methyl ethyl ketone, the k _i ^exp value for all inhibitors drops with increasing H₂O concentration. The interaction constants of solvated RO ₂ ^. ...H₂O peroxide radicals with the inhibitor and the equilibrium constants for the formation of H-bonds between inhibitor and water were studied. The k _i ^exp with hydroquinone in the oxidation of C₄H₈O in acetic acid were measured.     

On the mechanism of isomerization in the esters of some α,β-unsaturated carboxylic acids—II

The effect of a phenyl group on the mechanisms of isomerization in the ionized methyl esters of simple α,β-unsaturated acids (methyl acrylate and related compounds) has been investigated with the aid of deuterium labelling as well as information from mass analysed ion kinetic energy spectra and first field free region metastable peak shapes. Substitution of a hydrogen atom of the O? CH₃ group by a phenyl group (benzyl acrylate and homologues) greatly enhances the rate of [ester] → [acid] isomerizations (loss of H₂O and COOH˙). It is inferred that this is due to an accelerating effect of the phenyl group on the first and the third steps (ring opening of the key intermediate ion which has the structure of the ionized enol form of γ-butyrolactone) of the reaction whose mechanism is basically the same as that in methyl acrylate. A phenyl group present at the α- or β-position of the vinylic double bond appears to suppress the [ester] → [acid] isomerization in some compounds by promoting other reactions or opening up a new reaction pathway, i.e. the loss of CH₂O from ionized methyl atropate for which mechanisms are proposed.     

Conversion of methoxyperfluoroisobutene to α-methylhexafluoroisobutyric acid fluoride by a phase transfer catalyst

Methoxyperfluoroisobutene was converted to α-methylhexafluoroisobutyric acid fluoride by a catalytic amount of phase transfer catalyst in quantitative yield.Methoxyoctafluoroisobutane, (CF₃)₂CHCF₂OCH₃ (1) which is synthesized by the reaction of perfluoroisobutene and methanol is a useful starting material for producing various fluorochemicals. It is ready hydrolyzed in sulfuric acid to give the methyl ester of hexafluoroisobutyric acid [1, 2].Dehydrofluorination of the ether (1) gives a vinyl ether (2) which is converted to a useful monomer (3), made previously by another route [3].

     

Model porphyrin precursors: 1,2,4,5‐tetrakis(cyanomethyl)­benzene,methyl 3,4,5‐triacetoxy­benzoate and 2‐(N‐phthalimidomethyl)benzoic acid

In the crystalline state, the centrosymmetric mol­ecule 1,2,4,5‐tetrakis­(cyano­methyl)­benzene, C₁₄H₁₀N₄, has one cyano­methyl group in the benzene plane and one cyano­methyl group rotated 67.2 (2)° out of the benzene plane. Molecules of methyl 3,4,5‐tri­acetoxy­benzoate, C₁₄H₁₄O₈, form chains with each mol­ecule twisted 89.6 (1)° from the preceding mol­ecule. In this orientation, a close C—H?O contact is formed, with an H?O distance of 2.34 Å. The structure of 2‐(N‐phthalimido­methyl)­benzoic acid, C₁₆H₁₁NO₄, reveals hydrogen‐bonded dimers linked by the carboxyl groups of adjacent mol­ecules. The O4?O3 distance is 2.636 (2) Å and the O4—H?O3 angle is 171 (2)°.     

Basicity and structure of α,β-unsaturated heterocyclic ketones

The protolytic equilibrium constants in the system H₂SO₄-CH₃COOH and the shifts in frequency of the OH stretching vibrations ( _OH) of phenol and trifluoroacetic acid resulting from the perturbational effects of hydrogen bonding with the carbonyl group have been measured for -alkyl-substituted heterocyclic analogs of chalcone. It has been shown that introduction of a methyl group into the -position of five-membered heterocycles results in an increase in the proton-acceptor properties of chalcone analogs, and moreover, the influence of the methyl group on the polarization of the carbonyl group is substantially increased on passing from the furan ring to the hiophene and selephene rings, perhaps as a result of the participation of the d-orbitals of sulfur and selenium in the electronic interactions. The benzene ring transmits the electronic effect of the methyl group to almost the same extent as the furan ring.For Part VI, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1176–1180, September, 1970.     

Catalytic decompostiton of methyl nitrite over supported palladium catalysts in vapor phase

The vapor phase catalytic decomposition of methyl nitrite over supported palladium catalysts has been investigated. The catalytic activities were ranked in the following order: Pd/-Al₂O₃> Pd/A.C > Pd/-Al₂O₃ >Pd-Ti/-Al₂O₃. The acidic supports, such as HY zeolite, -Al₂O₃ and SiO₂ also exhibited moderate activity for methyl nitrite decomposition reactions. Several unusual features in the present decomposition reactions of methyl nitrite are discussed. A possible successive dehydrogenation mechanism was proposed to explain the facts observed in this study.     

Synthesis and properties of novel methanofullerenes having ethylthienyl and/or n-pentyl group for photovoltaic cells

Novel methanofullerenes 3 having ethylthienyl and/or n-pentyl groups were designed and synthesized for the purpose of developing new acceptors for an organic photovoltaic cell with higher performance than that of the [6,6]-phenyl-C₆₁-butylic acid methyl ester (PCBM) used as the standard acceptor. The electronic absorption spectra and cyclic voltammetry (CV) of 3, PCBM, and [6,6]-(thiophene-2-yl)-C₆₁-butylic acid methyl ester (ThCBM) were measured to estimate solubility and reduction potentials as characteristics of n-type semiconductor for organic photovoltaic devices. The CV measurements revealed reversible reduction waves for all of the methanofullerenes and the first reduction potentials of the n-pentyl-substituted 1-(5-ethylthiophene-2-yl)-[6,6]-methanofullerene[60] (3b) and 1-phenyl-[6,6]-methanofullerene[60] (3c) were negatively shifted compared to those of the corresponding terminal methyl ester-substituted homologues (3a and PCBM). The performances of photovoltaic devices consisting of 3b and 3c were slightly higher than those of PCBM.     

Polyphenols and acids of Ulugbekia tschimganica

Summary From the herbage ofUlugbekia tschimganica (B. Fedtsch.) Zak two new phenolcarboxylic acids have been isolated in the form of their methyl derivatives: methyl ulugbekate C₁₉H₁₈O₆ (I) and methyl ulugbinate acid C₂₀H₂₂O₇ (II), mp 228°C.It has been established that (I) most probably has the structure of 1,5-bis(3,4-dihydroxyphenyl)-3-methoxycarbonylpent-1-ene and (II) that of 1,5-bis(2,4-dihydroxyphenyl)-3-methoxycarbonylpent-1-ene and (II) that of 1,5-bis(2,4-dihydroxyphenyl)-3-methoxycarbonyl-4-methoxypent-2-ene.The presence of fumaric, caffeic, and chlorogenic acids, and also of mono and dimethyl fumarates has been established chromatographically.The roots have yielded a new phenolic terpenoid, C₁₆H₂₀O₄, for which 3-(2,4-dihydroxyphenyl)-1-(5,5-dimethyltetrahydropyran-2-ylidene)propene has been suggested as one of the most likely structures.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 601–607, September–October, 1976.     

Shock-initiated decomposition of tetramethylgermane and the reaction of methyl radicals with toluene

The shock-initiated decomposition of tetramethylgermane (1078–1242 K) has been found to involve successive elimination of methyl radicals with the rate constant k₁ for the first step given by In the presence of excess toluene the products were CH₄ (major), C₂H₄, and C₂H₆. Results relevant to the reaction of methyl radicals with toluene compared to methyl radical recombination are discussed.     

Telomerization of acrylic monomers with iodoform

Conclusions Together with dimethylformamide, iron pentacarbonyl initiates the telomerization of acrylonitrile, methyl acrylate, and methyl methacrylate with iodoform, resulting in the formation of telomeric homologs of the series CHI₂(CH₂CRI)_nR and CHI₂(CH₂CHR)_nR (n=1, 2; R=H, CH₃; R=CN, COOCH₃).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2284–2287, October, 1985.     

Synthesis of gibberellins A8 and A56 from gibberellin A3

A mixture of gibberellin A₃ derivatives with 1(10)-ene-2,3-diol and 1(10)-ene-2,3-diol (2:5) groups, readily obtained from gibberellin A₃, has been used for a new and simple synthesis of gibberellin A₈ and its esters. The hydrolysis of GA₃ and the iodolactonization of a mixture of the 2-epimers was carried out in aqueous solution in a single flask, as also was a synthesis of GA₅₆ from GA₃ by a method that we have modified. The mixture of 1-iodides of GA₈ and GA₅₆ was separated by chromatography on SiO₂ in the form of methyl or p-bromophenacyl esters which were then deiodinated and the methyl or p-bromphenacyl ester of GA₈ was isolated. Free GA₈ was obtained by the dephenylation of the latter ester. By two-dimensional NMR spectroscopy we succeeded in assigning all the signals in the¹³C and¹H NMR spectra of the methyl esters of GA₈ and GA₅₆. In an attempt to obtain GA₅ methyl ester by the action of trimethylchlorosilane/sodium iodide on the 2,3-diol system in GA₅₆ methyl ester, the 8,13-epimer of the latter was formed, the structure of its molecule being established from the results of X-ray structural analysis.Novosibirsk Institute of Organic Chemistry, Siberian Division of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 663–669, September–October, 1994.     

Spectral and kinetic characteristics of the α-propionic acid methyl ester radical in cyclohexane and water

The -propionic acid methyl ester radical was produced in dissociative electron capture reaction of 2-chloropropionic acid methyl ester. The absorption maxima of the radical are at 310 and 300 nm in cyclohexane and water with extinction coefficients of 440±50 and 400±50 mol^–1 dm³ cm^–1. The second order decay rate parameter in water is (2.3±0.5)×10⁹ mol^–1 dm³ s^–1. The peroxy radicals have the characteristics: _max=265–270 nm, _max=700–900 mol^–1 dm³ and 2k=(7±2)·10⁸ mol^–1 dm³ s^–1.