Charge-transfer polycondensation of diethyl chelidonate with hexamethylenediamine

Polycondensation of diethyl chelidonate (DEC) with hexamethylenediamine (HMD) took place very rapidly under mild conditions to form a corresponding polyamide. The polycondensation reaction proceeded through the formation of a charge-transfer complex between DEC and HMD, which transformed rapidly into polyamide. Various reaction conditions to form polyamide from DEC and HMD were investigated in terms of solvents, concentration, and temperature. Model reaction of DEC with primary or tertiary amines confirmed the formation of a charge-transfer complex which transformed into chelidonamide except tertiary amine. The polycondensation of DEC with HMD was accelerated by irradiation with light.     

Active polycondensation of diethyl 2,3,4,5-tetrahydroxyadipate with diamines

Polycondensation of diethyl 2,3,4,5-tetrahydroxyadipate with various diamines was carried out in solutions under mild conditions. The polycondensation reaction occurred rapidly even at room temperature in polar solvents such as alcohols, and in aqueous solution a cyclic product was obtained instead of linear polymers although the reaction with diamines was completed within several minutes. Polymers obtained from diethyl 2,3,4,5-tetrahydroxyadipate were a linear polyamide having pendant hydroxyl groups, which decomposed on heating at around 200°C. A solid-phase polycondensation of the precursor polyamide yielded a high molecular weight polyamide.     

少量水存在下桂利嗪和茜素在甲醇中的荷移反应

研究了在少量水存在下桂利嗪和茜素在甲醇介质中的电荷转移反应,确定了最佳反应条件。研究表明,反应生成1∶1型荷移络合物,该络合物的λmax=527nm,表观摩尔吸光系数ε=2.94×103L·mol-1·cm-1,桂利嗪浓度在25～200mg/L范围内符合比尔定律,相对标准偏差为1.55%(n=6),平均回收率在98%以上。     

Mono-acylation of symmetric diamines in the presence of water

Simply reacting equal equivalents of symmetric diamines with esters or carbonates in the presence of a suitable amount of water gave mono-acylated products in good to quantitative yields.     

Synthesis of hydrophilic polyamide from L-tartarate and diamines by active polycondensation

Dimethyl L-tartarate underwent polycondensation reaction with hexamethylenediamine in solutions at 30°C to form polyamide having pendent hydroxyl groups. Solvents had a great influence on polymer yields and diglyme, tetrahydrofuran (THF) or dimethylsulfoxide (DMSO) were favorable in respect of polymer yields. Solution viscosities of resulting polyamide were as low as 0.1 to 0.2. However, post-polycondensation of the precursor polyamide at solid phase yielded hydrophilic polyamide having film-forming ability. The polyamide decomposed at 210°C by heating.     

Synthesis of aromatic polyamides by 1-hydroxybenzotriazole-catalyzed polycondensation of active aromatic diesters with aromatic diamines

Catalytic actions of various additives were studied in the polycondensation of di(4-nitrophenyl) isophthalate with bis(4-aminophenyl) ether in N-methyl-2-pyrrolidone, and 1-hydroxybenzotriazole (HOBt) was found to be a highly effective catalyst that yielded high-molecular-weight polyamide. In addition to the polycondensation of the 4-nitrophenyl ester, the polymerization of negatively substituted phenyl esters like di(2,4,5-trichlorophenyl) isophthalate was also accelerated by HOBt. For the HOBt-catalyzed aminolysis of esters a bifunctional concerted mechanism that involves an eight-membered transition state was proposed.     

Direct polycondensation of hydroxybenzoic acids with diphenyl chlorophosphate in the presence of ethers

The effects of a modification of the relative reactivity of carboxyl groups to hydroxy groups in monomers on the direct polycondensation of hydroxybenzoic acids was investigated. Polycondensation with diphenyl chlorophosphate (DPCP) was largely promoted by carrying out the reaction in the presence of ethers which are capable of complexing with carboxyl groups in the monomers. The amount of alkyl ethers, such as, poly(ethylene oxide) (PEO) corresponding to an equivalent unit mole of carboxyl groups was effectively added. The molecular weights of the polymers produced increased with the higher molecular weights of PEO, showing maximum values by use of PEO of 1–2.5 × 10⁵.     

Selective Hofmann alkylation of aromatic-aliphatic diamines in the presence of carbon dioxide

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Synthesis of diethyl ether in presence of zeolite catalysts

Conclusions Ethanol, containing 10–30 mole% of C₂H₅I, is converted mainly to diethyl ether in the presence of zeolites NaX, NaY, HY, and HM, at a temperature of 160–200° and atmospheric pressure. Intense dehydration of the ethanol to ethylene occurs without the C₂H₅I.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 196–199, January, 1979.     

Microwave-assisted preparation of cyclic ureas from diamines in the presence of ZnO

A microwave-assisted facile method for the preparation of various ureas, cyclic ureas, and urethanes has been developed that affords nearly quantitative yield of products at 120 °C (150 W), 71 kPa within 10 min using ZnO as a catalyst. The enhanced selectivity in this reaction is attributed to the deployment of ZnO whose absence results in poor yield and the generation of byproducts.     

Charge transfer in the TCNQ-sexithiophene complex

Molecular crystals from thiophene molecules can be doped with TCNQ-F4 molecules for use in all-organic optoelectronic and semiconductor devices. The charge transfer and the molecular orbital energy level formation in between these two organic molecules are investigated here by density functional theory calculations. The isolated molecules are calculated nonbonded and bonded together, forming a charge transfer complex (CTC). The relaxed structure of the complex shows essentially coplanar and centered molecules with the alpha-sexithiophene rings tilted alternatingly by 4.8 degrees. The bond formation of these molecules results in a charge transfer of approximately 0.4 e from the alpha-sexithiophene to the TCNQ-F4 molecule. The highest occupied molecular orbital-lowest unoccupied molecular orbital gap width is reduced as compared to the isolated molecules due to the newly formed orbitals in the CTC. Upon adsorption on a Au(111) surface, electrons are transferred onto the molecule complex, thereby causing the molecular levels to align asymmetric with respect to the charge neutrality level. The theoretical results for the single molecule and CTC layer are compared to experimental photoemission and scanning tunneling spectroscopy results.     

Sulfur-containing polymers. V. Preparation of polyoxycarbonylsulfenamides by polycondensation of bis(oxycarbonylsulfenyl chlorides) with diamines

Polyoxycarbonylsulfenamides (POSA) have been prepared by interfacial polycondensation of bis(oxycarbonylsulfenyl chlorides) with diamines. The polymers obtained ranged in physical form from crystalline solids to resinous materials depending on the kind of both bis(oxycarbonylsulfenyl chlorides) and diamines used. Some of the polymers gave transparent pliable films from chloroform solution. The polymer films decomposed with liberation of carbonyl sulfide on being subjected to ultraviolet radiation.     

Esterification of allylic alcohols with benzoic acid in the presence of diethyl azodicarboxylate and triphenylphosphine

Stereoselectivity of esterification reaction of some allylic alcohols, mainly unsaturated pyranosides, with benzoic acid in the presence of diethyl azodicarboxylate and triphenyl phosphine was investigated. The reaction was found to proceed with inversion, without allylic rearrangement.     

Reaction of (ethoxycarbonylfuryl)methanephosphonates with diethyl carbonate in presence of sodium foil

Reaction of (ethoxycarbonylfuryl)methanephosphonates with diethyl carbonate in presence of sodium foil is studied. It is shown that if the acidifying group is conjugated with the carbanion center of 2-furylmethanephosphonate, addition of the carbanion to the carbonyl group of diethyl carbonate takes place to give 2-furylacetic acid derivatives in high yield. Sodium salts of these CH-acids are synthesized, isolated, and characterized. Their alkylation with alkyl bromoacetates is carried out. If ethoxycarbonyl group is not conjugated with the carbanion center, conversion of starting phosphonate and yield of adduct sharply decreases. Alkyl (2- and 4-ethoxycarbonylfur-3-yl)methanephosphonates immediately after acylation with diethyl carbonate are reduced with sodium-diethyl carbonate system to form alkyl 1-(2- and 4-ethoxycarbonylfur-3-yl)-ethanephosphonates. Formation of intermediate reduction product, the phosphorylated furylacetic aldehyde is also fixed spectroscopically. Simultaneously with the reduction dealkylation of ester group of starting phosphonates and alkyl 1-(3-furyl)ethanephosphonates takes place leading to the carboxylic acid salts. Alkyl (2-methyl-5-ethoxycarbonylfur-3-yl)methanephosphonate does not take part in condensation. It gives only the products of dealkylation under the action of sodium ethylate forming from diethyl carbonate.     

Photoelectric properties of the charge-transfer complex of polyvinylcarbazole with tetracyanoquinodimethane

Photoelectric properties of a polymeric PVK-TCNQ charge transfer complex have been investigated as a function of component weight ratio, wavelength and intensity of light, temperature and voltage; the investigation also covered the kinetics of photoconductivity. The results have been interpreted using Poole-Frenkel's theory and Onsager's theory of recombination.     

Uranyl ion complexation by citric and citramalic acids in the presence of diamines

Uranyl nitrate reacts with citric (H4cit) or d-(-)-citramalic (H3citml) acids under mild hydrothermal conditions and in the presence of diamines to give different complexes which are all characterized by the presence of 2:2 uranyl/polycarboxylate dianionic dimers or of polymeric chains based on the same dimeric motif. Each uranium ion is chelated by the two ligands through the alkoxide and the alpha- or beta-carboxylate groups, the second beta-carboxylic group in citrate being uncoordinated. The uranium coordination sphere is completed by either a water molecule or the beta-carboxylate group of a neighboring unit, thus giving zero- or one-dimensional assemblages, respectively. The evidence for [UO2(Hcit)]2 dimers in the solid state confirms previous results from potentiometric and EXAFS measurements on solutions. Depending on the diamine used (DABCO, 2,2'- and 4,4'-bipyridine, [2.2.2]cryptand) and its ability to form divergent hydrogen bonds or not, different uranyl/polycarboxylate topologies are obtained, thus evidencing template effects, and extended hydrogen bonding gives two- or three-dimensional assemblages. These results, together with those previously obtained with NaOH as a base, add to the knowledge of the uranyl/citrate system, which is much investigated for its environmental relevance.     

Conjugate reduction of aryl acrylates with tributyltin hydride in the presence of magnesium bromide diethyl etherate

The conjugate reduction of aryl acrylates performed with tributyltin hydride in the presence of magnesium bromide diethyl etherate in dichloromethane gave the corresponding saturated esters in moderate to high yields. The reduction of α-methylene-γ-benzyloxycarboxylic acid esters proceeded syn-selectively, but α-methylene-β-oxycarboxylic acid esters afforded reductive elimination products under the reaction conditions.