Kinetics and Mechanism of the Reaction between Barbituric Acid and Glycidol,Part III: Methylene Group Reaction with Glycidol at High Concentration

The reaction of barbituric acid and glycidol leads to formation of oligoetherols upon addition of glycidol both to the methylene group and imide groups of barbituric acid. The mechanism of reaction was established by kinetic studies on the reaction between 1,3‐dimethylbarbituric acid and glycidol used at high concentration. The obtained rate law and mechanism have been derived from kinetic studies and the results obtained before, where 1,3‐dimethylbarbituric acid and glycidol were used in comparable concentrations. The completed kinetic characteristics of the system is described. It has been found that glycidol reacted with methylene groups of 3‐dimethylbarbituric according to the equation: . The rate‐determining step was transformation of enolate into carbanion. Activation energy of the reaction was 61.3 kJ mol⁻¹ · K⁻¹. Proton transfer from methylene group of 1,3‐dimethylbarbituric into glycidol oxirane oxygen was observed by the ¹H‐NMR spectroscopy.     

The Kinetics and Mechanism of the Reaction between Barbituric Acid and Glycidol,Part II: Glycidol Reacts with Imide and Methylene Groups

Two derivatives of barbituric acid, 5,5‐diethylbarbituric acid and 1,3‐dimethyl‐barbituric acid, were used to react with glycidol. The kinetics of reactions was studied by continuous determination of epoxide number and acidic number in the reaction mixture aliquots. Based upon the kinetic experiments, the rate equation was formulated, which was consistent with product spectral identification of the derivatives as well as with previously studied reaction of barbituric acid with glycidol. Reaction mechanisms of glycidol with methylene and imide groups of barbituric acid have been proposed.     

Brazilian integrated sugarcane-soybean biorefinery: Trends and opportunities

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CO2与缩水甘油醚类单体共聚物的合成及表征

共聚反应;热性能;CO2与缩水甘油醚类单体共聚物的合成及表征     

Hyperbranched PEG by Random Copolymerization of Ethylene Oxide and Glycidol

The synthesis of hyperbranched poly(ethylene glycol) (hbPEG) in one step was realized by random copolymerization of ethylene oxide and glycidol, leading to a biocompatible, amorphous material with multiple hydroxyl functionalities. A series of copolymers with moderate polydispersity ( < 1.8) was obtained with varying glycidol content (3–40 mol‐%) and molecular weights up to 49 800 g mol⁻¹. The randomly branched structure of the copolymers was confirmed by ¹H and ¹³C NMR spectroscopy and thermal analysis (differential scanning calorimetry). MTS assay demonstrated low cell toxicity of the hyperbranched PEG, comparable to the highly established linear PEG.

     

Assessing the emerging biorefinery sector in Canada

The biorefinery is a key concept used in the strategies and visions of many industrial countries. The potential for Canadian biorefineries based on lignocellulosic forest and agricultural residues is examined. The sector is described in terms of research interests, emerging companies, and established corporate interests. It is found that the Canadian biorefining sector currently has an emphasis on specific bioproduct generation, and the process elements required for a true sugar-based process are in the research phase. A Canadian national strategy should focus on increasing forest industry participation, and increasing collaboration with the provinces, particularly in western Canada.     

The Kinetics and Mechanism of the Reaction between Barbituric Acid and Glycidol,Part I: The Products Analysis

The hydroxyalkyl derivatives of barbituric acid (BA) were formed in the reaction between BA and glycidol (GL). The reaction was performed at BA:GL 1:1, 1:2, and 1:4 molar ratios in DMF or without solvent. The progress of reaction was monitored by determination of the epoxide number and IR and NMR spectroscopy. It was found that primary reactive site of BA was C5 and further nitrogen ring atoms. BA was always involved in keto‐enol equilibrium, the latter form being less reactive. The isolated hydroxyalkyl derivatives are useful precursors of oligoetherols with the pyrimidine ring.     

Synthesis of Novel Glycidol Copolymers with Pendant Alkene and Hydroxyl Groups

A series of linear poly glycidol copolymers, tethering with both alkene and hydroxyl groups, were prepared by a combination of anionic ring-opening polymerization （ROP） using specific reactions of ethoxy ethyl glycidyl ether （EEGE） and allyl glycidyl ether （AGE） firstly, and subsequently removal of the protection group of glycidol in EEGE to achieve the linear copolymer pendant with both hydroxyl groups and double bonds. The EEGE/AGE monomer reactivity ratio is measured to be 3.30/1.13. The chemical compositions of the as-synthesized polymers were characterized by tH NMR and GPC, and the glass transition temperatures （Tg） of as-synthesized polymers were determined by DSC. The final copolymers have abundant double bonds and hydroxyl as side groups. Furthermore, the ratio of the double bonds to hydroxyl groups can be controlled by the ratio of the starting materials in a wide range.     

Nitrogen-capped pi-prismands: syntheses and conformational analyses

[structure: see text] The one-pot syntheses of the new diazabicyclophanes 5-7 are described. The benzene rings incorporated in the bridging chains exhibit rotational motion which is examined by means of variable-temperature NMR experiments and semiempirical calculations. X-ray analysis and NMR studies indicate that the metal ion in the endohedral silver(I) complex of 7 fluctuates between the two nitrogen atoms.     

Anthracene-BODIPY cassettes: syntheses and energy transfer

Compounds based on the 4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (BODIPY) framework are excellent fluorescent markers. When BODIPY dyes of this type are conjugated to functionalities that absorb at relatively short wavelengths, those functionalities can, in some molecules, transmit the absorbed energy to the BODIPY which then fluoresces. In such cases the BODIPY fragment acts as an acceptor while the other group serves as a donor. Energy transfer efficiencies in such donor-acceptor cassette systems must vary with the relative orientation of the two components, and with the structure of the linkers that attach them. This study was designed to probe these issues for the special case in which the linkers between the donor and acceptor fragments are conjugated. To do this, the cassettes 3-10 were prepared. Electrochemical studies were performed to provide insight into the degree of donor-acceptor conjugation in these systems. X-ray Crystallographic studies on single crystals of compounds 7 and 9 revealed the favored conformations of the donor and acceptor fragments in the solid state. Absorption, fluorescence, and time-resolved fluorescence spectra of the compounds were recorded, and quantum yields for the cassettes excited at the donor lambda(max) were measured. Fluorescence steady-state anisotropy data were determined for cassettes 3 and 9 to provide information about the mutual direction of the transition dipole moments.     

Recent application of biochar on the catalytic biorefinery and environmental processes

Biochar, produced and activated from thermochemical methods, was applied as catalyst for catalytic biorefinery and environmental pollutant removal. In this review, recent advanced studies of biochar catalyst were discussed.     

Fluoroaryl-substituted aminoalane dimers: syntheses and structures

Six dimeric aminoalanes of formula [Me(2)Al-mu-N(H)Ar(F)](2)(Ar(F)= 4-C(6)H(4)F (1), 2-C(6)H(4)F (2), 3,5-C(6)H(3)F(2)(3), 2,3,4,5-C(6)HF(4)(4), 2,3,5,6-C(6)HF(4)(5) and C(6)F(5)(6)) have been prepared by treatment of the appropriate fluoroaniline with AlMe(3) in toluene solution at 25 degrees C. The structures of 1-6 were determined by X-ray crystallography.     

Recent application of biochar on the catalytic biorefinery and environmental processes

Lignocellulosic biomass is an abundant and environment-friendly source for renewable energy production. The value and application of biochar, which is obtained from the thermochemical conversion of biomass, is increasing rapidly because of its high carbon content and porosity. The property of biochar, such as surface area, porosity, and number of functional groups, can be improved by controlling the conditions of biomass conversion, biochar activation, and functionalization methods. The production and activation of biochar as well as its potential use for soil remediation, pollutant adsorption, and biorefinery have been reviewed extensively over recent decades. This paper provides a conceptual approach for biochar production and activation together with its application as a catalyst for biorefineries and the removal of environmental contaminants.