STUDY ON THE CHAIN-EXTENDING REACTION OF POLY (ETHYLENE TEREPHTHALATE) WITH 2, 2′-BIS (4H-3, 1-BENZOXAZIN-4-ONE)

2,2'-Bis (4H-3, 1-benzoxazin-4-one) (BBON) has been proved to be an effective chainextender for poly (ethylene terephthalate) (PET). In order to study the reaction mechanismand kinetics of chain-extending reaction, β-bishydroxyethylene terephthalate (BHET) wasselected as model compound. The NMR data, IR spectra and number average molecularweight (M_n) of the products obtained from the reaction of BBON and BHET verify thatBBON is a hydroxyl-reactive extender. The mechanism was discussed. Kinetics dataindicate that extending reaction is a second order reaction, and BBON has high reactivity.The activation energy (E_a) was measured.     

纳米Cu2O催化二苯甲烷二氨基甲酸苯酯无溶剂热分解制备二苯甲烷二异氰酸酯

研究了无溶剂条件下纳米Cu₂O催化二苯甲烷二氨基甲酸苯酯(MDPC)热分解制备二苯甲烷二异氰酸酯(MDI),考察了纳米Cu₂O的制备条件与反应条件对MDPC热分解反应性能的影响.结果表明,水解法制备的纳米Cu₂O在Ar中于300℃焙烧2h,其催化性能最佳;最佳的反应条件为Cu₂O用量为原料总重的0.06%,反应温度220℃,反应压力0.6kPa,反应时间12min,此时MDPC转化率达到99.8%,MDI选择性86.2%.     

Synthesis of poly(4-vinylbenzocyclobutene) and its reaction with dienophiles

4-Vinylbenzocyclobutene ( 1 ) was prepared by the nickel-catalyzed coupling reaction of 4-bromobenzocyclobutene with vinylbromide in 70% yield. Radical homopolymerization of 1 at 60°C for 24 h afforded poly(4 vinylbenzocyclobutene) [poly( 1 )] in 89% yield and radical copolymerizations of 1 with styrene (St) or methyl methacrylate (MMA) were carried out to obtain the corresponding copolymers. The Q = 1.07, e = 0.046. As a model reaction of the polymer reaction of the polymer reaction of poly( 1 ) and poly(4-vinylbenzocyclobutene-co-styrene) [copoly( 1 -St)] with dienophiles, the Diels-Alder reaction of benzocyclobutene with N-phenylmaleimide (MI) or maleic anhydride (MANH) was carried out to determine the optimum reaction conditions. Under the optimum condition, the Diels-Alder reaction of poly( 1 ) and copoly( 1 -St) with MI and MANH in the presence of 4-tert-butyl-catechol as an inhibitor were carried out to yield the corresponding polymers in good yields. The properties (solubilities, T_g, and temperature of 10% weight loss) of the products obtained from the polymer reaction were different from these of poly( 1 ). © 1995 John Wiley & Sons, Inc.     

Kinetics of interaction of 3-aminopropyltriethoxysilane with silica gel using elemental analysis and 29Si NMR spectra

 Three silica gel sample systems, modified with 3-amino-propyltriethoxy silane (APTS), were prepared by sequentially sampling the reaction mixture at various time intervals. The concentrations of 3-aminopropylsilyl groups (APS) bound on the silica surface were determined by elemental analysis. For the same sample systems, ²⁹Si NMR intensities of an (–O)₄Si species belonging only to the silica gel particles and corrected by a cross-polarization correction factor were also measured. Both the APS-concentrations and the correc-ted ²⁹Si NMR intensities depended upon reaction time, reflecting the rate of the APTS–silica gel reaction. Kinetic analysis of these data was made by use of the Gauss–Newton method, and the overall reaction was found to consist of three reaction processes (an initial fast reaction, a slower second reaction and a much slower third reaction). In particular, the conversion of (–O)₃SiOH to (–O)₄Si is predominant in the second reaction process and the pore size of a silica gel particle affects the reaction mechanism. Received: 1 November 1996 Accepted: 24 January 1997     

Towards Stereoselective Synthesis of the C(31)–C(39) and C(20)–C(27) Fragments of Phorboxazole A

The stereoselective synthesis of the C(31)–C(39) and C(20)–C(27) fragments of phorboxazole A ( 1 ) was achieved from commercially available and inexpensive D ‐mannitol. Crimmins aldol reaction and a decarboxylative Claisen‐type reaction are the key steps for the C(31)–C(39) fragment, and L ‐proline‐catalyzed aldol reaction, Sharpless asymmetric epoxidation, and epoxide ring opening reaction with Gilman's reagent are the key steps for the C(20)–C(27) fragment of phorboxazole.     

Nucleophilic Addition to Carbonyl Compounds. Competition Between Hard (Amine) and Soft (Phosphite) Nucleophile

Abstract

In the reaction mixture of carbonyl compound, amine and diethyl phosphite several different reactions are observed. The formation of aminophosphonate (Kabachnik- Fields reaction) is frequently accompanied with the formation of hydroxyphosphonate (Pudovik reaction) or product of its rearrangement. ^1–3 This is due to the presence of one electrophile (carbonyl compound) and two nucleophiles (amine and phosphite) in the reaction mixture, which may compete for the electrophilic center.     

Microwave-induced domino-Knoevenagel-hetero Diels–Alder reaction—an easy route to di[1]benzopyrano[2,3-b:4′,3′-d]pyridine

MW-irradiation of a well-ground equimolar mixture of 2-(N-alkynyl-N-aryl)aminochromone-3-carbaldehyde and dimedone underwent domino-Knoevenagel-hetero Diels–Alder (DKHDA) reaction for nonterminal alkynes, whereas conventional heating of the above reaction mixture in ethanol in the presence of pyridine accomplished alkyne-carbonyl metathesis (ACM) reaction or both ACM and DKHDA reaction. Here is the first example of an organo-catalyzed ACM reaction.     

Precipitation polymerization of 2‐hydroxyethyl methacrylate in supercritical carbon dioxide

We report the successful precipitation polymerization of 2‐hydroxyethyl methacrylate (HEMA) in supercritical carbon dioxide (scCO₂) at pressures ranging from 15 to 27 MPa utilizing 2, 2′‐azobisisobutyronitrile (AIBN) as a free radical initiator. The effects of the reaction pressure, initiator concentration, monomer concentration, reaction temperature, and reaction time were investigated. Analyses by scanning electron microscopy (SEM) indicated that in all reaction conditions, polymerization in the absence of stabilizer led to the formation of large aggregates of partially coalesced particles, with diameters of approximate 1–10 µm. Analyses by gel permeation chromatography (GPC) indicated that for the reaction pressure, initiator concentration, monomer concentration, reaction temperature, and reaction time studied there are appreciable effect on product molecular weight. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermokinetics on the reaction of formation of Dy[(C5H8NS2)3(C12H8N2)]

The enthalpy change of formation of the reaction of hydrous dysprosium chloride with ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen•H₂O) in absolute ethanol at 298.15 K has been determined as (-16.12 ± 0.05) kJ•mol^-1 by a microcalormeter. Thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), rate constant and kinetics parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of the reaction have also been calculated. The enthalpy change of the solid-phase reaction at 298.15 K has been obtained as (53.59 ± 0.29) kJ•mol^t-1 by a thermochemistry cycle. The values of the enthalpy change of formation both in liquid-phase and solid-phase reaction indicated that the complex could only be synthesized in liquid-phase reaction.

     

Ab initio Mechanism Study on the Reaction of Chlorine Atom with Formic Acid

The potential energy surface(PES) for the reaction of Cl atom with HCOOH is predicted using ab initio molecular orbital calculation methods at UQCIDS(T,full)6-311 G(3df,2p)//UMP2(full)/6-311 G(d,P) level of theory with zero-point vibrational energy (ZPVE) correction.The calculated results show that the reaction mechanism of Cl atom with formic acid is a C-site hydrogen abstraction reaction from cis-HOC(H)O molecule by Cl atom with a 3.73kJ/mol reaction barrier height,leading to the formation of cis-HOCO radical which will reacts with Cl atom or other molecules in such a reaction system.Because the reaction barrier height of O-site hydrogen abstraction reaction from cis-HOC(H)O molecule by Cl atom which leads to the formation of HCO2 radical is 67.95kJ/mol,it is a secondary reaction channel in experiment,This is in good agreement with the prediction based on the previous experiments.     

Hypervalent Iodine Reagents Enable Chemoselective Deboronative/Decarboxylative Alkenylation by Photoredox Catalysis

Chemoselective C(sp³)? C(sp²) coupling reactions under mild reaction conditions are useful for synthesizing alkyl‐substituted alkenes having sensitive functional groups. Reported here is a visible‐light‐induced chemoselective alkenylation through a deboronation/decarboxylation sequence under neutral aqueous reaction conditions at room temperature. This reaction represents the first hypervalent‐iodine‐enabled radical decarboxylative alkenylation reaction, and a novel benziodoxole‐vinyl carboxylic acid reaction intermediate was isolated. This C(sp³)? C(sp²) coupling reaction leads to aryl‐and acyl‐substituted alkenes containing various sensitive functional groups. The excellent chemoselectivity, stable reactants, and neutral aqueous reaction conditions of the reaction suggest future biomolecule applications.     

Thermokinetics on the reaction of formation of Dy[(C<Subscript>5</Subscript>H<Subscript>8</Subscript>NS<Subscript>2</Subscript>)<Subscript>3</Subscript>(C<Subscript>12</Subscript>H<Subscript>8</Subscript>N<Subscript>2</Subscript>)]

The enthalpy change of formation of the reaction of hydrous dysprosium chloride with ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen?H₂O) in absolute ethanol at 298.15 K has been determined as (-16.12 ± 0.05) kJ?mol^-1 by a microcalormeter. Thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), rate constant and kinetics parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of the reaction have also been calculated. The enthalpy change of the solid-phase reaction at 298.15 K has been obtained as (53.59 ± 0.29) kJ?mol^t-1 by a thermochemistry cycle. The values of the enthalpy change of formation both in liquid-phase and solid-phase reaction indicated that the complex could only be synthesized in liquid-phase reaction.     

CIONO2与O(3P)的反应机理

采用密度泛函方法Ｂ３ＬＹＰ／６－３１Ｇ＾＊研究了反应Ｏ（＾３Ｐ）＋ＣｌＯＮＯ２→ＣｌＯ＋ＮＯ３反应Ｏ（＾３Ｐ）＋ＣｌＯＮＯ２→Ｏ２＋ＣｌＯＮＯ的反应机。该结果与大部分实验者的推论是一致的,对于后一反应,其两种反应途径的活化势垒较为相近,表明两种反应途径均是可能的。     

Kinetics of the Oxidation of Tartrazine with Peroxydisulfate in the Presence and Absence of Catalysts

 The food dye tartrazine is oxidized with peroxydisulfate in the absence and in the presence of Ag(I) and Fe(III) catalysts. In the absence of these metal ions, the reaction shows second-order kinetics, first-order in each of the reacting species. With the Ag(I) ion in the medium the reaction proceeds considerably faster, but still follows second-order kinetics. The reaction rate depends on the concentration of Ag(I) and S₂O₈ ²⁻, but is independent of the concentration of the substrate. When Fe(III) acts as the catalyst, a marked enhancement in the reaction rate is observed, and the reaction proceeds through two parallel pathways, the catalyzed and the noncatalyzed. The catalyzed path follows third order kinetics, being first-order in substrate, oxidant, and catalyst concentration. Mechanisms of the noncatalyzed as well as the Ag(I) and Fe(III) catalyzed reaction systems are proposed.     

Development of an efficient and safe process for a grignard reaction via reaction caloremetry

A Grignard reaction of reactantA and phenyl magnesium chloride is used to make a pharmaceutical intermediate at the production scale. The elimination of protecting groups onA was proposed as a means to reduce synthesis costs. This new synthesis route, however, had process efficiency and safety issues associated with it: (1) build-up of unreactedA in the reactor, (2) influence ofA's particle size on the reaction rate, (3) the sensitivity of the reaction rate to the reaction temperature and to the (changing) solvent composition, and (4) the highly exothermic nature of the reaction.The Mettler RC1 Reaction Calorimeter was used to quantify the influence of solvent composition, temperature, and particle size on the reaction rate. Results indicated a dramatic effect of solvent composition and reaction temperature on the reaction rate; for example, over a temperature range of just 30°C, the reaction time decreased from more than a day to just a few minutes. At such high reaction rates, the vessel jacket could not remove the reaction heat sufficiently and the internal temperature rose adiabatically.These results were used to make process design and operation recommendations for safe and efficient plant operation with this modified Grignard reaction system.The authors would like to thank the following for their assistance in this work: E. Daugs for preparing the Grignard reagents, K.L. Gonzales for her help in running the experiments and in the subsequent data work-up; P.M. Russell for his assistance in the design of the slurry addition assembly, and K. Chritz and J. Engel for performing the HPLC analyses of the samples.     

Homogeneous catalysis of O-silylation reactions using octacarbonyldicobalt(O)

Octacarbonyldicobalt(O) has been used to catalyze the reaction of R₃SiH (R = Et and EtO) with R′OH (R′ = Me, Et, n-Pr, i-Pr, and t-Bu). The reaction of MeOH with (EtO)₃SiH, in toluene at 27 °C, was first-order with respect to the catalyst, to the silane, and to the alcohol. The order of reactivity of the alcohols was MeOH > EtOH > n-PrOH > i-PrOH > t-BuOH, reflecting the steric effect associated with the size of the organic group. Addition of triphenyl phosphine (Ph₃P) to the reaction mixture slowed down the reaction. The reaction proceeds faster if nonpolar solvents are used, and the rate of the reaction is very sensitive to temperature.     

Chimie organométallique: IV. Réversibilité de l'amination des complexes diènes-palladium (II)

An elimination reaction takes place with palladium compounds arising from the reaction of benzylamine with 1,5-cyclooctadiene—PdCl₂ (IV) and 1,5-hexadiene—PdCl₂ (VI) complexes. Evidence for this retroamination reaction is given by the reaction of hydrogen chloride on the cyclooctadiene derivative (V) and by a study of the products resulting from the amination of the hexadiene complex (VI) under various conditions.     

碳纳米管的聚合物功能化与结构控制:聚合物接枝碳纳米管

碳纳米管高分子化是发展高性能的聚合物基纳米功能材料的重要研究方向,本文从"grafting-to"和"grafting-from"两种方式对聚合物接枝碳纳米管的最新进展进行了系统综述。"Grafting-to"方法主要包括羧基衍生反应(酰化、酯化)、加成反应(大分子自由基加成、叠氮环加成)和硫醇偶联反应。"Grafting-from"方法包括普通自由基聚合、可控/活性自由基聚合、离子聚合、开环聚合和逐步聚合反应,其中碳纳米管表面引发活性自由基聚合进一步分为原子转移自由基聚合、氮氧稳定自由基聚合和可逆加成-断链转移聚合。此外,本文还简述了碳纳米管自身的聚合反应,并探讨了目前聚合物修饰碳纳米管所面临的问题和今后的发展方向。     

Cu(II) catalyzed reaction between phenyl hydrazine and toluidine blue—dual role of acid

The detailed kinetics of Cu(II) catalyzed reduction of toluidine blue (TB⁺) by phenyl hydrazine (Pz) in aqueous solution is studied. Toluidine white (TBH) and the diazonium ions are the main products of the reaction. The diazonium ion further decomposes to phenol (PhOH) and nitrogen. At low concentrations of acid, H⁺ ion autocatalyzes the uncatalyzed reaction and hampers the Cu(II) catalyzed reaction. At high concentrations, H⁺ hinders both the uncatalyzed and Cu(II) catalyzed reactions. Cu(II) catalyzed had stoichiometry similar to the uncatalyzed reaction, Pz+2 TB⁺+H₂O=PhOH+2 TBH+2 H⁺+N₂. Cu(II) catalyzed reaction occurs possibly through ternary complex formation between the unprotonated toluidine blue and phenyl hydrazine and catalyst. The rate coefficient for the Cu(II) catalyzed reaction is 2.1×10⁴ M⁻² s⁻¹. A detailed 13‐step mechanistic scheme for the Cu(II) catalyzed reaction is proposed, which is supported by simulations. © 1999 John Wiley & Sons, Inc., Int J Chem Kinet 31: 271–276, 1999     

Stoichiometry of the reaction of diphenylchlorophosphine with dimethylformamide in the presence of NaI

Stoichiometric relations of initial compounds and reaction products in the synthesis of N,N-dialkyl-(diphenylphosphinomethylene)iminium are established; the second reaction product is diphenylphosphinic iodide. Bringing triphenylphosphine into the reaction increases the N,N-dialkyl(diphenylphosphinomethylene)-iminium yield approximately twice. One of the reaction intermediates is shown to be iododiphenylphosphine. The reaction can be regarded as disproportionation.