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991.
Vinh X. Truong Kun Zhou George P. Simon John S. Forsythe 《Macromolecular rapid communications》2015,36(19):1729-1734
This communication describes the first application of cycloaddition between an in situ generated nitrile oxide with norbornene leading to a polymer crosslinking reaction for the preparation of poly(ethylene glycol) hydrogels under physiological conditions. Hydrogels with high water content and robust physical strength are readily formed within 2–5 min by a simple two‐solution mixing method which allows 3D encapsulation of neuronal cells. This bioorthogonal crosslinking reaction provides a simple yet highly effective method for preparation of hydrogels to be used in bioengineering.
992.
Thermal behavior of 1,2,3-triazole nitrate 总被引:1,自引:0,他引:1
Liang Xue Feng-Qi Zhao Xiao-Ling Xing Zhi-Ming Zhou Kai Wang Hong-Xu Gao Jian-Hua Yi Si-Yu Xu Rong-Zu Hu 《Journal of Thermal Analysis and Calorimetry》2011,104(3):999-1004
The thermal decomposition behaviors of 1,2,3-triazole nitrate were studied using a Calvet Microcalorimeter at four different
heating rates. Its apparent activation energy and pre-exponential factor of exothermic decomposition reaction are 133.77 kJ mol−1 and 1014.58 s−1, respectively. The critical temperature of thermal explosion is 374.97 K. The entropy of activation (ΔS
≠), the enthalpy of activation (ΔH
≠), and the free energy of activation (ΔG
≠) of the decomposition reaction are 23.88 J mol−1 K−1, 130.62 kJ mol−1, and 121.55 kJ mol−1, respectively. The self-accelerating decomposition temperature (T
SADT) is 368.65 K. The specific heat capacity was determined by a Micro-DSC method and a theoretical calculation method. Specific
heat capacity equation is
C\textp ( \textJ mol - 1 \text K - 1 ) = - 42.6218 + 0.6807T C_{\text{p}} \left( {{\text{J mol}}^{ - 1} {\text{ K}}^{ - 1} } \right) = - 42.6218 + 0.6807T (283.1 K < T < 353.2 K). The adiabatic time-to-explosion is calculated to be a certain value between 98.82 and 100.00 s. The critical
temperature of hot-spot initiation is 637.14 K, and the characteristic drop height of impact sensitivity (H
50) is 9.16 cm. 相似文献
993.
Ting Chen Zhaona Liu Weijie Lu Xingfeng Zhou Houyi Ma 《Electrochemistry communications》2011,13(10):1086-1089
A novel converse dealloying method was developed to fabricate free-standing nanoporous silver (np-Ag). One remarkable characteristic of the new dealloying method is that inert component (Au) is selectively removed from Au–Ag alloys while active component (Ag) is left undissolved. Thiourea plays a key role in the formation of a free-standing porous Ag framework since it not only leads to anodic dissolution of Au component but also causes the surface passivation of Ag component. Because of the excellent electrocatalytic activity toward the reduction of trichloroacetic acid (TCA), the as-prepared np-Ag materials can be directly used as working electrodes to detect TCA in the concentration range from 2.50 to 25.0 mM. 相似文献
994.
Jian-Hua Yi Feng-Qi Zhao Ying-Hui Ren Bo-Zhou Wang Cheng Zhou Xiao-Ning Ren Si-Yu Xu Hai-Xia Hao Rong-Zu Hu 《Journal of Thermal Analysis and Calorimetry》2011,104(3):1029-1036
The high-pressure thermal properties and their correlation with burning rates of the composite modified double base (CMDB)
propellants containing 3,6-bis (1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine (BTATz), a substitute of hexogen (RDX),
were investigated using the high-pressure differential scanning calorimetry (PDSC). The results show that there is a main
exothermal decomposition process with the heating of each propellant. High pressure can restrain the volatilization of NG,
accelerate the main decomposition reaction, and make the reaction occur easily. High pressure can change the main decomposition
reaction mechanism function and kinetics, and the control process obeys the rule of Avrami–Erofeev equation at high pressure
and chemical reaction at normal pressure. However, the mechanism function can not be changed by the ballistic modifier. The
correlation between PDSC characteristic values and burning rates was carried out and found that u and
( p \Updelta H\textd / \Updelta T ) 1 / 2 \left( {p \, \Updelta H_{\text{d}} { / }\Updelta T} \right)^{ 1 / 2} keep a good linear relation, k
u
keeps a similar changing trend with u, and it can be used to study the effect of the ballistic modifier or the other component on the burning rates. 相似文献
995.
Alkali catalytic hydrolysis of poly(vinyl acetate) (PVAc) grafting onto polyurethane film surface was a heterogeneous reaction. The hydrolysis was carried on the PVAc particle surface, and the concentration of the alkali in the system was tested by titration method. The kinetics of PVAc surface hydrolytic reaction was studied by simple second-order reaction model. From linear regression analysis of experimental data, we inferred that the activation energy (E a ) and pre-exponential factor (A) of PVAc surface hydrolytic reaction were 70.7 ± 0.2 kJ mol?1 and (5.7 ± 0.5) × 1012 kg mol?1 s?1, respectively. The results of transmission electron microscopy stated that the apparent hydrolytic degree was 2.1% when the surface of PVAc particle hydrolyzed absolutely. 相似文献
996.
997.
Ming‐Zhong Wang Dr. Cong‐Ying Zhou Dr. Zhen Guo Dr. Ella Lai‐Ming Wong Dr. Man‐Kin Wong Prof. Chi‐Ming Che 《化学:亚洲杂志》2011,6(3):812-824
Chiral binuclear gold(I) phosphine complexes catalyze enantioselective intermolecular hydroarylation of allenes with indoles in high product yields (up to 90 %) and with moderate enantioselectivities (up to 63 % ee). Among the gold(I) complexes examined, better ee values were obtained with binuclear gold(I) complexes, which displayed intramolecular AuI AuI interactions. The binuclear gold(I) complex 4c [(AuCl)2( L3 )] with chiral biaryl phosphine ligand (S)‐(−)‐MeO‐biphep ( L3 ) is the most efficient catalyst and gives the best ee value of up to 63 %. Substituents on the allene reactants have a slight effect on the enantioselectivity of the reaction. Electron‐withdrawing groups on the indole substrates decrease the enantioselectivity of the reaction. The relative reaction rates of the hydroarylation of 4‐X‐substituted 1,3‐diarylallenes with N‐methylindole in the presence of catalyst 4c [(AuCl)2( L3 )] / AgOTf [ L3 =(S)‐(−)‐MeO‐biphep], determined through competition experiments, correlate (r2=0.996) with the substituent constants σ. The slope value is −2.30, revealing both the build‐up of positive charge at the allene and electrophilic nature of the reactive AuI species. Two plausible reaction pathways were investigated by density functional theory calculations, one pathway involving intermolecular nucleophilic addition of free indole to aurated allene intermediate and another pathway involving intramolecular nucleophilic addition of aurated indole to allene via diaurated intermediate E2 . Calculated results revealed that the reaction likely proceeds via the first pathway with a lower activation energy. The role of AuI AuI interactions in affecting the enantioselectivity is discussed. 相似文献
998.
Mingjie Wen Xiru Cao Yongqi Zhang Meng Liang Tianlei Zhang Balaganesh Muthiah Ke Zhou Soumendra K. Roy Makroni Lily 《International journal of quantum chemistry》2020,120(23):e26389
A detailed theoretical study on the reaction mechanisms for the formations of H2O2 + 3O2 from the self-reaction of HO2 radicals under the effect of NH3, H3N···H2O, and H2SO4 catalysts was performed using the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ method. The rate constant was computed using canonical variational transition state theory (CVT) with small curvature tunneling (SCT). Our results indicate that NH3-, H3N···H2O-, and H2SO4-catalyzed reactions could proceed through both one-step and stepwise routes. Calculated rate constants show that the catalyzed routes in the presence of the three catalysts all prefer stepwise pathways. Compared to the catalytic efficiency of H2O, the efficiencies of NH3, H3N···H2O, and H2SO4 are much lower due to their smaller relative concentrations. The present results have provided a definitive example of how basic and acidic catalysts influence the atmospheric reaction of HO2 + HO2 → H2O2 + 3O2. These results further encourage one to consider the effects of basic and acidic catalysts on the related atmospheric reactions. Thus, the present investigation should have broad implications in the gas-phase reactions of the atmosphere. 相似文献
999.
Yaosong Huang Yugong Chen Mingfei Zhou 《International journal of quantum chemistry》2020,120(24):e26415
Hexamethyldisiloxane [HMDSO, (CH3)3-SiOSi-(CH3)3] is an important precursor for SiO2 formation during flame-based silica material synthesis. As a result, HMDSO reactions in flame have been widely investigated experimentally, and many results have indicated that HMDSO decomposition reactions occur very early in this process. In this paper, quantum chemical calculations are performed to identify the initial decomposition of HMDSO and its subsequent reactions using the density functional theory at the level of B3LYP/6-311+G (d, p). Four reaction pathways—(a) Si O bond dissociation of HMDSO, (b) Si C bond dissociation of HMDSO, (c) dissociation and recombination of Si O and Si C bonds, and (d) elimination of a methane molecule from HMDSO—have been examined and identified. From the results, it is found that the barrier of 84.38 kcal/mol and Si O bond dissociation energy of 21.55 kcal/mol are required for the initial decomposition reaction of HMDSO in the first pathway, but the highest free energy barrier (100.69 kcal/mol) is found in the third reaction pathway. By comparing the free energy barriers and reaction rate constants, it is concluded that the most possible initial decomposition reaction of HMDSO is to eliminate the CH3 radical by Si C bond dissociation. 相似文献
1000.
Dr. Jian‐Bo Xie Prof. Jian‐Hua Xie Xiao‐Yan Liu Qian‐Qian Zhang Prof. Qi‐Lin Zhou 《化学:亚洲杂志》2011,6(3):899-908
The iridium complexes of chiral spiro aminophophine ligands, especially the ligand with 3,5‐di‐tert‐butylphenyl groups on the P atom ( 1c ) were demonstrated to be highly efficient catalysts for the asymmetric hydrogenation of alkyl aryl ketones. In the presence of KOtBu as a base and under mild reaction conditions, a series of chiral alcohols were synthesized in up to 97 % ee with high turnover number (TON up to 10 000) and high turnover frequency (TOF up to 3.7×104 h−1). Investigation on the structures of the iridium complexes of ligands (R)‐ 1a and 1c by X‐ray analyses disclosed that the 3,5‐di‐tert‐butyl groups on the P‐phenyl rings of the ligand are the key factor for achieving high activity and enantioselectivity of the catalyst. Study of the catalysts generated from the Ir‐(R)‐ 1c complex and H2 by means of ESI‐MS and NMR spectroscopy indicated that the early formed iridium dihydride complex with one (R)‐ 1c ligand was the active species, which was slowly transformed into an inactive iridium dihydride complex with two (R)‐ 1c ligands. A plausible mechanism for the reaction was also suggested to explain the observations of the hydrogenation reactions. 相似文献