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1.
Bogusława łęska Błażej Gierczyk Krystian Eitner Volodimir I. Rybachenko Grzegorz Schroeder 《Supramolecular chemistry》2013,25(5):303-310
Three types of silicon podands, Me2Si(OR)2, EtSi(OR)3 and PhSi(OR)3, where R is a polyoxaethylene chain with different numbers of oxygen atoms (two, three or four), were obtained and studied by 1H, 13C and 29Si NMR methods. NMR spectra of 1H, 7Li, 13C, 23Na and 29Si nuclei were also used for the study of lithium, sodium and rubidium complexes with the silicon podands. Theoretical calculations were performed using the PM3 hamiltonian. The heats of reactions between the compounds obtained and SbCl5 were determined. 相似文献
2.
G. Schroeder B. Gierczyk V. Rybachenko B. Brzezinski 《Journal of Molecular Structure》2000,526(1-3):159-163
The heats of reactions between the acyclic and cyclic macro-compounds are determined. The values can be used as a measure of the donor abilities of the macro ligands. Formation of two types of complexes between the macro compounds and SbCl5 is established. The acyclic macro-compounds form 1:1 complexes, whereas the macrocyclic compounds only 1:2 complexes. 相似文献
3.
We attempt to find out the origin of rate difference of the SN2 reaction in the gas phase and in the aqueous solution which is about twenty orders of magnitude. To do this, we calculate the interaction energies of both reactant-complex and activated-complex of the SN2 reaction with the hydrated water molecules and their interaction energy differences, varying the number of hydrated water molecules step by step. The calculated results show that the rate of the SN2 reaction decreases with an increase of the number of hydrated water molecules due to the increase of the reaction barrier height and also about sixty or more water molecules are needed to explain the rate difference of the SN2 reaction in the gas phase and solution. 相似文献
4.
Mohammad Hossein Mashhadizadeh Abbas Shockravi Zakiyeh Khoubi Davood Heidarian 《Electroanalysis》2009,21(9):1041-1047
A new podand of 1,1′‐thia‐bis‐[1‐(chloroethan‐2‐acetamid‐α‐oxy)] naphtol was synthesized and used as a suitable carrier for Ag+ PVC membrane electrode. The electrode exhibited linear response with a Nernstian slope of (59.5±0.8 mV/decade) within a wide concentration range of 1.0×10?7 to 1.5×10?2 mol L?1 silver ions. The electrode had a fast response time of <10 s and detection limit of 8.6×10?8 mol L?1 with a working pH range from 3.7 to 9.0. The electrode was highly selective for Ag(I) ions over a large number of cations such as alkali, alkaline earth, and heavy metal ions. The proposed sensor has been applied as an indicator electrode for indirect determination of vitamin B1 in tablets by determination of Cl? ions in this compound with a standard solution of Ag(NO3). 相似文献
5.
Barbara J. Barker Joseph Rosenfarb Joseph A. Caruso 《Angewandte Chemie (International ed. in English)》1979,18(7):503-507
N-Alkylated ureas, including cyclic derivatives, are readily obtained pure. These stable compounds are already used as industrial solvents owing to their considerable solvent power, their wide liquid range, and their favorable dielectric constants and dipole moments. They are being increasingly employed as reaction media for electrochemical and analytical studies. 相似文献
6.
《Analytical letters》2012,45(12):2243-2258
Abstract A procedure for the UV/VIS-spectroscopic determination of water by the use of a solvatochromic pyridiniumphenolate betaine is given. The water content of organic solvents is calculated by a two parameter equation from λmax of the dye. A typical, detection limit is of the order of 1 mg in 1 ml solvent for routine spectrometers. The parameters for the determination of water are given for a number of commonly used solvents. 相似文献
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《Analytical letters》2012,45(5):451-460
Abstract Tris (acetylacetonato)cobalt(III) and tris(acetylacetonato)-chromium(III) have been eluted by gel chromatography through styrene-divinylbenzene copolymer gel using an organic solvent as an eluent. Elution counts of these chelates in these solvents reflect some mutual interactions between metal chelate, gel and solvent. When benzene or chloroform was used as an eluent, sieving effect seems to be dominant for the separation of these chelates. Discussions were done in relation to solubility parameters of the solvent, the complex and the gel. 相似文献
9.
Xin Wen Sifan Du Prof. Li Zhang Prof. Minghua Liu 《Angewandte Chemie (International ed. in English)》2023,62(46):e202311816
Herein, chiral deep eutectic solvents (DES) are prepared by lauric acid as hydrogen bond donors (HBD) and chiral menthol as hydrogen bond acceptors (HBA). When achiral fluorescent molecules are dopedin the menthol-based chiral DES, they emit circularly polarized luminescence (CPL) with handedness controlled by the molecular chirality (l or d ) of menthol. Remarkably, the strategy is universal and a series of achiral fluorescent molecules can be endowed with CPL activity, showing a full-color and white CPL upon appropriate mixing, which paves the way to prepare white CPL materials. Interestingly, CPL appears only in a certain temperature range in the DES. Variable-temperature spectra and other characterization methods reveal that the H-bond network in the chiral DES plays an important role in inducing CPL. This work unveils how the interior structure as well as the hydrogen-bond network of a chiral DES can transfer its chirality to achiral luminophores for the first time and realizes a full-color and white CPL in a DES. 相似文献
10.
《Physics and Chemistry of Liquids》2012,50(6):703-714
Experimental solubilities are reported at 25.0°C for xanthene dissolved in 34 different organic nonelectrolyte solvents containing ether-, chloro-, hydroxy-, cyano and t -butyl-functional groups. Results of these measurements are used to test the applications and limitations of expressions derived from Mobile Order theory. For the 27 solvents for which predictions could be made computations show that Mobile order theory does provide fairly reasonable estimates of the saturation mole fraction solubilities. Average absolute deviation between predicted and observed values is 71.4%. 相似文献
11.
Dr. Ming Liu Dr. Na Li Dr. Xuemin Wang Jia Zhao Prof. Di-Chang Zhong Prof. Wei Li Prof. Xian-He Bu 《Angewandte Chemie (International ed. in English)》2023,62(20):e202300507
The mismatched fast-electron-slow-proton process in the electrocatalytic oxygen evolution reaction (OER) severely restricts the catalytic efficiency. To overcome these issues, accelerating the proton transfer and elucidating the kinetic mechanism are highly sought after. Herein, inspired by photosystem II, we develop a family of OER electrocatalysts with FeO6/NiO6 units and carboxylate anions (TA2−) in the first and second coordination sphere, respectively. Benefiting from the synergistic effect of the metal units and TA2−, the optimized catalyst delivers superior activity with a low overpotential of 270 mV at 200 mA cm−2 and excellent cycling stability over 300 h. A proton-transfer-promotion mechanism is proposed by in situ Raman, catalytic tests, and theoretical calculations. The TA2− (proton acceptor) can mediate proton transfer pathways by preferentially accepting protons, which optimizes the O−H adsorption/activation process and reduces the kinetic barrier for O−O bond formation. 相似文献
12.
Inorganic Molten Salts as Solvents for Cellulose 总被引:6,自引:0,他引:6
S. Fischer H. Leipner K. Thümmler E. Brendler J. Peters 《Cellulose (London, England)》2003,10(3):227-236
Inorganic molten salts can be used as efficient solvents for cellulose in a wide range of degrees of polymerization. Furthermore, molten salts can be applied as reaction medium for the derivatization of cellulose. For both dissolution and derivatization of cellulose, knowledge of the solution state as well as information about chemical interactions with the solvent system is essential. Using the melts of LiClO4·3H2O, NaSCN/KSCN/LiSCN·2H2O and LiCl/ZnCl2/H2O as cellulose solvents, factors which determine the dissolving ability will be discussed. Besides the specific structure of the molten salt hydrate, the cation and the water content of the melt are the most important factors for the dissolving capability of a molten salt hydrate system. FT-Raman spectroscopy, 7Li and 13C NMR spectroscopy were applied to describe solvent–cellulose interactions and the state of cellulose dissolved in the molten salts. Using Raman and solid state NMR spectroscopy it was proved that cellulose is amorphous in the frozen solvent system. The application of inorganic molten salts as a medium for cellulose functionalization is demonstrated for cellulose carboxymethylation and acetylation. 相似文献
13.
A Series of new heterocyciophosphorus compounds were synthesizec oy cyclocondensa-tion of 1-acetothiosemicarbazide with P(NR2)3. The further reaction of these compounds with P(NR2)3 gave different compounds depending upon different reaction conditions. The 1-acetothiosemicarbazide can also condense with PCl3 and PCl5 similarly, The reaction mechanism, the spectral properties and chemical properties of these products were also studied and discussed. 相似文献
14.
In this work, the absorption spectral characteristics and color‐change reaction mechanism of cobalt(II) chloride(CoCl2) in alcohol organic solvents has been investigated in the presence of water, and then the optimum conditions for determining the water content in the solvents were selected. Results indicated that the absorption spectra of CoCl2 in alcohols decreased with the increment of water content. At the maximum absorption wavelength of 656 nm, there were good linear relationships between the logarithm of the absorbance and the water content in organic solvents such as ethanol, n‐propanol, iso‐propanol and n‐butanol with related coefficients in the range of 0.9996?0.9998. For determining water content in organic solvents, this method is simple, rapid, sensitive, reproducible and environmentally friendly. Furthermore, the linear range cannot restrict determination of the water content in organic solvents. This method had been applied to determine the water content in ethanol and n‐butanol with satisfactory recovery of water in n‐butanol between 98.41%?101.29%. 相似文献
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16.
The B–B bond of bis(trisyl)oxadiborirane OB2R2 (R = C(SiMe3)3) is opened by amides R′CO(NHR″) to give the dioxaazadiboracyclohexanes [–BR–O–BR–NR″–CHR′–O–] (R′/R″ = H/H, H/Me, H/Et, Me/H: 5 a – d ). The amide MeCO(NHMe) yields 5 e (R′/R″ = Me/Me), when an excess of the amide is applied for 24 h, but yields an isomeric 1 : 1 adduct ( 6 e ), when a stoichiometric amount of the amide is applied for 15 h; upon refluxing this isomer in hexane, it is transformed into 5 e . 相似文献
17.
《Physics and Chemistry of Liquids》2012,50(3):255-268
Experimental solubilities are reported at 25.0°C for monuron (also called 3-(4-chlorophenyl)-1,1-dimethyl urea) dissolved in 18 different organic nonelectrolyte solvents containing ether-, chloro-, hydroxy-, ester, methyl- and t -butyl-functional groups. Results of these measurements, combined with published literature data, are used to test the applications and limitations of expressions derived from Mobile Order theory. For the 21 nonalcoholic solvents for which predictions could be made computations show that Mobile Order theory does provide fairly reasonable estimates of the saturation mole fraction solubilities. Average absolute deviation between predicted and observed values is 48.4%. Monuron solubilities in the alcohol solvents are used to calculate stability constants for presumed solute-solvent hydrogen bonds that are believed to occur in solution. 相似文献
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Contrary to widely held opinion, for many reactions in organic and organometallic chemistry it is possible to define nucleophilicity and electrophilicity parameters that are independent of the reaction partners. This phenomenon, discovered by Ritchie during the early 1970s for reactions of highly stabilized carbenium and diazonium ions with n-nucleophiles, also occurs with reactions of carbenium ions with aliphatic and aromatic π-electron systems and in hydride transfer reactions. With the aid of the scales of nucleophilicity and electrophilicity set out here, which extend over eighteen orders of magnitude, forecasts can be made about the feasibility and rate of a given CC bond formation, ionic reduction, or diazo coupling. Linkage with the reactivity scales of Ritchie and Sweigart/Kane-Maguire enables a unified treatment of a large number of polar reactions. 相似文献
20.
Thermal analysis techniques were performed to reveal ‘crystalline solvate’ behavior between organic compounds and polar solvents.
Diimide-dicarboxylic acid (DIDA) was formed by reacting 3,3'-diaminodiphenylsulfone (3,3'-DPS) or 4,4'-diaminodiphenylsulfone
(4,4'-DPS) with trimellitic anhydride (TMA) in some polar solvents (PSv). The products could crystallize upon cooling in a
polar solvent media to form a solvate containing a finite quantity of solvents, leading to what can be termed as ‘crystalline
solvates’ (CS). This study has demonstrated that sampling techniques in TG and DSC must be kept to be as similar as possible,
which is a critical point in practices of thermal analysis techniques. DSC analysis revealed that there are two endothermic
peaks in the CS, with the lower one being the de-solvate temperature of CS (T
d) at which the solvated solvent molecules were removed, and the higher peak being the melting point of the de-solvated DIDA
(T
m). T
d was found to vary with the types of polar solvents and structures of DIDA. The TG result indicated that most of the sulfone-based
DIDA-CS contained 2 moles of solvent per mole of solvate. X-ray analysis revealed that different crystalline structures were
found for DIDA-CS solvated with different solvent molecules, but all de-solvated DIDA possessed the same crystal unit.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献