共查询到20条相似文献,搜索用时 453 毫秒
1.
Katsuhiro Inomata Reina Doi Erina Yamada Hideki Sugimoto Eiji Nakanishi 《Colloid and polymer science》2007,285(10):1129-1137
Amphiphilic polymers Cn-PHEG consisting of water-soluble poly[N
5-2-(hydroxyethyl) l-glutamine] (PHEG) and hydrophobic alkyl chain (carbon number n = 12, 14, 16, or 18) attached at the PHEG terminal was prepared, and association behavior and structure of associate for
Cn-PHEG in selective solvent (water/ethylene glycol mixed solvent) have been investigated. α-Helix content of PHEG block for
all the polymers increased with weight fraction of ethylene glycol in the mixed solvent (W
EG). By light scattering measurements, formation of a small micelle was suggested for C14-, C16-, and C18-PHEG when W
EG = 0. With the increase in W
EG, appearance of a larger associate was revealed for C16- and C18-PHEG. Evaluated molecular weight and radius of gyration suggested
that the micelle is star-like sphere when W
EG = 0 and worm-like cylinder when W
EG = 0.7. C12-PHEG did not demonstrate any distinct micellization behavior because of the weak hydrophobicity of C12 chain. 相似文献
2.
27Al NMR spectroscopy is a power tool for investigation of the aluminate species existing in both aqueous and non-aqueous solutions. Aluminum-27 nuclear magnetic resonance (NMR) spectroscopy also can be used to determine thermodynamic properties of complexes in the solution. In this report, 27Al NMR spectroscopy was used to characterize species present in alkaline alcoholic aluminate solutions. (2-Hydroxyethyl)trimethylammonium (2-EHTMA) hydroxide was used as base. In solution of CH3OH and H2O in a mole ratio of 64:1 it was possible to detect five signals by aluminum-27 NMR, indicating formation of [Al(OH)4−n(CH3OH)n](n−1)+ (n = 0,1, 2, 3 and 4) species. Aluminum-27 NMR spectroscopy has also used for investigation of the species present in the ethanolic 2-HETMA aluminate solutions. The equilibrium constants for the formation of aluminate complexes were also determined for both methanolic and ethanolic aluminate solutions. Aluminum-27 NMR spectra of propanolic and butanolic 2-HETMA aluminate solutions were also studied. 相似文献
3.
A. A. Kamyshova A. Z. Kreindlin P. V. Petrovskii A. S. Peregudov Yu. A. Borisov A. A. Koridze 《Russian Chemical Bulletin》2005,54(12):2805-2812
The reaction of [Cp*2RuBr]+Br− with bromine in CH2Cl2 (CD2Cl2) in an inert atmosphere at room temperature produces the complexes [Cp*Ru(Br)C5Me4CH2Br]+Br3
− (syn conformer), [Cp*Ru(Br)C5Me3(CH2Br)2]+ (syn and anti conformers), and [Ru(Br)(C5Me4CH2Br)2]+ (syn conformer). All complexes were characterized by 1H and 13C NMR spectroscopy; the former complex, by elemental analysis. These complexes were also prepared by the reaction of [Cp*RuC5Me4CH2]+BF4
− with bromine in CH2Cl2.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2712–2718, December, 2005. 相似文献
4.
《International journal of mass spectrometry and ion processes》1986,68(1-2):99-110
The gas-phase clustering reactions of proton in propanol and acetone, and chloride ions in acetone were investigated. The −ΔHn−1,n values obtained for clustering reactions (n−1,n) were as follows: H+ (C3H7OH)n−1 + C3H7OH ⇄ H+ (C3H7OH)n, (2, 3) 18.9 kcal mol−1, (3, 4) 14.2 kcal mol−1, (4, 5) 11.7 kcal mol−1; H+ (CH3COCH3)2 + CH3COCH3 ⇄ H+ (CH3COCH3)3, 14.2 kcal mol−1; and Cl− + CH3COCH3 ⇄ Cl− (CH3COCH3), 12.4 kcal mol.−1. For clustering reactions, Cl− (CH3COCH3n−1 + CH3COCH3 ⇄ Cl− (CH3COCH3)n where n ≥ 2, the equilibria could not be established; probably due to the isomerization of ligand acetone molecules from the keto to enol form. 相似文献
5.
A. A. Medzhidov P. A. Fatullaeva S. M. Peng R. G. Ismaiylov G. H. Lee S. R. Garaeva 《Russian Journal of Coordination Chemistry》2012,38(2):126-133
Reactions of N-(2-hydroxy-3,5-R1,R2-benzyl)-4-aminoantipyrines with copper acetate in ethanol gave complexes with Schiff bases (SBs) rather than the expected
complexes with reduced SBs; i.e., the starting ligands undergo oxidative dehydrogenation during the complexation reaction.
The corresponding complexes with reduced SBs were obtained from sodium salts of the ligands and cupric sulfate in aqueous
solutions. Kinetic measurements showed that oxidative dehydrogenation occurs in the heteroleptic complexes Cu(L
i
)(CH3COO)(X) (L
i
H are derivatives of N-(2-hydroxy-3,5-R1,R2-benzyl)-4-aminoantipyrines; i = 6–10; X = H2O, CH3OH, CH3CH2OH) but does not occur in the complexes CH3OH, CH3CH2OH. The absence of oxidative dehydrogenation of the ligands in Cu(L
i
)2 · H2O can be explained by the octahedral environment of the Cu2+ ion and, accordingly, the absence of the coordination site for molecular oxygen. The molecular structures of two Cu(II) complexes
with SBs were determined by X-ray diffraction. 相似文献
6.
Lenoble V Garnier C Masion A Ziarelli F Garnier JM 《Analytical and bioanalytical chemistry》2008,390(2):749-757
This work allowed the characterization of the Cd-binding sites of two compounds taken as models for exudates, the main components
of soil organic matter (SOM). The studied compounds were exopolysaccharides (EPS), specifically exudates of roots (polygalacturonic
acid) and of soil bacteria (Phytagel). Potentiometric acid–base titrations were performed and fitting of the obtained results
indicated the presence of two main classes of acidic sites, defined by their pK
a values, for both EPS but of a different nature when comparing the two compounds. The two studied exopolysaccharides presented
different acidic/basic site ratios: 0.15 for Phytagel and 0.76 for polygalacturonic acid. Spectroscopic techniques (13C/113Cd NMR, FTIR) distinguished different Cd surroundings for each of the studied EPS, which is in agreement with the titration
results. Furthermore, these analyses indicated the presence of –COOH and –OH groups in various proportions for each exopolysaccharide,
which should be linked to their reactivity towards cadmium. Cadmium titrations (voltammetric measurements) also differentiated
different binding sites for each compound and allowed the determination of the strength of the Cd-binding site of the EPS.
Fitting of the results of such voltammetric measurements was performed using PROSECE (Programme d’Optimisation et de Speciation Chimique dans l’Environnement), a software coupling chemical speciation calculation and binding parameter optimization. The fitting, taking into account
the Cd2+/H+ competition towards exopolysaccharides, confirmed the acid-base titrations and spectroscopic analyses by revealing two classes
of binding sites: (i) one defined as a strong complexant regarding its Cd2+–EPS association (logK = 9–10.4) and with basic functionality regarding H+–EPS association (pK
a = 11.3–11.7), and (ii) one defined as a weak complexant (logK = 7.1–8.2) and with acidic functionality (pK
a = 3.7–4.0). Therefore the combination of spectroscopic analyses, voltammetry, and fitting allowed the precise characterization
of the binding sites of the studied exopolysaccharides, mimicking the main SOM components. Furthermore, the binding parameters
obtained by fitting can be used in biogeochemical models to better define the role of key SOM compounds like exudates of roots
and of soil bacteria on trace metal transport or assimilation. 相似文献
7.
The mass spectra of the dissociative electron-impact ionization products of telomers formed upon the radiation-chemical telomerization
of tetrafluoroethylene in acetone were measured over the range of m/z from 1 to 204. The most intense bands at m/z = 43, 51, and 57 were attributed to the CH3CO+, CF2H+ and CH3COCH2+ cations—the main dissociation products of the H(C2F4)
n
CH2COCH3 telomers. The telomer composition was consistent with a radical telomerization mechanism, in which chain growth and chain
transfer are due to the formation of the CH3COCH2· radical. Based on published data supplemented with quantum-chemical calculations, the enthalpies of formation of the radicals
R(CF2)
n
(n = 2–8; R = H, CH3, CH3CO, and CH3COCH2) were tabulated. The formation of telomers with the same terminal groups is consistent with thermodynamic data and a polymerization
mechanism in which the chain growth reaction is diffusion-limited and the chain transfer reaction is activated hydrogen-atom
transfer. 相似文献
8.
Various kinds of aluminum species in dealuminated mordenite were investigated in detail, and the quadrupole coupling constants
(QCCs) for aluminum atoms associated with these species were obtained by means of the newly introduced1H/27 AI TRAPWR method as well as27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR). QCC values of 11.3, 15.3, 13.3 and (14.0± 0.6) MHz were determined
from the TRAPDOR profiles for Lewis acid sites, Bronsted acid sites (SiOHAl) and two kinds of non-framework aluminum species
Al(OH)
n
, respectively. The source of the “invisible Al” is discussed on the basis of the NMR experimental results. 相似文献
9.
Hitomi Saito Yuki Nishio Manabu Kobayashi Yoshiyuki Sugahara 《Journal of Sol-Gel Science and Technology》2011,57(1):51-56
The hydrolysis behavior of 1,4-bis(triethoxysilyl)benzene (BTB), a precursor of bridged polysilsesquioxane, was investigated
with high-resolution 29Si nuclear magnetic resonance (29Si NMR) spectroscopy at ambient temperature in a system with BTB:ethanol:water:HCl = 1:10:x:0.8 × 10−4 (x = 3, 6 or 9). Signals due to hydrolyzed triethoxysilyl groups as well as unhydrolyzed triethoxysilyl groups [−Si(OEt)3, −Si(OEt)2(OH), −Si(OEt)(OH)2 and −Si(OH)3 (OEt = OCH2CH3)] formed four sub-regions based on the number of hydroxyl groups bound to a silicon atom. In addition, one silicon environment
influenced the other silicon environment by an intra-molecular interaction between two silicon atoms, and each sub-region
for monomeric species thus contained four signals. Based on the development of signal intensity, it is revealed that one of
the two triethoxysilyl groups in BTB is hydrolyzed preferentially. Thus, when a triethoxysilyl group is hydrolyzed, the −Si(OH)
x
(OEt)3−x
(x = 1, 2) groups formed undergo further hydrolysis, which is opposite to the tendency expected from the hydrolysis behavior
of organotrialkoxysilanes under acidic conditions. 相似文献
10.
Nizam M. El-Ashgar Issa M. El-Nahhal Mohamed M. Chehimi Michel Delamar Florence Babonneau Jacques Livage 《Journal of Sol-Gel Science and Technology》2007,41(1):3-10
A new insoluble solid functionalized ligand system bearing chelating ligand group of the general formula P-(CH2)3-N[CH2CONH(C6H4)NH2]2, where P represents [Si–O]
n
polysiloxane network, was prepared by the reaction of the immobilized diethyliminodiacetate polysiloxane ligand system, P-(CH2)3N(CH2CO2Et)2 with 1,2-diaminobenzene in toluene. 13C CP-MAS NMR, XPS and FTIR results showed that most ethylacetate groups (–COOEt) were converted into the amide groups (–N–C=O).
The new functionalized ligand system exhibits high capacity for extraction and removal of the metal ions (Fe3+, Co2+, Ni2+, Cu2+ and Zn2+) with efficiency of 95–97% after recovery from its primary metal complexes. This functionalized ligand system formed 1:1
metal to ligand complexes. 相似文献
11.
The reaction mechanism of (CH3)3CO. radical with NO is theoretically investigated at the B3LYP/6-31G* level. The results show that the reaction is multi-channel
in the single state and triplet state. The potential energy surfaces of reaction paths in the single state are lower than
that in the triple state. The balance reaction: (CH3)3CONO⇔(CH3)3CO.+NO, whose potential energy surface is the lowest in all the reaction paths, makes the probability of measuring (CH3)3CO. radical increase. So NO may be considered as a stabilizing reagent for the (CH3)3CO. radical. 相似文献
12.
Lang SM Claes P Neukermans S Janssens E 《Journal of the American Society for Mass Spectrometry》2011,22(9):1508-1514
Structural information on free transition metal doped aluminum clusters, Al
n
TM
+ (TM = Ti, V, Cr), was obtained by studying their ability for argon physisorption. Systematic size (n = 5 – 35) and temperature (T = 145 – 300 K) dependent investigations reveal that bare Al
n
+ clusters are inert toward argon, while Al
n
TM
+ clusters attach one argon atom up to a critical cluster size. This size is interpreted as the geometrical transition from
surface-located dopant atoms to endohedrally doped aluminum clusters with the transition metal atom residing in an aluminum
cage. The critical size, n
crit
, is found to be surprisingly large, namely n
crit = 16 and n
crit = 19 – 21 for TM = V, Cr, and TM = Ti, respectively. Experimental cluster–argon bond dissociation energies have been derived as function of cluster size from
equilibrium mass spectra and are in the 0.1–0.3 eV range. 相似文献
13.
Ribeiro Guevara S Zizek S Repinc U Pérez Catán S Jaćimović R Horvat M 《Analytical and bioanalytical chemistry》2007,387(6):2185-2197
Mercury tracers are powerful tools that can be used to study mercury transformations in environmental systems, particularly
mercury methylation, demethylation and reduction in sediments and water. However, mercury transformation studies using tracers
can be subject to error, especially when used to assess methylation potential. The organic mercury extracted can be as low
as 0.01% of the endogenous labeled mercury, and artefacts and contamination present during methylmercury (MeHg) extraction
processes can cause interference. Solvent extraction methods based on the use of either KBr/H2SO4 or HCl were evaluated in freshwater sediments using 197Hg radiotracer. Values obtained for the 197Hg tracer in the organic phase were up to 25-fold higher when HCl was used, which is due to the coextraction of 197Hg2+ into the organic phase during MeHg extraction. Evaluations of the production of MeHg gave similar results with both MeHg
extraction procedures, but due to the higher Hg2+ contamination of the controls, the uncertainty in the determination was higher when HCl was used. The Hg2+ contamination of controls in the HCl extraction method showed a nonlinear correlation with the humic acid content of sediment
pore water. Therefore, use of the KBr/H2SO4 method is recommended, since it is free from these interferences. 197Hg radiotracer (T
1/2 = 2.673 d) has a production rate that is about 50 times higher than that of 203Hg (T
1/2 = 46.595 d), the most frequently used mercury radiotracer. Hence it is possible to obtain a similar level of performance
to 203Hg when it is used it in short-term experiments and produced by the irradiation of 196Hg with thermal neutrons, using mercury targets with the natural isotopic composition. However, if the 0.15% natural abundance
of the 196Hg isotope is increased, the specific activity of the 197Hg tracer can be significantly improved. In the present work, 197Hg tracer was produced from mercury 51.58% enriched in the 196Hg isotope, and a 340-fold increase in specific activity with respect to natural mercury targets was obtained. When this high
specific activity tracer is employed, mercury methylation and reduction experiments with minimum mercury additions are feasible.
Tracer recovery in methylation experiments (associated with Me197Hg production from 197Hg2+ spike, but also with Hg2+ contamination and Me197Hg artefacts) with marine sediments was about 0.005% g−1 WS (WS: wet sediment) after 20 h incubation with mercury additions of 0.05 ng g−1 WS, which is far below natural mercury levels. In this case, the amount of Hg2+ reduced to Hg0 (expressed as the percent 197Hg0 recovered with respect to the 197Hg2+ added) varied from 0.13 to 1.6% g−1 WS. Me197Hg production from 197Hg2+ spike after 20 h of incubation of freshwater sediment ranged from 0.02 to 0.13% g−1 WS with mercury additions of 2.5 ng g−1 WS, which is also far below natural levels. 197Hg0 recoveries were low, 0.0058 ± 0.0013% g−1 WS, but showed good reproducibility in five replicates. Me197Hg production from 197Hg2+ spiked in freshwater samples ranged from 0.1 to 0.3% over a period of three days with mercury additions of 10 ng L−1. A detection limit of 0.05% for Me197Hg production from 197Hg2+ spike was obtained in seawater in a 25 h incubation experiment with mercury additions of 12 ng L−1. 相似文献
14.
A. N. Simonov O. P. Pestunova L. G. Matvienko V. N. Parmon 《Russian Chemical Bulletin》2005,54(8):1967-1972
Isomerization of D-glucose to fructose and mannose in aqueous solutions of Ca(OH)2 with the initial pH 11.4 in a temperature interval of 20–90 °C was studied by 13C NMR spectroscopy in the presence and absence of dissolved oxygen. In the presence of oxygen, the apparent equilibrium isomerization
constant is much lower than that in the absence of oxygen. This is related to the oxidation of monosaccharides to formic and
aldonic acids, a decrease in the pH of solutions, and cessation of isomerization at pH < 9.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1909–1913, August, 2005. 相似文献
15.
Dibutylmagnesium (contaminated with Al(n-Bu)3; nMg:nAl ca. 1:0.2) was found to react with MeOCH2CH2OH followed by the addition of PhSCH(Me)Ph in the presence of 0.2 equiv n-butyllithium yielding [Mg7(μ3-OCH2CH2OMe)6(μ-OCH2CH2OMe)6][Al(n-Bu)4]2 (1) as the principal product (yield 40–45% referred to MeOCH2CH2OH). The single-crystal X-ray diffraction analysis revealed that the centrosymmetric cationic heptamagnesium complex is built up from seven edge-shared MgO6 octahedra. The [Al(n-Bu)4]− anions adopt approximately a tetrahedral AlC4 symmetry. 1H, 13C and 27Al NMR spectroscopic measurements showed that in THF solution the structures both of the heptamagnesium complex and the tetrabutylaluminate anion are preserved and that there are no cation–anion interactions reducing the symmetry. The 27Al resonance (151.6 ppm) was found to be very sharp (w1/2 = 5 Hz), the coupling constant 1J(27Al,13C) amounts to 72.3 Hz. 相似文献
16.
Summary. The two new compounds Mn(dien)2[MoS4] (1) and Mn(dien)2[Mo2O2S6] (2) (dien = diethylenetriamine) were prepared under solvothermal conditions. Both compounds were obtained as phase-pure products. The
structures consist of new [Mn(dien)2]2+ cations and isolated tetrahedral [MoS4]2− (1) or [Mo2O2S6]2− (2) anions. Between the anions and the cations, hydrogen bonding is observed. Compound 1 crystallizes in the tetragonal space group I (a = 10.219(2), c = 9.259(2) ?, Z = 2), whereas 2 crystallizes in the monoclinic space group P21/c (a = 8.703(2), b = 18.390(4), c = 14.603(3) ?, β = 103.18(3)°, Z = 4). The thermal behaviour of the thiomolybdates was investigated using difference thermoanalysis (DTA) and thermogravimetry
(TG). Both compounds decompose under argon with a single endothermic signal in the DTA curve (peak maximum: 252 (1) and 242°C (2)).
Received November 5, 2001. Accepted December 27, 2001 相似文献
17.
Chang Ju Choi Kwang Woo Jung Wee Kyung Kang Dae Young Youn Kyung-Hoon Jung Dongho Kim 《Journal of mass spectrometry : JMS》1993,28(9):931-939
Reactions that proceed within mixed ethylene–methanol cluster ions were studied using an electron impact time-of-flight mass spectrometer. The ion abundance ratio, [(C2H4)n(CH3OH)mH+]/[(C2H4)n(CH3OH)m+], shows a propensity to increase as the ethylene/methanol mixing ratio increases, indicating that the proton is preferentially bound to a methanol molecule in the heterocluster ions. The results from isotope-labelling experiments indicate that the effective formation of a protonated heterocluster is responsible for ethylene molecules in the clusters. The observed (C2H4)n(CH3OH)m+ and (C2H4)n(CH3OH)m–1CH3O+ ions are interpreted as a consequence of the ion–neutral complex and intracluster ion–molecule reaction, respectively. Experimental evidence for the stable configurations of heterocluster species is found from the distinct abundance distributions of these ions and also from the observation of fragment peaks in the mass spectra. Investigations on the relative cluster ion distribution under various conditions suggest that (C2H4)n(CH3OH)mH+ ions with n + m ≤ 3 have particularly stable structures. The result is understood on the basis of ion–molecule condensation reactions, leading to the formation of fragment ions, $ {\rm CH}_2=\!=\mathop {\rm O}\limits^ + {\rm CH}_3 $ and (CH3OH)H3O+, and the effective stabilization by a polar molecule. The reaction energies of proposed mechanisms are presented for (C2H4)n(CH3OH)mH+(n + m ≤ 3) using semi-empirical molecular orbital calculations. 相似文献
18.
R. G. Bulgakov Yu. G. Ponomareva Z. S. Muslimov F. G. Valyamova R. A. Sadykov R. F. Tuktarov 《Russian Chemical Bulletin》2007,56(2):211-219
Fullerenyl radicals (FR) RC60
· and chemiluminescence (CL) are generated in the presence of O2 in C60—R3Al (R = Et, Bui) solutions in toluene (T = 298 K). The FR are formed due to the addition of the R· radical, which is an intermediate of R3Al autooxidation, to C60. Mass spectroscopy and HPLC were used to identify EtnC60Hm (n, m = 1–6), EtpC60 (p = 2–6), and dimer EtC60C60Et as stable products of FR transformations. As found by ESR, the EtC60
· radical (g = 2.0037) is also generated by photolysis of solutions obtained after interaction in the (C60— R3Al)—O2 system. In the presence of dioxygen, the FR is not oxidized but yields complexes with O2, which appear as broadening of the ESR signals. Chemiluminescence arising in the (C60—R3Al)—O2 system is much brighter (I
max = 1.86·108 photon s−1 mL−1) than the known background CL (I
max = 6.0·106 photon s−1 mL−1) for the autooxidation of R3Al and is localized in a longer-wavelength spectral region (λmax = 617 and 664 nm). This CL is generated as a result of energy transfer from the primary emitter 3CH3CHO* to the products of FR transformation: RnC60Hm, RpC60, and EtC60C60Et.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 205–213, February, 2007. 相似文献
19.
采用溶胶凝胶法合成了一系列有序性好且酸性较强的介孔硅铝酸盐材料。利用X射线粉末衍射(XRD)、透射电镜(TEM)、27Al核磁共振(27Al NMR)、氨气程序升温脱附(HN3-TPD)及吡啶吸附红外光谱(Py-FT-IR)对制备的介孔硅铝酸盐材料的结构和性能进行表征,并考察了材料在苯甲醚和苯甲醇的傅克烷基化反应中的催化活性。实验结果表明:合成过程中,表面活性剂的用量、硅铝物质的量之比会影响材料结构的有序性,醋酸用量对材料结构有序性影响很小;进一步研究结果表明,nSi/nAl比会影响材料的酸催化活性,当nSi/nAl=10时材料的酸催化活性最高。氨气程序升温脱附和吡啶吸附红外光谱表明nSi/nAl=10的材料含有最多的B酸酸量。 相似文献
20.
Andrew Y. Platonov Alexander V. Kurzin Andrey N. Evdokimov 《Journal of solution chemistry》2010,39(3):335-342
The composition of the vapor and liquid phases of the KOH + CH3OH system has been studied by the gas chromatography (GC) method at 25 °C. It has been found that the methanol vapor concentration,
and the quantity of potassium methoxide formed as a result of the acid–base reaction of potassium hydroxide with methanol,
both depend on the KOH/CH3OH mole ratio. The maximum mass fraction of potassium methoxide that forms is 2.6% at the mole ratio 0.018. 相似文献