共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
Lapteva U. A. Baranov A. Yu. Samsonenko D. G. Artemev A. V. 《Journal of Structural Chemistry》2022,63(4):663-668
Journal of Structural Chemistry - A four-nuclear complex [Ag4(Lut3P)2(MeCN)2](BF4)4 is synthesized by treating tris[(6-methylpyridin-2-yl)methyl]phosphine (Lut3P) with AgBF4 in a MeCN solution. The... 相似文献
3.
4.
《Mendeleev Communications》2020,30(2):223-225
- Download : Download high-res image (137KB)
- Download : Download full-size image
5.
《中国化学快报》2020,31(5):1337-1341
The three-component reaction of triphenylphosphine, dimethyl hex-2-en-4-ynedioate and arylidene N,N'-dimethylbarbituric acids in dry methylene dichloride at room temperature afforded trans-1,3-disubstituted 7,9-diazaspiro[4.5]dec-1-enes in good yields and with high diastereoselectivity. However, the similar three-component reaction with arylidene Meldrum acids resulted in a mixtures of cis/trans-1,2-disubstituted 7,9-dioxaspiro[4.5]dec-1-enes. Additionally, the three-component reaction of triphenylphosphine, dimethyl but-2-ynedioate and arylidene Meldrum acids gave polysubstituted 5-(triphenyl-λ5-phosphanylidene)cyclopenta-1,3-dienes. A plausible reaction mechanism was proposed for the formation of various products with different regioselectivity and diastereoselectivity. 相似文献
6.
《Mendeleev Communications》2020,30(1):15-17
- Download : Download high-res image (90KB)
- Download : Download full-size image
7.
《高等学校化学学报》2015,(8)
研究了新型萃取剂N,N'-二乙基-N,N'-二(丙氧基苯基)-2,6-吡啶二酰胺(1a~1c)对铀酰离子(UO2+2)的络合萃取.结果表明,当不加硝酸或硝酸浓度为6 mol/L时,化合物1a对UO2+2的萃取率分别高达99%和94%.在6 mol/L HNO3的高酸度条件下,化合物1a能实现UO2+2和镧系元素(La,Eu及Yb)的选择性分离[分离比SFU(Ⅵ)/Ln(Ⅲ)20];而化合物1b和1c则可以实现UO2+2和轻镧系元素(La,Eu)之间的分离.双对数图(lg-lg plot)实验结果表明,化合物1a~1c与UO2+2的萃合比在1~2之间,表明同时存在2∶1和1∶1两种比例的萃合物.核磁共振波谱和红外光谱数据证明吡啶氮和羰基氧参与了对UO2+2的配位. 相似文献
8.
9.
10.
The influence of substitution of amidine group on tautomeric equilibria constants and basicities is discussed. Equations based on correlation analysis methods are derived enabling predictions of both, microscopic pKa, values of individual tautomers, measured macroscopic pKa values of the tautomeric mixture, as well as the tautomeric equilibrium constant (as pKT). It is shown that pKarn values of unsymmetrically N,N'-disubstituted amidines should obey a non-linear relation with σ° constants, and only for symmetrically N,N'-disubstituted amidines obey the linear Hammett equation. Tautomeric equilibrium constants of N,N'-disubstituted amidines correlate withσ° substituent constants. The methods of prediction of pKa value of both tautomers and pKT value are proposed.Derived relations are applied to the series of N,N'-diphenylacetamidines and benzamidines. 相似文献
11.
12.
A convenient and efficient strategy for the synthesis of 2-acyl benzothiazoles/thiazoles has been developed. The treatment of benzothiazole/thiazole with allylic Grignard reagents readily generates the corresponding 2-Grignard reagents, which is followed by a reaction with N,N'-carbonyldiimidazole activated carboxylic acids to afford various 2-acyl benzothiazoles/thiazoles products. The synthetic method is applicable to a wide array of carboxylic acids and allows easy access to 2-acyl benzothiazoles/thiazoles with considerable yields under mild reaction conditions. 相似文献
13.
Qing-de Chen Xing-hai Shen 《高分子科学》2005,(6):635-642
In the UV-Vis spectra of pure light-scattering systems, there is an exponential relationship between absorbance and wavelength (A = Kλ^-n). Here, the exponent n is named as flocculation-coagulation parameter. In the present paper, the effects of different additives on the stability of poly(N,N'-methylenebisacrylamide-co-4-vinylpyridine) (poly(Bis-co-4-VP)) microgel dispersion were studied in detail via this parameter. The results showed that the stability of the dispersion mainly comes from the ionization of pyridine groups, making the microgel positively charged on its surface. This was confirmed by the measurement of Zeta potential and the result of conductometric titration. The result of fluorescence analysis indicated that the hydrophobicity in the microgels is enhanced with the increase in total 4-VP unit content. 相似文献
14.
《International Journal of Radiation Applications and Instrumentation. Part C. Radiation Physics and Chemistry》1988,31(3):465-473
The overlapping transient optical absorption spectra obtained from pulse radiolysis experiments in which the hydrated electron reacted with adenine, adenosine, 5'-adenosine monophosphate and polyadenylic acid were measured and analysed. The analysis consists of a multicomponent analysis which yields the number of different species and a set of orthonormal basis spectra. From this set of basis spectra together with a number of trial models for the possible kinetics of the different species the best model is determined by fitting the original data. In this way the molar absorptivity spectra and the kinetics of the species can be found. To describe all the spectra of the adenine-containing compounds in a consistent way we need, at most, three different species. The following reaction scheme is obtained: e-aq + A → A-., A-. + H2O →2 A′H. + OH-, A-. → A″H. and A'H.(A″H.) + A'H.(A″H.). The radicals A'H. and A″H. are both protonated electron adducts, while P appears to be “stable” product with a decay time of the order of 1 day. 相似文献
15.
Ronald Grigg M. Ruhul A. Sarkar Abirami Thayaparan Visuvanathar Sridharan Colin W.G. Fishwick 《Tetrahedron》2007,63(30):7213-7228
A Pd(0) catalyzed three-five-component cascade involving an aryl iodide, allene and a heterocyclic pronucleophile is used to prepare 2-arylallyl derivatives (10-12 and 16-24) from 3-phenyl-5-isoxazolone (6) and 1-phenyl-3-methylpyrazolin-5-one (7) in moderate yield. Similar cascade allylation of masked amino acids 4-methyl-2-phenyl-4H-oxazol-5-one (8a), 4-benzyl-2-phenyl-4H-oxazol-5-one (8b) and 4-isopropyl-2-phenyl-4H-oxazol-5-one (8c) gave analogous products (25-37) in good yield. N,N-Dimethylbarbiturates (38-49) are similarly prepared from N,N-dimethylbarbituric acid (9) in excellent yield. 相似文献
16.
A measure of the strength of a synthetic strategy is its versatility: specifically, whether it allows structurally distinct targets to be prepared. Herein we disclose a unified approach for the total synthesis of natural products of three distinct structural types, all of which occur naturally as racemic mixtures. The point of divergence involves the terminal alkylation of a conjugated tetrayne, and culminates in a significantly shortened synthesis of endiandric acid A (8 steps), the first total synthesis of kingianic acid E (8 steps), and a second-generation synthesis of kingianins A, D, and F (11 steps). Evidence for redox catalysis in the biosynthesis of kingianic acid E is presented. 相似文献
17.
18.
Heba A. Gaballa Luke M. Geever John A. Killion Clement L. Higginbotham 《Journal of Polymer Science.Polymer Physics》2013,51(21):1555-1564
Physically crosslinked hydrogels based on N‐vinylcaprolactam/acrylic acid and N‐vinylcaprolactam/methacrylic acid were prepared via free radical polymerization. These temperature responsive hydrogels were characterized in terms of glass transition, phase separation temperature, potentiometric titration and swelling properties. Results showed that phase transition temperature was dependent on the pH value of the solution; increasing pH led to higher lower critical solution temperature (LCST) values which was related to the dissociative behaviors of the carboxylic group of MAc in the buffered solutions. Additionally, with the incorporation of N,N‐dimethylacrylamide into the system, cloud point measurements and MDSC showed an increased in the LCST. This increase was based on hydrophilicity, the hydrophilic–hydrophobic balance was disturbed, and consequently, the LCST behavior was shifted. The pKa of the copolymers ranged between 5.6 and 6.5, while for the terpolymers pKa ranged between 5.3 and 6. At high pH (>10), the ? COOH group is deprotonated and negatively charged (? COO?), while at low pH (1–3) the carboxylic group remains protonated which results in hydrogen bonding between the hydroxyl groups (from NaOH) and the excess of HCl. These results correlate with swelling studies where above the pKa value the hydrogels dissolved rapidly compared to below pKa they did not dissolve at all. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1555–1564 相似文献
19.
The cyclopentadienyl molybdenum hydride compounds, CpRMo(PMe3)3–x(CO)xH (CpR = Cp, Cp*; x = 0, 1, 2 or 3), are catalysts for the dehydrogenation of formic acid, with the most active catalysts having the composition CpRMo(PMe3)2(CO)H. The mechanism of the catalytic cycle is proposed to involve (i) protonation of the molybdenum hydride complex, (ii) elimination of H2 and coordination of formate, and (iii) decarboxylation of the formate ligand to regenerate the hydride species. NMR spectroscopy indicates that the nature of the resting state depends on the composition of the catalyst. For example, (i) the resting states for the CpMo(CO)3H and CpMo(PMe3)(CO)2H systems are the hydride complexes themselves, (ii) the resting state for the CpMo(PMe3)3H system is the protonated species [CpMo(PMe3)3H2]+, and (iii) the resting state for the CpMo(PMe3)2(CO)H system is the formate complex, CpMo(PMe3)2(CO)(κ1-O2CH), in the presence of a high concentration of formic acid, but CpMo(PMe3)2(CO)H when the concentration of acid is low. While CO2 and H2 are the principal products of the catalytic reaction induced by CpRMo(PMe3)3–x(CO)xH, methanol and methyl formate are also observed. The generation of methanol is a consequence of disproportionation of formic acid, while methyl formate is a product of subsequent esterification. The disproportionation of formic acid is a manifestation of a transfer hydrogenation reaction, which may also be applied to the reduction of aldehydes and ketones. Thus, CpMo(CO)3H also catalyzes the reduction of a variety of ketones and aldehydes to alcohols by formic acid, via a mechanism that involves ionic hydrogenation. 相似文献
20.
I. Capek 《Central European Journal of Chemistry》2003,1(3):291-304
The kinetics of free-radical copolymerization and terpolymerization of acrylamide (AAm), N, N′-methylenebis(acrylamide) (MBA) and methacrylic acid (MA) in the inverse water/monomer/cyclohexane/Tween 85 miniemulsion was
investigated. Polymerizable sterically-stable miniemulsions were formulated in cyclohexane as a continuous medium. Polymerizations
are very fast and reach the final conversion within several minutes. The dependence of the polymerization rate vs. conversion
is described by a curve with two nonstationary rate intervals. The maximum rate of polymerization slightly increases with
increasing concentration of crosslinking monomer (MBA) and strongly decreases by the addition of MA. The rate of polymerization
is inversely proportional to the 0.9
th
and 1.8
th
power of the particle concentration without and with MA, respectively. The number of polymer particles is inversely proportional
to the 0.18
th
and 0.13
th
power of MBA concentration. The kinetic and colloidal parameters of the miniemulsion polymerization are discussed in terms
of microemulsion polymerization model. 相似文献