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1.
The results of systematic XPS measurements of all alkali metal carbonates (Li, Na, K, Rb and Cs) are presented. The first set of experiments was performed with “as received” commercial carbonate powders under liquid nitrogen conditions using a precooling procedure. A second set of experiments was performed under similar experimental conditions after a preliminary grinding (mechanical activation) of the carbonates. In addition, Na2CO3 *1H2O, NaHCO3 and KHCO3 powders were studied. It was found that sample pre-cooling allows distinction between hydrocarbonates and carbonate hydrates. Storage in air leads to formation of hydrocarbonates at the surface of Li2CO3 and Na2CO3. This phenomenon being more pronounced in the former. In contrast, K2CO3 forms a hydrate with one H2O molecule. Rb2CO3 and Cs2CO3 have hydrocarbonates as well as hydrates at the surface and this is more pronounced for Cs2CO3. Grinding of the carbonates results in the formation of hydrocarbonates at the surface, the tendency to do so was found to increase down the group IA, namely, K<Rb≪Cs. For the most part, the hydrocarbonates formed were unstable in vacuum even under liquid nitrogen conditions. Chemical trends in C 1s and O 1s binding energies in carbonates and hydrocarbonates of the Group IA are discussed and related to the nature of the anion and alkali cation.  相似文献   

2.
Preparation, Crystal Structure Determination, and Vibrational Spectroscopy on Cs2Ba2(CO3)3 A new alkali metal alkaline earth metal double carbonate, Cs2Ba2(CO3)3, was obtained by the reaction of cesium carbonate and barium oxalate in the solid state using elevated pressure (2.026GPa). It has been characterized by single X-ray diffraction: 1162 diffractometer data, space group I213, a = 10.349(2) Å; Z = 4; Rw = 0.026. The internal vibrations of the carbonate group exhibit unusually pronounced splittings caused by crystal field effects. All vibrational absorptions in the IR spectrum as to be expected at the level of the factor group approximation have been observed at recording the IR spectrum at low temperatures (?196°C).  相似文献   

3.
Heterogeneous carbonate salt catalyzed acetylation of alcohols via a transesterification process has been developed. Various esters are furnished up to 97% yield. Established procedure is simple and air‐tolerant with readily available reagents. Ethyl acetate and isobutyl acetate are used as not only acetylating agents, but also reaction solvents in transesterification. Aliphatic linear alcohols, allylic alcohols and benzyl alcohols show high reactivities in the presence of 1 or 5 mol% Cs2CO3 at 125°C. Cesium carbonate can be recycled by pumping liquid phase out of reactor after reaction. During four cycle runs for reaction of 2‐phenylethanol and ethyl acetate, high yields of phenethyl acetate are provided (>60% yield). Based on experiments and 1H NMR investigation, bifunctional catalysis is proposed, alcohol activated by carbonate ion is confirmed, and higher activity of catalytic amount than stoichiometric cesium carbonate is interpreted.  相似文献   

4.
Several quadruply bridged calix[6]arenes were prepared in high yield by the reaction of various 1,4-di-O-alkylated calix[6]arenes with 1,2,4,5-tetrakis-(bromomethyl)benzene in the presence of Cs2CO3. The alkali metal extraction study established that this compound shows the high selectivity toward Cs+ among alkali metal cations. The cesium binding characteristics were investigated with 1H NMR and UV spectroscopy.  相似文献   

5.
The inherent formation of salt waste in C−H carboxylations is a key obstacle precluding the utilization of CO2 as C1 building block in the industrial synthesis of base chemicals. This challenge is addressed in a circular process for the production of the C4 base chemical dimethyl succinate from CO2 and acetylene. At moderate CO2 pressures, acetylene is doubly carboxylated in the presence of cesium carbonate. Hydrogenation of the C−C triple bond stabilizes the product against decarboxylation. By increasing the CO2 pressure to 70 bar, the medium is reversibly acidified, allowing an esterification of the succinate salt with methanol. The cesium base and the hydrogenation catalyst are regenerated and can be reused. This provides the proof of concept for a salt-free route to C4 chemicals from biogas (CH4/CO2). The origin of this reversible acidity switch and the critical roles of the cesium base and the NMP/MeOH solvents were elucidated by thermodynamic modeling.  相似文献   

6.
Efficient methods for the synthesis of carbazates and dithiocarbazates have been developed. In the presence of cesium carbonate (Cs2CO3) and tetrabutylammonium iodide (TBAI) a hydrazine, CO2 or CS2, and an alkyl halide underwent a three-component coupling at room temperature. Various unprotected hydrazines and alkyl halides were examined and the results demonstrated this methodology was highly chemoselective. Applications toward the synthesis of azadepsipeptides and other pseudopeptides are described.  相似文献   

7.
A mild and convenient synthesis for phosphonates using cesium carbonate (Cs2CO3), tetrabutylammonium iodide (TBAI) and DMF was developed at room temperature. Numerous dialkyl phosphites were screened using a diverse array of alkyl halides and these reaction conditions were found to be highly efficient producing various phosphonates exclusively in moderate to high yields.  相似文献   

8.
Syntheses of Some Carbonates with CO2 under High Pressures Carbonates of the alkali metals and of some transition metals are prepared from their solutions, hydroxides, or oxides by reactions with CO2 using pressures of 600–4500 at and temperatures of 100– 400°C. The carbonates MnCO3, FeCO3, CoCO3, NiCO3, ZrCO3 · 2H2O, Th(CO3)2 · 0.5 H2O and the carbonates of the alkali metals are characterized by infrared spectroscopy and X-ray investigations. The structures of Rb2CO3 (1) and Cs2CO3 (2) are presented. They are both monoclinic, space group P 21/c (No. 14) with a = 5.87 (1), 6.13 (2); b = 10.13 (1), 10.28 (2); c = 7.33 (1), 8.15 Å (2), β = 97.65° (1), 95.85° (2) and Z = 4.  相似文献   

9.
The hydration of propargylic alcohols is a green route to synthesize α-hydroxy ketones. Herein a CO2-reactive ionic liquid (IL), [Bu4P][Im], was found to display high performance for catalyzing the hydration of propargylic alcohols in the presence of atmospheric CO2, and a series of propargylic alcohols could be converted into the corresponding α-hydroxy ketones in good to excellent yields. In the IL/CO2 reaction system, CO2 served as a cocatalyst by forming α-alkylidene cyclic carbonates with propargylic alcohols, and was released via the rapid hydrolysis of the carbonates catalysed by the IL. This is the first example of the efficient hydration of propargylic alcohols under metal-free conditions.  相似文献   

10.
A silver(I)‐catalyzed three‐component reaction of propargylic alcohols, CO2, and monohydric alcohols was successfully developed for the synthesis of β‐oxopropyl carbonates. As such, a series of β‐oxopropyl carbonates were exclusively produced in excellent yields (up to 98 %), even under atmospheric pressure of CO2. The silver catalyst works efficiently for both the carboxylative cyclization of propargylic alcohols with CO2 and subsequent transesterification of α‐alkylidene cyclic carbonates with monohydric alcohols; thus this tandem process performs smoothly under mild conditions. This work provides a versatile and thermodynamically favorable approach to dissymmetric dialkyl carbonates.  相似文献   

11.
Rémi D. Bergougnant 《Tetrahedron》2007,63(44):10751-10757
The macrocycle 4-tert-butylcalix[8]arene (L) was reacted with alkali metal carbonates (Li2CO3, Na2CO3, K2CO3, Rb2CO3, and Cs2CO3) at the interface of a biphasic THF/water system. Needle-like crystals with a general formula [Ax(4-tert-butylcalix[8]arene-xH)(THF)y(H2O)z] (with A=Li, Na, K, Rb, Cs, x=1, 2, y=4, 5, 8, and z=6, 7) were thereby obtained. The solid state structures were investigated by X-ray diffraction of single crystals and by TGA measurements. They do not appear to be maintained in solution.  相似文献   

12.
A convenient and efficient electrochemical method has been developed for the synthesis of the α-alkylidene cyclic carbonates from carbon dioxide (CO2) and propargyl alcohols at room temperature. The electrosynthesis was successfully carried out with a copper anode and a nickel cathode in an undivided cell containing n-Bu4NBr-MeCN electrolyte with a constant current under 3 MPa pressure of CO2, and the α-alkylidene cyclic carbonates were obtained in good to excellent isolated yields in the secondary and tertiary terminal propargylic alcohols cases. The experimental results show that the electrogenerated Cu+ ions and strong bases in situ could efficiently catalyze or promote the coupling reaction under the cooperation of electrolytic medium MeCN and supporting electrolyte n-Bu4NBr. The plausible mechanism of the coupling reaction was also discussed briefly.  相似文献   

13.
Akio Saito 《Tetrahedron letters》2010,51(11):1471-4661
In the presence of Pd2(dba)3-Cy3P catalyst, IPr·HCl salt [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene], and Cs2CO3, N-propargylamides react with allyl carbonates to give 2,5-disubstituted oxazoles having homoallyl groups through the tandem cycloisomerization-allylation.  相似文献   

14.
With Cs9Pt4H a new representative of ionic compounds featuring metal anions can be added to this rare‐membered family. Cs9Pt4H exhibits a complex crystal structure containing Cs+ cations, Pt2? and H? anions. Being a red, transparent compound its band gap is in the visible range of the electromagnetic spectrum and the ionic type of bonding is confirmed by quantum chemical calculations. This cesium platinide hydride can formally be considered as a double salt of the “alloy” cesium–platinum, or better cesium platinide, Cs2Pt, and the salt cesium hydride CsH according to Cs9Pt4H≡4 Cs2Pt?CsH.  相似文献   

15.
The thermal decomposition of alkali tris(maleato)ferrates(III), M3 [Fe(C2 H2 C2 O4 )3 ] (M =Li, Na, K) has been studied isothermally and non-isothermally employing simultaneous TG-DTG-DTA, XRD, Mössbauer and IR spectroscopic techniques. The anhydrous complexes decompose in the temperature range 215–300°C to yield Fe(II)maleate as an intermediate followed by demixing of the cations forming α-Fe2 O3 and alkali metal maleate/oxalate in successive stages. In the final stage of remixing of the cations (430–550°C) a solid state reaction occurs between α-Fe2 O3 and alkali metal carbonate leading to the formation of fine particles of respective ferrites. The thermal stabilities of the complexes have been compared with that of alkali tris(oxalato)ferrates(III).  相似文献   

16.
Optimum conditions for the solid–liquid phase alkylation of methylenebis(diphenylphosphine oxide) (MBDPPO) and ethyl cyanomethylphosphonate (ECMP) were explored studying the role of phase transfer catalysis and microwave (MW) irradiation, as well as the effect of the cation of the alkali carbonate. It was found that the alkylation of MBDPPO may be best accomplished in acetonitrile, in the presence of a quaternary ammonium salt and Cs2CO3, while that of ECMP in the absence of catalyst and solvent using K2CO3. MW irradiation was beneficial in both cases. During the alkylation of ECMP, by‐products coming from the alcoholysis of the diethyl ester were also identified. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:174–179, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20673  相似文献   

17.
A three-dimensional ordered polyoxometalate periodic film was synthesized using dodecatungstophosphoric acid (H3PW12O40) and Cs2CO3 as precursors and colloidal crystals as templates by an inverse opal method. The samples were characterized by elemental analysis, XRD, IR spectra, UV-Vis diffuse reflectance spectra (DR-UV-Vis) and SEM techniques. This arrayed film constructed by pure cesium salt of dodecatungstophosphoric acid Cs2.5H0.5PW12O40 nanoparticles shows well-defined lamellar array with inverse opal structure, which exhibits a well-defined photonic band gap.  相似文献   

18.
Among Cambridge substances, which always include “organic”carbon, i.e., carbon contained in molecules or molecular ions,ion-molecular crystals (particularly, carbonates or alkaline-earthand alkaline metals) are of special interest. Some of such carbonatescontain pronounced Van der Waals (vdw) contacts between oxygenatoms of carbonate groups. Thus, agglomerates (layers or columns)formed by contacting carbonate groups arise (columns beingconnected in a frame), and in the cavities between these agglomeratescations are situated. The structure looks like an inclusion compound,the carbonate groups being hosts and the cations being guests. Todiscuss this question we used the refined value of vdw radius of oxygenwhich was obtained by statistical treatment of 8200 crystal structuresfrom Cambridge Structural Database (CSD) and is equal to 1.53 Å for the O?O contacts. Hence the length of a normal supporting vdw contact O?O is 3.06 ± 0.15 Å. Such contacts are present in MgCO3 and CaCO3 (calcite) and in α-Na2CO3. There are contacts O?O that are even shorter (2.74–2.81 Å)in CaCO3 (aragonite), SrCO3, BaCO3 and Li2CO3.So it is possible to suppose the existence of specific (partly covalent)contacts O?O in these substances. In β-Na2CO3, all forms of K2CO3, Rb2CO3 and Cs2CO3 the vdw contacts of CO3 groups are absent; therefore they are ionic (not inclusion) compounds.  相似文献   

19.
Current approaches to lowering the pH of basic media rely on the addition of a proton source. An alternative approach is described herein that involves the liquid–liquid extraction‐based removal of cesium salts, specifically CsOH and Cs2CO3, from highly basic media. A multitopic ion‐pair receptor ( 2 ) is used that can recognize and extract the hydroxide and carbonate anions as their cesium salts, as confirmed by 1H NMR spectroscopic titrations, ICP‐MS, single‐crystal structural analyses, and theoretical calculations. A sharp increase in the pH and cesium concentrations in the receiving phase is observed when receptor 2 is employed as a carrier in U‐tube experiments involving the transport of CsOH through an intervening chloroform layer. The pH of the source phase likewise decreases.  相似文献   

20.
近些年来,将CO2转化为高附加值化学品受到广泛关注。其中,CO2、炔丙醇和亲核试剂的三组分反应可用于制备用途广泛的羰基化合物,该方法具有步骤经济性、原子经济性等优点。由于CO2分子具有热力学稳定性和动力学惰性,多数CO2参与的化学反应在热力学上不支持。然而,CO2、炔丙醇和双亲核试剂三组分反应是热力学有利的CO2转化反应,实现了邻二醇或氨基醇和CO2到环状碳酸酯以及2-噁唑啉酮的高效转化。本综述旨在于总结并讨论近年来CO2、炔丙醇和亲核试剂三组分反应制备多种羰基化学物的主要进展。  相似文献   

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