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1.
The synthesis of the new tetraazamacrocycle [20]N4 is briefly described; complexation of F by the fully protonated [16]N4, [18]N4 and [20]N4 macrocycles is investigated.  相似文献   

2.
The structure of NiI2, 6 H2O has been determined by X-ray diffraction techniques. The dimensions of the hexagonal unit cell are: a = 7.638 ± 0.005 Å and c = 4.876 ± 0.005 Å, with Z = 1. The space group is P3m1. The structure was deduced from Patterson and Fourier syntheses and refined by least-squares method to a final R value of 0.09. It is almost a layer structure, each layer is composed by n complex ions [Ni(H2O)6]2+ surrounded by 2 n ions I?; this is in agreement with the good cleavage of crystals and with the marked anisotropy in the thermal expansion. But the structure may also be regarded as a derivation of NiAs structure, with only 18 of octahedral holes occupied. A structural classification of compounds MX2, 6 H2O is proposed.  相似文献   

3.
Graft copolymers have been obtained through the polymerization of indene initiated with diethylaluminium chloride and tert, butyl chloride, in the presence of ethylene-propylene-diene terpolymers. In the case of polymers with unhindered unsaturated units, like those derived from 1,4-hexadiene and dicyclopentadiene, the increase of Mn is mainly due to backbone duplication, and grafting efficiencies are low. Terpolymers with sterically hindered units, like those derived from ethylidene norbornene, yield graft copolymers with high grafting efficiencies (up to 50%). In this case, an initiation mechanism involving the unsaturated unit is proposed in order to explain the difference between these two types of reactions.  相似文献   

4.
Cationic grafting of indene onto chlorinated butyl rubber (CBC), initiated with diethylaluminium monochloride in a mixture of methylene dichloride and methylcyclohexane, has been carried out at ?50°. Grafting efficiencies near 100% and complete conversion of indene were obtained. The polymerization rate is proportional to indene concentration and to (initiator concentration)12, as in reactions carried out in the presence alkyl halide cocatalysts. No simple dependence on cocatalytic chlorine could be found. Influence of the concentration of reagents on the nature of the reaction products, especially of the ratios
(CBC)(indene)(AlEt2Cl)and(AlEt2Cl)
has been measured. Since transfer reactions occur during polymerization, the high grafting efficiencies are attributed to grafting of transfered polyindene chains.  相似文献   

5.
The cationic homopolymerization of 1-chlorobutadiene and its copolymerization with isobutene have been carried out in dichloromethane solution. The catalyst-cocatalyst pairs used were AlEt2Cl-(CH3)3CCl and AlEtCl2-(CH3)3CCl. In the latter case, the use of (CH3)3CCl was not necessary. According to experimental conditions, high molecular weight copolymers (Mn = 200,000) insoluble in CH2Cl2, or soluble low polymers (Mn = 20,000) were obtained. Homopoly-1-chlorobutadienes were soluble low molecular weight polymers (Mn = 10,000). The 1-chlorobutadiene units in the polymers are nearly exclusively 3,4 (mainly trans). Consequently, this method is not convenient to prepare elastomers with a 1,4 structure similar to that of chlorinated butyl rubber.  相似文献   

6.
Copper(I) salts of arylacetic acids 1 RCO2H readily undergo a catalytic and quantitative decarboxylation in acetonitrile leading to hydrocarbons 2 RH when the corresponding carbanions R are stabilized by resonance and/or electronwithdrawing substituents.  相似文献   

7.
The structure of wüstite Fe1?zO is studied by neutron diffraction on one polycrystalline sample under equilibrium conditions at high temperature. The mean isotrope temperature factor B is expressed as a sum of two parts, BTh and BSt, which vary linearly with a single parameter, respectively temperature and z. A classification is established for clusters (mn) settled from m vacancies in octahedral sites and n FeIII ions in interstitial sites. Sixteen values have been experimentally determined for the vacancies to interstitials ratio ? = (z + t)t = mn. A constant value of ?, which is lower than 3, is observed. This result characterizes the short-range order. It eliminates several possibilities of clusters like those obeying the relation ? = (1 + 3n)n. Other clusters, namely (166) or (4014), might agree. The (83) and (94) clusters obtained from (41) clusters joined by an edge would be the more likely. An analysis of diffuse scattering eliminates the hypothesis of large domains with inverse spinel structure. The structural differences between the three varieties W1, W2 and W3 would not be found in a structural change of clusters.  相似文献   

8.
Single crystals of zirconium arsenotelluride (PbFCl type) have been prepared by direct synthesis from the elements. Chemical analysis gives: AsZr = 1.43 ± 0.02 and TeZr = 0.46 ± 0.01, in atoms. Lattice constants are: a = 3.82 ± 0.01 Å and c = 8.17 ± 0.02Å. Experimental density is equal to 7.14 ± 0.05. Unit cell thus contains Zr2.00As2.86Te0.92. The structure has been solved with 227 reflections of a single crystal recorded at room temperature. The final R factor is 0.081, excluding zero reflections. Part of the arsenic atoms fills a site and the remainder is located in a second site, the occupation of which is completed by a part of zirconium atoms. The third site is occupied, but not filled, by the tellurium atoms and the remainder of zirconium atoms.  相似文献   

9.
Photoirradiated in presence of acetophenone, benzo[b]selenophene and its 3-methyl derivative add to dimethyl acetylenedicarboxylate. In each ease, the primary reaction product is unstable and has not been isolated. Photoexeited in its triplet state (the energy of which is in the neighbourhood of 69 kcalmole) benzo[b]selenophene and its 2- and 3-methyl, 2,3 dimethyl, 3 acetoxy and 2-methyl-3-acetoxy derivatives add to 1,2 dichloroethylene leading to cyclobutanes. Neither cyclo-addition occurs in absence of photosensitiser. Single-crystal X-ray analysis gave the structures of the two adducts of 3-acetoxybenzo[b]selenophene with trans-1,2-dichloroethylene. In both compounds the chlorine atoms are trans.  相似文献   

10.
The structure of sarothamnoside (genistein 7,4′-di-O-[4-O-β-D-glucopyranosyl-β-D-apiofuranoside]), a new isoflavone glycoside from Sarothamnus scoparius and S, patens, has been established by spectral analysis, mainly 13C NMR.  相似文献   

11.
1,3-bis(4-vinylnaphthyl)propane and 1-(4-vinylnaphthyl)-3-(p-vinylphenyl)propane, were cyclocodimerized with indene to afford indenyl-substituted [3.3](1,4)naphthalenophanes and [3.3]paracyclo(1,4)naphthalenophanes.  相似文献   

12.
The electron deficient acetylene, hexafluorobut-2-yne, reacts with molybdenum and tungsten methanethiolate derivatives (prepared in situ) to give vinyl and three-, five-, or six-membered heterocyclic derivatives: [Cp(OC)- MoC(O)C(CF3)C(CF3)C(O)SMe], [Cp(OC)2MC(CF3)C(CF3)C(CF3)C(O)SMe], [CpW(CO)3C(CF3C(CF3)SMe], [CpW{η3-C(CF3)C(CF3)C(SMe)OC(O)}-(CO)2]. These reactions contrast with those of trifluoropropyne where no organometallic species are obtained. On heating or irradiation with CF3CCCF3 [CpMH(CO)3] gives known bridged species and in the presence of dimethyl disulphide the vinyl derivative [CpM(CO)3C(CF3)C(CF3)H]and an isomer of undetermined structure.  相似文献   

13.
The reaction of HMPT with POCl3 was studied by 31P NMR at various temperatures and stoechiometries. Progressive substitution of chlorine atoms of phosphoryl chloride by HMPT molecules was observed. Six new species were involved in the system. The main produce was the 11 adduct, (Me2N)3P+Cl, O2PCl2?, analogous to Vilsmeier complex.  相似文献   

14.
In the presence of AlCl3, [1-β-chloroethyl-3,4-dimethylphosphole]pentacarbonyltungsten(1) rearranges into [1-chloro-3,4-dimethyl-6,7-dihydrophosphepin]pentacarbonyltungsten (3).  相似文献   

15.
Random copolymers with high molecular weights of indene and p‐methylstyrene (pMeSt) were synthesized by cationic polymerization with trichloroacetic acid/tin tetrachloride in CH2Cl2 at low temperatures. When indene and pMeSt (1:1 v/v), for example, were polymerized at ?40 °C, both monomers were consumed at very similar rates to give a copolymer with high molecular weight [number‐average molecular weight (Mn): 8–9 × 104]. This is indeed quite unexpected behavior for the combination of these two monomers because pMeSt polymerized over 1000 times faster than indene in the homopolymerization under the reaction conditions previously described. The product copolymer of indene and pMeSt had a random monomer sequence in it that was confirmed by NMR analyses and thermal‐property measurements. In sharp contrast with pMeSt, styrene and p‐chlorostyrene, which have no electron‐donating groups on the phenyl ring, led to low molecular weight polymers (Mn < 10,000) in the copolymerization with indene (1:1 v/v). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2449–2457, 2002  相似文献   

16.
The copolymerization of acrylic acid with methacrylic acid in bulk is investigated at 40 and 60°. It is confirmed that a “matrix effect” occurs only for high contents of acrylic acid. The critical concentration beyond which the matrix effect disappears is shifted towards lower acrylic acid contents for higher temperatures. The copolymer composition is independent of temperature. The copolymerization of acrylic acid with methyl acrylate is investigated in a mixture which determines an “exaltation of the matrix effect” in the homopolymerization of acrylic acid (molar fractions: mMonomers = 0.34; mn-Hexane = 0.52; mMethanol = 0.14). The resulting copolymers are found to contain a much larger fraction of acrylic acid residues than the copolymers formed in bulk or in toluene or DMF solutions.  相似文献   

17.
An amide group is shown to be capable of intramolecular participation in the formation of an 1,3-dioxolan 2-ylium cation giving a tricyclic organic cation of a new type 5a,b. This cation may be considered as a model of an electrophilic intermediate which might be formed from a peptidyl t-RNA during protein biosynthesis.The tricyclic salt 5a,b reacts with water and methanol like a classical dioxolenium salt. An amide acetal 18 can be obtained from dimethylamine and 5a; hydrolysis of 18 does not lead to the corresponding amide 20 but to the cleavage of the CN. bond.  相似文献   

18.
We demonstrate, in this article, the facile synthesis of a broad class of low‐polydispersity ethylene–norbornene (E–NB) copolymers having various controllable comonomer composition distributions, including gradient, alternating, diblock, triblock, and block–gradient, through “living”/quasiliving E–NB copolymerization facilitated with a single Pd – diimine catalyst ( 1 ). This synthesis benefits from two remarkable features of catalyst 1 , its high capability in NB incorporation and high versatility in rendering E–NB “living” copolymerization at various NB feed concentrations ([NB]0) while under an ethylene pressure of 1 atm and at 15 °C. At higher [NB]0 values between 0.42 and 0.64 M, E–NB copolymerization with 1 renders nearly perfect alternating copolymers. At lower [NB]0 values (0.11–0.22 M), gradient copolymers yield due to gradual reduction in NB concentration, with the starting chain end containing primarily alternating segments and the finishing end being hyperbranched polyethylene segments. Through two‐stage or three‐stage “living” copolymerization with sequential NB feeding, diblock or triblock copolymers containing gradient block(s) have been designed. This work thus greatly expands the family of E–NB copolymers. All the copolymers have controllable molecular weight and relatively low polydispersity (with polydispersity index below 1.20). Most notably, some of the gradient and block–gradient copolymers have been found to exhibit the characteristic broad glass transitions as a result of their possession of broad composition distribution. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013  相似文献   

19.
During the Michael addition of chiral α-sulfinyl eser (+) 1R on αβ-unsaturated esters, an extent of 24% of asymmetric induction was observed. It is shown that the addition products can be transformed into optically active δ-lactones.  相似文献   

20.
In di-tertiary groups like (Me3C)213C, the sixth methyl substituent inverts or attenuates the induced 13C chemical shift of sp2 or sp3 sites (Bσ and yπ effects).  相似文献   

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