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31.
Anju Midha Rajender D. Verma K. Brown R. V. Parish 《Monatshefte für Chemie / Chemical Monthly》1983,114(6-7):661-667
Mixed dialkytin(IV) trifluoroacetates,Me EtSn(O2CCF3)2,Et Pr
n
Sn(O2CCF3)2 andPr
n
Bu
n
Sn(O2CCF3)2 have been prepared by metathetical reactions of the corresponding dialkyltin(IV) chlorides with silver trifluoroacetate in CH2Cl2. They are monomeric in benzene and nonconducting inMeNO2 andMeCN. Bidentate trifluoroacetate groups are indicated by their IR spectra.Mössbauer spectra confirmtrans-arrangement of theR-Sn-R moiety.1H,19F NMR and mass spectra are also discussed.
Gemischte Dialkylzinn(IV)-trifluoracetate
Zusammenfassung Die gemischten Dialkylzinn(IV)-trifluoroacetateMe EtSn(O2CCF3)2,Et Pr n Sn(O2CCF3)2 undPr n Bu n Sn(O2CCF3)2 wurden über Metathese-Reaktionen der entsprechenden Dialkylzinn(IV)-chloride mit Silbertrifluoracetat in CH2Cl2 dargestellt. Sie sind monomer in Benzol und nichtleitend inMeNO2 undMeCN. Die IR-Spektren zeigen zweizähnige Trifluoracetat-Gruppen an. DieMössbauer-Spektren bestätigen dietrans-Anordnung derR-Sn-R-Einheit. Die1H-,19F-NMR und die Massenspektren werden ebenfalls diskutiert.相似文献
32.
《印度化学会志》2021,98(10):100156
Corona virus disease 2019 (COVID-19) endemic has havoc on the world; the causative virus of the pandemic is SARS CoV-2. Pharmaceutical companies and academic institutes are in continuous efforts to identify anti-viral therapy or vaccines, but the most significant challenge faced is the highly evolving genome of SARS CoV-2, which is imparting evolutionary selective benefits to the virus. To understand the viral mutations, we have retrieved nine hundred and thirty-four samples from different states of India via the GISAID database and analyzed the frequency of all types of point mutation in all structural, non-structural proteins, and accessory factors of SARS CoV-2. Spike glycol protein, nsp3, nsp6, nsp12, N and NS3 were the most evolving proteins. High frequency point mutations were Q496P (nsp2), A380V (nsp4), A994D (nsp3), L37F (nsp6), P323L & A97V (nsp12), Q57H (ns3), D614G (S), P13L (N), R203K (N), G204R (N) and S194L (N). 相似文献
33.
CNDO/force calculations have been employed to calculate the O-H stretching force constants for various structures of associated
water species such as water-dimethylether, water-acetonitrile, water-lithium fluoride, linear and cyclic water polymers. The
variation in the O-H stretching force constant in Am… O-H… Dn species where Am
and Dn represent, respectively,m number of electron-acceptor andn number of electron-donor molecules, is explained on the basis of the cooperativity effect. With increasing electron-acceptor
power of A and electron-donor power of D, the hydrogen-bonded O-H stretching force constant is significantly reduced. The
results obtained in these studies are in general agreement with experimental observations reported earlier. 相似文献
34.
毛茛科植物贡嘎乌头 ( Aconitum liljestrandii)具有镇痛、镇静、祛风湿等功效 ,产于我国西藏东部及四川西部 [1] .我们从其块根中分得 1 8个单体 ,其中 1 6个为已知生物碱 [2 ,3] ,2个为新生物碱 [3] .本文报道新的 C19-二萜生物碱贡乌生 ( Liljestrandisine) 1的结构 .1 实验部分1 .1 仪器与试剂 Boetius微量熔点测定仪 ;Nicolet FTIR2 0 0 SXV型红外光谱仪 ,KBr压片 ;BrukerAC- E2 0 0和 Varian Unity INOVA40 0 /5 4核磁共振仪 ,溶剂为 CDCl3,TMS为内标 ;VG Autospec30 0 0型和 VG70 A型质谱仪 ;Pekin Polarimete… 相似文献
35.
Ezer Melzer 《Letters in Mathematical Physics》1994,31(3):233-246
We prove an identity between three infinite families of polynomials which are defined in terms of bosonic, fermionic, and one-dimensional configuration sums. In the limit where the polynomials become infinite series, they give different-looking expressions for the characters of the two integrable representations of the affine su(2) algebra at level one. We conjecture yet another fermionic sum representation for the polynomials which is constructed directly from the Bethe-ansatz solution of the Heisenberg spin chain. 相似文献
36.
V. Suresh 《K-Theory》1996,10(6):597-610
Let X be a smooth projective surface over a number field k. Let (CH0(X)) denote the Chow group of zero-cyles modulo rational equivalence on X. Let CH0(X) be the subgroup of CH
0(X) consisting of classes which vanish when going over to an arbitrary completion of k. Bloch put forward a conjecture asserting that this group is isomorphic to the Tate-Shafarevich group of a certain Galois module atttached to X. In this paper, we disprove this general conjecture. We produce a conic bundle X over an elliptic curve, for which the group (CH0(X) is not zero, but the Galois-theoretic Tate-Shafarevich group vanishes. 相似文献
37.
Ayelet Lindenstrauss 《K-Theory》1996,10(3):239-265
Topological Hochschild homology is calculated for the rings /p[x]/(f(x)) (where p is prime and f(x) /p[x] any polynomial), [x]/(x
n) and [x]/(x
n–1). A spectral sequence argument is used for calculating the homology of the topological Hochschild homology spectrum, from which its stable homotopy structure can be read off since the spectrum is known for a priori reasons to be a restricted product of Eilenberg-MacLane spectra. 相似文献
38.
D. N. Kravtsov A. S. Peregudov L. S. Golovchenko E. I. Smyslova 《Russian Chemical Bulletin》1996,45(5):1194-1199
19F NMR spectroscopy was used to study the exchange reactions involving 4-fluorothiophenoxides, 4-nitrophenoxides, chlorides, and acetates of arylmercury and triphenylphosphinegold. The analysis of the data on equilibrium constants allows one to obtain information on the comparative chemical hardness of ArHg+ and Ph3PAu+ cations. The increase in the electron-donating ability of aryl ligands enhances the chemical hardness of ArHg+ cations, their influence being best described by 0 constants of substituted phenyl groups.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1255–1260, May, 1996. 相似文献
39.
David G. Wagner 《Order》1993,10(2):161-181
Order series of labelled posets are multi-analogues of the more familiar order polynomials; the corresponding multi-analogues of the related representation polynomials are calledE-series. These series can be used to describe the effect of composition of labelled posets on their order polynomials, whence their interest for us. We give a reciprocity theorem forE-series, and show that for an unlabelled poset the form of theE-series depends only upon the comparability graph of the poset. We also prove that theE-series of any labelled poset is a rational power series (in many indeterminates) and give an algorithm for computing it which runs in polynomial time when the poset is strictly labelled and of bounded width. Finally, we give an explicit product formula for theE-series of strictly labelled interval posets.This research was supported by the Natural Sciences and Engineering Research Council of Canada under operating grant #0105392. 相似文献
40.
Compounds of general formulatrans-ArNi(PR3)2OAr' (R = Et, cyclohexyl; Ar = 2-MeC6H4, 2-FC6H4; Ar' = 4-FC6H4, 4-NO2C6H4) were synthesized by the reaction of Ar'OK with cationic nickel complexes generated by treatment of ArNi(PR3)2Cl with TlBF4. Syntheses of 4-fluorophenoxide complexes, ArNi(PR3)2OC6H4F-4, additionally give some quantities oftrans-[ArNi(PR3)2OC6H4F-4][HOC6H4F-4] adducts. Exchange reactions MeC6H4Ni(PEt3)2OC6H4F-4 + XC6H4OH 2-MeC6H4Ni(PEt3)2OC6H4X + 4-FC6H4OH were studied in THF. The equilibrium is shifted to the right as the acidity of ArOH increases. A linear relationship between lgK
eq and pK
a of XC6H4OH in DMSO was found. A conclusion concerning the strong polarization of the Ni-O bond was made on the basis of an analysis of the chemical shifts of fluorine atoms in 2-MeC6H4Ni(PEt3)2OC6H4F-4.Translated fromIvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2266–2271, November, 1995. 相似文献