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991.
S. Banerjee S. N. Ganguli A. Gurtu P. K. Malhotra R. Raghavan A. Subramanian K. Sudhakar M. M. Agarwal J. M. Kohli J. P. Lamba I. S. Mittra J. B. Singh P. M. Sood Dev Anand P. V. K. S. Baba G. L. Kaul Y. Prakash N. K. Rao G. Singh R. Hamatsu T. Hirose S. Kitamura T. Yamagata 《Zeitschrift fur Physik C Particles and Fields》1985,28(2):163-170
992.
J. S. Baijal P. Sumitra Deepika Kothari Chandra Prakash Pran Kishan 《Hyperfine Interactions》1987,35(1-4):879-882
57Fe Mössbauer effect studies were made on titanium substituted Li?Zn ferrite with composition Li0.45+0.5tZn0.1 Tit Fe2.45–1.5tO4 (t=0.0 to 1.2) at 300K. The Mössbauer spectra for t≤0.4 show two well defined Zeeman sextets corresponding to the Fe3+ ions at tetrahedral (A) and octahedral (B) sites. The spectra for t=0.6, 0.8 and 0.9 show relaxation but can still be resolved into 2 sextets. The spectra for t=1.0, 1.2 show strong ferrimagnetic relaxation with the spectra for t=1.2 exhibiting an additional central doublet. The effect of Ti4+ substitution on the Isomer shift (I.S), Quadrupole splitting (Q.S.) and nuclear magnetic fields of Li?Zn ferrites have been reported in this paper. The I.S. was found to be independent of substitution level t, while the quadrupole splitting was observed to be negligible. The variation of hyperfine field with t has been explained on the basis of superexchange interaction and cation distribution. 相似文献
993.
Mössbauer studies at room temperature and down to liquid nitrogen temperature were supplemented with magnetic and infrared studies of Monochloroferricbis (X-benzoate) and monochloroferricbis (X-chloroacetate). Mössbauer parameters indicate that all the complexes possess high spin configuration in the trivalent and monomeric states. Positive value of Vzz indicates that there is more negative charge in the x-y plane than in along z-axis, suggesting that Fe is penta-coordinated. Molecular weight determination also confirms that the complexes are mononuclear. The effective magnetic moment of the complexes points out to a weak field iron configuration. An attempt has been made to interpret the structure of these complexes on the basis of the measured data. 相似文献
994.
995.
S. Prakash 《Fresenius' Journal of Analytical Chemistry》1964,206(1):37-38
Ohne Zusammenfassung 相似文献
996.
Electronic structures and energies of superelectrophilic dications derived by protonation of methyl- and dimethylmethyleniminium (R'R' 'C=N+R'R' '; R', R' ' = CH3 or H) ions were calculated at the ab initio MP2/6-311+G level. The calculations identified the N-protonated isopropyleniminium dication 14 as a minimum structure. On the basis of computed energies, deprotonation energies of the global minimum structures were also calculated. The 13C NMR chemical shifts of the intriguing dication 14 were calculated using the GIAO-MP2 method. The 13C NMR chemical shifts of the isoelectronic analogue tert-butyl cation were also calculated at the same level in order to explore the effect of an additional charge in dications 14. 相似文献
997.
UV-vis spectrophotometry is utilized to measure the relative efficiency of lithium acetate, tetrabutylammonium trifluoroacetate, and triethylamine as catalysts for the conversion of 4-methoxycinnamic acid to 4-methoxy-beta-bromostyrene. In acetonitrile-water as solvent, the efficiency order is lithium acetate > triethylamine > tetrabutylammonium trifluoroacetate. For triethylamine as catalyst, solvent-dependent order is acetonitrile-water > dichloromethane > acetonitrile. Using triethylamine as catalyst (5-20 mol %), cinnamic acids, and propiolic acids are converted to corresponding beta-bromostyrenes and 1-halo-1-alkynes in 60-98% isolated yields within 1-5 min. 相似文献
998.
Bucsi I Török B Marco AI Rasul G Prakash GK Olah GA 《Journal of the American Chemical Society》2002,124(26):7728-7736
The preparation, (1)H, (13)C, and (19)F NMR structural characterization as well as with DFT-based theoretical calculations of stable dialkyl ether/poly(hydrogen fluoride) complexes are reported. Dimethyl ether/poly(hydrogen fluoride) (DMEPHF), are stable complexes of particular interest and use. The DFT calculations, that are in agreement with NMR data, suggest a cyclic poly(hydrogen fluoride) bridged structure for DMEPHF. The complex, DME-5 HF was found to be a convenient and effective new fluorinating agent with the ease of workup and applied to several fluorination reactions, such as the hydrofluorination and bromofluorination of alkenes, and fluorination of alcohols giving good to excellent yield with high selectivity. Homologous dialkyl ether/poly(hydrogen fluoride) (R(2)O/[HF](n,), R = Et, nPr) systems are also stable and suitable for fluorination reactions. 相似文献
999.
1000.
Structures of the tri(amino)amine N(NH(2))(3)(2+) and the tri(azido)amine N(N(3))(3)(2+) dications were calculated at the density functional theory (DFT) B3LYP/6-311+G level. The tri(amino)amine dication (NH(2))(3)N(2+) (1) was found to be highly resonance stabilized with a high kinetic barrier for deprotonation. The structures of diamino(azido)amine dication (NH(2))(2)N(N(3))(2+) (2), amino(diazido)amine dication (NH(2))N(N(3))(2)(2+) (3), and tri(azido)amine dication (N(3))(3)N(2+) (4) were also found to be highly resonance stabilized. The structures and energetics of the related mixed amino(azido)ammonium ions (N(3))(x)N(NH(2))(4-x)(+) (x = 0-4) were also calculated. 相似文献