共查询到20条相似文献,搜索用时 15 毫秒
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Frank Herwig Köhler Hans Jürgen Kalder Ernst Otto Fischer 《Journal of organometallic chemistry》1976,113(1):11-22
The nuclear spin coupling constants1J(183W13C) and in some cases 2J(183W13C) and 3J(183W13C) are determined for 10 tungsten carbene and 9 tungsten carbyne complexes. 1J is of analytical importance, being characteristically greater for WC than for WC bonds. This is due to different hybridisation at the carbon atom, and provides information about bond angles and polarities of WC and WCR units.Substituents R and R' in (CO)5WCRR' and X(CO)4WCR as well as the halogens X lead to minor changes in 1J. These changes are comparable to those of 1J(13C1H) in correspondingly substituted methanes. Unexpectedly 1J in_ creases with X = Cl, Br, I. 2J(183W13C) though being much smaller than 1J reflects different hydridisation at the β carbon atom. 相似文献
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13C-NMR spectra of fluorinated molecules are difficult to observe under conventional broad-band proton decoupling. The large coupling constants involved make polarization transfer between fluorine and carbon, using INEPT or DEPT experiments very effective while broad band fluorine decoupling collapses the multiplet pattern. 相似文献
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The 13C chemical shifts of the 6-membered nitrogen heteroaromatic compounds pyridine, pyrazine, pyrimidine, pyridazine, quinoline and isoquinoline have been measured as functions of PH in aqueous solutions. On protonation of the nitrogen, the 13C signals of the C atoms in α position usually suffer an upfield shift; the signals of the more removed C atoms are mostly shifted to lower field. The PH shifts can reach amounts in the order of 10 ppm. The PH dependences of chemical shifts of the six heterocyclic compounds investigated follow classical titration curves, whose turning-points yield the PK values of the bases in good agreement with other methods of measurement. 相似文献
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Bernd Wrackmeyer 《Journal of organometallic chemistry》1978,145(2):183-188
Chemical shifts δ(13C), δ(119Sn) and coupling constants J(119Sn13C) for alkynylstannanes of the type R4-nSn(CCR′)n (n = 1–4) are reported. The values of 1J(119Sn13C) and 2J(119SnC13C) depend upon the nature of the substituent R′. 1J(119Sn13C) in Sn(CCCH3)4 is 1168 Hz, much larger than a value predicted in the literature of ca. 700 Hz. The comparison of δ(119Sn) for (CH3)2Sn(CCR′)2 and 1,1,4,4-tetramethyl-1-stannacyclohexadi-2,5-ene suggests that the δ(119Sn) of alkynylstannanes are determined only to a small extent by the diamagnetic anisotropic effect of the CC-triple bond. 相似文献
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The results of proton and carbon magnetic resonance studies on pleiadiene (1) are reported. Data are discussed with respect to the structure of 1. Proton resonance studies indicate for 1 a rather planar configuration. Bonding phenomena in the two six-membered rings are only small affected by the 1,8 bridging of the naphthalene. As nonalternant 14 π-electron system 1 shows a carbon-13 spectrum typical for such compounds. The carbon-13 chemical shifts are discussed in comparison to related hydrocarbons. 相似文献
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[4-13C]- Azulene and [4-13C]-4-methylazulene have been synthesized. The 13C13C spin coupling constants have been measured and interpreted in terms of πMO theory. 相似文献
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By application of a modified LAOCN-3 program a complete elucidation of the 1H NMR spectra of 2,3-unsaturated glycosyl phosphonates 1–5 could be achieved. The exactly determined nJ(H, H) and novel nJ(C, P) coupling constants are discussed, and permit a conclusive deduction of the conformations. The 13C NMR spectra of 1 to 6 can be fully interpreted. By a close inspection of chemical shifts as well as 1J(C-H) and nJ(C, P) coupling constants the conformational assignment is supported. For all the derivatives the correlations 1J(C-1,He)>1J(C-1, Ha) and 1J(C-1, Pe) >1J(C-1, Pa) can be used for the assignment of anomers. The crystal structure of 1 is in accordance with this assignment of anomers and displays an unexpected conformation. Calculations by MINDO-3 in resembling model compounds serve to elucidate such conformative effects. 相似文献