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Na2C2 and K2C2: Synthesis, Crystal Structure, and Spectroscopic Properties By the reaction of sodium or potassium solved in liquid ammonia with acetylene and subsequent heating in high vacuum Na2C2 and K2C2 could be synthesised as single phase products. The crystal structures described by Föppl could be confirmed by X-ray and neutron diffraction experiments (K2C2) on powdered samples. Both compounds crystallise in a tetragonal structure (I41/acd, no. 142, Z = 8) which can be described as a distorted variant of the antifluorite-structure type. At temperatures above room temperature (Na2C2: 580 K, K2C2: 420 K) a reversible phase transition (1st order transition) to a cubic modification (Fm 3 m, no. 225, Z = 4) has been observed, analogous to the alkaline earth metal acetylides. This high temperature modification represents an undistorted antifluorite structure with disordered C22– dumbbells. The results of raman- and 13C-MAS-NMR-spectroscopic investigations are in agreement with acetylide dumbbells in the title compounds and allow a comparison to the respective monoalkalimetal and alkaline earth metal acetylides. 相似文献
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Starting from the 12,13-epoxy-trichothecanes roridin C (trichodermol) ( 1 ), verrucarol ( 15 ) and trichothecolone ( 25 ), the isomeric 2β, 13-epoxy-apotrichothecanes 9, 20 and 33 have been synthesized. In these compounds the oxetane group proved to be unexpectedly stable to mineral acids and complex metal hydrides, probably due to its fusion to a cyclopentane ring. The IR. and NMR. spectra of the oxetanes are discussed. 相似文献
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《Journal of organometallic chemistry》1987,327(1):7-15
77Se and 13C NMR chemical shifts and 77Se-13C spinspin coupling constants of mono- and bis(organylseleno)acetylenes and organyl selenocyanates are shown. The changes of 77Se chemical shifts caused by variation of the organyl groups are well reflected by known increments. The δ(77Se) and 1J(77Se13C) values of the investigated compounds are discussed in relation to the corresponding alkyl- and vinyl-selenides. The 1J(77Se13C) values of the selenoacetylenes and selenocyanates as well as alkyl- and vinyl-selenides are linearly dependednt (i) on 1J(13C1H) values of the corresponding hydrocarbons, hydrogen cyanide respectively and (ii) on the product of the s-characters of the coupled Se and C atoms. These linear correlations prove the predominance of the Fermi contact term for changes of the one-bond 77Se13C coupling in dependence on hybridization. 相似文献
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13C Homonuclear decoupling experiments led to the assignment of the carbon-carbon coupling constants of 13C-enriched 1-nitronaphthalene obtained by nitration of [1-13C]naphthalene. The effects of substituents on coupling constants can be explained on the basis of the electronegativity of the first atom of the substituent, and the observed substituent effects are shown to be parallel to previous data for oxygen containing substituents. 相似文献
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Synthesis and Characterization of the Fullerene Co-Crystals C60 · 12 C6H12, C70 · 12 C6H12, C60 · 12 CCl4, C60 · 2CHBr3, C60 · 2CHCl3, C60 · 2H2CCl2 By crystallization of fullerenes from non-polar solvents (C6H12, CCl4, CHBr3, CHCl3, H2CCl2) compounds of the following compositions were obtained: C60 · 12C6H12, C70 · 12C6H12, C60 · 12CCl4, C60 · 2CHCl3, C60 · 2CHBr3 and C60 · 2H2CCl2. Lattice parameters have been determined by X-ray diffraction of powder samples; according to single-crystal examinations on C60 · 12C6H12, C60 · 12CCl4 and C60 · 2CHBr3 the fullerene is orientationally disordered. C60 · 12C6H12, cubic, a = 28.167(1) Å; C70 · 12C6H12, cubic, a = 28.608(2) Å; C60 · 12CCl4, cubic, a = 27.42(1) Å; C60 · 2CHBr3, hexagonal, a = 10.212(1), c = 10.209(1) Å; C60 · 2CHCl3, hexagonal, a = 10.08(1), c = 10.11(2) Å; C60 · 2H2CCl2, tetragonal, a = 16.400(1) Å, c = 11.645(7) Å. 相似文献
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Distinction of Symmetrically Substituted Carbocyclic Compounds by 13C, 13C Spin-Spin Coupling. Comparison of Conventional and INADEQUATE13C-NMR Spectroscopy 13C,13C spin-spin couplings allow an easy distinction of symmetrically substituted carbocyclic compounds. On the basis of the number and ratio of 13C,13C satellite pairs, for instance head to head and head to tail products of photodimerisations can be distinguished. The informations derived from a conventional and an INADEQUATE 13C-NMR spectrum are compared. 相似文献
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Michael Stcker Martin Klessinger Konrad Wilhelm 《Magnetic resonance in chemistry : MRC》1981,17(2):153-155
One bond 13C,13C- and 13C,1H-coupling constants have been measured for some 1,2-dimethylene-cycloalkanes, as well as for 2,3-dimethylbuta-1,3-diene and methylenecyclobutane. The results for 2,3-dimethylbuta-1,3-diene confirm the findings for buta-1,3-diene, i.e. that J(C-1, C-2) is smaller for the diene than for the correspondingly substituted monoene. No differences have been found between the 1J(CC) exocyclic coupling constants of the dimethylene and monomethylene cycloalkanes. 相似文献
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Synthesis and NMR Spectra of Some 13C-Labelled Thio- and Seleno-ethers, -acetals, and -orthoesters Twenty-seven different open-chain and cyclic derivatives (RX)nCH4-n and (RX)nCH3-nR′ with n = 1?3, X = S or Se, R,R′ = alkyl or aryl, 1,3,5-trithiane, and bis-(dimethylsulfonio)methane and -methanide with single or multiple 13C-labelling have been synthesized. The 13C-NMR spectra of the sulfur and selenim compounds have been measured, and the dependence of the chemical shifts (δc) and coupling constants [′J(C,H), ′J(Se,C)] from the substitution pattern in discussed (Fig. 1) and compared with the polyhalogeno-methanes (Fig. 2). 相似文献
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D. L. Ward 《Acta Crystallographica. Section C, Structural Chemistry》1993,49(10):1789-1792
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Robert Pendrill Ole W. Sørensen Göran Widmalm 《Magnetic resonance in chemistry : MRC》2014,52(3):82-86
Site‐specific 13C isotope labeling is a useful approach that allows for the measurement of homonuclear 13C,13C coupling constants. For three site‐specifically labeled oligosaccharides, it is demonstrated that using the J‐HMBC experiment for measuring heteronuclear long‐range coupling constants is problematical for the carbons adjacent to the spin label. By incorporating either a selective inversion pulse or a constant‐time element in the pulse sequence, the interference from one‐bond 13C,13C scalar couplings is suppressed, allowing the coupling constants of interest to be measured without complications. Experimental spectra are compared with spectra of a nonlabeled compound as well as with simulated spectra. The work extends the use of the J‐HMBC experiments to site‐specifically labeled molecules, thereby increasing the number of coupling constants that can be obtained from a single preparation of a molecule. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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