共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
4.
5.
《Acta Crystallographica. Section C, Structural Chemistry》2018,74(6):721-727
The crystal structures of hydrothermally synthesized (T = 493 K, 7–9 d) rubidium aluminium bis[hydrogen arsenate(V)], RbAl(HAsO4)2, caesium iron bis[hydrogen arsenate(V)], CsFe(HAsO4)2, rubidium dialuminium arsenic(V) hexakis[hydrogen arsenate(V)], RbAl2As(HAsO4)6, and caesium diiron arsenic(V) hexakis[hydrogen arsenate(V)], CsFe2As(HAsO4)6, were solved by single‐crystal X‐ray diffraction. The four compounds with the general formula M+M3+(HAsO4)2 adopt the RbFe(HPO4)2 structure type (Rc) and a closely related new structure type, which is characterized by a different stacking order of the building units, leading to noncentrosymmetric space‐group symmetry R32. The second new structure type, with the general formula M+M3+2As(HAsO4)6 (Rc), is also a modification of the RbFe(HPO4)2 structure type, in which one third of the M3+O6 octahedra are replaced by AsO6 octahedra, and two thirds of the voids in the structure, which are usually filled by M+ cations, remain empty to achieve charge balance. 相似文献
6.
Leszek Konopski 《Journal of mass spectrometry : JMS》1990,25(4):204-208
The presence of the [M + H]+ ions and the absence of the monomer molecular ions M+· in the mass spectra of some tertiary α- and γ-nitrosocarbonyl compounds is reported. This effect is caused by the rearrangement of the mobile hydrogen in the α-carbonyl position in the fragmentation pattern of the dimer molecular ions 2M+·. 相似文献
7.
Thomas Sürig Hans-Friedrich Grützmacher Norbert de Kimpe 《Journal of mass spectrometry : JMS》1991,26(10):882-888
A series of α-chloro- and α-bromoketimines compounds (1-9) with different substituents at the α-position and at the imino group has been investigated by electron impact mass spectrometry as possible precursors of the correspondingly substituted α-imidoyl carbenium ion, an important class of destabilized carbenium ions. The main fragmentation of the molecular ions of compounds, 1-9 in the ion source corresponds to an α-cleavage at the imino group; however, fragment ions are also formed by loss of the α-halo substituent. These fragment ions correspond at least formally to α-imidoyl carbenium ions. Their further reactions in dependence on the type of substituents at the imino group and at the α-C atom, were studied by mass-analysed ion kinetic energy and collisional activation mass spectrometry. The results agree with the initial formation of destabilized α-imidoyl carbenium ions but indicate an easy rearrangement of these ions in the presence of suitable alkyl substituents by 1,2- and 1,4-hydrogen shifts to more stable isomers. 相似文献
8.
9.
C.Akira Horiuchi Akinori Takeda Wen Chai Kishoh Ohwada Shun-Jun Ji T.Tomoyoshi Takahashi 《Tetrahedron letters》2003,44(52):9307-9311
A novel reaction of α-iodo ketone (α-iodocycloalkanone, α-iodo-β-alkoxy ester, and α-iodoacyclicketone) with irradiation under a high-pressure mercury lamp gave the corresponding α-hydroxyketone in good yields. In the case of α,α′-diiodo ketone, α,α′-dihydroxyketone which little has been reported until now was obtained. This reaction affords a new, clean and convenient synthetic method for α-hydroxy- and α,α′-dihydroxyketone. 相似文献
10.
11.
Wilder Carrillo-Cabrera Nubia Caroca-Canales Hans Georg von Schnering 《无机化学与普通化学杂志》1994,620(2):247-257
K21–δNa2+δIn39 with δ = 2.82 was synthesized (melted at 973 K, annealed at 623 K) from the elements in sealed niobium ampoules. The compound forms prismatic crystals with silver metallic lustre and is unstable in air and moisture. The crystal structure of K21–δNa2+δIn39 (orthorhombic; space group Pnma, No. 62; a = 17.844(5) Å, b = 17.192(3) Å, c = 25.078(7) Å; Z = 4; Pearson code oP248; δ = 2.82, obtained from the structure refinement) contains eight empty In icosahedra of two types, A (12 exo-bonds) and B (7 exobonds), and four open In15 clusters (15 exo-bonds). The latter are centered by K atoms and belong to C units, which are defined as [K(Na2M3In15)] heteroatomic clusters (M = K + Na). The spatial distribution of the In icosahedra A, B and heteroatomic clusters C is that of the atoms in the cubic Laves phase MgCu2: MgCu2 ? [K(Na2M3In15)][In]2. All the Inn clusters are interconnected by exo-bonds forming a covalent three-dimensional framework (d(In? In) = 2.832 to 3.301 Å). The remaining alkali metal atoms build up a three-dimensional M136 network of the clathrate-II type with (16 + 8) cages, which envelopes the In icosahedra and [K(Na2M3In15)] clusters. This structure can be described as a cluster-replacement derivative of the clathrate-II structure: (H2S)16(CCl4)8 · (H2O)136 ? [In]16[K(M5In15)]8M136, and is one member of a novel hierarchical structure family, based upon cluster-replacement. The bonding as well as the structural relationships to other phases are discussed. 相似文献
12.
13.
14.
15.
16.
17.
18.
Bonkoch Tarnchompoo Chachanat Thebtaranonth Yodhathai Thebtaranonth 《Tetrahedron letters》1987,28(52)
Diene
readily adds primary amines to give
which can cyclize either in a Michael addition fashion or via a displacement reaction to give, respectively, pyrrolidine
or methylene lactam
which further isomerizes to
under the employed reaction conditions. Compound
can be obtained as the sole product from the reaction of diene precursor
with amines followed by vacuum pyrolysis. 相似文献
19.
Carbon-13 spectra of a series of 26 unsaturated ketones (ortho- and para-cyclo-hexadienones and corresponding open-chain analogues) have been measured by Fourier-transform. Pulse spectroscopy. A complete analysis has been achieved by means of double resonance experiments using noise-modulated and coherent off-resonance proton irradiation and with the aid of non-decoupled spectra. Chemical shifts are interpreted in terms of charge distribution in the dienone system and of methyl substituent effects. Carbon chemical shifts were also obtained for O-protonated ortho- and para-cyclohexadienones. One-bond and long-range carbon-proton and carbon-fluorine spin coupling constants are reported for several compounds. 相似文献