Temperature-dependent, effective structures of the 14NH3 and 14ND3 molecules

Measurements result in effective, usually temperature-dependent structural parameters of molecules, and never directly in equilibrium structures, which are theoretical constructs. A recent high-accuracy semiglobal potential energy surface of the electronic ground state of the ammonia molecule, called NH3-Y2010 (J. Mol. Spectrosc. 2011, 268, 123), which exhibits mass-independent equilibrium NH bond length and a HNH bond angle of 1.0109 ? and 106.75°, respectively, is employed together with the variational nuclear motion code GENIUSH (J. Chem. Phys. 2009, 130, 134112; 2011, 134, 074105) to determine directly measurable, effective structural parameters of the (14)NH(3) and (14)ND(3) molecules. The effective r(g)- and r(a)-type NH(ND) distances determined at 300 K are 1.0307(1.0254) and 1.0256(1.0217) ?, respectively, with an estimated accuracy of 2 × 10(-4) ?. The effective θ(g) HNH and DND bond angles at 300 K are 106.91° and 106.85°, respectively. The root-mean-square amplitudes of vibration, l(g), for the NH(ND) distances at 300 K are 0.073(0.062) ?. These structural parameters confirm the less accurate results of a room-temperature gas-electron-diffraction study (J. Chem. Phys. 1968, 49, 2488, all data in ?): r(g)(NH) = 1.030(2), l(g)(NH) = 0.073(2), r(g)(ND) = 1.027(3), and l(g)(ND) = 0.061(2). The computed difference in the r(g,T)(NH) bond lengths of the two spin isomers (ortho and para forms) of (14)NH(3) is 3 × 10(-5) ? at 0 K, the difference diminishes at temperatures of about 30-50 K.     

Neue Vertreter des K2Li14[Pb3O14]-Typs Cs2Li14[Tb3O14] und K2Li14[Zr3O14] [1, 2]

Inhaltsübersicht. Erstmals wurden klar durchscheinende, orange-farbene Einkristalle von Cs₂Li₁₄[Tb₃O₁₄] aus Cs₂TbO₃ und Li₂O (Tb: Li = 1:5) dargestellt [550°C, 21 d, verschlossenes AuRohr]. Es liegt der K₂Li₁₄[Pb₃O₁₄]-Typ vor [Vierkreisdiffraktometerdaten, PW 1100, MoKä-Strahlung, 660 I_o(hkl), R = 4,8%, R_w = 3,4%, Immm, a = 1293,5(8), b = 792,6(3), c = 740,4(3) pm, Z = 2, d_rö = 4,65]. Ebenfalls neu wurde K₂Li₁₄[Zr₃O₁₄] in Form farbloser Einkristalle durch Tempern inniger Gemenge von K₂O, Li₂O und ZrO₂ (K: Li: Zr = 1:4:1,5) dargestellt [900°C, 14 d, geschlossene Ni-Bombe] und röntgenographisch untersucht. Die Strukturverfeinerung [612 I_o(hkl), Vierkreisdiffraktometerdaten, PW 1100, MoKα-Strahlung, R = 5,9%, R_w = 5,3%, Immm, a = 1244,6, b = 776,4, c = 724,3 pm, Z = 2] bestätigt die Isotypie mit K₂Li₁₄[Pb₃O₁₄]. Der Madelunganteil der Gitterenergie, MAPLE, Effektive Koordinationszahlen, ECoN, diese über Mittlere Effektive Ionenradien, MEFIR, wurden berechnet. Für die nun bekannten Vertreter dieses Typs wurde ein Isotypievergleich vorgenommen. New Compounds of the K₂Li₁₄[Pb₃O₁₄] Type: Cs₂Li₁₄[Tb₈O₁₄] and K₂Li₁₄[Zr₃O₁₄] For the first time Cs₂Li₁₄[Tb₃O₁₄] has been prepared as orange single crystals from Cs₂TbO₃ and Li₂O (Tb: Li = 1:5) [550°C, 21 d, sealed Au-Tube]. Structure Refinement [four-circle diffractometer data, PW 1100, MoKα radiation, 660 I_o(hkl), R = 4.8%, R_w = 3.4%, Immm, a = 1293.5(8), b = 792.6(3), c = 740.4(3) pm, Z = 2, d_rö = 4.65] confirms isotypy with K₂Li₁₄[Pb₃O₁₄]. K₂Li₁₄[Zr₃O₁₄] has also been prepared as colorless single crystals from K₂O, Li₂O, and ZrO₂ (K: Li: Zr = 1:4:1.5), [900°C, 14 d, closed Ni-cylinder] and investigated by x-ray [612 I_o(hkl), four-circle diffractometer data, PW 1100, MoKα radiation, R = 5.9%, R_w = 5.3%, Immm, a = 1244.6, b = 776.4, c = 724.3 pm, Z = 2]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, the latter derived from Mean Effective Fictive Ionic Radii, MEFIR, are calculated. A detailed comparison of the structures is carried out.     

Syntheses,Crystal Structures,and Properties of New Ternary Chalcogenides of Group 4 Metals: Rb4Ti3S14, Cs4Zr3S14, K4Hf3Se14, and K4ZrHf2Se14

The new ternary compounds Rb₄Ti₃S₁₄, Cs₄Zr₃S₁₄, K₄Hf₃Se₁₄, and K₄ZrHf₂Se₁₄ were prepared by reacting the respective transition metals in alkali metal polychalcogenide melts. Two crystallographically independent transition metal cations are present that are coordinated by eight chalcogen atoms (Q) in an irregular fashion or by seven chalcogen atoms yielding a distorted pentagonal bipyramid. The M(1)Q₈ and M(2)Q₇ polyhedra are connected by sharing common edges or trigonal faces leading to the formation of infinite linear one‐dimensional anionic chains running parallel to the [101] direction. The chains are separated by alkali metal cations. The optical band gaps determined are 1.59 eV for Rb₄Ti₃S₁₄, 2.35 eV for Cs₄Zr₃S₁₄, and 2.02 eV for K₄Hf₃Se₁₄. In‐situ X‐ray powder diffractometry demonstrates that Rb₄Ti₃S₁₄ decomposes at 430 °C into Rb₂S₅ and TiS. During the cooling cycle the re‐formation of the polysulfide is observed. According to this result the polysulfide could be prepared using TiS instead of metallic Ti as well.     

新型尼龙214,414,614,814,1014和1214的合成与表征

用熔融缩聚法基于十四碳二酸合成了一系列偶偶尼龙，包括尼龙2 14，4 14， 6 14，8 14，10 14，12 14。用红外光谱、元素分析、核磁共振、差示扫描热分析 、热失重分析、热机械分析、粘度法对合成尼龙的结构与性能进行了表征。同时还 初步研究了尼龙12 14的物理性能，发现其物理性能介于尼龙66和聚乙烯之间。     

Rovibrational spectra of ammonia. II. Detailed analysis, comparison, and prediction of spectroscopic assignments for 14NH3, 15NH3, and 14ND3

Several aspects of ammonia rovibrational spectra have been investigated using the new HSL-2 potential energy surface that includes an approximate correction for nonadiabatic effects. The unprecedented accuracy of rovibrational energy levels and transition energies computed using HSL-2 was demonstrated in Part I of this study. For (14)NH(3), new assignments for a few ν(3) + ν(4) band transitions and energy levels are suggested, and discrepancies between computed and HITRAN energy levels in the 2ν(4) band are analyzed (2ν(4) is the most difficult band below 5000 cm(-1)). New assignments are suggested for existing or missing 2ν(4) levels. Several new vibrational bands are identified from existing, unassigned HITRAN data, including 2ν(2) + ν(4), (ν(3) + ν(4)) -A(')∕A("), ν(1) + 2ν(2), and 2ν(2) + 2ν(4). The strong mixing between the 2ν(4) and 2ν(2) + ν(4) bands is carefully examined and found to be the source of the difficulties in the experimental modeling of 2ν(4). Discussion is presented for preliminary J = 10 results, where the overall root-mean-square error is estimated to be less than 0.039 cm(-1). The analysis of the 4ν(2) band demonstrates both the reliability and the accuracy of predictions from HSL-2. The full list of computed J = 0 band origins (with assignments) and the inversion splittings up to 7000-8000 cm(-1) above the zero-point energy are presented. J = 0-2 levels are reported for those bands below 5100 cm(-1) that are missing from the HITRAN database. For (15)NH(3), excellent agreement is found for the available ν(2) and ν(3) + ν(4)(E) transition energies, but significant deficiencies are shown for HITRAN levels and several corrections are suggested. The (15)N isotopic effects are presented for the J = 0-6 levels of 13 HITRAN bands. For (14)ND(3), we reproduce the pure rotational inversion spectra line frequencies with an accuracy similar to that for (14)NH(3). However, it is not possible to reproduce simultaneously all four pairs of inversion-split vibrational fundamentals to better than 0.05 cm(-1) uncertainty. It is suggested that a reanalysis of some suspicious (14)ND(3) fundamental bands is required. The analyses presented here and in Part I show that rovibrational energy levels and transition frequencies computed with HSL-2 (with nonadiabatic corrections) remain highly accurate well beyond the experimental data used in the refinement procedure. Calculations using HSL-2 are capable of revealing many deficiencies in experimental analyses of ammonia spectra and provide reliable predictions with similar accuracy. It is expected that the results of this study will be useful in the future interpretation of high-resolution spectra from laboratory experiments or from astronomical observations. The present work represents a very significant advance in the state of our knowledge of the spectroscopy of ammonia and its isotopologues.     

Cyclization of 3-methoxy-8, 14-seco-D-homoestra-1, 3, 5(10), 9(11)-tetraene-14, 17a-dione into D-homoestrone derivatives

Conclusions In the cyclization of 3-methoxy-8, 14-seco-D-homoestra-1,3,5,(10),9(11)-tetraene-14, 17a-dione (I) the stereoisomeric 14-hydroxy-3-methoxy-D-homoestra-1,3,5(10),9(11)-tetraen-17a-ones (III) and (IV) are formed at first, and after dehydration and isomerization these are converted into 3-methoxy-D-homoestra-1,3,5(10),8,14-pentaen-17a-one (II). The ketol (IV) is much more readily dehydrated than the ketol (III) and is probably themain intermediate product in the cyclization of the diketone (I).Translated from Izvestiya Akadeemii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1413–1416, August, 1965 Original article submitted June 24, 1963     

Stability of nitrogen-oxygen cages N12O2, N14O2, N14O3, and N16O4

Molecules consisting entirely of nitrogen have been studied extensively for their potential as high energy density materials (HEDM). However, many such molecules are too unstable to serve as practical energy sources. This has prompted many studies of molecules that are mostly nitrogen but which incorporate heteroatoms into the structure to provide additional stability. In the current study, cages of three-coordinate nitrogen are viewed as candidates for stabilization by insertion of oxygen atoms into the nitrogen framework. Cages of N12, N14, and N16 with four-membered rings are studied because four-membered rings have been previously shown to be a destabilizing influence. Insertion of oxygen atoms, which converts N-N bonds to N-O-N bonding groups, relieves ring strain and can potentially result in stable molecules. These molecules are studied by theoretical calculations, using Hartree-Fock and Moller-Plesset (MP3 and MP4) theories, to determine the dissociation energies of the molecules. The primary result of the study is that stable molecules can result from oxygen insertion but that oxygen-oxygen proximity destabilizes the insertion products.     

Editorial board page for “Synthetic Communications”, Volume 14, Number 3

This is a scanned image of the original Editorial Board page(s) for this issue.     

Editorial board page for “Liquid Crystals”, Volume 14, Number 3

Abstract

This is a scanned image of the original Editorial Board page(s) for this issue.