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1.
Karl Hassler 《Monatshefte für Chemie / Chemical Monthly》1988,119(8-9):851-862
Trisilylphosphanes of the type PSi3
Me
x
Ph
9–x
are formed when sodium/potassiumphosphide reacts with methylphenylchlorosilanesMe
n
Ph
3–n
SiCl or with mixtures of methylphenylchlorosilanes. The phosphanes (SiMe
3)
n
P (SiMe
m
Ph
3–m
)3–n
(n, m=0, 1, 2, 3) were separated and purified by destillation or crystallization and their29Si as well as31P-NMR-spectra were recorded. 相似文献
2.
Keitaro Kiyosawa 《Journal of solution chemistry》1991,20(6):583-588
Freezing-point depression of mixtures of H
2
16
O and H
2
18
O were measured. The results showed that the freezing point of the mixture rose linearly with an increase in the molal concentration of H
2
18
O. The results suggested the formation of a solid solution of H
2
16
O and H
2
18
O by freezing, similar to that formed by H
2
O–D
2
O, and that H
2
18
O behaves as a different molecule than H
2
16
O. 相似文献
3.
Dhanpat Rai Dean A. Moore Nancy J. Hess Linfeng Rao Sue B. Clark 《Journal of solution chemistry》2004,33(10):1213-1242
Chromium(III)-phosphate reactions are expected to be important in managing high-level radioactive wastes stored in tanks at many DOE sites. Extensive studies on the solubility of amorphous Cr(III) solids in a wide range of pH (2.8–14) and phosphate concentrations (10–4 to 1.0 m) at room temperature (22±2)°C were carried out to obtain reliable thermodynamic data for important Cr(III)-phosphate reactions. A combination of techniques (XRD, XANES, EXAFS, Raman spectroscopy, total chemical composition, and thermodynamic analyses of solubility data) was used to characterize solid and aqueous species. Contrary to the data recently reported in the literature,(1) only a limited number of aqueous species [Cr(OH)3H2PO–4, Cr(OH)3(H2PO4)2–2), and Cr(OH)3HPO2–4] with up to about four orders of magnitude lower values for the formation constants of these species are required to explain Cr(III)-phosphate reactions in a wide range of pH and phosphate concentrations. The log Ko values of reactions involving these species [Cr(OH)3(aq)+H2PO–4⇌Cr(OH)3H2PO–4; Cr(OH)3(aq)+2H2PO–4⇌Cr(OH)3(H2PO4)2–2; Cr(OH)3(aq)+HPO2–4⇌Cr(OH)3HPO2–4] were found to be 2.78±0.3, 3.48±0.3, and 1.97±0.3, respectively. 相似文献
4.
将以烯烃为原料通过Sharpless不对称双羟化等多步反应合成的8种手性β-氨基醇, 作为有机小分子催化剂, 用于催化α,β-不饱和酮的不对称环氧化反应.考察了影响对映选择性的催化剂结构、催化剂用量、氧化剂种类、溶剂、反应温度等因素.结果表明, 当催化剂用量为30 mol%、氧化剂为TBHP(叔丁基过氧化氢)、正己烷溶剂、在室温下、以(1S,2R)-(+)-1,2-二苯基-2-甲氨基乙醇(3)作催化剂时, 所得环氧化物的对映体过量最高为70% ee, 产率最高为84%. 相似文献
5.
6.
In the system U–La–N a new phase of composition La2U2N5 was observed. The differaction pattern of this phase can be indexed with a tetragonal unit cell:a=8.43 Å,c=8.50 Å andc/a=1.008. The pseudocubic sub-cell withaca/2 is closely related to the CsCl-type.
Auszug aus der von der Technisch-Naturwissenschaftlichen Fakuktät der TU Wien approbierten Diplomarbait des Herrn Dipl.-Ing.J. Waldhart. 相似文献
7.
Summary Stepwise electrophilic bromination of hypericin in pyridine as the solvent yields regioselectively 2,5-dibromohypericin, 2,5,9-tribromohypericin, and 2,5,9,12-tetrabromohypericin. The compounds were characterized by means of NMR-, UV-Vis-, and fluorescence-spectra, andpK
a
andpK*
a
measurements. These properties were compared with those of hypericin on the one hand and of the recently isolated gymnochromes on the other hand.
Zur Bromierung des Hypericins: Die Gymnochrom-Chromophore
Zusammenfassung Schrittweise elektrophile Bromierung von Hypericin in Pyridin als Lösungsmittel liefert regioselektiv 2,5-Dibromhypericin, 2,5,9-Tribromhypericin und 2,5,9,12-Tetrabromhypericin. Diese Verbindungen wurden durch NMR-, UV-Vis- und Fluoreszenz-Spektrometrie sowie durchpK a - undpk* a -Messungen charakterisiert. Diese Eigenschaften wurden mit jenen des Hypericins und der kürzlich isolierten Gymnochrome verglichen.相似文献
8.
G. Chambaud W. Gabriel T. Schmelz P. Rosmus A. Spielfiedel N. Feautrier 《Theoretical chemistry accounts》1993,87(1-2):5-17
Summary The three-dimensional potential energy functions have been calculated from highly correlated multireference configuration interaction electronic wavefunctions for theX
3
B
1,a
1
A
1, andb
1
B
1 states of the NH
2
+
ion. For the quasi-linear electronic ground state this information and the electric dipole moment functions have been used to calculate spectroscopic constants, line intensities and rotationally resolved absorption spectra. For thea
1
A
1-b
1
B
1 bent/quasi-linear Renner-Teller system ro-vibronic energy levels have been obtained from a variational approach accounting for anharmonicity, rotation-vibration and electronic angular momenta coupling effects. The vibronic levels are given for energies up to 13 500 cm–1 for the bending levels and up to 8000 cm–1 for the stretching and combination levels.Dedicated in the honor of Prof. Werner Kutzelnigg 相似文献
9.
The Wiener index of a graph G is defined as
, where V(G) is the set of all vertices of G and for
denotes the length of a minimal path between x and y. A
C
4
C
8 net is a trivalent decoration made by alternating squares C
4 and octagons C
8. It can cover either a cylinder or a torus. In this paper, an algorithm for computing the distance matrix of a C
4
C
8(R) nanotorus T = T[p,q] is given. Using this matrix, the Wiener index of T is computed. 相似文献
10.
Dmitrenok A. S. Radhika P. Anjaneyulu V. Subrahmanyam C. Subba Rao P. V. Dmitrenok P. S. Boguslavsky V. M. 《Russian Chemical Bulletin》2003,52(8):1868-1872
Sphingolipids and glycolipids including previously unknown (2S,3S,4R)-1,3,4-trihydroxy-2-(2-(R)-hydroxyoctadecanoylamino)octadec-8E-ene, (2S,3R)-1,3-dihydroxy-2-octadecanoylamino-4E,8E-hexadecadiene, and (2-hydroxy-3-hexadecyloxypropyl)--L-fucopyranoside were isolated from soft corals collected on the shelf near the Andaman Islands (Indian Ocean). The structures of all compounds were established by spectroscopic methods and chemical analyses. The lipids possessed antibacterial activity against Bacillus subtilis, Bacillus pumilus, Escherichia coli, and Pseudomonas aeruginosa and antifungal activity against Aspergillus niger, Rhizopus oryzae, and Candida albicans. 相似文献
11.
《Journal of Coordination Chemistry》2012,65(12):2074-2086
Mercury cyanide complexes of alkyldiamines (1–6), [Hg(L)(CN)2] (where L?=?en (1,2-diaminoethane), pn (1,3-diaminopropane), N-Me-en, N, N′-Me2-en, N, N′-Et2-en, and N, N′-ipr2-en), have been synthesized and characterized by elemental analysis, IR, 13C, and 15N solution NMR in DMSO-d6, as well as 13C, 15N, and 199Hg solid-state NMR spectroscopy. Complexes 1 and 2 have been studied computationally, built and optimized by GAUSSIAN03 using DFT at B3LYP level with LanL2DZ basis set. Binding modes of en and bn (where bn?=?1,4-diaminobutane) toward Hg(CN)2 are completely different. Complexes with en and pn show chelating binding to Hg(II), while bn behaves as a bridging ligand to form a polymeric structure, [Hg(CN)2-bn]∞ [B.A. Al-Maythalony, M. Fettouhi, M.I.M. Wazeer, A.A. Isab. Inorg. Chem. Commun., 12, 540 (2009).]. The solution 13C NMR of the complexes demonstrates a slight shift of the ?C≡N (0.9 to 2?ppm) and ?C–NH2 (0.25 to 6?ppm) carbon resonances, while the other resonances are relatively unaffected. 15N labeling studies have shown involvement of alkyldiamine ligands in coordination to the metal. The principal components of the 13C, 15N, and 199Hg shielding tensors have been determined from solid-state NMR data. Antimicrobial activity studies show that the complexes exhibit higher antibacterial activities toward various microorganisms than Hg(CN)2. 相似文献
12.
H. K. Gakhar Satish Chand Naresh Kumar 《Monatshefte für Chemie / Chemical Monthly》1981,112(8-9):1083-1090
Zusammenfassung Es wurde eine Reihe von 5,12a-Dihydro-6-alkyl/aryl-6H-benzothiazolo [3,2-c]-1,3-dioxolo[4,5-g]chinazoline, sowohl mitcis-als auchtrans-ständigen Wasserstoffatomen an Kohlenstoff 6 und 12a, synthetisiert. Ebenso wurden auch Verbindungen dieses Systems mit Thiazol an Position 6 hergestellt. Die Strukturen wurden mittels IR- und NMR-spektroskopischen Daten abgesichert.
Benzothiazolo[3,2-c]-1,3-dioxolo[4,5-g]quinazolines
Some 5,12a-dihydro-6-alkyl/aryl-6H-benzothiazolo[3,2-c]-1,3-dioxolo [4,5-g]quinazolines withcis as well astrans stereochemistry of the hydrogens at carbon 6 and 12a have been synthesised. The synthesis of another series of compounds of the above system with thiazole ring at position 6 has also been accomplished. The structures have been established on the basis of IR and PMR data.相似文献
13.
Molar excess volumes, V
ijk
E, and speeds of sound, U
ijk
, of o-toluidine (i) + benzene (j) + cyclohexane or n-hexane or n-heptane (k) ternary mixtures have been measured as a function of composition at 308.15 K. The observed speed of sound data have been
utilized to determine the excess isentropic compressibilities, (K
S
E)
ijk
, of the ternary (i+j+k) mixtures. The Moelywn-Huggins concept (Huggins in Polymer 12: 389–399, 1971) of connectivity between the surfaces of the binary mixture constituents has been extended to ternary mixtures (using the
concept of a connectivity parameter of third degree of molecules, 3
ξ, which in turn depends on its topology) to obtain an expression that describes well the measured V
ijk
E and (K
S
E)
ijk
data. The observed data have also been analyzed in terms of Flory’s theory. 相似文献
14.
Xuean Chen Fangping Song Xinan Chang Hegui Zang Weiqiang Xiao 《Journal of solid state chemistry》2009,182(11):3091-3097
Two oxoborates, (Pb3O)2(BO3)2MO4 (M=Cr, Mo), have been prepared by solid-state reactions below 700 °C. Single-crystal XRD analyses showed that the Cr compound crystallizes in the orthorhombic group Pnma with a=6.4160(13) Å, b=11.635(2) Å, c=18.164(4) Å, Z=4 and the Mo analog in the group Cmcm with a=18.446(4) Å, b=6.3557(13) Å, c=11.657(2) Å, Z=4. Both compounds are characterized by one-dimensional chains formed by corner-sharing OPb4 tetrahedra. BO3 and CrO4 (MoO4) groups are located around the chains to hold them together via Pb–O bonds. The IR spectra further confirmed the presence of BO3 groups in both structures and UV–vis diffuse reflectance spectra showed band gaps of about 1.8 and 2.9 eV for the Cr and Mo compounds, respectively. Band structure calculations indicated that (Pb3O)2(BO3)2MoO4 is a direct semiconductor with the calculated energy gap of about 2.4 eV. 相似文献
15.
E. G. Zinurova T. V. Khakimova L. V. Spirikhin M. S. Yunusov 《Chemistry of Natural Compounds》2000,36(4):387-389
The alkaloids atisine, lappaconitine, and leucostine were isolated fromAconitum septentrionaleL. seeds. The last was examined by
1
H and
13
C NMR. 相似文献
16.
J. V. Brenčič L. Golič I. Leban P. Šegedin 《Monatshefte für Chemie / Chemical Monthly》1979,110(5):1221-1228
Mo2Cl4
Pic
4·CHCl3 (A) (Pic=4-methylpyridine) and Mo2Br4
Pic
4 (B) crystallize in the monoclinic space group.A inC2/c (No. 15) witha=15.175 (4),b=10.847 (2),c=19.946 (6) and =104.52 (2)°;D
o=1.71 (2),D
c
=1.72 gcm–3 forZ=4.B inP2l/n
(No. 14) witha=9.270 (3),b=16.614 (5),c=9.305 (3) and =91.96 (5)°;D
o=2.03 (3),D
c
=2.05 gcm–3 forZ=2.Two halogens and 4-methylpyridines of the MoX
2
Pic
2 group are in the trans position. Mo–Mo bond lengths are 2.153 96) forA and 2.150 92) forB. Both molecules are situated on the inversion center resulting in the eclipsed configuration of the ligands around the molybdenum pair. The structure ofB has been refined to the conventionalR factors of 0.08 and 0.098. Disorder on the part of 4-methylpyridines and chloroform molecules stopped the refinement ofA at the endR value of 0.175.Mean Mo–X and Mo–N bonding distances are 2.40 (2), 2.25 (5) forA and 2.53 (3), 2.25 (1) forB. 相似文献
17.
Peter Gajdoš Soňa Pavlíková Filip Bureš Alžbeta Krutošíková 《Central European Journal of Chemistry》2005,3(2):311-325
The synthesis and reactions of methyl 2-[3-(trifluoromethyl)phenyl]-4H-furo[3,2-b]pyrrole-5-carboxylate (1a) are described. Upon reaction with methyl iodide, benzyl chloride, or acetic anhydride, this compound gave N-substituted products 1b-d. By hydrolysis of compounds 1a-c, the corresponding acids 2a-c were formed, or by reaction with hydrazine-hydrate, the corresponding carbohydrazides 3a-c were formed. By heating 2-[3-(trifluoromethyl)phenly]-4H-furo[3,2-b]pyrrole-5-carboxylic acid (2a) in acetic anhydride, 4-acetyl-2-[3-(trifluoromethyl)phenyl]furo[3,2-b]pyrrole (4) was formed. By hydrolysis of 4, 2-[3-(trifluoromethyl)phenyl]-4H-furo[3,2-b]pyrrole (5a) was formed, and reactions with methyl iodide or benzyl chloride gave N-substituted products 5b-c. The reaction of 4 with dimethyl butynedioate gave substituted benzo[b]furan 6. Compound 3a reacted with triethyl orthoesters giving 7a-c, which afforded with phosphorus (V) sulphide the corresponding thiones 8a-c. The thiones 8a-c reacted with hydrazine hydrate to form hydrazine derivatives 9a-c. The reaction of triethyl orthoformiate with compounds 9a-c led to furo[2′,3′: 4,5]pyrrolo[1,2-d][1,2,4]triazolo[3,4-f][1,2,4]triazines 10a-c. Hydrazones 11a-c were formed from 3a-c and 5-[3-(trifluoromethyl)phenyl]furan-2-carboxaldehyde. The effect of microwave irradiation on some condensation reactions
was compared with “classical” conditions. The results showed that microwave irradiation shortens the reaction time while affording
comparable yields. 相似文献
18.
The structure and stability of classical and bridged C2H
3
+
is reinvestigated. The SCF and CEPA-PNO computations performed with flexibles andp basis sets including twod-sets on carbon confirm our previous results. We find the protonated acetylene structure to be more stable than the vinyl
cation by 3.5–4 kcal/mol. The energy barrier for the interconversion of these two structures is at most a few tenths of a
kcal/mol. The equilibrium SCF geometries of Weberet al. [15] are affected insignificantly by further optimization at the CEPA-PNO level.
Several structures for the interaction of C2H
3
+
with HF have been investigated at the SCF level. With our largest basis set which includes a complete set of polarization
functions we find a remarkable levelling of the stabilities of most of the structures. In these cases the stabilization energy
ΔE ranges from −10 to −13 kcal/mol. 相似文献
19.
Aristophanes Metropoulos 《Theoretical chemistry accounts》1990,77(5):333-341
Summary This work is concerned with the application of a one-channel model to obtaining predissociation lifetimes and transition rates in a system of crossing diabatic states. The calculation focuses on the first shape resonance of the 1
g
2
2
g
diabatic state of He
2
+
, which is relatively stable with respect to tunneling. This resonance predissociates as a result of the 1
g
2
2
g
state being crossed by the 1
g
1
u
2
dissociative diabatic state near the resonance level. We have estimated its predissociation lifetime to be of the order of 10–11 s. 相似文献
20.
The oscillator strengthsf forE1 transitions along an isoelectronic sequence can be written asf=aK
2+bK+c whereK is a gauge parameter representing the gauge condition of the electromagnetic field. The coefficientsa,b, andc are functions of length (f
l) and velocity (f
v) values of the oscillator strengths at the Hartree-Fock level. We have shown by making a perturbation expansion of oscillator strengthsf,f
l andf
v that the gauge parameterK is independent of the nuclear charge. This property has been exploited to extrapolatef values along the isoelectronic sequence of Boron for some representativeE1 transitions within then=2 complex. We obtain good agreement between the extrapolated results with the configuration interaction results. 相似文献