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1.
Dialkylcarbodiimides, , react with iminium salts, , to afford the formal 1,1-diaminosubstituted 2-azaallenium salts . According to dynamic NMR measurements compounds must be regarded as alkylidene-guanidinium salts , undergoing a fast topomerization via a transition state with allene geometry (2G=265 = 45.9 ± 1 kJmol-1 for ) and a slower rotation around the peripheral C-N bonds (transition state ; 2G=290= 58.0 ± 1 kJmol-1 for ). 相似文献
2.
A simple method for the determination of molybdenum and tungsten in sea and surface water is presented. Molybdenum and tungsten are concentrated on activated charcoal by adsorption as the ammonium pyrrolidine dithiocarbamate complex; the optimal pH for adsorption is 1.3. Mo and W are then determined by thermal neutron activation, forming 99Mo (T = 66.7 h) and 137W (T = 23.8 h), respectively. The 99mTc daughter of 99Mo is measured as soon as the equilibrium between 99mTc(T= 6 h) and 99Mo is established. The detection limits are 0.05 μg Mo l-1 and 0.05 μg W l-1 (or 0.001 μg W l-1 after a simple chemical separation). 相似文献
3.
Methods of substituting pyridine by perhalogenomethylmercapto groups are discussed. The side chain chlorination of 2-(methylmercapto)pyridine leads gradually to 2-(trichloromethylmercapto)pyridine hydrochloride () and 2-(trichloromethylmercapto)pyridine (). Neither a direct reaction of pyridine with CF3SCl nor the way over a Grignard reaction or a sulfenylcarboxylate lead to CF3S-substituted products. Reactions of pyridine and bromopyridines with Hg(SCF3)2 yield 1:1-adducts () only. Lithium tetrakis(1,2-dihydro-1-pyridyl)aluminate (LDPA) reacts with CF3SCl to give 3-(trifluoromethylmercapto)pyridine (); in addition a disubstituted product can be identified massspectroscopically. 1H- and 19F-NMR-spectra are reported. 相似文献
4.
The 1H and 13C nmr spectra of , -9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d6 or alkaline D2O, clearly show that it exists in a --conformation with carboxyl groups, thus being the first case of - preference of a bicyclo[3.3.1] nonan-9-one due to the presence of ,-2,4- substituents. 相似文献
5.
57Fe Mössbauer spectra have been obtained for Fe(p-CH3C6H4SO3)2 between 2.3 and 300 K in zero field, and at 2.3 and 4.2 K in longitudinal applied magnetic fields ranging from 1.1 to 5.6 T. The complex is a fast-relaxing paramagnet under all conditions studied and there is no evidence of antiferromagnetic exchange coupling. The FeO6 chromophore is distorted by a trigonal elongation and the orbital ground state is the [()|±2〉 ? ()|?1〉] doublet. The temperature dependence of the quadrupole splitting has been analysed via a crystal-field model to provide estimates of the axial field splitting parameter Ds = -93 cm-1, spin-orbit coupling constant λ = -70 cm-1, and fine structure constant Dσ = -28 cm-1. The magnetic properties of the complex are described by treating the ground state as a non-Kramers doublet with fictitious spin ? = . Five separate Mössbauer-Zeeman spectra can be fitted in this spin-hamiltonian approximation with identical values of the g- and A-tensor components, viz. g⊥ = 1.0, gu = 9.0; A⊥ ≈ 2.0 mm s-1. Au = -1.79 mm s-1. The trigonal z axis, the z axis of the electric field gradient tensor, and the easy axis of magnetisation are collinear, and the saturation value of the internal hyperfine field along this axis is +13.0 T. 相似文献
6.
Electron-deficient aromatics, such as 2,5-bis(trifluoromethylmercapto)thiophene () or (trifluoromethylmercapto)benzene (), react with F3CSCl in the presence of F3CSO3 as a catalyst to give mainly 3-chloro-2,5-bis(trifluoromethylmercapto)thiophen () and 1-chloro-4- or 2-(trifluoromethylmercapto)benzene (, respectively. This reaction competes with the one expected to result in 2,3,5-tris(trifluoromethylmercapto)thiophene () and 1,4- and 1,2-bis(trifluoromethylmercapto)benzene (,), respectively. Further reactions of deactivated aromatics with Cl3-nFnCSCl show that the chlorine substitution is in general catalysed by strong acids. Reaction mechanisms are proposed for both Substitutions. The Cl3-nFnCS group in aromatics exerts a -M-effect in the case of an attack of a positive ion, e.g. H⊕, the well-known +M-effect in the case of reactions with positively polarized molecules, e.g. CF3Sβ+Clβ-. 相似文献
7.
Kenichi Takeuchi Toshikazu Kitagawa Akihiko Ueda Yoshihide Senzaki Kunio Okamoto 《Tetrahedron》1985,41(23):5455-5463
7-Cyano-7-methylcycloheptatrienes containing one t-butyl group on the 1-position () or two t-butyl groups on the 1- and 3-, 1- and 4-, or 1- and 5-positions (, , or , respectively) were synthesized and their cyclo- heptatriene (CHT)-norcaradiene (NCD) equilibria measured by variable-temperature 1H NMR for CS2-CD2Cl2 solutions. The 1H NMR chemical shifts of the 7-methyl group indicate that these compounds are composed of essentially one CHT and one NCD tautomer with an endo geometry of the methyl group. The introduction of a t-butyl group at the 1-position of 7-cyano-7-methylcycloheptatriene () markedly shifts the equilibrium to the NCD side and the addition of the second t-butyl group further favors the NCD form, with the NCD populations for , , , and at 25 °C 70.9, 96.5, 92.3, and 99.3%, respectively. An application of molecular mechanics (MMPI) calculations to various t-butylated CHT-NCD systems suggests that the t-butyl groups sterically destabilize the CHT form more than the NCD form, bringing about increased NCD populations. 相似文献
8.
Felix H. Cano Concha Foces-Foces Manuel Bernabe Jesus Jimenez-Barbero Manuel Martin-Lomas Soledad Penades-Ullate 《Tetrahedron》1985,41(18):3875-3886
X-Ray and 1H N.M.R. studies on pyranoid rings 1,2--fused to dioxolane rings in acetylated -gluco- and --galactopyranose derivatives demonstrate that the configuration of the dioxolane ring influences the conformation of the pyranoid ring in the -gluco but not in the -galactopyranose series. The crystal structure of 3,4,6-tri--acetyl-1,2--(R)--(l-cyano-ethylidene)-α--glucopyranose () and 3,4,6-tri--acetyl-1,2--()-(1-cyano-ethylidene)-α--galactopyranose ()have been determined by X-ray analysis. Lattice parameters for are a=20.6021 (11), b=8.0438 (2), c=5.5541 (1) Å and β= 95.588 (3)° for a cell with P21 symmetry. These parameters for are a=20.3361 (7), b=10.0907 (2), c=18.9115 (5) Å, β =112.399 (2)°, C2, with two crystallographycally independent molecules. The conformation of the pyranoid ring in both compounds can be described as flattened 4C1 and that of the dioxolane ring as distorted E1. The importance of the torsion angles for describing problems of configuration is remarked and the use of relative configurational angles is stressed. The 1H N.M.R. spectra of and and 3,4,6-tri--acetyl-1,2-O-(S)- and (R)-ethylidene-α--glucopyranose ( and ), 3,4,6-tri-O-acetyl--1,2-O-(S)- and ()-ethylidene-α--galactopyranose ( and ), and 3,4,6-tri--acetyl-1,2--()-and ()-benzylidene-α--glucopyranose ( and ) have been analyzed by using iterative computer methods and N.O.E. measurements. The results indicate that the major solution conformation of the pyranoid ring of the derivatives in the -gluco series , and may be described as flattened 4C1 and that of and as 25. The major solution conformation of the pyranoid ring in all compounds in the -galacto series (,,,) may be described as flattened 41. 相似文献
9.
The following reactions: NpO2++4 HCl ? Np4+ + 2 H2O + Cl2 + 3Cl- NpO2++ Cl2 ? NpO22+ +Cl- 2HCl+O2- ? H2O +Cl- have been examined quantitatively. The reactions were studied in fused LiCl-KCl sparged with gas mixtures of definite compositions. The concentrations of the diffrent neptunium species were measured by absorption spectrophotometry. The values of respective equilibrium constants are: K = (9.3±0.4)· 10-6 atm(-); K1 = (2.3±0.1)·10-2 atm(-); k = 103.8 1 mol-1 atm-1 The standard potential of the system NpO22+ / NpO2+ was determinedto be E0 = 0.220 V (vs.standard chlorine electrode). 相似文献
10.
(1R,5S)-2S-Deuteriobicyclo[3.2.1]octan-3-one () and (1R,5S)-2R-Deuteriobicyclo[3.2.1]octan-3-one (), prepared by diazomethane ring enlargement of (1S,4R)-2(exo)-deuteriobicyclo-[2.2.1] heptan-2-one and (1S,4R)-2(endo)-deuteriobicyclo[2.2.1]heptan-2-one respectively, both gave (?) n-π* circular dichroism (CD) Cotton effects, Δεmax294 = ?0.05 and Δεmax294=?0.1, respectively, in hydrocarbon solvent. (1S,5R)-2S-Deuterio-6,6-diaethylbicyclo[3.1.1] heptan-3-one () and (1S,5R)-2R-deuterio-6,6-dimethylbicyclo[3.1.1] heptan-3-one (), prepared from (-) myrtenal, both exhibited extraordinary vibrational fine structure for the n-π* CD transitions observed in hydrocarbon solvent and oppositely?signed CEs, Δεmax282=?0.01 and Δεmax279=+0.01 respectively in CF3CH2OH solvent. 相似文献
11.
tert-Butyl azidoformate () reacts with the conjugate bases of , , (R1 = R2 = CH3), and (R1 = CH3, R2 = H) to give products [, , , and , respectively] in addition to the expected N-(tert-butoxycarbonyl)indole derivatives. 相似文献
12.
Comparative study on the proton and carbon NMR spectra for a series of - and -acyl substituted monohydroxypyridines (C5H4NO: =-H, -CHO, -COCH3, -COC(CH3)3, -COCF3, -COC6H5, -SO2CH3, -SO2C6H4CH3 is reported. p]Characteristic 1H, 13 NMR and IR spectral features allow simple and unambiguous distinction between the isomeric - and/or -acyl-derivatives of 2-, 3- and 4-hydroxypyridines, so that both forms can clearly be identified when tautomeric equilibria occur, since the tautomerism rate is slow on the NMR time scale 相似文献
13.
K. Nakatsu Y. Inai T. Mitsudo Y. Watanabe H. Nakanishi Y. Takegami 《Journal of organometallic chemistry》1978,159(1):111-122
The crystal structure of a bis(triphenylphosphine)iminium salt of the 1:1 adduct of [FeH(CO)4]? and dimethyl acetylenecarboxylate has been determined from three-dimensional X-ray data collected by the counter method. Single crystals belong to the triclinic space space group P, with two units of [C36H30NP2]+[C10H7FeO8]? in a cell of dimensions: = 13.918(2), = 15.669(5), = 9.909(2) Å, = 91.22(3), = 94.83(2), and = 77.62(2)°. The structure was refined to a conventional of 0.068 for 5373 observed reflections. The resulting structure indicates that the complex anion is η3-[-2,3-bis(methoxycarbonyl)acryloyl]tricarbonylferrate, the coordination around the iron atom being described as a considerably distorted trigonal bipyramid. A comparison of the present structure with the structures of related complexes suggests that the η3-acryloyl portion is best represented as an intermediate of (η3-allyl) with the oxygen atom and (η2-olefin + η1-acyl). The short Fe-C(acyl) length of 1.897(5) Å implies an enhanced back-donation of electrons from the iron atom to the acyl group. 相似文献
14.
Sigeru Torii Hideo Tanaka Norio Saitoh Takashi Siroi Michio Sasaoka Junzo Nokami 《Tetrahedron letters》1982,23(21):2187-2188
Synthesis of 3-chloromethyl-Δ3-cephems from 4-arenesulfonylthioazetidin-2-ones , derived from penicillins G and V, has been achieved by the electrolytic ene-type chlorination of in a CHC13-aqueous NaCl-H2SO4-(Pt electrodes) system and subsequent ring closure with NH3 in DMF. 相似文献
15.
The addition of phenylhydrazine to phenylazo-alkenes yields α-(1-phenylhydrazino)-phenylhydrazones . The reaction of phenylhydrazine with α-halogenated carbonyl compounds affords either or the isomeric α-(2-phenylhydrazino)-phenylhydrazones . Structures and (>N-NH2 and-NH-NH- groups, respectively) can be differentiated by 1H NMR in DMSO-D6 solution. Possible pathways of the reactions leading to either or are discussed. Compounds are found to be precursors of phenylosazones . 相似文献
16.
The ā2E → X?2E (Σ= + , - ) electronic transitions of rotationally/vibrationally cooled CH3CCCCH- cation, as well as the d1-/d3-/d4-substituted species, were studied by emission spectroscopy. Ion emission was obtained by electron impact on the neutral species seeded in a helium supersonic free jet. Vibrational frequencies in both electronic states are inferred to within ±1 cm-1. Spin-orbit splittings are observed and interpreted on the basis of non-linear vibronic couplings. Rotational subbands are observed, yielding rotational and Coriolis parameters as well as rotational temperatures. 相似文献
17.
The production of I(2P) in the photolysis of CH2I2 has been studied optoacoustically at excitation wavelengths between 365.5 and 247.5 nm. Bands found at 32200 and 47000 cm?1 correlate with I(2P) whilst those at 34700 and 40100 cm?1, which correlate with I(2P), give final 2P/2P ratios of 1.75 and 1.1, respectively, after curve crossing. 相似文献
18.
In the 1B2u-1Ag system of naphthalene in a supersonic jet, rotational contour calculations show rotational temperatures of 2–60 K for argon carrier gas pressures of 1520-120 Torr. The b1u vibration v24 shows a high vibrational temperature which corresponds to the seeding temperature for pressures <400 Torr. 相似文献
19.
The thiiranium ion formed by the reaction of -1-phenylpropene and (4-ClC6H4S)2SC6H4ClSbCl6 in CH2Cl9 at ?70°C reacts with Cl? to form both - and -Markownikoff B-chlorosulfides. 相似文献
20.
Reaction of -(Gly--Cys-Gly)3 with 1,3,5--bromomethylbenzene yields a thioether of the cyclic nonapeptide in 28% yield. Both 1H and 13C NMR spectra are consistent with a molecule of 3-fold symmetry; the temperature dependences of chemical shifts of the amide hydrogens are consistent with a structure composed of three β-turns. 相似文献