共查询到20条相似文献,搜索用时 62 毫秒
1.
From a carbon magnetic resonance study of several alkylcobaloximes RCo(DMG)2B (DMG = dimethylglyoximate monoanion), it was possible to estimate the α, β and γ effects of the Co(DMG)2B group on the chemical shifts of the carbon atoms of various alkyl groups R. The chemical shifts of the carbon atoms belonging to the equatorial ligands and to the axial base B are not significantly affected by structural modification of the R groups. Values of δ in benzylcobaloximes XC6H4CH2Co(DMG)2B agree with a donor effect of the ? CH2Co(DMG)2B radical. Values of 1J(13C? H) coupling constants, measured in 13C enriched methylcobaloximes, do not vary appreciably when B is changed (J(13C? H) = 137 ± 1 Hz) and are close to the value obtained for methylcobalamine. 相似文献
2.
H. Nery D. Canet B. Azoui L. Lalloz P. Caubre 《Magnetic resonance in chemistry : MRC》1977,10(1):240-244
13C chemical shifts, 1-bond and 3-bond (meta) 13C? H coupling constants have been determined in a series of trisubstituted benzene; the substituents are Cl, NH2, N(C2H5)2, N(iC3H7)2, N(C2H4)2O. Chemical shifts are only in moderate agreement with the usual additivity rules. Additivity rules relative to the above mentioned coupling constants are proposed. With few exceptions, the difference between predicted and observed values is less than 10%. 相似文献
3.
Several 15N enriched oximes of heterocyclic aldehydes have been prepared in syn and anti forms. The less stable form may be obtained by UV irradiation of the other one. The geminal 15N? H coupling in the R? CH?15N? OH fragment allows an immediate and unambiguous assignment of the configuration to be made, being 13 to 16 Hz and 2 to 3 Hz for the anti and syn forms, respectively. Whereas oximes 1 to 4 are preferentially in the anti form, the N-methylpyridinium aldoxime iodides (2-PAM, 3-PAM, 4-PAM) are found to be syn in the stable form and not anti as previously thought. This reassignment is of special interest, since 2-PAM ( 8 ), which is an excellent antidote against alkyl phosphate nerve poisoning, has been used to study the geometry of the acetylcholinesterase active site of the enzyme. 相似文献
4.
Marie-Paule Simonnin Claude Charrier Marie-Jos Lecourt 《Magnetic resonance in chemistry : MRC》1969,1(1):27-49
The signs of the phosphorus-proton coupling constants in various allenic organophosphorus compounds have been determined by either analysis of the AB2X spectra or double resonance. Probable absolute signs have been obtained by taking 3J(P? H) as positive. In allenic phosphine oxides, the following signs are obtained: 2J(P? H) +ve, 3J(P? H) +ve, 4J(P? H) ?ve, 5J(P? H) +ve and the 4J(P? H) coupling constant varies mostly with the inductive effect of the substituents bound to the phosphorus atom. In allenic phosphines, these sings are: 2J(P? H) +ve, 3J(P? H) +ve, 4J(P? H) ?ve and +ve and the 4J(P? H) coupling constant varies with both the inductive and resonance effects to the substituents. This coupling constant is negative except when the phosphorus atom is bound to groups which are electron-donating by resonance effects. These results are discussed in relation to the pπ? dπ bonding in phosphine. 相似文献
5.
A series of sugar oximes and O-methyloximes of the general formula RCH?NOR′ (R′ ? H, CH3) have been studied by PMR. spectroscopy. These compounds exist in solution as a mixture of the syn and anti isomers. The conformational equilibrium of the syn isomers seems to consist exclusively of the eclipsed rotamers, whereas for the anti isomers there appears to be a significant contribution from bisecting rotamers. Using tris-dipivaloylmethanato-europium it is found that the α proton of the anti oximes is much more deshielded than the corresponding proton of the syn isomers, which means that the downfield shift of a particular proton does not depend exclusively on its distance from the oxygen of the oxyimino group. 相似文献
6.
Marie-Paule Simonnin Minh Lequan Marie-Jos Lecourt 《Magnetic resonance in chemistry : MRC》1970,2(4):369-378
Satellites corresponding to metal-proton coupling constants through two and four bonds are observed in PMR spectra of Pb, Sn and Hg allenic derivatives. The relative signs of these coupling constants are deduced from analysis of the satellite spectra: 2J(X? H) and 4J(X? H) are of opposite signs for X = 207Pb, 119Sn, 117Sn and of same sign for X = 199Hg. Probable absolute signs of reduced coupling constants are discussed in relation to published data: 2K(X? C? H) is probably positive for X = 207Pb, 119Sn, 117Sn and 199Hg. 4K(X? C?C?C? H) is probably negative for X = 207Pb, 119Sn, 117Sn and positive for X = 199Hg. 相似文献
7.
8.
Jean-Pierre Albrand Didier Gagnaire Jean Martin Jean-Bernard Robert 《Magnetic resonance in chemistry : MRC》1973,5(1):33-41
The proton NMR spectral analysis of eight different 1,3,2-dithiaphospholanes with various groups attached to the phosphorus atom has been performed. The AA′BB′X (X phosphorus atom) system shows that the two 3J(P? S? C? H) coupling constants have a small magnitude and opposite signs. Using the 3J(HH) values, the torsion about the C4—C5 bond has been evaluated. The conformational requirements in the two isomers of the 2 phenyl-4-methyl-1,3,2-dithiaphospholane are also discussed. 相似文献
9.
Josiane Durrieu Raymond Kraemer Jacques Navech 《Magnetic resonance in chemistry : MRC》1973,5(9):407-412
The PMR spectra of some new 1,3,2-oxazaphosphorinanes are analysed. In one case, after elimination of the P? H spin coupling, the spectra give rise to a particular ABKLXY pattern in which certain coupling constants between vicinal protons are zero. The ABKLXY system where JAK = JAL = JBK = JBL is studied and most of the parameters of the related compound are calculated. The ring conformation is discussed and the free energy is given; for one oxazaphosphorinane, the calculation of the torsional angle of the C4? C5 and C5? C6 fragments is described. 相似文献
10.
T. Bottin-Strzalko M. J. Pouet M. P. Simonnin 《Magnetic resonance in chemistry : MRC》1974,6(8):419-420
INDOR experiments indicate 4J(P? C? C? O? H) to be positive for the β-hydroxyphosphonate ester RS,RS dissolved in (CD3)2CO or (CD3)2SO. The higher value observed in (CD3)2SO than in (CD3)2CO shows that a W geometry makes this coupling constant more positive. 相似文献
11.
Ivan Leban Boenna Golankiewicz Joanna Zeidler Gerald Giester Joe Kobe 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):o133-o135
In the title compound, C13H13N5O4·H2O (4,5′‐cyclowyosine·H2O), the cyclization forces a syn arrangement of the aglycon with respect to the sugar moiety. The ribofuranose part of the molecule displays a β‐d configuration with an envelope C1′‐endo pucker. The molecules are arranged in columns along the short a axis and are linked to water molecules through O—H?O and O—H?N hydrogen bonds. 相似文献
12.
Armand Buchs 《Helvetica chimica acta》1970,53(8):2026-2035
Molecular ionization potentials for series of compounds of the type X? C6H4? CN, X? C6H4CH2? CN and X? C6H4? N(CH3)2 have been measured using the retarding potential difference technique (RPD. technique). The effect of the various substituents X is better correlated through the electrophilic Brown σp+ constants than through Hammett's σp values. No meta-para orientation effect is observed. For all the disubstituted phenyl compounds studied, the effect of the second substituent is affected by the electron-releasing power of the original substituent. Ionization potentials calculated by using the semi-empirical method of equivalent orbitals are in good agreement with the experimental values. 相似文献
13.
Jean Devillers Jacques Navech Jean-Pierre Albrand 《Magnetic resonance in chemistry : MRC》1971,3(2):177-186
The 31P decoupled PMR spectra of the title oxazaphospholanes give rise to well resolved ABXY patterns. Among the eight possible solutions, six can be readily eliminated from chemical shifts considerations and the choice between the remaining two is based on tickling experiments. Good fits are observed between experimental and calculated spectra. The relative signs of the 3J(P? O? C? H) and 3J(P? N? C? H) coupling constants are given by tickling and Indor experiments. The ring conformation is discussed. 相似文献
14.
Josiane Durrieu Raymond Kraemer Jacques Navech 《Magnetic resonance in chemistry : MRC》1972,4(5):709-719
After elimination of the P? H spin coupling, the PMR spectra of the title 1,3,2-oxazaphosphorinanes give rise to an ABXY pattern where JAX = JAY = JBX = 0. The particular ABXY system where JAY = JBX = 0 is studied to calculate the expression of the E7, E8, E9 and E10 energy-levels and the frequency of the transitions connected to these energy-levels. The relative sign of the 3JP? O? C? H and 3JP? N? C? H coupling constants is given by INDOR experiments. The ring conformation is discussed. 相似文献
15.
Chemical shifts and coupling constants of five 2-fluorobenzothiazoles 6-substituted by Me, H, F, Cl and NO2 are given. A large cross-ring coupling constant (J26 = 10·4 Hz) is found in the 2,6-difluorobenzothiazole. 相似文献
16.
The PMR spectra of six primary aziridinyl carbinols are studied over a temperature range of ?30°C to +100°C. Nitrogen configuration is determined. When the inversion process is effective, kinetic parameters are evaluated. Rotational isomerism about the ‘ring? CH2OH’ bond is studied from vicinal coupling constants associated with the two diastereotopic protons on the ? CH2OH group. From the J(HOCH) coupling constant (in CCL4) rotamer populations of the hydroxyl group are determined in some cases and the overall conformational distribution can be established. 相似文献
17.
The synthesis of a series of keto derivatives of cyclopentane is described. The configurations of these derivatives have been determined by chemical methods and verified by IR. and NMR. spectroscopy. The preferred conformation of the cyclopentane part of the molecule has been established by the study of intramolecular hydrogen bonds and the values of the coupling constants JH? C? OH and JH, H. 相似文献
18.
Hongpu Huang Jia Qu Ling He 《Journal of polymer science. Part A, Polymer chemistry》2016,54(3):381-393
A series of amphiphilic silica/fluoropolymer nanoparticles of SiO2‐g‐P(PEGMA)‐b‐P(12FMA) were prepared by silica surface‐initiating atom transfer radical polymerization (SI‐ATRP) of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and poly dodecafluoroheptyl methacrylate (P12FMA). Their amphiphilic behavior, lower critical solution temperature (LCST), and surface properties as protein‐resistance coatings were characterized. The introduction of hydrophobic P(12FMA) block leads SiO2‐g‐P(PEGMA)‐b‐P(12FMA) to form individual spherical nanoparticles (~150 nm in water and ~170 nm in THF solution) as P(PEGMA)‐b‐P(12FMA) shell grafted on SiO2 core (~130 nm), to gain obvious lower LCST at 36–52 °C and higher thermostability at 290–320 °C than SiO2‐g‐P(PEGMA) (LCST = 78–90 °C, Td = 220 °C). The water‐casted SiO2‐g‐P(PEGMA)‐b‐P(12FMA) films obtain much rougher surface (125.3–178.4 nm) than THF‐casted films (11.5–16.9 nm) and all SiO2‐g‐P(PEGMA) films (26.8–31.3 nm). Therefore, the water‐casted surfaces exhibit obvious higher water adsorption amount (Δf = ?494 ~ ?426 Hz) and harder adsorbed layer (viscoelasticity of ΔD/Δf = ?0.28 ~ ?0.36 × 10?6/Hz) than SiO2‐g‐P(PEGMA) films, but present loser adsorbed layer than THF‐casted films (ΔD/Δf = ?0.29 ~ ?0.63 × 10?6/Hz). While, the introduction of P(12FMA) segments does not show obviously reduce in the protein‐repelling adsorption of SiO2‐g‐P(PEGMA)‐b‐P(12FMA) films (△f = ?15.7 ~ ?22.3 Hz) compared with SiO2‐g‐P(PEGMA) films (△f = ?8.3 ~ ?11.3 Hz) and no obvious influence on water adsorption of ancient stone. Therefore, SiO2‐g‐P(PEGMA)‐b‐P(12FMA) is suggested to be used as protein‐resistance coatings. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 381–393 相似文献
19.
The radical (ΦNH)2P· is trapped by annealing at 100°C an X-irradiated single crystal of N? N diphenyl phosphondiamide and has been studied by electron spin resonance. The isotropic and anisotropic 31P coupling constants are discussed. The principal values and direction cosines of the g tensor are also given. 相似文献
20.
Jean-Marc Bourgeois 《Helvetica chimica acta》1974,57(8):2553-2557
Treatment of 3-C-cyano-1,2:5,6-di-O-isopropylidene-3-O-(toluene-p-sulfonyl)-α-D -allofurannose with AlLiH4 or RMgX yields spiro-aziridines with two identical substituents on C(3′) (? H, ? CH3, ? C2H5). Reactions of these products and their derivatives are briefly described. If the C(3′) substituents are protons, the aziridine ring is easily opened. In acidic media (HCl), an amino-sugar containing the branched chain ? CH2Cl is produced; with hydrogenation, a ? CH3 branched chain results. If the C(3′) substituents are methyl groups, the aziridine ring cannot be opened neither with HCl nor with hydrogen. The acetylated derivative of this latter compound rearranges to the corresponding allylamide with HCl. For both types of spiro-aziridine, the nitrous deamination leads to the corresponding alkene. 相似文献