Spectral assignment

The umbelliferone ether structure 1 was suggested for a natural product which was isolated from galbanum resin Does this structure fit the NMR results 48 Is it possible to give a complete spectral assignment despite lack of resolution of the proton signals at 200 MHz What statements can be made about the relative configuration ... 

In addition to sample rotation, a particular solid state NMR experiment is further characterized by the pulse sequence used. As in solution NMR, a multitude of such sequences exist for solids many exploit through-space dipolar couplings for either signal enhancement, spectral assignment, interauclear distance determination or full correlation of the spectra of different nuclei. The most commonly applied solid state NMR experiments are concerned with the measurement of spectra in which intensities relate to the numbers of spins in different environments and the resonance frequencies are dominated by isotropic chemical shifts, much like NMR spectra of solutions. Even so, there is considerable room for useful elaboration the observed signal may be obtained by direct excitation, cross polarization from other nuclei or other means, and irradiation may be applied during observation or in echo periods prior to... 

The mass spectral assignments for Au SG (1-9) were confirmed by comparing the spectra with that calculated using the isotopic abundance and those of Au S(h-G) clusters with the same mobility (10-14). Clusters 1-9 can be assigned to Auio(SG)io, Aui5(SG)i3, Auis(SG)i4,... 

Copper(II) complexes of 2,6-lutidylphenylketone thiosemicarbazone, 38, have been prepared from copper(II) chloride and copper(II) bromide [186]. Similar to 2-pyridyl thiosemicarbazones, 38-H coordinates via the ring nitrogen, the azomethine nitrogen and the thiol sulfur based on infrared spectral assignments. Magnetic susceptibilities and electron spin resonance spectra indicate dimeric complexes and both are formulated as [Cu(38-H)A]2 with bridging sulfur atoms. The electronic spectra of both halide complexes show band maxima at 14500-14200 cm with shoulders at 12100 cm S which is consistent with a square pyramidal stereochemistry for a dimeric copper(II) center. 

A. M. Gil, I. Duarte, E. Cabrita, B. J. Goodfellow, M. Spraul, R. Kerssebaum 2004, (Exploratory applications of diffusion ordered spectroscopy to liquid food an aid towards spectral assignment), Anal. Chim. Acta 506 (2), 215—223. 

The other application of HSQC-1,1-ADEQUATE to structure elucidation/ spectral assignment that has appeared was for the cyclin-dependant kinase-2 inhibitor dinaciclib (48).97 The overlaid multiplicity-edited GHSQC and 40 Hz optimized 1,1-ADEQUATE spectra are shown in... 

The 1H NMR spectrum of (DL)-penicillamine in D20 was obtained on a Bruker 500 MHz instrument, and the resulting spectrum is shown in Fig. 3. Confirmation of the spectral assignments was derived from a COSY experiment (see Fig. 4), and these assignments are summarized in Table 3. 

The use of solid state NMR for the investigation of polymorphism is easily understood based on the following model. If a compound exists in two, true polymorphic forms, labeled as A and B, each crystalline form is conformationally different. This means for instance, that a carbon nucleus in form A may be situated in a slightly different molecular geometry compared with the same carbon nucleus in form B. Although the connectivity of the carbon nucleus is the same in each form, the local environment may be different. Since the local environment may be different, this leads to a different chemical shift interaction for each carbon, and ultimately, a different isotropic chemical shift for the same carbon atom in the two different polymorphic forms. If one is able to obtain pure material for the two forms, analysis and spectral assignment of the solid state NMR spectra of the two forms can lead to the origin of the conformational differences in the two polymorphs. Solid state NMR is thus an important tool in conjunction with thermal analysis, optical microscopy, infrared (IR) spectroscopy, and powder... 

The transient triplet carbene formed from irradiation of DABA in benzene can be observed to react with styrene. For this process laser spectroscopy reveals a bimolecular rate constant (ksty) equal to 1.2 x 107M-1s-1. The product of the reaction is the expected cyclopropane. This observation clearly supports the spectral assignment of the carbene made above. When deuteriated a-methylstyrene is substituted for styrene as a trap for the carbene, the cyclopropane that results is a 1 1 mixture of stereoisomers, (20) (Table 6). This finding indicates that BA is reacting in this sequence exclusively from its ground triplet state. 

The NMR spectrum of calcitriol, recorded on a Varian XL-100/Nicolet TT-100 pulsed Fourier Transform NMR spectrometer, with internal deuterium lock, is shown in Figure 2 (2). The spectrum was recorded using a solution of 0.84 mg of sample dissolved in 50 microliters of CD OD (100%D) containing 1% v/v tetramethylsilane in a 1.7 mm capillary tube. The spectral assignments are given in Table I. 

Infrared Spectral Assignments for Triprolidine Hydrochloride Monohydrate... 

Suitable reference compounds, preferably measured together with the catalysts, to confirm spectral assignments. 

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