Similarity, spectra

Solutions of the radical cations of 65b (R = H, Me, Ph) were conveniently generated by the addition of bromine to dichloromethane solutions of the correspondingTTDAF (93CC1226 94JOC2997). All radical cations exhibit similar spectra with g = 2.0071. In the case of R = H, Me, the signal con-... 

Typical Mossbauer spectra for the fresh, reduced, carblded and used Fe/ZSM-5 system are shown in a composite Fig. 5. Similar spectra were obtained for the Fe-Co/ZSM-5 system. The product distribution for the F-T reaction, using the Fe and Fe-Co systems, are shown in Table 1. The gasoline range hydrocarbon yield increased from 75 to 94%, when the Fe-Co clusters were used in place of Fe only. In a typical CEMS (Conversion Electron Mossbauer Spectroscopy) of the Fe-Co system, no spectrum for 57pg vas observed even after one week from this. It was concluded that in the Fe-Co clusters Co was predominantly in the "mantle" and Fe species were In their "core," in the parlance of metallurgy/geophysics. This model Is sometimes referred to as the cherry model. 

The elimination of HX(X = SOCH3, SCHj) from the [M-STol]- and [MH-HSTol] cations (Tol = CHjCgH ) from 5-9 under electron impact and chemical ionization depends strongly on the spatial orientation of the vicinal substituents . The intensity of the [M — STol] ion is appreciably higher when X and Y are cis than when they are trans. The stereochemistry of the sulfoxide group is not important since 7 and 8 exhibit very similar spectra. The elimination of HSOCHj occurs more easily from 7 and 8... 

PCP produced electrical seizure activity at 12.8 mg/kg IV, EEG spectra were clearly different from those produced by lower doses in that fast-frequency, high-amplitude EEG waves occurred and resulted in a spectral peak at about 15 Hz. EEG activity from 0 to 35 Hz occurred during seizures in contrast to subseizure doses, which produced EEG with little activity beyond 10 Hz. Generally, these seizures occurred immediately after IV injections and lasted 1 to 3 minutes. Similar spectra were obtained with NsBPCA (12.8 mg/kg), SKF-10,047 (25.6 mg/kg), and even with ketamine despite the absence of overt convulsant activity. Motor manifestations of EEG seizure activity included whole body tremors and vigorous twitches of the face and vibrissae. 

Simulated results of Pulvermacher and Ruckenstein (P10) have demonstrated that the similarity spectra are established in very short agglomeration times irrespective of the initial granule size distribution, and that the size dispersion decreases with an increase in the value of the exponent y. 

The two compounds will give very similar spectra and you would not be able to tell which isomer your sample is without an authentic spectrum of at least one of the isomers, for comparison. The only unambiguous way to tell these isomers apart, in the absence of an authentic spectrum, would be... 

It has been long recognized that vibrational spectra often have more easily accessible structural information than similar spectra in the visible or uv regions. This is due to the finite IR spectral shifts associated with even... 

E in GeV), giving a flat spectrum for E <Heavy nuclei have similar spectra in energy per nucleon. 

The spectrum of GeF2 trapped in a neon matrix is shown in Fig. 3. The ratio of GeF2/rare gas in the matrix was 1 1000. When new matrices were prepared similar spectra were obtained, even when the ratio of diluent was changed or the temperature of deposition was altered. This indicated that the splitting seen in the spectrum was due to isotope effects and was not due to matrix effects. As can be seen the intensities of the various peaks are in the same ratio as the abundant isotopes of germanium, providing additional evidence that the splitting is due to isotope effects. 

First of all it is helpful to check the presence of similar spectra in the available spectral databases. Ideally the task may be completely resolved at this stage. The library search may help to refer the sample to a certain class of organic compounds, to get some clues on the presence of heteroatoms and functional groups. 

Cyclooctadienes, Cyclooctatrienes and Cyclooctatetraene. As mentioned in Section III.E, the 70 eV El mass spectra of the isomeric cyclooctadienes are strikingly different87. Not surprisingly, the three possible stereoisomeric 1,5-cyclooctadienes give similar spectra, the product ions C4H6+ of the apparent [4 + 4] cycloreversion, i.e. loss of... 

It can be seen in Fig. 3 that similar spectra are obtained in salt solutions at neutral pH, and that spectra are only slightly modified in mixed solvents, probably due to modifications in pX. Note the transformation of the shoulder at 298 nm into a peak in methanol (40%), MPD (50%), and a much more pronounced perturbation in 70% MPD. 

Even if HPLC is chosen as the main stability indicating method, CE will be useful as orthogonal technique, especially in cases where the reason of mass balance deviations is unclear. In addition, due to its increased peak capacity and selectivity in comparison to HPLC, the detection of possible enantiomers, stereoisomers, and position isomers, having the same molecular weight and equal/similar spectra as the drug substance may be separated by a secondary CE method. 

The bottleneck in utilizing Raman shifted rapidly from data acquisition to data interpretation. Visual differentiation works well when polymorph spectra are dramatically different or when reference samples are available for comparison, but is poorly suited for automation, for spectrally similar polymorphs, or when the form was previously unknown [231]. Spectral match techniques, such as are used in spectral libraries, help with automation, but can have trouble when the reference library is too small. Easily automated clustering techniques, such as hierarchical cluster analysis (HCA) or PCA, group similar spectra and provide information on the degree of similarity within each group [223,230]. The techniques operate best on large data sets. As an alternative, researchers at Pfizer tested several different analysis of variance (ANOVA) techniques, along with descriptive statistics, to identify different polymorphs from measurements of Raman... 

One of the crncial factors to ensnre adeqnate selectivity in constructing a spectral library is the choice of an appropriate threshold value or acceptance criteria. Such a threshold is the lowest value (for correlation) required to unequivocally assign a given spectrnm to a specific class. Too low a threshold can lead to ambiguities between substances with similar spectra, whereas too high a threshold can resnlt in spectra belonging... 

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