The concentration of aromatic compounds, such as naphthalenes, phenanthrenes, dibenzothiophenes and their structural isomers
are at present attracting increasing attention as maturity indicators for coals and shale source rocks.
On the other hand the low energy barrier between the cis and the trans isomer seem to indicate a fast interconversion between these two structural isomers
. Details on the calculated geometry of the reaction's products have not yet been fully explored and more theoretical work is needed to present a conclusive possible reaction's pathway for this reaction.
Four mixtures of two structural isomers
of ursane and oleanane derivatives, in the ratio 2:1, were isolated for the anti-inflammatory activity assay.
The reagent produces a strongly basic derivative, which enhances the response of all organic acids in the positive-ion mode without any differences in fragmentation between the structural isomers MMA and SA.
In the negative-ion mode, the structural isomers MMA and SA are indistinguishable from each other (Fig.
To support the hypothesis that positive-ion formation takes place through a resonance of keto-enol equilibrium within the part of the MMA molecule between the two carboxyl groups, we evaluated, along with other acids, fragmentation of n-butyl diesters of two other structural isomers dicarboxylic acids, DiMMA and EMA acids (Fig.
. Functional groups: alcohols, carboxylic acids, and esters.
For structural isomers
, we use the nomenclature defined by Benskin et al.
The nanoparticles act as multifunctional single units, which form reversible, noncovalent bonds at specific bond angles and organize themselves into a highly ordered polymer.""We developed a new approach that enables a quantitative prediction of the architecture of linear, branched, and cyclic self-assembled nanostructures, their aggregation numbers and size distribution, and the formation of structural isomers
."Kumacheva was joined in the research by postdoctoral fellows Kun Liu, Nana Zhao and Wei Li, and former doctoral student Zhihong Nie, along with Professor Michael Rubinstein of the University of North Carolina.
The only pertinent weakness, besides the expense of instrumentation and the labeled standards, is the inability to qualitatively distinguish among certain isomers that have similar chromatographic properties and mass spectral fragmentation patterns (i.e., structural isomers
that coelute); in such cases, Fourier-transform infrared spectroscopy can be used, even though it does not have the same inherent sensitivity as MS in the selected ion monitoring mode.