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A theoretical study for the determination of chemical reactivity of a series of 2‐adamantyl‐thiazolidine‐4‐one derivatives was performed. These molecules are inhibitors of inverse transcriptase activity of human immunodeficiency virus type 1 (HIV‐1) that prevents the replication of HIV‐1 in cells without causing an appreciable effect on other retroviral particles or cellular polymerases. To determine the nature of the bond, enzyme substrate was used for quantum similarity molecular calculations, using the alignment of topo‐geometrical superposition approach, solving the problem of finding the best alignment. The reactivity descriptors provide an appropriate methodology to evaluate molecular quantum similarity of these molecular structures, in the context of the density functional theory, taking into account the electronic effects quantified by the quantum similarity descriptor of Coulomb, which turned out to be the best molecular descriptor to describe the electron correlation structures; the determination of the reactive sites is of great importance for the determination of chemical reactivity, providing a bridge between the fields of chemical reactivity, and molecular quantum similarity allows us to find new characteristics and properties of reactivity on these kinds of molecules. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

A methodology for structurally representing the molecules of three Colombian vacuum residues (538+ °C) and one Mexican atmospheric residue (300+ °C) is reported. Information obtained by Fourier transform ion cyclotron resonance mass spectrometry coupled to positive electrospray ionization, negative electrospray ionization, and positive atmospheric pressure photoionization sources and conventional standardized analytical methods was used for molecular representation of the samples. The generation of molecules was performed by a Monte Carlo technique, obtaining a set of representative structures for the global representation through attributes for each residue. The structural attributes considered are CH, CH 2 , and CH 3 in paraffinic chains, number of naphthenic rings, CH 2 and CH naphthenic number of aromatic rings, aromatic carbon type, cataand peri-condensed carbons, number of sheets in asphaltenes, −SH, aromatic S (thiophene), aromatic N (pyridine and pyrrole), and −NH 2 . Each attribute in the residues can be represented by a probability density function (PDF), which is optimized for the purpose of adjusting the structures of residues and their composition to the experimental data. The PDFs for aromatics and nitrogen and sulfur components were obtained by ultrahigh mass resolution data. As a result, 150 molecules per each residue were obtained, and the mode of representation was single-feed (only one feed is characterized at the same time). The bulk properties for each residue were in good agreement with the experimental structural information.

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