Least-squares and neural-network forecasting from critical data

J. Chem. Inf. Comput. Sci.

2004

Self Cite

Generations of Soviet scientists contributed invaluable insights into molecular classification. Unfortunately, this research is little appreciated in much of the world. Among these workers S. A. Shchukarev was of great importance. His and his followers' legacy includes a host of graphical displays showing enthalpies of formation of gaseous molecules from free atoms DeltaH(a) and standard enthalpies of formation of substances plotted on the atomic number of the central elements, on their oxidation states, their internuclear separations, and other variables for a wide range of molecules. These graphs serve as databases, from which data can be extracted, to moderate precision, visually. We discuss graphs for one very limited set, or "pleiade" (gas-phase oxides of nitrogen), and for three much broader sets, or subsystems (gas-phase fluorides of all main subgroup atoms and oxides of transition-metal atoms in gas-phase and in STP conditions). When dissolved in water, molecules lose their identities but periodicity is echoed in the acids and aquocations that are formed. We show, as an example in tabular form, that redox potentials of high-oxygen acids containing S, Se, and Te change concomitantly with DeltaH(a ) and DeltaH(f) of their hexafluorides. We present graphical evidence that three properties for cations of groups 1-3 (in the short version of the periodic chart) behave similarly and share the periodicity of the elements. One of the properties is related to the ionization potential, which is shown in a tabular example to vary concomitantly with energy of hydration. It was the ultimate goal of S. A. Shchukarev that the transformation of any one graphical database into any other, having different molecules under different conditions, would be made mathematically.

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confidence: 58%

Section: Introductionmentioning

confidence: 79%

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confidence: 99%

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Periodic Systems of Molecules as Elements of Shchukarev's “Supermatrix”, i.e. the Chemical Element Periodic System

Latysheva

J. Chem. Inf. Comput. Sci.

2004

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“…On this boundary lie CFN (at n e =16 and C 2 = 7, impossible), NOO and FOC (at n e =17 and C 2 = 6), FNO (at n e = 18 and C 2 = 5), FCNe (at n e = 19 and C 2 = 4, possible only under special conditions), and NeCNe (at n e = 20 and C 2 = 4, also possible only under special conditions). Other molecules at intersections of mesh lines can be inferred from n e and C 2 ; some of them are shown explicitly shown in the similar Figure of ref . …”

Section: Graphical Analyses For Triatomic Moleculesmentioning

confidence: 80%

Molecular Similarity for Small Species: Refining the Isoelectronic Index

J. Chem. Inf. Comput. Sci.

Matus

2001

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This paper tests a chemical-similarity model against properties of gas-phase neutral triatomic and four-atom molecules. The model is a variant of the Diatomics-in-Molecules (DIM) picture, which considers a molecule to be the superposition of all diatomic molecules that could be formed from adjacent atoms in the molecule. The variant is that adjacent atoms are counted as a diatomic molecule only if they are bonded. The tests consist of investigating whether molecules with the same number of electrons, computed by the adjacent-DIM model, have data more similar than do molecules selected at random. The tests vindicate the model for the heat of atomization and for the equilibrium constant for formation, they agree with the model with lesser confidence for the entropy and the partition function, and they show that the model fails for the ionization potential. The model applies with most confidence to molecules with the more electronegative atoms from rows 2 or 3 (those of greatest interest in organic chemistry) and with lesser confidence otherwise. For these properties and these molecules, the model passes graphical and statistical tests at least as well as does the traditional isoelectronic model. Thus, this work refines what may be called the isoelectronic index.

Periodic trends in constants of triatomic molecules

Barrow

Caviness

et al. 2016

Int. J. Quantum Chem.

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Working from the arrangements of both row and group numbers developed within Mendeleev's periodic table of elements, periodic trends can be shown to exist in many constants of triatomic molecules: an extension of the Periodic Law for atoms to the realm of molecules. Trends are identified for vibrational frequencies, bond lengths, and to a lesser extent interior angles. This work includes empirical sources for such data, supplemented with calculations using diatomic analogs where possible. Otherwise, computation is used for all possible configurations of row two and row three main‐group elements to both corroborate and extend empirical results. Organization of this data into a detailed, highly symmetric, multidimensional coordinate system allows for robust graphical and statistical analysis of all constants and associated trends, which in turn permits rapid identification of suspect data to be rechecked. All collected empirical and computational data, along with several interactive visualizations highlighting these results, is available online. © 2016 Wiley Periodicals, Inc.