Molecular topological

Extension of the appHcations of polymethine dyes has required special spectral and other characteristics. As a rule, the search for and synthesis of promising new compounds having desired properties imply the preliminary estimation of their most important parameters on the basis of elaborated theoretical conceptions. Thus, an effective way of governing electron properties consists of the variation of molecular topology of polymethines. 

The property of chirality is determined by overall molecular topology, and there are many molecules that are chiral even though they do not possess an asymmetrically substituted atom. The examples in Scheme 2.2 include allenes (entries 1 and 2) and spiranes (entries 7 and 8). Entries 3 and 4 are examples of separable chiral atropisomers in which the barrier to rotation results from steric restriction of rotation of the bond between the aiyl rings. The chirality of -cyclooctene and Z, -cyclooctadiene is also dependent on restricted rotation. Manipulation of a molecular model will illustrate that each of these molecules can be converted into its enantiomer by a rotational process by which the ring is turned inside-out. ... 

Supramolecules and supramolecular assemblies including silsesquioxanes and azacrown ethers fragments as liquid crystals with restricted molecular topology 98CC2057. 

Blood-brain barrier permeation of 7, among other drugs, was predicted from its three-dimensional molecular structure by a computational method (0OJMC2204). The combination of molecular topological methods using 137 quinolones, including 7 provided an excellent tool for the design of new... 

Zander, M Molecular Topology and Chemical Reactivity of Polynuclear Benzenoid Hydrocarbons. 153, 101-122 (1990). 

Ivanov J, Karabunarliev S, Mekenyan O. 3DGEN a system for exhaustive 3D molecular design proceeding from molecular topology. J Chem Inf Comput Sci 1994 34 234-43. 

The following steps contain the build-up of the molecular topology and the choice of the convenient general simulation conditions. 

Huuskonen, J. Estimation of aqueous solubility for a diverse set of organic compounds based on molecular topology. J. Chem. Inf. Comput. Sd. 2000, 40, m-111. 

M. J. Randic, On the recognition of identical graphs representing molecular topology. J. Chem. Physics, 60 (1974) 3920-3928. 

Sabljia132 presents very accurate equations for predicting the Koc of both polar and nonpolar organic molecules based on molecular topology, provided the organic matter percentage exceeds... 

Sabljia, A., On the prediction of soil sorption coefficients of organic pollutants from molecular structure application of molecular topology model, Environ. Sci. Technol., 21, 358-366, 1987. 

Complex polymers are distributed in more than one molecular property, for example, comonomer composition, functionality, molecular topology, or molar mass. Liquid chromatographic techniques can be used to determine these properties. However, one single technique cannot provide information on the correlation of different properties. A useful approach for determining correlated properties is to combine a selective separation technique with an information-rich detector or a second selective separation technique. 

Huuskonen, J., Salo, M., Taskinen, J., Aqueous solubility prediction of drugs based on molecular topology and neural network modeling, J. 

Schultz MTI by valence vertex degrees Gutman Molecular Topological Index Gutman MTI by valence vertex degrees Xu index... 

Meylan, W. M., Howard, P. H., Boethling, R. S. (1992) Molecular topology/fragment contribution for predicting soil sorption coefficient. Environ. Sci. Technol. 26, 1560-1567. 

Sabljic, A. (1984) Predictions of the nature and strength of soil sorption of organic pollutants by molecular topology. J. Agric. Food Chem. 32, 243-246. 

However, we should emphasize that the NBO/NRT concepts of hybridization, Lewis structure, and resonance differ in important respects from previous empirical usage of these terms. In earlier phases of valence theory it was seldom possible to determine, e.g., the atomic hybridization by independent theoretical or experimental procedures, and instead this term became a loosely coded synonym for the molecular topology. For example, a trigonally coordinated atom might be categorized as sp2-hybridized or an octahedrally coordinated atom as d2sp3-hybridized, with no supporting evidence for the accuracy of these labels as descriptors of actual... 

It is always advisable to examine the complete molecular topology in the neighborhood of the chiral carbon atom and to confirm the results by employing another analytical method before the final assignment. In conclusion, Prelog s rule does predict the steric course of an asymmetric synthesis carried out with a chiral a-keto ester, and the predictions have been found to be correct in most cases. Indeed, this method has been widely used for determining the absolute configuration of secondary alcohols. 

Schultz, H. P., Schultz, E. B., Schultz, T. P. Topological organic chemistry. 9. Graph theory and molecular topological indices of stereoisomeric organic compounds. J. Chem. Inf. Comput. Sci. 1995, 35, 864-870. 

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