Phase diagrams of binary symmetric double-tailed alkylbenzenesulfonate surfactant/water systems, as well as the structure of the phases, were determined using crossed polars, polarized light ...microscopy,2H NMR spectroscopy, Nomarski differential interference contrast optics, and cryo-transmission electron microscopy. The isotropic phase, the lamellar phase, and a high-viscosity solution representing an intermediate between the isotropic phase and the mesophase, which refers to the beginning of the formation of vesicles, were found. As may be expected, the isotropic phases at higher concentrations are formed mostly at higher temperatures. Isotropic regions are followed by regions characterized as the isotropic solutions containing vesicles; the optically isotropic phase contains a lamellar dispersion of vesicles in solution. The viscosity of these phases is found to be high near the borderline of the two-phase regions. At the same concentrations two-phase regions were found to contain the isotropic + lamellar phases at the higher temperature and the isotropic + crystalline phase at the lower temperature. Molecular-mechanical and semiempirical quantum-mechanical calculation searches for the global minimum in the conformational space of alkylbenzenesulfonate ions were conducted to examine the influence of monomer molecular structure on the micellar shape.
Graphical bond orders: Novel structural descriptors Randic, Milan; Mihalic, Zlatko; Nikolic, Sonja ...
Journal of chemical information and computer sciences,
03/1994, Volume:
34, Issue:
2
Journal Article, Conference Proceeding
We outline an algorithm for construction of novel molecular descriptors from known structural invariants or molecular properties viewed as descriptors. The novel descriptors are bond-additive ...quantities derived by assigning to each bond a contribution x' obtained by evaluating invariant X for graph G'-e, which is attained from graph G (representing a given molecule) by deleting edge e. The molecular descriptor X'/X is obtained as a normalized sum of bond contributions, where X' is equal to the sum of bond orders x'. The approach is illustrated by presenting X'/X descriptors for smaller alkanes for several well-known topological indices, including the connectivity index, Hosoya's Z index, the Wiener index, and others. The algorithm is quite general and allows one to include molecular properties as source data for the construction of novel descriptors. This is particularly important in view of a limited number of properties used as descriptors in traditional quantitative structure-activity studies. The new algorithm literally doubles the number of descriptors available to traditional chemometricians in their quest for novel property-activity relationships.
»...the Fact is the basis, the foundation; Imagination the building material; the Hypothesis the ground plan to be tested; the Truth or Reality is the building...«
J. H. van’t Hoff
Some of the mathematical properties of buckminsterfullerene are considered, that is, geometrical, topological, group-theoretical and graph-theoretical properties. These mathematical properties are ...used to predict several structural and chemical properties of buckminsterfullerene.
