Croatica Chemica Acta 

About: Croatica Chemica Acta is an academic journal published by Croatian Chemical Society. The journal publishes majorly in the area(s): Adsorption & Crystal structure. It has an ISSN identifier of 0011-1643. It is also open access. Over the lifetime, 2087 publications have been published receiving 22971 citations.

A Description of the Chemical Bond in Terms of Local Properties of Electron Density and Energy

Abstract: Chemical bonding is described in terms of the properties of the one-electron density f2 (r) and the local energy density H (r) = G (r) + V (r). Analysis of a variety of different bonds suggests that covalent bonding requires the existence of ao saddle point rP of f2 (r) in the internuclear region (necessary condition) and a predominance of the local potential energy V (r) at r P : J VP J > GP and, hence, HP< O. A covalent bond can be characterized by the position of r P, the value and the aonisotropy of f!p · These properties of f2 (r) can be used to define polarity, order and n-character of the bond. Information about concentration and depletion of electronic charge at rP is provided by the Laplacian of f2p• \1 2 f!p· Investigation of \1 2 (! (r) does not suffice to detect weak covalent bonds, an observation which is aolways valid if accumulation of electronic charge in the internuclear region is taken as the sole indicator for bonding. Interactions between closed shell systems as experienced in ionic, hydrogen bonded or van der Waals systems lead to a positive value of HP. In this case, shared electron density causes destabilization rather than stabilizaotion of the molecule.

Structure-radical scavenging activity relationships of flavonoids

Abstract: The relationship between the structural characteristics of 29 flavonoids and their antiradical activity was studied. The obtained results suggest that the free radical scavenger potential of these polyphenolic compounds closely depends on the particular substitution pattern of free hydroxyl groups on the flavonoid skeleton. The possible mechanism of action of flavonoids lacking B ring OHs as free radical scavengers has been proposed.

The Zagreb Indices 30 Years After

Abstract: The original formulation of the Zagreb indices is presented and their relationship to topological indices such as self-returning walks, Platt, Gordon-Scantlebury and connectivity indices is discussed. Their properties are also listed. Modified Zagreb indices are introduced and the Zagreb complexity indices reviewed. Their use in QSPR is illustrated by modeling the structure-boiling point relationship of C3–C8 alkanes using the CROMRsel procedure. The obtained models are in fair agreement with experimental data and are better than many models in the literature. However, in general, the Zagreb indices do not contribute to the best structure-boiling point models of alkanes. Nevertheless, it is interesting to note that the best five-descriptor model that we found in the literature contains the Zagreb M2 index.

Degree-Based Topological Indices

Abstract: The degree of a vertex of a molecular graph is the number of first neighbors of this vertex. A large number of molecular-graph-based structure descriptors (topological indices) have been conceived, depending on vertex degrees. We summarize their main properties, and provide a critical comparative study thereof.

Specific Chemical Interaction Affecting the Stability of Dispersed Systems

Abstract: 1) Sorbable species may destabilize colloids at much lower concentrations than nonsorbable ions. The VODL double layer model neglects the dominating role that chemical forces play in causing adsorption and is restricted in its application to lyophilic colloids and simple electrolytes. 2) The distribution of ions in an oxide-electrolyte interface can be evaluated from alkalimetric and acidimetric titration curves of aqueous dispersions of these oxides. 3) A comparison of the differential capacity of the interface at an oxide-electrolyte interface with that of Hg or Ag! shows much larger capacitance values for the hydrophilic strongly aquated oxide surface than for the more hydrophobic surface of Hg and Ag!. The difference is caused primarily by the strongly structured, extensively hydrogen-bonded and chemisorbed water layer immediately adjacent to the solid oxide surface. Ions tend strongly to penetrate (specific sorption) into the compact part of the double layer adjoining the oxide surface, and may thus exert a marked effect on the surface chemical properties beyond those observed by a mere compaction of the diffuse part of the double layer. 4) Association of oxide surfaces with H+, and other cations can, similar as with polyelectrolytes, be characterized by acidity and stability constants. The latter constants can be expressed as intrinsic constants if they are cor rected to a hypothetically chargeless surface. The specificity of the interaction with H+ and cations can be understood by considering simple electrostatic models. This association of oxide surfaces with cations can be used to explain the effect of cations such as Ca2+ on the stability of hydrous oxide colloids, and on the deposition of Mn02 particles on sand surfa ces. The extent to which a coagulant species is specifically adsorbed is reflected in the c. c. c. necessary to produce a ggregation. When the specifically adsorbed species and the colloid are of opposite charge, the sorbed species act to reduce the surface charge of the colloid. The destabilizing agent can, in some cases, even reverse the colloid charge and restabilization will occur. 5) Specific cation interactions as described here represent a basis of related ion specific processes, such as the behavior of ion selective glass or membrane electrodes; the selective ion permeability of cell membranes and potential generating mechanisms in the living cell.