Non‐Stoichiometric Polycondensations and the Synthesis of High Molar Mass Polycondensates

This report presents a general overview of non‐stoichiometric step‐growth polymerizations (polycondensations). Three kinds of non‐stoichiometric polycondensations are defined and discussed for a₂ + b₂ monomer combinations. Depending on the kinetic scenario and on the experimental conditions, the excess of one monomer either strongly reduces or strongly enhances the average degree of polymerization (DP) relative to a stoichiometric polycondensation under identical conditions. As a result, telechelic oligomers or extremely high molar mass polymers (DPs > 1000) may be formed. Stoichiometric imbalance has in all cases the consequence that cyclization is largely suppressed in early stages of a polycondensation. Finally, non‐ stoichiometric “ a₂ + b_n ” polycondensations are discussed.     

Oligomerization of 3,5-dimethyl benzyl alcohol promoted by clay: experimental and theoretical study

Linear oligomerization of 3,5-dimethyl benzyl alcohol is induced by a montmorillonite clay (Tonsil Optimum Extra), producing 1,3,5,7-tetramethyl-9,10-dihydro-anthracene, which, by loss of protons results in the product 1,3,5,7-tetramethylanthracene. It was also found that the compounds 4-(3′,5′-dimethylbenzyl)-1,3,5,7-tetramethyl-9,10-dihydroanthracece and 4-(3′,5′-dimethylbenzyl)-1,3,5,7-tetra-methylanthracene were formed from 1,3,5,7-tetramethyl-9,10-dihydroanthracene. 1,3,5,7-Tetramethylanthryl radical cation was formed from 1,3,5,7-tetramethyl-9,10-dihydroanthracene; it was characterized by Electronic Paramagnetic Resonance (EPR). On the other hand, a theoretical analysis was performed, allowing the rationalization of the observed products and some of the key reaction steps.     

On magnetic ordering in colloids of single-domain particles

Observed data supporting the possibility of magnetic ordering in magnetic colloids are reported. Conditions under which magnetized structures arise in magnetic colloids, initial samples in which these magnetized structures can be formed, and colloids with a developed system of magnetized aggregates are analyzed.     

Synthesis and study of new indoline spiropyran and its derivative with α-lipoic acid exhibiting low cytotoxicity

Russian Chemical Bulletin - New indoline spiropyran was synthesized by the cyclocondensation of 5-chlorine-substituted Fischer base with 2,7-dihydroxy-1-naphthaldehyde. This spiropyran was used to...     

Homoligand Tris-o-Dioxolene Complexes. Peculiarities of the Molecular Structures and Magnetic Properties

Russian Journal of Coordination Chemistry - Metal tris-o-dioxolene (o-quinone, o-semiquinone, and catecholate) complexes represent an interesting and vivid model system for the demonstration of a...     

Formation of nanostructured carbon films in gas-discharge plasmas

Deposition of carbon materials from methane-hydrogen gas mixtures in a DC gas discharge is investigated. Parameters ensuring stable discharge conditions and synthesis of diamond and graphite-like films are determined. Optical emission spectroscopy is used to analyze the composition of the activated gas phase in the course of carbon film deposition. Synthesis of graphite-like carbon nanotubes and nanocrystallites is shown to correlate with the presence of C₂ dimers in the plasma. A noncatalytic mechanism of synthesis of nanostructured graphite in a carbon-containing gas phase is proposed.     

Kinetics and Mechanism of the Pudovik Reaction in the Azomethine Series: II.1 Hydrolysis and Catalysis in the Reaction of Dialkyl Phosphites with Benzalaniline

A ³¹P NMR study show that diisopropyl phosphite and benzalaniline do not react with each other as individual components. Adduct formation is made possible by partial hydrolysis of the dialkyl phosphite.     

DFT and local MP2 study of switching process in a pH controllable molecular “shuttle”

A pH controllable molecular “shuttle,” comprising of dibenzo 24 crown‐8 (DB24C8) macroring bound to a “finger” molecule possessing two different recognition sites has been studied at the density functional theory (DFT) and Møller‐Plesset second‐order (MP2) levels of theory. The calculation confirmed experimental results that translational conformer with DB24C8 located around NH station has the lowest energy, while the conformer with DB24C8 located around NH station shows the highest energy. It has been found that Bpym2+ unit consists of two “substations” separated by an energy barrier of 3–17 kcal/mol depending on the state of the NH–NH station. The translational conformers are stabilized by NH…O, ⁺NH…O, ⁺NCH…OH‐bonds, and π–π stacking with different contributions, depending on the conformer type. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem 2007