Polyfunctional complex sulfur-containing additives to SKI-3 rubber and vulcanizates thereof

The performance of new polyfunctional additives containing bis(2,6-di-tert-butyl-4-hydroxyphenyl) polysulfide and dicyclopentadiene-sulfur copolymer was studied with respect to SKI-3 and vulcanizates thereof. These additives act not only as stabilizers but also as vulcanizing agents improving a number of physicomechanical characteristics of the vulcanizates.     

Quantum-chemical study of thermodynamics of hydrogen-bonded methylamine-methanol complexes reaction with dimethyl carbonate

Thermodynamic parameters of the reactions of dimethyl carbonate cis-cis and cis-trans conformers with methylamine, methylamine dimer, and methylamine complexes involving linear methanol associates have been computed with the B3LYP and WB97XD quantum-chemical methods. The both methods have given similar results. Thermodynamically, reactions of the cis-trans conformer are preferred over the analogous reactions of the cis-cis conformer, and the reactions with methylamine dimer and methylamine-methanol trimer complex are preferred over the reactions with methylamine monomer. The acid-base properties of the hydrogen-bonded methanol complexes are significantly enhanced with increasing degree of association. Stability of the methylamine complexes with methanol clusters is increased with more of the alcohol molecules involved.     

Quantum-chemical study on the reaction of phenyl isocyanate with linear methanol associates. Addition at the C=N bond

Quantum-chemical calculations at the B3LYP/6-311++G(df,p) level of theory showed that reactions of phenyl isocyanate with methanol associates involve formation of pre-and post-reaction complexes. The reactions proceed through late asymmetric cyclic transition states. The height of the energy barrier decreases as the degree of association of the alcohol increases. The relative change in the Gibbs energy in the reaction of phenyl isocyanate with methanol also becomes smaller as the degree of alcohol association increases.     

Esterification of dicarboxylic acids with benzyl alcohol under the action of the microwave radiation

Reaction of dicarboxylic acid with benzyl alcohol under the microwave irradiation proceeds faster as compared to the thermal conditions. The main reaction products are alkyl dicarboxylates, and the monoester and dibenzyl ether are formed as the side products. A proposal about the nature of the nonthermal effect in the reactions stimulated by the microwave irradiation is considered.     

Quantum-chemical study on the reaction of phenyl isocyanate with linear methanol associates: II. Addition at the C=O bond

Addition of linear methanol associates at the C=O group of phenyl isocyanate involves a concerted cyclic asymmetric late transition state. The reaction is accompanied by formation of pre- and post-reaction complexes. Isomerization of intermediate methyl hydrogen phenylimidocarbonate into methyl phenylcarbamate is characterized by a considerable energy barrier. The reactivity of methanol molecules increases in parallel with the degree of their association, which is related to increase in their electron-donor power. Comparison of the calculated parameters for the addition of methanol associates at the C=N and C=O bonds of phenyl isocyanate clearly indicates that the first path is preferred.