Polyurethanes based on anionic macroinitiators,aromatic isocyanates,and 4,4′-dihydroxy-2,2-diphenylpropane

Polyurethanes prepared from anionic initiators, 4,4′-dihydroxy-2,2-diphenylpropane, and aromatic isocyanates were studied by IR spectroscopy. The hydroxy groups in 4,4′-dihydroxy-2,2-diphenylpropane are completely involved in the urethane formation. Variation of the molar ratio of isocyanate and hydroxy groups in the polymer-forming system allows control both of the rigid segment length and of the content of the isocyanurate component in the polymeric matrix. The physicomechanical properties of the polymeric film samples were studied. An increase in the size of the aromatic block is accompanied by enhancement of the strength and plastic deformation of the polymers.     

Vinylation of pyrroles in dimethyl sulfoxide

A number of 1-vinylpyrroles were obtained in up to 97% yields by base-catalyzed addition of substituted pyrroles to acetylene in dimethyl sulfoxide at 80–100°C.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 213–214, February, 1977.     

Pyrroles from ketoximes and acetylene.

2-Aryl- and 1-viny1-2-pyrroles were synthesized by condensation of p-substituted acetophenone oximes with acetylene under pressure in superalkaline media (KOH/DMSO). The initially formed nitrogen-unsubstituted pyrroles can be vinylated in the presence of acetylene. Lithium hydroxide, which is completely inactive in the vinylation step, was found to be a selective catalyst for the construction of a pyrrole ring from oximes of aliphatic aromatic ketones. In the case of aliphatic and cycloaliphatic ketoximes (for example, cyclohexanone oxime) LiOH has virtually no catalytic effect on the reaction. The yields of 1-viny1-2-ary1-pyrroles depend substantially on the substituent in the phenyl ring. The structures of the synthesized compounds were confirmed by the IR, PMR, UV, and ¹³C NMR spectra.See [1] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 489–491, April, 1978.     

Quantum-chemical study on reactions of isocyanates with linear methanol associates: VII. Effect of nonspecific solvation on the reaction of methyl isocyanate with linear methanol associates

The effect of nonspecific solvation on the reactivity of methyl isocyanate toward linear methanol associates and thermodynamic parameters of this reaction was studied at the B3LYP/6-311++G(df,p) level of theory in terms of the polarizable continuum model (PCM). Transformations in the liquid phase are more exothermic than in the gas phase. Change of the solvent nature leads to variation of the geometric parameters and intrinsic free energies of the reactants and transition states. Increase in solvent polarity is accompanied by increase in the degree of asymmetry and polarity of transition states. As the dielectric permittivity rises, the polar constituent of the Gibbs energy of solvation decreases, while its nonpolar constituent increases. Owing to the opposite variations of these constituents of the Gibbs energy of activation, the reaction is weakly sensitive to solvent polarity.     

Quantum-chemical study of thermodynamics of ethylene carbonate reactions with methanol

Thermodynamic parameters of the major and side reactions in the course of dimethyl carbonate formation from ethylene carbonate and methanol have been determined by means of the B3LYP/6-311++G(df,p) quantum-chemical method. Enthalpy and entropy of the reactions have increased with enhanced association of the alcohols. Temperature dependences of the equilibrium constants have been determined. Technological conditions of dimethyl carbonate production via ethylene carbonate methanolysis have been elaborated.     

Synthesis of Ureidocarboxylic Acids and Hydantoins by Reaction of Aminocarboxylic Acids or Their Esters with Trichloroacetamides

The reactivity of N-aryltrichloroacetamides as in situ generating isocyanates is used in the reaction with aminocarboxylic acids and their esters. N-aryl ureido-carboxylic acids, their esters or hydantoins are the obtained compounds.     

Thermal transformations of urea in ethylene glycol: II. Reaction of isocyanic acid with ethylene glycol associates

The reaction of isocyanic acid with ethylene glycol associates was studied by the B3LYP/6–311++G(df,p) quantum chemical method. The reaction mechanism includes formation of pre- and post-reaction complexes and cyclic asymmetric late transition states. The energy barrier decreases with increase in the degree of association of ethylene glycol.     

Quantum-chemical study on reactions of isocyanates with methanol associates: VI. Quantum-chemical characterization of the relative reactivity of linear and cyclic methanol trimers in the addition to methyl isocyanate

Quantum-chemical study on the reaction of methyl isocyanate with cyclic methanol trimer at the B3LYP/6-311++G(df,p) level of theory showed that the process involves concerted asymmetric transition state in which the formation of new N-H bond outstrips the formation of new C-O bond. The reaction of methyl isocyanate with linear methanol trimer was found to be both kinetically and thermodynamically more favorable than with cyclic trimer.     

Quantum-chemical investigation of isocyanate reactions with linear methanol associates: IV. Mechanism of autocatalytic reaction of methyl isocyanate with linear methanol associates

It was shown by quantum-chemical method B3LYP/6-311++G(df,p) that in the autocatalytic reaction the molecules of methyl carbamate formed prereaction complexes with the monomer and dimer of methanol. The complexes possess higher electron-donor properties than free alcohol molecules thus increasing the activity of complexes in the reaction with isocyanates. The products of the autocatalytic reaction are new molecules of carbamate and azomethinenol. The conversions occur through concerted asymmetric late transition states. The isomerization of azomethinenols into carbamates is catalyzed by molecules of alcohols and their associates. The autocatalytic reaction of isocyanates with alcohols becomes possible owing to the ability of alcohols to catalyze the mentioned isomerization.