Formation of charge-transfer complexes in systems containing substituted aromatic hydrocarbons and electron-donating organic compounds

Binary systems of monosubstituted benzene derivatives of type C₆H₅X (X=CN, NO₂, COMe, F, Cl, Br, I) and furan, pyrrole, thiophene, pyridine, tetrahydrofuran, and piperidine are analyzed physicochemically by a refractometric method.From deviations from additivity of n (V) isotherms for systems containing furan plus C₆H₅CN, C₆H₅NO₂, or C₆H₅COMe, conclusions can be drawn about interactions of components leading to formation of charge-transfer complexes (CTC) of 21 composition.With pyrrole possible intermolecular interaction must be confirmed by other methods of physicochemical analysis.Almost all of the systems containing tetrahydrofuran investigated, differ by showing more marked interaction between the components, giving CTC of 11 composition.n (V) isotherms for systems containing pyridine and C₆H₅NO₂ are slightly concave to the composition axis. At the same time piperidine clearly reacts with C₆H₅CN and C₆H₅NO₂, giving a 21 complex with the former, and a colored mixture with the latter, (formation of a complex in this case requires confirmation by other methods).All the thiophene binary systems investigated are characterized by linear refractive index isotherms, i.e., they are refractometrically ideal.The electron-donor properties of the heterocyclic compounds investigated vis a vis the aromatic ring with a lowered-electron density lie in the order tetrahydrofuran > furan > piperidine > pyrrole > thiophene.For Part III see [6].     

Laser-initiated polymerization of charge-transfer monomer systems

The laser-initiated polymerization of charge-transfer monomer complexes was investigated with a pulsed nitrogen laser and an argon laser. Several donor-acceptor monomer charge-transfer systems were screened for polymerization in different solvents. Polymerization by laser initiation was achieved in two of these systems; that is, 2-vinylnaphthalene/fumaronitrile and 9-vinylanthracene/fumaronitrile. The best polymer yields were obtained with the 2-vinylnaphthalene/fumaronitrile system in sulfolane solvent. The influences on the polymer yield and composition of solvents, varying focal path length, glass conditioning, initiation sources, environment, and monomer feed ratios were evaluated. Infrared (IR) spectral studies, gel permeation chromatography (GPC), and chemical analyses were performed to characterize the polymer products arising from the polymerization of 2-vinylnaphthalene/fumaronitrile in sulfolane. The polymer contained a high percentage of sulfolane (ca. 1/3 mol fraction), presumably arising from solvent transfer to the growing polymer chains during the propagation phase of the polymerization.     

Synthesis of polysiloxanes with electron-donating groups by anionic ring-opening polymerization

Anionic kinetically controlled ring opening polymerization of cyclotrisiloxane is explored as a method of synthesis of copolymers having the chain composed of dimethylsiloxane units and siloxane units bearing an uncharged nucleophilic (electron-donating, ED) group. Model monomers for these studies are derived from hexamethylcyclotrisiloxane (D₃) in which one methyl group is replaced by the organophosphorus group of general formula - (CH₂) _nP(X)Ph₂ where X is lone pair, O or S. This method is shown to give significant advantages over the thermodynamically controlled homopolymerization and copolymerization of nucleophile-substituted cyclosiloxanes which have so far been used for synthesis of ED substituted siloxane copolymers. The yield of the copolymers is much higher and the molecular weight distribution is narrow. The arrangement of the ED substituents along the chain, although not purely uniform, is much more regular as compared with the statistical distribution. The content of cyclic oligomers was higher than in the polymerization of unsubstituted D₃, which is rationalized on the basis of intramolecular interaction of the counter-ion with the ED groups.     

The substitution structure of nitroethylene

The ^15N- and ¹⁸O-species of nitroethylene have been assigned in natural abundance using microwave-microwave double resonance techniques. Additional transition frequencies have been measured for previously assigned isotopic species in order to have the same set of transitions for all species. The ground state rotational constants of nitroethylene, all eight mono-, three di- and two trisubstituted species have been used to determine the complete substitution structure. The results of the conventional Kraitchman-Constain method are compared to those of a least-squares method.     

Dispersion polymerization in polar solvents

The effect of the nitrogen purge, monomer purification, type of agitation, and presence of costabilizer on the particle size distribution (PSD) was investigated in the dispersion po-lymerization of styrene in ethanol and in the dispersion copolymerization of styrene and butyl acrylate in a water–ethanol mixture. Purging with nitrogen and, to a lesser extent, monomer purification, were of paramount importance to achieve monodispersity. The type of agitation had a week effect on the PSD, whereas the presence of costabilizer had no effect on the PSD. © 1995 John Wiley & Sons, Inc.     

Pronounced solvatochromism of charge-transfer complexes in strongly hydrogen bonding solvents

A large bathochromic shift is reported for the charge-transfer (CT) transition in complexes of π-electron donors with electron acceptors containing CO groups in strongly H-bonding solvents such as trifluoroacetic acid and hexafluoroisopropanol. The results of ¹³C-NMR measurements and SCF-LCAOMO calculations indicate that this effect can be attributed to an increased electronegativity of the acceptor upon hydrogen bond formation with the solvent.     

Radiation-induced postpolymerization of nitroethylene

Radiation-induced postpolymerization of nitroethylene in 2-methyltetrahydrofuran glass has been studied and discussed in reference to the results obtained from ESR measurements. No postpolymerization occurred at the temperature below ?150°C. In the temperature range between ?135°C and ?78°C, the polymer yield decreased with increasing postpolymerization temperature. The polymer yield increased linearly with the increase of the preirradiation dose in the range below 0.9 × 10⁶ r. The mean value for chain initiation was estimated to be about 1.3. The following correlations were observed between the results of the postpolymerization and ESR measurements. The postpolymerization started in the temperature range between ?140°C and ?135°C, where the ESR spectrum due to the anion radicals of nitroethylene disappeared. The polymer yield of the postpolymerization decreased with the photoirradiation at ?196°C before warming the samples in parallel with the photobleachability of the anion radicals observed in the glassy mixture by the ESR method. It was concluded from these results that the radiation-induced postpolymerization was initiated by the anion radicals of nitroethylene formed by the capture of electons.     

A spectroscopic study on defluorination of poly(tetrafluoroethylene) by alkyllithium/electron-donating solvents

Defluorination of PTFE by alkyllithium/electron-donating solvents such as N,N,N',N'-tetramethylethylenediamine (TMEDA), hexamethylphosphoramide (HMPA) was studied by means of spectroscopy such as ESR, 7Li- and 13C-NMR, XPS, UV-Vis and IR. Based on the experimental results, it was concluded that an electron from radical species, which was generated in the alkyllithium/electron-donating solvent, was transferred onto PTFE molecule so as to eliminate fluorine atoms from the PTFE and to form carbon-centered radicals on the PTFE; concomitantly, the alkyl group of the alkyllithium was transferred onto the PTFE. Combined with the experimental results of the phenyllithium/HMPA system, mechanism of the fluorine atom elimination reactions from PTFE by the radical species is discussed.     

Electronic spectra of nitroethylene

A systematic study of the electronic excited states of nitroethylene (C₂H₃NO₂) was carried out using the approximate coupled‐cluster singles‐and‐doubles approach with the resolution of the identity (RI‐CC2), the time dependent density functional theory with the CAMB3LYP functional (TDDFT/CAMB3LYP) and the DFT multireference configuration interaction (DFT/MRCI) method. Vertical transition energies and optical oscillator strengths were computed for a maximum of 20 singlet transitions. Semiclassical simulations of the ultraviolet (UV) spectra were performed at the RI‐CC2 and DFT/MRCI levels. The main features in the UV spectrum were assigned to a weak n‐π* transition, and two higher energy π_CC+O‐π* bands. These characteristics are common to molecules containing NO₂ groups. Simulated spectra are in good agreement with the experimental spectrum. The energy of the bands in the DFT/MRCI simulation agrees quite well with the experiment, although it overestimates the band intensities. RI‐CC2 produced intensities comparable to the experiment, but the bands were blue shifted. A strong π_CC+O‐π* band, not previously measured, was found in the 8–9 eV range. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Vibrational spectrum of nitroethylene

Conclusions On the basis of the infrared and Raman spectra of normal and isotope-substituted nitroethylenes, the authors offer an interpretation of the frequencies of nitro-groups conjugated with a multiple C=C bond.Translated from Izvestiya Akademii Nauk SSR, Seriya Khimicheskaya, No. 8, pp. 1870–1871, August, 1968.We are grateful to E. F. Ponizovtsev and S. S. Bulakov for their help with the experiments.     

Spectrophotometric study of the charge-transfer complexes of iodine with antipyrine in organic solvents

The charge-transfer complex formation of iodine with antipyrine has been studied spectrophotometrically in chloroform, dichloromethane (DCM) and 1,2-dichloroethane (DCE) solutions at 25 degrees C. The results indicate the formation of 1:1 charge-transfer complexes. The observed time dependence of the charge-transfer band and subsequent formation of I(3)(-) in solution were related to the slow transformation of the initially formed 1:1 antipyrine:I(2) outer complex to an inner electron donor-acceptor (EDA) complex, followed by fast reaction of the inner complex with iodine to form a triiodide ion. The values of the equilibrium constant, K, are calculated for each complex and the influence of the solvent properties on the formation of EDA complexes and the rates of subsequent reaction is evaluated.     

Peroxidase-catalyzed polymerization and depolymerization of coal in organic solvents

Peroxidases from horseradish roots (HRP) and soybean hulls (SBP) catalyze the efficient polymerization of a 4-kDa dimethylformamide (DMF)-soluble fraction of Mequininza (Spanish) lignite in 50% (v/v) DMF with an aqueous component consisting of acetate buffer, pH 5.0. Under these conditions, HRP and SBP catalyze the oxidation of free phenolic moieties in the coal matrix, thereby leading to oxidative polymerization of the low-molecular-weight coal polymers. The high fraction of nonphenolic aromatic moieties in coal inspired us to examine conditions whereby such coal components could also become oxidized. Oxidation of nonphenolic aromatic compounds was attempted using veratryl alcohol as a model substrate. SBP catalyzed the facile oxidation of veratryl alcohol at pH <3.HRP, however, was unable to elicit veratryl alcohol oxidation. The potential for SBP to catalyze interunit bond cleavage on complex polymeric substrates was examined using l-(3,4-dimethoxyphenyl)-2-(phenoxy)propan-1,3-diol (1) as a substrate. SBP catalyzed the Cα-Cβ and β-ether bond cleavage of this compound, suggesting that similar reactions on coal, itself, could lead to depolymerization. Depolymerization of a >50 Da coal fraction was achieved using SBP in 50% (v/v) DMF with an aqueous component adjusted to pH 2.2. Approximately 15% of the initial high-molecular-weight lignite fraction was depolymerized to polymers 4 Da in size. Hence, SBP is capable of catalyzing the depolymerization of coal in organic solvents, and this may have important ramifications in the generation of liquid fuels from coals.     

Radical polymerization of vinyl acetate in individual and mixed solvents

The kinetics of polymerization of vinyl acetate in individual and mixed solvents was studied. The reaction rate constant and the rate of chain transfer in the mixed solvent were calculated, molecular weights and some adhesive characteristics of poly(vinyl acetate) obtained by the radical polymerization in solution were determined. A comparative analysis of the polymers obtained in the individual and mixed solvents was performed. It is shown that the change in the solvent composition can affect the rate of reaction and the poly-(vinyl acetate) adhesive properties.     

Radical polymerization of various alkyl methacrylates in liquid crystalline solvents

The polymerization of methacrylates of methyl, ethyl, butyl, hexyl, octyl, dodecyl, and octadecyl alcohols was studied with 2,2′-azobisisobutyronitrile in the smectic, nematic, cholesteric, and isotropic liquid phases at 50–75°C. N-(4-Methoxyphenylmethylene)phenylamine, N-(4-ethoxyphenyl-methylene)-4-butylphenylamine, cholesteryl octadecanoate, and benzene were used as the solvents. The viscosities of the polymers were enhanced in the mesomorphic solvents. The polymer was converted to the corresponding poly(methyl methacrylate) through hydrolysis and esterification. Tacticities of the resultant poly(methyl methacrylates) were determined by nuclear magnetic resonance spectroscopy. The isotacticities of the polymers obtained in the smectic and the nematic phases were basically the same and appeared to be larger than those of the polymers in the cholesteric and isotropic liquid states. The polymerization of the methacrylates of butyl and longer-chain alcohols deviated from Bernoullian statistics and gave polymers more isotactic than those of methyl and ethyl methacrylates.     

Cationic polymerization of allyl glycidyl ether in solvents of different basicity

The boron trifluoride tetrahydrofuranate-catalyzed cationic polymerization of allyl glycidyl ether in carbon tetrachloride proceeds via an oxirane cycle to form initially cyclic products and, at later stages, high-molecular-mass products. In the case of 1,2-dimethoxyethane, the polymerization of allyl glycidyl ether occurs via insertion of the monomer into a dissociated bond of a Lewis acid-dimethoxyethane complex and yields a linear polymer with end methoxy groups.     

Effect of electron-donating ability of terminal groups of cationic polymethine dyes on thermal polymerization of methyl methacrylate in solution

Thermal polymerizability of methyl methacrylate solution was examined in dimethylformamide in the presence of cationic symmetric and asymmetric polymethine dyes with different terminal electron-donating groups by dilatometric method. It was found that the polymethine dyes according to the electronic structure can initiate or inhibit the polymerization of methyl methacrylate both in the presence of standard initiator, azoisobutyronitrile, and in its absence by a radical mechanism. It was shown that the initiating ability was weakened with altering an electron-donating activating ability of terminal groups of dyes from the average level in both directions of its increasing or decreasing. The transition from symmetric to asymmetric dyes in the same structural type is accompanied by a loss of initiating ability. Based on the comparison of experimental kinetic data of polymerization of methyl methacrylate in the presence of dyes and quantum chemical calculations of electronic structure for dyes it was demonstrated that a HOMO energy value of an initiating dye must be higher and that of an inhibiting dye, lower than the methyl methacrylate value.     

电荷转移聚合法合成聚丙烯酸叔丁酯的研究

本文以丙烯酸叔丁酯为单体,苯胺与二苯甲酮络合物为引发剂,四氢呋喃为溶剂,在紫外光照射下通过电荷转移聚合(CTP)合成了具有苯亚胺基链端的聚丙烯酸叔丁酯(PtBA),并用FT-IR、1H-NMR和GPC等对其进行了表征.同时考察了反应时间、引发剂浓度、反应温度等因素对单体转化率和聚合物分子量的影响.结果表明,聚合反应动力...