Solutions In Aprotic Solvents Research Articles

CASPT2 study of the electronic structure and photochemistry of protonated N-nitrosodimethylamine (NDMA-H+) at 453 nm.

In this work, we have studied the photodissociation of the protonated derivatives of N-nitrosodimethylamine [(CH3)2N-NO] with the CASPT2 method. It is found that only one of the four possible protonated species of the dialkylnitrosamine compound absorbs in the visible region at 453nm, that is, N-nitrosoammonium ion [(CH3)2NH-NO]+. This species is also the only one whose first singlet excited state is dissociative to directly yield the aminium radical cation [(CH3)2NHN·]+ and nitric oxide. In addition, we have studied the intramolecular proton migration reaction {[(CH3)2N-NOH]+ → [(CH3)2NH-NO]+} both in the ground and excited state (ESIPT/GSIPT); our results indicate that this process is not accessible neither in the ground nor in the first excited state. Furthermore, as a first approximation, MP2/HF calculations on the nitrosamine-acid complex indicate that in acidic solutions of aprotic solvents, only [(CH3)2NH-NO]+ is formed.

Conductivity and intermolecular interactions in proton‐conducting gel electrolytes

ABSTRACTProton‐conducting gel electrolytes based on poly(methyl methacrylate) (PMMA), poly(vinylidene fluoride) (PVdF), and mixtures of PMMA with PVdF or poly(vinyl chloride) doped by acid solutions in aprotic solvents were synthesized and are discussed in this article. The gel conductivity as a function of the concentrations of acid and polymer and the polymeric matrix composition has been analyzed. Extreme dependence of the conductivity on acid and polymer concentrations was found. It was revealed that within the acid concentration range studied, the gel conductivity was higher than the conductivity of the corresponding liquid electrolytes used for the synthesis. The increase in the electrical conductivity with the growth of the systems viscosity is discussed as an indication of a certain involvement of the polymer matrix in the increase of the charge carrier mobility within the frame of a Grotthuss mechanism. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40674.

Conformational analysis of 2-acetylcyclopentanone by the density functional and MP2 methods

Two-dimensional potential energy surfaces for internal rotation of the acetyl substituent and inversion of the five-membered ring in the gas phase and in acetonitrile were constructed by the B3LYP/6-31G(d) method for the diketo form of the 2-acetylcyclopentanone (2-ACPN) molecule. The diketo form of 2-ACPN exists in the gas phase and in low-polarity cyclohexane as a mixture of four rotamers K1, K2, K3, and K4. The fifth isomeric form K3a exists in polar acetonitrile. The estimation of the tautomeric composition of 2-ACPN taking into account the influence of the cyclohexane medium in the framework of the polarizable continuum model (PCM) using the MP 2/cc-pVTZ method agrees better with experimental data than the estimate obtained by the B3LYP/cc-pVTZ method. The constants of the enol-enol and keto-enol tautomeric equilibria of the 2-ACPN tautomers in solutions of aprotic solvents were estimated.

Electroosmotic transport of water and aprotic solvent in heterogeneous membranes

Electrosmotic water transport in MK-40, MA-40, and MA-41 electrodialysis membranes before and after their treatment by aprotic solvent solution and electroosmotic permeability of a MK-40/MA-40 membrane couple in water and N,N-dimethyl acetamide were studied for the first time. It is found that N,N-dimethyl acetamide produces practically no effect on the properties of the studied ion-exchange materials and its transport number through the MK-40/MA-40 membrane couple is independent both of the initial lithium chloride concentration in a desalting cell of the concentrator electrodyalizer and its volume fraction in the solution. The initial concentration of lithium chloride in the desalting cell does not affect the transport numbers of water in the studied membrane couple either. However, these depend on the volume fraction of the organic component in the solution and this dependence features an extremum. A method for estimation of electroosmotic permeability of the membrane couple in aqueous-organic solutions of electrolytes is suggested.

Conductivity and thermal stability of proton-conducting electrolytes at confined geometry of polymeric gel

The proton-conducting gel electrolytes based on poly(methyl methacrylate) (PMMA) doped by acid solutions in aprotic solvents were synthesized and discussed in this work. The gel conductivity as a function on concentrations of acid and polymer as well as of molecular mass of PMMA has been analyzed. The thermal stability of electrolytes was estimated and discussed. Extreme dependence of the conductivity on concentration is found to be for the gel (at a concentration of PMMA from 5 to 15 wt.%). The increase of electrical conductivity in the concentration range from 5 to 10 wt.% of PMMA with an increase in viscosity of the system is discussed as an indication of an involvement of the polymer matrix in increasing the mobility of the charge carriers in frame of Grotthuss mechanism.

Manifestation of enol–enol tautomerism in IR spectra of 2-acetylcyclopentanone-d1

IR spectroscopy was used to show that 2-acetylcyclopentanone (2-ACPN) exists in solutions of aprotic organic solvents as a mixture of three tautomeric forms. Assignments of absorption bands in IR spectra of 2-ACPN and its deuterated analog 2-ACPN-d1 were made based on calculations of normal mode frequencies by a B3LYP/6-311++(2 d,2p) method for the gas phase and taking into account the influence of aprotic solvents in the framework of a polarizable continuum model (PCM). The enol–enol tautomeric equilibrium constant was evaluated for 2-ACPN-d1 in solutions of the aprotic solvents. The content of the diketo form of 2-ACPN was shown to depend strongly on the solvent polarity and increased with it.

Thermodynamic Study of Phenyl Salicylate Solutions in Aprotic Solvents at Different Temperatures

Phenyl salicylate is employed as a nervous system depressant as well as an intestinal antiseptic owing to its antibacterial activity upon hydrolysis in the small intestine. Various partial molar quantities, namely, apparent molar volume (V Φ ), partial molar volume (V° m ), thermal expansion coefficient (α 2 ), and (∂ 2 V° m /∂T 2 ), of phenyl salicylate in aprotic solvents, i.e., acetonitrile, dimethyl sulfoxide, tetrahydrofuran, and 1,4-dioxane, at T = (293.15 to 313.15) K have been determined. The density and viscosity data were obtained with the help of a vibrating-tube densimeter and viscometer in a concentrarion range of (9.6·10 -3 to 33.0·10 -3 ) mol·kg -1 . The viscosity data have been analyzed using the Jones-Dole equation and the derived parameter B has also been interpreted in terms of solute-solvent interactions.

Radical anions containing the dioxidated 1,2,5‐thiadiazole heterocycle

AbstractRadical anions of 3,4‐aryl disubstituted 1,2,5‐thiadiazole 1,1‐dioxide were obtained by chemical and electrochemical reduction of their substrates, and characterized by ESR spectroscopy and cyclic voltammetry. The radical anion of the phenanthro[9,10‐c]‐1,2,5‐thiadiazole 1,1‐dioxide was found to be very stable in an aprotic solvent solution and did not react readily when water was added to the aprotic solvent, or the solution was saturated with oxygen gas. The radical formation chemical reaction competed with nucleophilic addition to the CN bond of the thiadiazoles. A possible reaction mechanism, and a common reaction intermediate, supported by density functional theory calculations, is presented for the most stable radical. Copyright © 2009 John Wiley & Sons, Ltd.

Thermodynamic Study of Phenyl Salicylate Solutions in Aprotic Solvents at Different Temperatures

Phenyl salicylate is employed as a nervous system depressant as well as an intestinal antiseptic owing to its antibacterial activity upon hydrolysis in the small intestine. Various partial molar quantities, namely, apparent molar volume (Vϕ), partial molar volume (V°m), thermal expansion coefficient (α2), and (∂2V°m/∂T2), of phenyl salicylate in aprotic solvents, i.e., acetonitrile, dimethyl sulfoxide, tetrahydrofuran, and 1,4-dioxane, at T = (293.15 to 313.15) K have been determined. The density and viscosity data were obtained with the help of a vibrating-tube densimeter and viscometer in a concentrarion range of (9.6·10−3 to 33.0·10−3) mol·kg−1. The viscosity data have been analyzed using the Jones−Dole equation and the derived parameter B has also been interpreted in terms of solute−solvent interactions.

Electrochemical deposition of tellurium from TeCl4 solutions in aprotic solvents

Electrolysis of 0.01–0.1 M TeCl4 solutions in dimethyl sulfoxide, dimethylformamide, and acetonitrile was studied in the temperature range 20–60°C. The microscopic structure of cathode deposits was analyzed.

π-Allylnickel-Catalyzed Living Coordination Polymerization of Allene Having Homochiral Phenylcarbamoyloxy-Substituted Binaphthyl Function

The allylnickel-catalyzed living coordination polymerization of an allene derivative possessing a homochiral substituent, (R)-2-allenyloxy-2‘-(phenylcarbamoyloxy)-1,1‘-binaphthyl (2), gave a chiral polymer which was found to have a single-handed helical conformation in solution of aprotic solvents such as chloroform and tetrahydrofuran on the basis of its circular dichroism (CD) spectra and specific rotation. The chiral higher-order conformation of the polymer was supposed to be stabilized by elongation of the repeating unit. That is, the CD spectra and the specific rotation of the polymer solution in aprotic solvents were found to be influence by the degree of polymerization until it reaches about 55. The temperature-independent and solvent-dependent nature of the CD spectra indicated that the chiral conformation of the polymer is stable at least in the range of 0−60 °C in tetrahydrofuran which disappears by addition of protic solvents such as methanol.

Reactions of the activated, rigid, α‐diazomethine group of 1,2,5‐thiadiazole 1,1‐dioxides with nitrogenated nucleophiles. Part III: aliphatic monoamines and phenylhydrazine

AbstractThe reactions of n‐butylamine (BuNH2), 2‐aminoethanol (H2N(CH2)2OH), diethylamine (Et2NH), and phenylhydrazine (PhN2H3) with 3,4‐diphenyl‐(1a) and phenanthro[9,10‐c]‐1,2,5‐thiadiazole 1,1‐dioxide (1b) were studied by cyclic voltammetry (CV) and 1H‐ and 13C‐NMR in aprotic solvent solution. The course of the reactions depended on the substrate‐nucleophile combination: Et2NH added to 1a or 1b, forming the corresponding thiadiazolines in an equilibrium monoaddition reaction. The equilibrium constants were evaluated and compared. With primary amines and PhN2H3, the nucleophile added to both CN double bonds of 1a and displaced the sulfamide moiety. In the case of the reaction of 1a with PhN2H3, the intermediate monoaddition thiadiazoline, 3‐(2‐phenylhydrazino)‐3,4‐diphenyl‐1,2,5‐thiadiazoline 1,1‐dioxide, was also isolated. BuNH2 and H2N(CH2)2OH reacted with 1a to give α‐bis‐imines, while 1a with PhN2H3 gave the α‐bis‐hydrazone. The configurations of benzil bis(ethanolimine) and benzilosazone were determined by single crystal x‐ray diffraction analysis as Z,Z. BuNH2 and PhN2H3 reduced 1b to the corresponding thiadiazoline compound 1bH2. Copyright © 2006 John Wiley & Sons, Ltd.

Ionizing properties of complexes with strong symmetrical hydrogen bonds in acid solutions in aprotic solvents

Ionizing properties of complexes with strong symmetrical hydrogen bonds in acid solutions in aprotic solvents

Ionizing properties of complexes with strong symmetrical hydrogen bonds in acid solutions in aprotic solvents

The acidity functions H0 of solutions of trifluoroacetic acid (TFA) in DMF and methanesulfonic acid (MSA) in 2-pyrrolidone over an acid (HA) concentration range of 0–100% and of H2SO4 solutions in 2-pyrrolidone (66.7–100 mol % HA) at 25°C were determined using the indicator method. Data were obtained on the relative ionizing powers of the quasi-ion pairs S⋯H⋯A (S is a solvent molecule) formed by DMF with acids (HCl, MSA, and TFA) and by MSA with DMF and 2-pyrrolidone. The effects of the acid anion (with MSA and H2SO4 solutions in 2-pyrrolidone acting as examples) and the counterion SH+ (with MSA solutions in DMF and 2-pyrrolidone acting as examples) on the ionizing power of (A⋯;H⋯A)− ions with strong symmetrical H-bonds were studied. It was found that, under comparable conditions, the replacement of a 2-pyrrolidone molecule by a DMF molecule in the SH+ cation insignificantly decreased the acidity of solution, whereas the (A⋯;H⋯A)− ions in H2SO4 solutions exhibited a much higher ionizing power than that of structurally similar anions in MSA solutions.

Ionizing properties of complexes with strong symmetrical hydrogen bonds in acid solutions in aprotic solvents

Ionizing properties of complexes with strong symmetrical hydrogen bonds in acid solutions in aprotic solvents

The Effect of the Steric Bulk of the Ligand on the Geometry of the Species Self‐Assembled from CoIII Bis(dioximates) and Boronic Acids

AbstractThe synthesis and characterization of the products of the reactions between the bis(diphenylglyoximato)cobalt(III) complexes [Co(CH3)(dpgH)2L] [L = py or H2O; dpgH2 = bis(diphenylglyoxime)] and 4‐pyridinylboronic acid (1) and 3‐aminophenylboronic acid (2) are described. The crystals of both 1 and 2 are built up by dimeric units arranged on a crystallographic symmetry center, so that the 4‐pyridinyl (in 1) or the 3‐aminophenyl residue (in 2) of one moiety coordinates to the Co atom of the symmetry‐related unit. 1H NMR spectra show that both 1 and 2 are stable in solution in aprotic solvents: they do not dissociate and are not in equilibrium with species having different nuclearity. The geometry of 1 is very similar to that of the species assembled from the corresponding bis(dimethylglyoximato)cobalt(III) complex and 4‐pyridinylboronic acid. On the contrary, the replacement of the methyls by phenyls prevents the trimeric arrangement previously found in the supramolecular species assembled from methylcobaloxime and 3‐aminophenylboronic acid and leads to the dimeric species 2. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The addition reaction of diamides to 1,2,5‐thiadiazole 1,1‐dioxide derivatives

AbstractThe reactions of several derivatives of 1,2,5‐thiadiazole 1,1‐dioxide [3,4‐diphenyl‐(1a), 3,4‐bis(p‐methoxyphenyl)‐(1b), phenanthro[9,10‐c]‐(1c) and acenaphtho[1,2‐c]‐1,2,5‐thiadiazole 1,1‐dioxide (1d), 3,4‐diphenyl‐1,2,5‐thiadiazoline 1,1‐dioxide (2a) and 4‐ethoxy‐5‐methyl‐3,4‐diphenyl‐1,2,5‐thiadiazoline 1,1‐dioxide (2b)], with reagents possessing two nucleophilic nitrogen atoms (urea, N,N′‐dimethylurea, thiourea, N‐methylthiourea, N‐ethylthiourea, N‐allylthiourea, N,N′‐diethylthiourea, N,N′‐diphenylthiourea, dithioxamide and sulfamide), were followed by cyclic voltammetry (CV) and UV–visible spectrophotometry in aprotic solvent solution. The products were isolated, characterized by IR, 1H NMR and 13C NMR methods and their structure was confirmed by single‐crystal x‐ray diffraction. Several substrate–nucleophile combinations (1a–d and 2a with some ureas and thioureas) reacted to give good yields of new compounds formed by the addition reaction of the two nitrogen atoms of the nucleophile to the two >CN— double bonds of the 1,2,5‐thiadiazole 1,1‐dioxide ring. Some systems (1a–dithioxamide and 2b–thiourea) did not react, whereas in others (e.g. 1a–sulfamide) a monoaddition equilibrium reaction was observed. Copyright © 2004 John Wiley & Sons, Ltd.

Thermal Decomposition of 5-Nitraminotetrazole of 3-Azolylamino-2-polyfluorobenzoylacrylates

Thermal decomposition of 5-nitraminotetrazole in solid phase and diluted solutions in aprotic solvents was investigated. The kinetic and thermodynamic parameters of the process were established. A mechanism of unimolecular decomposition was assumed including isomerization into the nitroguanyl azide followed by decomposition of he azide function.

Reactant solvation and kinetics of simple charge-transfer electrode reactions in mixed solvents

The rate of the interfacial charge transfer in the V(III)/V(II) system at the mercury electrode in H 2O+DMPU 1 1 Abbreviations: DMPU, 1,3-dimethyl-3,4,5,6-tetrahydro-2-(1 H)-pyrimidinone; DMF-dimethylformamide; AN = acetonitrile; HMPA = hexamethylphosphorotriamide. +0.4 mol dm −3 HClO 4 mixtures was found to increase when x DMPU was raised from 0.1 to 0.8. The solvatochromism of the electronic d-d transitions within the vanadium ions was used to leam about their resolvation with DMPU molecules. It was found that, under the experimental conditions used, the charge transfer occurs at the electrode surface which is already largely covered by DMPU (θ DMPU = 0.9 to 1.0) and the interfacial kinetics are determined mainly by the solvation state of reactant in the bulk solution. Our observation of a close correspondence between log k s, and the reactant inner-shell composition can be considered as a result of the prevailing non-continuum contributions to the activation energy arising from the elimination of specific short-range, quo-ligand-solvent (hydrogen bond) interactions by coordinated DMPU molecules which are not hydrogen-bond donors. It seems that generally such effects could be kinetically significant also in other aqueous solutions of aprotic solvents (e.g. DMF, AN, HMPA).

Structure of dimethylammonium bromide in solutions in aprotic solvents

The structure of the dimethylammonium bromide molecule in solution has been studied on the basis of IR absorption spectra and low-temperature1H NMR spectra. An analysis of the spectroscopic characteristics of the compounds shows that the most preferable of the possible structures is an ion pair with equivalent NH protons and two hydrogen bonds, which form a stable four-membered ring.