Carbon Tetrachloride Solution Research Articles

Hydrogen Bonding and Cation Coordination Effects in Primary and Secondary Amines Dissolved in Carbon Tetrachloride

Raman and infrared spectroscopy were used to investigate hydrogen-bonding interactions and cation coordination effects in solutions of lithium triflate (LiCF3SO3) dissolved in two primary amines, hexylamine (HEXA) and N,N-dimethylethylenediamine (DMEDA), and in a secondary amine, dipropylamine (DPA). Strong intermolecular hydrogen-bonding interactions and weaker intramolecular hydrogen-bonding interactions that occur only in DMEDA were spectroscopically distinguished in a comparison of pure HEXA, pure DMEDA, and the dilute solutions of these amines in CCl4. The spectroscopic shifts in intensity and frequency in the NH stretching region of DPA and DPA diluted in CCl4 were similar to those of HEXA. Dilute electrolyte solutions in carbon tetrachloride were prepared to analyze specifically the cation coordination effect. In these solutions, limited intermolecular hydrogen-bonding interactions are present, and the observed spectral shifts correspond primarily to the cation-induced shifts. The symmetric SO3 stretching region of the triflate anion was investigated to probe further the coordination of the cation. The local structures of the triflate ions and the amine groups in the electrolyte solutions dissolved in CCl4 are similar to the local structures in the corresponding amine-salt crystals previously reported by us.

Study on multimers and their structures in molecular association mixture

Self-association system of ( R )-1,3-butanediol in dilute carbon tetrachloride (CCl 4 ) solution is studied as a model of molecular association mixture. Analysis methods including FSMWEFA (fixed-size moving window evolving factor analysis) combined with PCA (principal component analysis), SIMPLISMA (simple-to-use interactive self-modeling mixture analysis), and ITTFA (iterative target transformation factor analysis) are adopted to resolve infrared spectra of ( R )-1,3-butanediol solution. Association number and equilibrium constant are computed. ( R )-1,3-butanediol in dilute inert solution is determined as a monomer-trimer equilibrium system. Theoretical investigation of trimer structures is carried out with DFT (density functional theory), and structural factors are analyzed.

An Experimental Raman and Theoretical DFT Study on the Self-Association of Acrylonitrile

The liquid structure of acrylonitrile (propenenitrile) has been investigated using Raman spectroscopy and density functional theory (DFT) ab initio calculations with the 6-311++G** basis set. Two different and complementary experimental approaches were undertaken: FT-Raman spectra of 13 acrylonitrile solutions in carbon tetrachloride (concentration range=0.25-12.0 mol.L-1) were studied in detail including principal component analysis (PCA) of the CN stretching band. Furthermore, dispersive Raman spectra of neat acrylonitrile were obtained at eight different temperatures from 238 up to 343 K. The complex and asymmetric acrylonitrile Raman CN stretching band can be decomposed into two components attributed to monomeric and self-associated forms. Ab initio results fully support this assignment and suggest that the self-associated complex is a nonplanar trimer held together by dipole-dipole interactions. At ambient temperature, the composition of acrylonitrile can be expressed as a mixture of 25% monomers and 75% trimers. Close to the boiling point, trimers still represent 65% of the liquid composition. The corresponding enthalpy of association was estimated to be -22+/-2 kJ.mol-1.

Crosslinking High Free Volume Polymers - Effect on Gas Separation Properties

AbstractCrosslinkable nanoparticle-filled poly(4-methyl-2-pentyne) [PMP] membranes were cast from carbon tetrachloride solutions containing PMP, hydrophobic fumed silica, and 4,4¡¯-(hexafluoroisopropylidene)diphenyl azide [HFBAA]. The composite membranes were crosslinked by UV irradiation at room temperature. Low levels of the bis azide were effective in rendering the membranes insoluble in cyclohexane and carbon tetrachloride, both good solvents for PMP. The process is simple and effective, and thus PMP can be easily converted to mechanically stable membranes. Compared to the pure PMP membrane, the permeability of the crosslinked membrane is initially reduced for all tested gases due to the crosslinking. By adding nanoparticles, the permeability is again increased, crosslinking is successful in maintaining the permeability and selectivity of PMP over time.

Proton transfer in hydrogen-bonded pyridine/acid systems: the role of higher aggregation

In this work the role of higher molecular aggregation in the proton transfer processes within hydrogen bond (H-bond) is investigated. The H-bonded complex consisting of 4-cyanopyridine (CyPy) with trichloroacetic acid (TCA) has been studied in the solutions of acetonitrile, carbon tetrachloride, chloroform and dichloroethane as solvent by FTIR spectroscopy and quantum chemical DFT calculations. In order to illustrate the effect of increasing H-bond strength FTIR investigations have also been performed on solutions of CyPy with H(2)O, acetic-, trifluoroacetic- and methanesulfonic acids. Proton states in the H-bond have been monitored using vibrational CyPy ring modes in FTIR spectra. The stabilization of the CyPy/TCA complex in its protonated form upon increasing polarity of the solvent has been evidenced. It was shown that formation of the CyPy/(TCA)(2) aggregates in the solutions favors the proton transfer process. An X-ray diffraction study has been performed on a single 1 : 2 co-crystal of pyridine/3,5-dinitrobenzoic acid. The H-bond motif found in this system exhibits the same connectivity by strong hydrogen bonds N-H(+)[dot dot dot]O(-) and O-H[dot dot dot]O as that in the CyPy/(TCA)(2) complex predicted by DFT calculation. Certain discrepancies are observed in C-H[dot dot dot]O connectivity only. The networks of H-bonds in both assemblies differ from those usually pictured for 1 : 2 base/carboxylic acid complexes in the literature.

N–H⋯O hydrogen bonding: FT IR, NIR and 1H NMR study of N-methylpropionamide – Cyclic ether systems

The paper reports the results of FT IR, NIR and 1H NMR study of N-methylpropionamide (NMP) in carbon tetrachloride solution and in presence of cyclic ethers as the O-electron donors: tetrahydrofuran (THF) and tetrahydropyran (THP). The spectroscopic characteristics for N–H⋯O hydrogen bonded complexes are given. Also, the equilibrium constants for 1:1 complex formation, at 25 °C were determined using IR, NIR and 1H NMR measurements.

Dimerization and Double Proton Transfer-Induced Tautomerism of 4(3H)-Pyrimidinone in Solution Studied by IR Spectroscopy and Quantum Chemical Calculations

The tautomerism and dimerization of 4(3H)-pyrimidinone (4(3H)Pyr) in carbon tetrachloride (CCl4) and chloroform (CHCl3) solutions were investigated using IR spectroscopy and quantum chemical calculations. The observed IR spectra in the NH and OH stretching regions clearly revealed the predominance of the keto tautomer in both solvent systems. The enol form only exists in a very small proportion in the CCl4 solution. The tautomeric constant for the two monomers KT[OH/NH] = 0.012 and DeltaE = 2.62 kcal/mol were estimated at 25 degrees C. This result was supported by the self-consistent reaction field/polarizable continuum (SCRF/PCM) calculation at the MP4(full, SDQ)/aug-cc-pVDZ level, which predicted DeltaE = 3.06 kcal/mol in CCl4. In the C=O stretching region, two bands were observed, suggesting the coexistence of two keto structures at equilibrium. The calculated IR spectra indicated that the bands at 1711 and 1675 cm(-1) arise from the keto monomer and keto-keto (KK) ring dimer, respectively. At elevated temperature, the populations of both the keto and enol monomers increased for the CCl4 solution. The present study revealed that the keto <--> enol tautomerization does not occur in the isolated monomer molecule. The double proton transfer (DPT) reaction in the KK ring dimer presumably plays a substantial role in the population increase of the enol monomer. To our knowledge, this may be the first observation of the tautomerization in a model base pair via the temperature-induced ground-state DPT reaction under a nonpolar liquid environment reported so far. This tautomerism can serve as a mimic circumstance for the spontaneous mutations induced by proton transfer in the DNA base pairs.

Spectroscopic and Quantum Mechanical Studies of Substituted Anilines and their Charge-Transfer Complexes with Iodine in Different Solvents

Equilibrium constants and molar extinction coefficients for 1:1 charge-transfer complexes between 2-hydroxyaniline (HA), 5-chloro-2-hydroxyaniline (CHA), and 4-bromo-2,6-dimethylaniline (BMA) as donors and iodine, as a typical σ-acceptor were determined spectrophotometrically in chloroform, dichloromethane, and carbontetrachloride solutions. Spectral characteristics and formation constants are discussed in terms of donor molecular structure and solvent polarity. The stoichiometry of the complexes was established to be 1:1. For this purpose, optical data were subjected to the form of the Rose-Drago equation for 1:1 equilibria. Electronic absorption spectra of the studied anilines were measured in different solvents. Spectral data were reported and band maxima were assigned to the appropriate molecular orbital transitions (π–π* and n–π* electronic transition). Solvent effects on the electronic transitions were discussed. Optimized geometry of the studied anilines was obtained at B3LYP/6-31 + G(d). The effect of the electronic factors of the substituents on the geometrical parameters of the ring has been explored. Geometrical values of the ring deviate from the regular hexagonal ring. Intramolecular H-bonds in HA and CHA have been computed at B3LYP/6-31 + G(d) and MP2/6-31 + G(d) levels. The H-bonding distance was calculated to be 2.105 A in HA and 2.127 A in CHA.

NMR study of hydrogen bonding in methanol – carbon tetrachloride solutions

The nuclear magnetic resonance (NMR) frequencies of the hydroxyl protons of methanol clusters in carbon tetrachloride were measured as a function of concentration between 245.4 and 320.2 K. The size of the methanol cluster (n) and the enthalpy and entropy of methanol self-association were obtained from nonlinear least-squares fittings to a model that assumed that only one dominant cluster was in equilibrium with the monomer at each temperature. The chemical shift measurements at 273 and 299.1 K fit best to theoretical curves calculated for a monomer–tetramer equilibrium. However, at higher and lower temperatures, the analyses indicate that the most dominant clusters are smaller and larger, respectively.Key words: alcohol liquid solutions, structure, hydrogen bonding, thermodynamics of self-association, nuclear magnetic resonance.

Aggregation of [70]fullerene in presence of acetonitrile: A chemical kinetic experiment

[70]fullerene solutions in carbon tetrachloride and o-xylene exhibit a noteworthy spectral variation with time when acetonitrile is added. This has been ascribed to self-aggregation of [70]fullerene caused by the repulsion between polar acetonitrile and hydrophobic [70]fullerene, and the aggregation numbers have been determined from a kinetic scheme and also from a scanning electron microscopic study. The numbers thus obtained follow a cuboctahedral stacking pattern proposed recently and also agree with the magic formula n=55+3m (m=1 to 14) proposed by Branz et al. for [60]fullerene clusters [Phys. Rev. B. 66, 094107 (2002)].

Self-association and stereochemistry study of (5R)-4-methyl-5-phenyl-1,3,4-oxadiazinan-2-one

Abstract C10H12N2O2, M r = 191.21, P21, a = 5.5771(7), b = 27.841(3), c = 6.906(1) Å, β = 111.937(9)°, Z = 4, R 1 = 0.0462. The two independent molecules in the asymmetric unit are linked through two very strong quasi centro-symmetric hydrogen bonds. The oxadiazinone rings, of both molecules, show the pyramidal inversion at N-4 nitrogen, thus resulting in a C(R)N(S)—C(R)N(R) diastereomeric pair. The analysis of the IR N-H stretching band (in the solid and in carbon tetrachloride solution) and the 13C NMR experiment at low temperature are in agreement with the X-ray crystal structure.

Serum and liver iron concentration in dogs with experimentally induced hepatopathy

Iron (Fe) status is altered in human and experimental animal hepatopathies. In dogs limited data are available. The aim of this study was to investigate serum iron (SI), total iron binding capacity (TIBC), percentage transferrin saturation (SAT) and Fe status in the liver of dogs with experimentally induced hepatopathy. Fourteen 1-year-old dogs were divided into two equal groups. In order for hepatopathy to be induced, 0.25 mL/kg body weight of carbon tetrachloride (CCl4) solution was administered once daily, orally, for a 10-week period in group B dogs, while group A dogs were used as controls. SI, TIBC and SAT values were measured 3 times before the beginning (baseline value) and 10 times at weekly intervals during the experiment. Liver samples, obtained before the administration of CCl4 and at the end of the experimental period (10 weeks), were subjected to Fe determination, as well as to histopathological and histochemical analysis. At the end of the experiment SI, TIBC and liver iron concentration, as well as liver total iron score were significantly increased in group B dogs. Distribution of granular hemosiderin iron in hepatocytes, Kupffer cells, and portal triads was noticed. Positive correlations were found between SI and liver Fe concentration, as well as histochemically determined Fe. Moreover, positive correlations were evident between liver fibrosis and serum, as well as liver Fe values. Experimentally induced chronic hepatopathy in dogs causes Fe status disturbances. Increased serum and liver iron concentration produces liver histopathological deterioration and it may be worth attention during laboratory evaluation in canine hepatopathy.

Spectroscopic studies of molecular interactions involving 2,6-diethylaniline and N-ethylaniline donors and iodine as an electron acceptor in different solvents

The charge-transfer complexes of 2,6-diethylaniline (DEA) and N-ethylaniline (NEA) with iodine, as a typical σ-acceptor were studied spectrophotometrically in chloroform, dichloromethane and carbontetrachloride solutions. Spectral data, formation constants and effect of solvent have been determined. Spectral characteristics and formation constants are discussed in the terms of donor molecular structure and solvent polarity. The stoichiometry of the complexes was established to be 1:1. For this purpose, optical data were subjected to the form of the Rose–Drago equation for 1:1 equilibria. The formation constant ( K AD) and molar absorptivities ( ɛ λ) of complexes were determined by least square method. Electronic absorption spectra of the anilines were measured in different solvents. Spectral data were reported and band maxima were assigned to the appropriate molecular orbital transitions. Quantum chemical calculations were performed with the aid of the Gaussian 98 set of programs. The structure were fully optimized at MP2 level using 6-31 + G** basis set. The computations show that DEA is not planner with the amino group having a somewhat sp 3 hybridization-like character.

Kinetics of iodine complexes with Triton X-100 in aqueous and non-aqueous media

Triton X-100 (TX-100) forms 1: 1 charge-transfer (CT) complexes with iodine in aqueous as well as in carbon tetrachloride solution. The equilibrium constant (K c ) and molar extinction coefficient (e c ) of iodine-TX-100 complex in both media have been determined from the spectral studies. From the kinetic studies of complex formation in both media, the rate constants (both forward and backward) and equilibrium constant have also been determined. The same equilibrium constant and rate constant values indicate that the hydrophilic head group of TX-100 is involved in the complex formation with iodine in both media.

Chirality of camphor derivatives by density functional theory

Infrared (IR) and vibrational circular dichroism (VCD) spectra of chiral camphor, camphorquinone and camphor-10-sulfonic acid (CSA), known as standard compounds for electronic circular dichroism (ECD) spectroscopy, are measured and their vibrational frequencies, infrared intensities, and rotational strengths are calculated using density functional theory (DFT). The observed IR and VCD spectra of chiral camphor and camphorquinone in carbon tetrachloride solution are reproduced by the DFT calculations, but those of CSA are not. DFT calculations of hydration models, where an anionic CSA specifically binds a few water molecules, are carried out. The average of the simulated VCD spectra in the hydration models is more consistent with the observed spectra. In addition, the wavelengths and dipole and rotational strengths for chiral camphor, camphorquinone, anionic CSA, and the hydration models were calculated by time-dependent DFT. In the region of 280-300 nm, the calculated wavelengths of the ECD bands for chiral camphor and camphorquinone coincide with the observed wavelengths that have been reported, and the calculated wavelengths for the hydration models are closer to the observed wavelengths reported than are those calculated for chiral anionic CSA. Consequently, the analysis combined with VCD and ECD spectroscopy using DFT calculations can elucidate the chirality of optically active molecules, even in an aqueous solution.

A TRIR, TREPR and Computational Study on the Reactivity and Structure of the 2,2,2-Trifluoroethoxycarbonyl Radical†

The 2,2,2-trifluoroethoxycarbonyl radical, 3b, has been generated by pulsed irradiation of 9-fluorenone oxime 2,2,2-trifluoroethyl oxalate 1b in carbon tetrachloride and acetonitrile solution. It was characterized by time-resolved electron paramagnetic resonance spectroscopy (EPR) and infrared spectroscopy. The radical has a lifetime in the range of microseconds and can be detected within the rise time of our time-resolved equipment before undergoing recombination or reactions with the solvent. No decarbonylation or decarboxylation was observed. In the presence of oxygen, the radical is quenched to yield the 2,2,2-trifluoroethoxycarbonylperoxy radical 4b, which has again a lifetime in the range of several microseconds. Time-resolved electron paramagnetic resonance spectroscopy (TREPR) allowed for the detection of a 1 : 1 : 1 triplet of the fluorene-9-iminyl radical 7 at g = 2.0032 and a 1 : 3 : 3 : 1 quartet with additional hyperfine splitting (HFS) due to proton coupling at g = 2.001 for the trifluoroethoxycarbonyl radical 3b. Calculations indicate that alkoxycarbonyl radicals can exist in conformations that are s-trans or s-cis with respect to the R-O-C(O) x dihedral. A comparison of experimental TREPR spectra with simulations indicates that the s-trans conformer is observed in the case of the ethoxycarbonyl radical, 3a. In the case of the trifluorethoxycarbonyl radical, 3b, however, the additional proton HFS observed shows that it is the s-cis conformer that is formed. As calculations give evidence for a fairly high activation enthalpy for s-cis-s-trans interconversion of alkoxycarbonyl radicals, this discrepancy is likely due to differing conformational preferences of the precursor molecules.

Time-Resolved Spectroscopic Study of the Reaction Cl + n-C5H12 → HCl + C5H11 in Solution

We study the hydrogen abstraction reaction from pentane by chlorine radicals using four different experimental approaches. We use two different solvents (CH2Cl2 and CCl4) and two different chlorine atom sources (photodissociation of dissolved Cl2 and two-photon photolysis of the solvent) to investigate their effects on the recombination and reactivity of the chlorine radical. All four experimental schemes involve direct probing of the transient chlorine population via a charge transfer transition with a solvent molecule. In one of the four approaches, photolysis of Cl2 in dichloromethane, we also monitor the nascent reaction products (HCl) by transient vibrational spectroscopy. Probing both the reactants and the products provides a comprehensive view of this bimolecular reaction in solution. Between one-third and two-thirds of the chlorine radicals that initially escape the solvent cage undergo diffusive geminate recombination with their partner radical (either another chlorine atom or the solvent radical). The rest react with pentane with the bimolecular rate constants k(bi) = (9.5 +/- 0.7) x 10(9) M(-1) s(-1) in CH2Cl2 and k(bi) = (7.4 +/- 2) x 10(9) M(-1) s(-1) in CCl4. The recombination yield phi(rec) depends on both the chlorine atom precursor and the solvent and is larger in the more viscous carbon tetrachloride solutions. The bimolecular reaction rate k(bi) depends only on the solvent and is consistent with a nearly diffusion-limited reaction.

Reversal of chemical-induced liver fibrosis in Wistar rats by puerarin

Puerarin is a major isoflavonoid compound isolated from Pueraria lobata, an edible vine used widely for various medicinal purposes. It has been used for centuries in China to counteract alcohol intoxication. However, the effects of puerarin on chemical-induced liver fibrosis have not been reported. In the present study, we investigated the effects of puerarin on liver fibrosis in Wistar rats induced by alcohol plus carbon tetrachloride administration. Liver fibrosis was produced in rats by treatment with a mixture (50% alcohol, 8 g/kg per day; corn oil, 2 g/kg per day; pyrazole, 24 mg/kg per day; ig) once a day and by intraperitoneal injection of 0.25 ml/kg of a 25% solution of carbon tetrachloride in olive oil twice a week for 8 weeks. After 8 weeks, treatment with puerarin (0.4 and 0.8 g/kg ig, daily for 4 weeks) was conducted to examine its therapeutic effects. At the same time, the model group and treatment group continued to receive the chemical mixture, while the control group received saline instead of the chemical mixture. Upon pathological examination, the puerarin-treated rats significantly reversed the symptoms of liver fibrosis and other hepatic lesions. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as indexes of hepatic cell disruption, were reduced with puerarin treatment, whereas no significant effect was discovered in the levels of alkaline phosphatase (ALP) and γ-glutamyltransferase (GGT) activities. A significant increase in apoptosis of activated hepatic stellate cell (HSC) was found by flow cytometric analysis of the hepatic tissues. And the expression of bcl-2 mRNA was down-regulated after puerarin administration. Consequently, all these results showed that puerarin could effectively reverse chemical-induced liver fibrosis in experimental rats, via the recovery of hepatic injury as well as the induction of apoptosis in activated HSC.

Sound speed and density measurements for tetra- n-butylammonium bromide in benzene and carbon tetrachloride solutions at T = 298.15 K

The density and sound speed measurements have been carried out for the binary systems consisting of tetra- n-butylammonium bromide (Bu 4NBr) as a solute in benzene and CCl 4 at T = 298.15 K (concentration range 0.01 mol · kg −1 to ∼0.8 mol · kg −1). The apparent molar volumes ( ϕ V) and apparent molar isentropic compressibility ( ϕ K S ) have been calculated and the values at infinite dilution are estimated. These data for Bu 4NBr in benzene and CCl 4 solutions are combined with the literature data of Bu 4NBr in water to obtain transfer compressibility of Bu 4NBr molecules from non-aqueous to aqueous solutions. The ϕ V behaviour as a function of concentration in benzene solutions indicates formation of reverse micelles and having critical micelle concentration (cmc) around 0.01 x 2 of Bu 4NBr (∼0.13 mol · kg −1). The compressibility data are further used to estimate hydration number of Bu 4NBr in aqueous solutions by applying Shiio’s method. The hydration number calculated for compressible organic electrolyte shows good agreement with the number obtained for clathrate hydrate of Bu 4NBr using the chemical analysis and X-ray diffraction.

Stable spiro-endoperoxides by sunlight-mediated photooxygenation of 1,2- O-alkylidene-5( E)-eno-5,6,8-trideoxy-α- d- xylo-oct-1,4-furano-7-uloses

Sunlight-mediated photooxygenation of 3- O-acetyl and 3- O-methyl derivatives of 1,2- O-alkylidene-5( E)-eno-5,6,8-trideoxy-α- d- xylo-oct-1,4-furano-7-uloses ( 1a– e) in carbon tetrachloride solution gave stable 4,7-epidioxy derivatives in 4 R ( 2a– e) and 4 S ( 3a– e) configurations. The presence of an endo alkyl, on the 1,2- O-alkylidene group and its size, resulted in an increase of the yield of the 4 S isomers. 3- O-Acetyl derivatives yielded products as a mixture of C-7 anomers, whereas 3- O-methyl derivatives gave pure single stereoisomers.