Formamide Solution Research Articles

The effect of an anti-hydrogen bond on Fermi resonance: A Raman spectroscopic study of the Fermi doublet ν1−ν12 of liquid pyridine

The effects of an anti-hydrogen bond on the ν1−ν12 Fermi resonance (FR) of pyridine are experimentally investigated by using Raman scattering spectroscopy. Three systems, pyridine/water, pyridine/formamide, and pyridine/carbon tetrachloride, provide varying degrees of strength for the diluent-pyridine anti-hydrogen bond complex. Water forms a stronger anti-hydrogen bond with pyridine than with formamide, and in the case of adding non-polar solvent carbon tetrachloride, which is neither a hydrogen bond donor nor an acceptor and incapable of forming a hydrogen bond with pyridine, the intermolecular distance of pyridine will increase and the interaction of pyridine molecules will reduce. The dilution studies are performed on the three systems. Comparing with the values of the Fermi coupling coefficient W of the ring breathing mode ν1 and triangle mode ν12 of pyridine at different volume concentrations, which are calculated according to the Bertran equations, in three systems, we find that the solution with the strongest anti-hydrogen bond, water, shows the fastest change in the ν1−ν12 Fermi coupling coefficient W with the volume concentration varying, followed by the formamide and carbon tetrachloride solutions. These results suggest that the stronger anti-hydrogen bond-forming effect will cause a greater reduction in the strength of the ν1−ν12 FR of pyridine. According to the mechanism of the formation of an anti-hydrogen bond in the complexes and the FR theory, a qualitative explanation for the anti-hydrogen bond effect in reducing the strength of the ν1−ν12 FR of pyridine is given.

Experimental studies on heat and mass transfer in tubular generator for R134a-DMF absorption refrigeration system

Experimental investigations have been carried out to study heat and mass transfer during desorption of Tetrafluoro ethane (R134a) from R134a and Dimethyl formamide (DMF) solution in a tubular generator. Absorption refrigeration system has been built with brazed plate heat exchangers as condenser, absorber, evaporator and solution heat exchanger and with stainless steel concentric tubes as the generator. Effects of operational parameters viz., solution two phase Reynolds number, driving temperature ratio, driving pressure ratio, solution initial concentration on generator performance are analyzed. Desorption ratio, Sherwood number and Nusselt number increase as the solution Reynolds number, solution initial concentration, driving temperature ratio increase whereas these parameters decrease as the driving pressure ratio increases. Finally a correlation for Nusselt number and Sherwood number are proposed based on the experimental studies.

Fe3O4/carbon composite nanofiber absorber with enhanced microwave absorption performance

Abstract Fe3O4/carbon composite nanofibers were prepared by electrospinning polyacrylonitrile (PAN)/acetyl acetone iron (AAI)/dimethyl formamide (DMF) solution, followed by stabilization and carbonization. SEM and TEM observations reveal that the fibers are lengthy and uniform, and are loaded with well-distributed Fe3O4 nanoparticles, which are evidenced by XRD. Electrical and magnetic properties of the samples were studied to show the effect of enhancement of electrical conductivity and magnetic hysteresis performance. Finally, the permittivity and permeability parameters were measured by a vector network analyzer, and the reflectivity loss was calculated based on Transmission Line Theory. Results show that Fe3O4/C composite nanofibers exhibit enhanced properties of microwave absorption as compared to those of pure carbon nanofibers by: decreasing reflectivity loss values; widening absorption width and improving performance in low frequency (2–5 GHz) absorption. Absorption properties can be tuned by changing AAI content, carbonization temperature, composite fiber/paraffin ratio and coating thickness. It is shown that with coating thickness of 5 mm and fiber/paraffin ratio of 5 wt.%, the bandwidth for reflection loss under −5 dB can reach a maximum of 12–13 GHz in the range of 2–18 GHz, accompanying with a minimum reflection loss of −40 to −45 dB, and preferred low frequency band absorption can also be obtained. The mechanisms for the enhanced absorption performance were briefly discussed. It is supposed that this kind of composite material is promising for resolving the problems of weak absorption in the low frequency range and narrow bandwidth absorption.

Amine-Templated Polymeric Lanthanide Formates: Synthesis, Characterization, and Applications in Luminescence and Magnetism

The novel polymeric formates of general formula [(Fmd)Ln(III)(HCOO)(4)](∞) (Fmd(+) = NH(2)-CH(+)-NH(2); Ln = Eu (1), Gd (2), Tb (3), Dy (4)] were synthesized through solvothermal methods in formamide solutions. The compounds are isotructural; they crystallize in the orthorhombic C222(1) chiral space group. The coordination geometry at the metal centers is square antiprismatic (coordination number eight), with each formate ligand bridging adjacent lanthanide ions. The overall negative three-dimensional (3D) framework charge is balanced by the formamidinium cations sitting inside the channels along the a axis, forming extensive N-H···O hydrogen bonding with the surrounding cage. All the compounds have been characterized through single-crystal/powder X-ray diffraction, IR spectroscopy, and TG-MS analysis. Finally, their luminescence and magnetic properties have been assessed, leading to remarkable emission intensities, especially for the Tb(III) compound (Φ = 0.83), with corresponding lifetime decays in the micro (Dy) and millisecond (Tb, Eu) time scale. A weak but sizable antiferromagnetic interaction has been observed for the Gd(III) derivative.

Effect of Organic Solvents on the Electrodeposition of Copper from Acidified CuSO4

Metals are deposited in a very rough or powdery form when the electrolysis is carried out at the limiting current. This seems to be a general rule in the case of copper. The possibility of preventing powder formation at the limiting current by means of a suitable additive is of great interest in electroplating and in electrometallurgy in general. Some organic substances are used as additives in electroplating, electrowinning, and electroforming in order to improve the quality of the electrodeposits, since they produce fine-grained smooth bright deposits. The electrodeposition of copper in cells using copper anodes was studied in the presence of organic solvents as pyridine, DMF, DMSO, ACN, dioxane, formamide, MCS, and BCS. It has been found that the rate of electrodeposition is decreased by amount ranging from zero to 46.67% when using copper anodes, depending on the concentration of organic solvents and time. Langmuir, kinetic, and Freundlich isotherms are applied. The rate of electrodeposition increases with the increasing rate of the rotation of the cylinder electrode. This proves that the electrodeposition process is diffusion controlled dimensionless groups are given. The data can be relation by the following equations at 25°C: 1 For pyridine solutions Sh = 0.1105 Re0.695 Sc0.33 2 For dimethylformamide solution Sh = 0.1096 Re0.696 Sc0.33 3 For dimethylsulphoxide solutions Sh = 0.1087 Re0.697 Sc0.33 4 For formamide solutions Sh = 0.1077 Re0.698 Sc0.33 5 For acetonitrile solutions Sh = 0.1096 Re0.696 Sc0.33 6 For 1,4-dioxane solutions Sh = 0.1077 Re0.698 Sc0.33 7 For 2-methoxyethanol solutions Sh = 0.1106Re0.695 Sc0.33 8 For 2-butoxyethanol solutions Sh = 0.1107 Re0.695 Sc0.33

Selective Adsorption/Absorption of Formamide in NaCl Crystals Growing from Solution

NaCl crystals were obtained from water–formamide (H–CO-NH2) solutions, either by slow evaporation at 30 °C or by programmed cooling of solutions saturated at 95 °C, the formamide concentration ranging from 0 to 100% (in weight). Accordingly, the crystal morphology changes from {100} (pure aqueous solution) to {100} + {111} (water-formamide solutions) to {111} (pure formamide solution). X-ray powder diffraction diagrams, carried out on the bulky crystallized population, prove that formamide is not only adsorbed on the {111}NaCl octahedron but is also selectively captured within the {111} growth sectors. The excellent two-dimensional lattice coincidences between the d101 layers of formamide and the NaCl - d111 ones suggest that formamide can be adsorbed in the form of ordered epitaxial layers; further, the striking equivalence between the thickness of the elementary layers d111NaCl and d101formamide indicates that formamide is allowed to be buried (absorption) in the growing crystal. Moreover, empirical force field calculations carried out on reconstructed {111} NaCl surfaces, both Na+ and Cl– terminated, allowed to evaluate the adhesion energy between the formamide epitaxial layers and the underlying {111}NaCl substrate. Hence, one can definitively state that formamide is not only an habit modifier of NaCl crystals, but that “anomalous NaCl/formamide mixed crystals” form, limited to the {111} NaCl growth sectors.

Solution properties of dextran in water and in formamide

AbstractWe investigate here solution properties of the common polysaccharide dextran (with various molecular weight fractions: T70, T110, T500, and T2000) in aqueous and in formamide solutions at 20°C and 40°C, as obtained from viscosity measurements. Dextran behaves as a random coil in water and formamide solutions on the basis of the Mark‐Houwink‐Sakurada constant being in the range 0.5< α < 0.8 and the molecular weight dependence of the hydrodynamic coil radius,Rcoil∼MW1/2. Dextran segments interact more favorably with the formamide solvent molecules than with water, as attested by higher intrinsic viscosity,Rcoil, and hydrodynamic expansion factor αηvalues in formamide compared to aqueous solutions. This can be attributed to formamide offering more readily available sites (CO and NH3) to form hydrogen bonds with dextran. Apparently the stronger cohesive forces (reflected in higher surface tension σ and solubility parameter δ values) between water molecules make it harder for dextran to break them, thus the dextran coils swell less in this medium. As the temperature increases from 20°C to 40°C, dextran is driven toward theta conditions in both water and formamide solutions. Upon heating, the polymer segments interact less with the solvent molecules and adopt a less expanded conformation in the solution; the solvent quality decreases, and the coils contract. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Experimental studies on bubble characteristics for R134a–DMF bubble absorber

Experimental investigations have been carried out to visualize bubble behavior and effect of gas flow rate and liquid concentration on bubble characteristics of Tetrafluoro ethane (R134a) in liquid R134a–Dimethyl Formamide (DMF) solution in a glass absorber. Bubble behavior was studied in still as well as flowing solution. At lower gas flow rates, bubbles tend to be spherical due to the dominance of surface tension. At higher gas flow rates, bubbles tend to be hemispherical due to the dominance of inertia force. Bubble diameter during detachment increases with increase in gas flow rates. Also, the bubble diameter initially increases as the solution concentration increases up to 0.075kgkg−1 and then starts decreasing as the solution concentration increases further. At lower solution concentrations, effect of absorption driving potential (xeq−xl) is dominant than that of surface tension, due to this bubble diameter increases. When the solution concentration is increased further, effect of surface tension is dominant resulting in decrease in bubble diameter. Bubble diameter measured from the experiments is compared with that of the numerical model developed by the authors and other literature experimental correlations and it is found that the agreement is good. A correlation for bubble diameter during detachment is presented from the experimental studies, which can be useful for the design of R134a–DMF bubble absorber.

One-step solid state preparation of reduced graphene oxide

We have developed an easy and scalable chemical reduction method assisted by microwave irradiation for the synthesis of reduced graphene oxide (RGO) nanosheets in solid state. The as-synthesized RGO is characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetry, X-ray diffraction, X-ray photoelectron spectroscopy and atomic force microscopy. It is revealed that the bulk of the oxygen-containing functional groups are removed from graphene oxide with this one-step reduction method and monolayer RGO sheets are got from its N,N-dimethyl formamide solution. It is found that the ammonium bicarbonate plays a key role in the preparation of RGO. Considering the analysis results, a mechanism for the formation of RGO is proposed. Besides being eco-friendly, when compared to previous chemical techniques, this process has several advantages like low cost, simplicity and short processing times, which may find practical applications in the preparation of graphene-based composites.

PVDF-based Polymer Blend Films for Fuel Cell Membranes

ABSTRACTWe report the preparation and characterization of binary blend films of poly(vinylidene fluoride) (PVDF) and poly(1- ethyl-3-vinylimidazolium trifluoromethylsulfonylimide) (PVIm+TFSI-) derived from ionic liquid imidazolium monomers and doped with TFSI- salt. The potential utility of such materials in capacitive electronic devices and in proton exchange membrane fuel cells is of particular interest. Thin PVDF/ PVIm+TFSI- films were fabricated from solutions of dimethly formamide (DMF) by doctor blading. The nature of the PVDF crystalline polymorph and degree of crystallinity were evaluated as a function of the volume fraction of imidazolium polymer and thermal treatment. The morphology, thermal and mechanical characteristics and crystallinity of PVDF, in semicrystalline blend films was studied by wide angle X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetry, and dynamic mechanical analysis. In these materials, conditions such as choice of solvent, drying conditions, and thermal treatment affect the crystal phase, crystallite size, and degree of crystallinity of PVDF as well as the distribution of the minor component, the vinylimidazolium polymer. The polar beta phase of PVDF crystals dominates in as-cast films, while the non-polar alpha phase is observed after cooling from the melt. PVDF imparts mechanical strength and chemical stability to the composite films, and because of its high crystal melting point (Tm > 160 °C), serves to improve the high temperature stability of resulting films.

Specific adsorption of bromide and iodide ions from N-methyl formamide solutions with constant ionic strength on liquid ga electrode

The differential capacitance curves were measured with an ac bridge in the Ga/[N-MF + 0.1 m M KBr + 0.1 (1 − m) M KClO4] and Ga/[N-MF + 0.1 m M KI + 0.1 (1 − m) M KClO4] systems at the following fractions m of surface-active anions: 0, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1. As compared with other solvents, N-methyl formamide (N-MF) enables one to realize the largest positive charges of Ga electrode, at which it remains ideally polarizable (up to 20 μ/cm2). The data on the specific adsorption of Br− and I− anions in the system can be quantitatively described by the Frumkin’s isotherm; to the first approximation, free energy of halide ion (Hal−) adsorption \(\Delta G_{adsHal^{ - 1} } \) is a linear function of electrode charge. It is found that, in contrast to the Hg/N-MF interface, \(\Delta G_{adsHal^{ - 1} } \) at the Ga/N-MF interface varies in the reverse order: Brt— ∼ I− \Delta G_{M - Br^ - } > \Delta G_{M - I^ - } \) and the difference \((\Delta G_{Ga - Hal_1^ - } - \Delta G_{Ga - Hal_2^ - } )\) is larger than the difference between the solvation energies of \(Hal^ - (\Delta G_{S - Hal_1^ - } - \Delta G_{S - Hal_2^ - } )\).

Using vibrational and electronic spectroscopies to investigate different complexes in the formamide/nickel chloride system

Raman, IR and UV–vis–NIR experiments of formamide (FA) and nickel chloride solutions at different compositions were carried out. The quantitative Raman study at the νCN region shows that 5 FA molecules are coordinated to Ni (II) and the sixth position of the octahedron is occupied by one chloride, with preferential formation of [Ni(FA)5Cl]Cl in concentrations near 0.1molkg−1. In higher concentrations the [Ni(FA)4Cl2] complex becomes the most abundant. The downshift of the νCO mode of FA was evidenced by the appearance of a new band at 1640cm−1 in the IR spectra of the most concentrated salt solutions. Also, the downshift of the δOCN mode combined with the upshift of the νCN vibration have allowed us realize that Ni (II) is coordinated by the O atom of FA. The d orbital splitting (Δo) has been directly determined from the electronic spectrum of the [Ni(FA)6]Cl2 complex and FA has been included in the spectrochemical series.

Polymorph‐Dependent Solid‐State Fluorescence and Selective Metal‐Ion‐Sensor Properties of 2‐(2‐Hydroxyphenyl)‐4(3H)‐quinazolinone

2-(2-Hydroxy-phenyl)-4(3H)-quinazolinone (HPQ), an organic fluorescent material that exhibits fluorescence by the excited-state intramolecular proton-transfer (ESIPT) mechanism, forms two different polymorphs in tetrahydrofuran. The conformational twist between the phenyl and quinazolinone rings of HPQ leads to different molecular packing in the solid state, giving structures that show solid-state fluorescence at 497 and 511 nm. HPQ also shows intense fluorescence in dimethyl formamide (DMF) solution and selectively detects Zn(2+) and Cd(2+) ions at micromolar concentrations in DMF. Importantly, HPQ not only detects Zn(2+) and Cd(2+) ions selectively, but it also distinguishes between the metal ions with a fluorescence λ(max) that is blue-shifted from 497 to 420 and 426 nm for Zn(2+) and Cd(2+) ions, respectively. Hence, tunable solid-state fluorescence and selective metal-ion-sensor properties were demonstrated in a single organic material.

The Synthesis of Comb-Like Polymeric Prodrugs of 5-Fluorouracil Derivatives

Two comb-like polymeric prodrugs of 5-fluorouracil derivatives (p(MAA-PEG400-5Fu), p(MAA-PEG2000-5Fu)) were synthesized from monomers, methacryloyl (polyethylene glycol 5-fluorouracil acetyl) (MAA-PEG-5Fu) through radical polymerization using azobisisobutyronitrile (AIBN) as initiator in N,N-dimethyl formamide solution, which structures were confirmed by means of IR, 1HNMR, UV-Vis, MS and GPC spectroscopy. The drug loading rates of the two prodrugs (p(MAA-PEG400-5Fu), p(MAA-PEG2000-5Fu)) were 25.51%, 10%, respectively.

Preparation of Carbon Nanofibers from Polyacrylonitrile Nanofibers by Electrospinning

Ultrafine fibers were electrospun from polyacrylonitrile (PAN)/N,N-dimethyl formamide (DMF) solution as a precursor of carbon nanofibers. The effects of solution concentration, applied voltage and flow rate on preparation and morphologies of electrospun PAN fibers were investigated. Morphologies of the green fibers, stabilized fibers and carbonized fibers were compared by scanning electron microscope (SEM). The diameter of PAN nanofibers is about 450nm and the distribution of diameter is well-proportioned. Characterization of the elements changes of fibers were performed by X-ray photoelectron spectroscopy (XPS).

Molecular Insights into DNA Polymerase Deterrents for Ribonucleotide Insertion

DNA polymerases can misinsert ribonucleotides that lead to genomic instability. DNA polymerase β discourages ribonucleotide insertion with the backbone carbonyl of Tyr-271; alanine substitution of Tyr-271, but not Phe-272, resulted in a >10-fold loss in discrimination. The Y271A mutant also inserted ribonucleotides more efficiently than wild type on a variety of ribonucleoside (rNMP)-containing DNA substrates. Substituting Mn(2+) for Mg(2+) decreased sugar discrimination for both wild-type and mutant enzymes primarily by increasing the affinity for rCTP. This facilitated crystallization of ternary substrate complexes of both the wild-type and Y271A mutant enzymes. Crystallographic structures of Y271A- and wild type-substrate complexes indicated that rCTP is well accommodated in the active site but that O2' of rCTP and the carbonyl oxygen of Tyr-271 or Ala-271 are unusually close (∼2.5 and 2.6 Å, respectively). Structure-based modeling indicates that the local energetic cost of positioning these closely spaced oxygens is ∼2.2 kcal/mol for the wild-type enzyme. Because the side chain of Tyr-271 also hydrogen bonds with the primer terminus, loss of this interaction affects its catalytic positioning. Our results support a model where DNA polymerase β utilizes two strategies, steric and geometric, with a single protein residue to deter ribonucleotide insertion.

DFT study of ionization potentials and electron affinities of formamide and its methylation derivatives

The ionization potentials (IPs) and electron affinities (EAs) of formamide in the gas phase have been calculated using density functional theory (DFT), ab initio HF and Moller-Plesset perturbational theory (MP) at 6-311++G** basis set. The results indicate that the IPs of formamide obtained with DFT and MP are in agreement with the results obtained from experiment. And B3LYP has been confirmed to be the most accurate method in calculating the AIPs and VIPs of formamide through our work. IPs and EAs of formamide in solution are not known experimentally, therefore IPs and EAs of formamide in chloroform, acetone, and dimethylsulfoxide have been calculated using polarized continuum model (PCM) with B3LYP/6-311++G** level and have been compared with the values in the gas phase. The AIPs and VIPs of formamide have been compared with those of its methylation derivatives. All EAs of methylation derivatives of formamide are bigger than those of formamide conformers in the gas phase with BLYP, B3LYP, and B3P86 methods at 6-311++G** basis set. All these indicate that all anions of methylation derivatives of formamide are more stable than anions of formamide with respect to electron detachment adiabatically and vertically in the gas phase.

Influence Factors for the Preparation of Kaolinite-Formamide Intercalation

Kaolinite-formamide intercalation compound was prepared by solution intercalation method. The intercalation ratio(I.R.) was evaluated based on the ratio of II /(II+IK).The influence factors on intercalation efficiency such as the type and contents of solvent, the temperature of intercalation reaction and the particle size of kaolinite sample were studied. The results shown that the highest intercalation ratio was 96% under room temperature. The formamide solution with vol.9% of water, methanol or ethanol is propitious to intercalation. The kaolinite sample with particle size more than 1.5μm, high purity and good dispersion in solution, is adequate for preparation high I.R. intercalation compound.

Vertically Oriented Ti–Pd Mixed Oxynitride Nanotube Arrays for Enhanced Photoelectrochemical Water Splitting

In recent years, considerable efforts have been made to design and discover photoactive nanostructured materials that can be used as anodes in water photoelectrolysis cells. Herein, we report on the growth of a novel photoanode material composed of self-ordered, vertically oriented nanotube arrays of titanium-palladium mixed oxynitride films via anodization of Ti-Pd alloy in an electrolyte solution of formamide containing NH(4)F at room temperature, followed by annealing in an ammonia atmosphere. The nanostructure topology was found to depend on both the anodization time and the applied voltage. Our results demonstrate the ability to grow mixed oxynitride nanotube array films that are several micrometers thick. The Ti-Pd oxynitride nanotube array films were utilized in solar-spectrum water photoelectrolysis, demonstrating a photocurrent density of 1.9 mA/cm(2) and a ∼5-fold increase in the photoconversion efficiency under AM 1.5 illumination (100 mW/cm(2), 1.0 M KOH) compared to pure TiO(2) nanotubes fabricated and tested under the same conditions. The obtained efficiency is among the highest reported values for a TiO(2) nanotube-based photoelectrochemical cell. This enhancement in the photoconversion efficiency is related to the synergistic effects of Pd alloying, nitrogen doping, and the unique structural properties of the fabricated nanotube arrays.

Hydrophobic hydration and hydrophobic interaction in tetraalkylammonium salt solutions: The cation size effect

The heats of solution of tetrahexylammonium and tetraheptylammonium bromides in water and aqueous solutions of formamide and hexamethylphosphoric triamide have been measured at 318 and 338 K. The standard enthalpies and heat capacities of solution and the enthalpic and heart capacity parameters of amide-electrolyte pair interaction have been determined. It has been confirmed that the standard heat capacities of solution and the amide-electrolyte interaction parameters as a function of the cation size pass through an extremum. The hydrophobic hydration effect is weaker for large tetraalkylammonium cations.