Neutron scattering experiments on fully deuterated liquid N-methylformamide DCONDCD3 at various temperatures and under pressure. Comparison to X-ray results

Neutron scattering experiments are performed on fully deuterated liquid N-methylformamide (C2D5NO) at various temperatures and under pressure. The recorded data at atmospheric pressure and room temperature are analyzed to yield the molecular form factor and the distinct pair correlation function. Our measurements clearly show that the hydrogen-bond network, of which the parameters are deduced, persists locally in the liquid. The experimental structure factor could be explained in terms of short-range crystal structure. The r(N...O) distance decreases with increasing temperature from 293 to 398 K, whereas no significant variation of the intermolecular structure is detected when varying pressure from 1 bar to 4 kbar. Along the study, some comparison is made with complementary X-ray results.     

Low-frequency Raman spectra of liquid formamides and aqueous solutions of formamide

Low-frequency Raman scattering of liquid formamide, aqueous solutions of formamide, liquid N-methylformamide and N,N-dimethylformamide are studied by construction of a quantity R(V). Previous experimental observations (far-infrared and Raman) in this frequency region are compared to those obtained from the R(v?) representation.     

Liquid structure and preferential solvation of metal ions in solvent mixtures of N,N-dimethylformamide and N-methylformamide

Raman spectra of aprotic N,N-dimethylformamide (DMF) and protic N-methylformamide (NMF) mixtures containing manganese(II), nickel(II), and zinc(II) perchlorate were obtained, and the individual solvation numbers around the metal ions were determined over the whole range of solvent compositions. Variation profiles of the individual solvation numbers with solvent composition showed no significant difference among the metal systems examined. In all of these metal systems, no preferential solvation occurs in mixtures with DMF mole fraction of x(DMF) < 0.5, whereas DMF preferentially solvates the metal ions at x(DMF) > 0.5. The liquid structure of the mixtures was also studied by means of small-angle neutron scattering (SANS) and low-frequency Raman spectroscopy. SANS experiments demonstrate that DMF molecules do not appreciably self-aggregate in the mixtures over the whole range of solvent composition. Low-frequency Raman spectroscopy suggests that DMF molecules are extensively hydrogen-bonded with NMF in NMF-rich mixtures, whereas NMF molecules extensively self-aggregate in DMF-rich mixtures, although the liquid structure in neat NMF is partly ruptured. The bulk solvent structure in the mixtures thus varies with solvent composition, which plays a decisive role in developing the varying profiles of the individual solvation numbers of metal ions in the solvent mixtures.     

N-甲替甲酰胺-水的氢键团簇的从头计算研究

The N-methylformamide（NMF）-water clusters were studied by ab inito calculations at MP2/6-31+G** and MP2 / 6-311 ++ G（d,p）levels. The equilibrium geometries and the dissociation channels and dissociation energies of both neutral and ionic NMF-H2O clusters are presented. For N-methylformamide,cis-form has lower energy than trans-form. In NMFH+,the proton prefers to link with the O atom of N-methylformamide. The results show that both cis- and trans- form of NMF can form a linear hydrogen bond with water. Although the energy of trans-NMF is higher than cis-NMF,trans-form exits more stably because it can form a double hydrogen bond with water. After the ionization of the NMF-H2O cluster,both the cis- and the trans-form will produce protonated products.     

Comparative study of Cl<Superscript>−</Superscript>, Br<Superscript>−</Superscript>, and I<Superscript>−</Superscript> ion adsorption from N-methylformamide at Ga-, (In-Ga)-, and (Tl-Ga)-electrodes

Adsorption of Cl⁻, Br⁻, and I⁻ (Hal⁻) ions from their 0.1 M solutions in N-methylformamide, a solvent with the highest permittivity (182.4 at 25°C), at liquid Ga-, (In-Ga)-, and (Tl-Ga)-electrodes with refreshable surface was studied by the measuring of differential capacitance and by using an open-circuit jet electrode. It is shown that the adsorption parameters and the surface activity series depend significantly on the metal nature. For the (In-Ga)- and (Tl-Ga)-electrodes, like for Hg-electrode, the halogenide-ion surface activity increases in the following series: Cl⁻ < Br⁻ < I⁻; for the Ga-electrode, it varies in the opposite sequence: I⁻ < Br⁻ < Cl⁻. By example of the Ga-electrode in N-methylformamide, it is shown for the first time that the phenomenon of the surface activity series reversal can be observed not only in aprotic solvents but also in protonic ones. The data obtained in N-methylformamide is compared with that obtained in dimethyl formamide and acetonitrile. The halogenide-ion adsorption at the Ga-, (In-Ga)-, and (Tl-Ga)-electrodes decreases in the series N-methylformamide < dimethyl formamide < acetonitrile. The results in aggregate are explained in terms of the Andersen-Bockris model. The data obtained in N-methylformamide, dimethyl formamide, and acetonitrile evidence the increase of ΔG _M-Hal ⁻in the series (Tl-Ga) < (In-Ga) < Ga, that is, with the increasing of the metal work function. This points out the donor-acceptor nature of the metal-halogenide-ion interaction, in which the halogenide-ions are donors of electron pair with respect to the metals.     

N-甲基甲酰胺与醇的氢键相互作用

The hydrogen bonding interactions between N-methylformamide and primary, secondary, and tertiary alcohols have been studied using the FT1R spectroscopic method. The most likely association complex between alcohol and N-methylformamide is the 1:1 stoichiometric complex formed between the hydroxyl group of alcohol and the carbonyl group of N-methylformamide. The formation constant of the 1:1 complexes has been calculated using the Nash method. It appears that the primary alcohols have larger formation constant compared with the secondary and tertiary alcohols. The results showed that the proton-donating ability of the alcohols decreased in the order: primary＞secondary＞tertiary, and that the association constant increased with the increase in carbon chain of the alkyl group of alcohols.     

N-甲基甲酰胺与醇的氢键相互作用

Amides are used as synthetic reagents and as starting mate- rials for the preparation of insecticides and pharmaceuticals products[1]. Alcohols are industrially and scientifically important organic compounds, and their physical and chemical properties are…     

A study of solute-solute interactions of amides dissolved in N-methylformamide by enthalpic interaction coefficients

Enthalpies of dilution of formamide, acetamide, propionamide, butyramide and hexanamide, dissolved in N-methylformamide have been measured calorimetrically at 25°C. From the results McMillan-Mayer coefficient related enthalpic pair and triplet interaction coefficients have been calculated. Except for those of formamide, all pair coefficients are negative, whereas the triplet terms are positive. The values in the protic solvent N-methylformamide presented in this paper together with those published before are compared with results for corresponding solutes dissolved in the aprotic solvent N,N-dimethylformamide. A discussion of the dependence of the interaction coefficients on the applied concentration scale is given and conversion factors are presented. The influence of hydrogen bonding, of substituent effects on this hydrogen bonding, and of polarophobic interaction is discussed. The latter is comparable in N,N-dimethyl-and N-methylformamide. The enthalpic pair interaction coefficients have been correlated with the Excess Group Additivity approach.To whom correspondence should be addressed.     

Estimating of surface activity of Cl− and Br− ions in the (In-Ga)/[N-methylformamide + mc KCl + (1 − m)c KClO4] and (In-Ga)/[N-methylformamide + mc KBr + (1 − m)c KClO4] systems by different methods

Differential capacitance curves in the (In-Ga)/[N-methylformamide + mc KCl + (1 ? m)c KClO₄] and (In-Ga)/[N-methylformamide + mc KBr + (1 ? m)c KClO₄] systems are measured using an ac bridge for the following molar portions m of the surface-active anion: 0, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1. The Cl^? and Br^? anions specific adsorption in the systems can be described quantitatively by the Frumkin isotherm. The principal parameters of Cl^? and Br^? anions adsorption at the (In-Ga)/N-methylformamide interface are determined by different methods. Unlike Ga/N-methylformamide interface, where the adsorption energy increased in the sequence I^? ≈ Br^? < Cl^?, at the (In-Ga)/N-methylformamide interface it increased in the reverse sequence: Cl^? < Br^? < I^?. The adsorption parameters at the charge density q = 0, obtained by three different methods, are close to each other. However, the parameters α₁ and α₂, which characterize the charge effect on the adsorption energy, when determined by the analyzing of dependences of adsorption potential drop E _ads on ln(mc), differ from those determined by two other methods. The error may be caused by the assuming that the adsorption potential drop is proportional to the coverage of dense layer with the specifically adsorbed ions.     

Dipole-stabilized carbanions: a computational study of N-methylformamide anion and methyl N-methylcarbamate anion

The relative energies of the rotamers of the carbanions derived from N-methylformamide and methyl N-methylcarbamate have been studied at the MP2/6-311+G and B3LYP/6-311+G theoretical levels. There results are in good agreement but differ substantially from previously reported HF/6-31G calculations for the N-methylformamide anions. Transition states for rotation and inversion of the anions were located. The methoxy group in methyl N-methylcarbamate has a large effect on the relative energies of the anions. The results are compared with those previously reported for the N-(methoxycarbonyl)piperidine anions, and it is found that the decreased conformational flexibility has an effect on the relative energies of these ions.     

On the fractality of Hg/non-aqueous solution interfaces

The fractal morphology of adsorbed triphenylphosphine oxide layer at the hanging mercury drop electrode is investigated in pure formamide, N-methylformamide and N,N-dimethylformamide solutions. Although no typical indications are detected for the occurrence of a phase transition during the development of the adsorbed film, the increase of fractal dimension from 2.00 to non-integer greater than 2.00 values, by the introduction of triphenylphosphine oxide, is systematically confirmed for the above solvents except N,N-dimethylformamide. These findings are interpreted at a qualitative level in terms of the structure making ability of the interfacial solvent.     

Non empirical quantum mechanical calculations of the1H,13C,15N and17O magnetic shielding constants and of the spin-spin coupling constants in formamide,hydrated formamide and N-methylformamide

The magnetic shielding constants of the different atoms of formamide, hydrated formamide and N-methylformamide are calculated by anab initio method. For the protons of formamide the measured differences between their chemical shifts are correctly reproduced by theory, provided that the molecular geometry used as input is carefully chosen. The differences between the values of the magnetic shielding constants calculated for formamide and hydrated formamide show that intermolecular hydrogen bonding produces variations of chemical shifts for all the atoms of the molecule except the formyl proton. The calculated chemical shift variations between formamide and N-methylformamide are compared to the experimental values and discussed in relation with different hydrogen bonding possibilities of the two molecules. The calculation of the contact term of the spin-spin coupling constants of formamide and hydrated formamide shows that in most cases the measured trends are satisfactorily reproduced and that the variations of these terms upon hydration are less than 3%.     

Different approaches to the estimating of surface activity of I− ions in the (In-Ga)/[N-methylformamide + mc KI + (1 − m)c KClO4] system

Differential capacitance curves in the (In-Ga)/[N-methylformamide + mc KI + (1 - m)c KClO₄] system are measured using an ac bridge for the following molar portions m of the surface-active anion: 0, 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1. The I^? anion specific adsorption in the system can be described quantitatively by the Frumkin isotherm. The principal parameters of I^? anion adsorption at the (In-Ga)/N-methylformamide interface are determined by different methods.     

First example of monodispersed (Mo3Se3)1∞ clusters

The close relationship of the structure of ternary molybdenum chalcogenides to molecular cluster compounds suggests that these chalcogenides might be synthesized from such clusters or be solubilized as clusters. However, in contrast to molybdenum halide clusters which can be obtained in solution from the solid phase, many attempts to solubilize these chalcogenide clusters were unsuccessful. This is the first report that some of the pseudo-one-dimensional compounds (M₂Mo₆X₆, X = Se, Te; M = Li, Na) can be dissolved when exposed to highly polar solvents such as dimethylsulfoxide or N-methylformamide. We show using optical microscopy, TEM, and light scattering that some of these solutions contain individual (Mo₃X₃)¹_∞ chains. This is also the first example of a purely inorganic transition-metal polymer solution. The behavior with respect to flocculation is consistent with the double layer theory. We show that the (Mo₃X₃)¹_∞ chains can be oriented in solution.     

Isothermal vapor–liquid equilibria for binary mixtures of benzene, toluene, m-xylene, and N-methylformamide at 333.15 K and 353.15 K

Isothermal vapor–liquid equilibrium (VLE) at 333.15 K and 353.15 K for four binary mixtures of benzene + toluene, benzene + N-methylformamide, toluene + m-xylene and toluene + N-methylformamide have been obtained at pressures ranged from 0 kPa to 101.3 kPa. The NRTL, UNIQUAC and Wilson activity coefficient models have been employed to correlate experimental pressures and liquid mole fractions. The non-ideal behavior of the vapor phase has been considered by using the Soave–Redlich–Kwong equation of state in calculating the vapor mole fraction. Liquid and vapor densities were also measured by using two vibrating tube densitometers. The P–x–y diagram and the activity coefficient indicate that two mixtures of benzene + toluene and toluene + m-xylene were close to the ideal solution. However, two mixtures containing N-methylformamide present a large positive deviation from the ideal solution. The excess Gibbs energy in the benzene + toluene mixture is negative indicates that it is an exothermic system.     

Zur Reaktion von Carbonsäureanhydriden mit Formamid und N-Methylformamid

Zusammenfassung Das Erhitzen von (in der Mehrzahl) aromatischen intramolekularen Dicarbonsäureanhydriden mit einem Überschuß an Formamid bzw. N-Methylformamid stellt eine sehr einfache und allgemein anwendbare Darstellungsweise für die entsprechenden Imide bzw. N-Methylimide dar. Es zeigt sich, daß die für die Umsetzung nötigen Temperaturen für Anhydrid- und Carboxylgruppen vom Formamid über N-Methylformamid zum Dimethylformamid ansteigen. Durch Reaktion von Trimellithsäureanhydrid entsteht mit N-Methylformamid das Trimellithsäure-N-methylimid. Die Umsetzung von Terephthalsäure mit N-Methylformamid in Gegenwart von P₄O₁₀ führt in guter Ausbeute zum Terephthalsäure-N,N-bis(methylamid).

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Reaction of carboxylic anhydrides with formamide and N-methylformamide

The reaction of (mostly) aromatic carboxylic anhydrides with an excess of formamide or N-methylformamide at elevated temperatures is a very simple and useful synthesis for the appropiate imides or N-methylimides. The reaction temperature increases from formamide to N-methylformamide to dimethylformamide. Trimellitic anhydride yields with N-methylformamide trimellitic acid-N-methylimide. Excellent yields of terephthal-N,N-bis(methylamide) are obtained by the reaction of terephthalic acid with N-methylformamide in the presence of P₄O₁₀.

     

Amide-induced phase separation of hexafluoroisopropanol-water mixtures depending on the hydrophobicity of amides

Amide-induced phase separation of hexafluoro-2-propanol (HFIP)-water mixtures has been investigated to elucidate solvation properties of the mixtures by means of small-angle neutron scattering (SANS), (1)H and (13)C NMR, and molecular dynamics (MD) simulation. The amides included N-methylformamide (NMF), N-methylacetamide (NMA), and N-methylpropionamide (NMP). The phase diagrams of amide-HFIP-water ternary systems at 298 K showed that phase separation occurs in a closed-loop area of compositions as well as an N,N-dimethylformamide (DMF) system previously reported. The phase separation area becomes wider as the hydrophobicity of amides increases in the order of NMF < NMA < DMF < NMP. Thus, the evolution of HFIP clusters around amides due to the hydrophobic interaction gives rise to phase separation of the mixtures. In contrast, the disruption of HFIP clusters causes the recovery of the homogeneity of the ternary systems. The present results showed that HFIP clusters are evolved with increasing amide content to the lower phase separation concentration in the same mechanism among the four amide systems. However, the disruption of HFIP clusters in the NMP and DMF systems with further increasing amide content to the upper phase separation concentration occurs in a different way from those in the NMF and NMA systems.     

Catalytic Metathesis of N-Methylformamide with Dimethyl Carbonate by Alcohol Associates

Russian Journal of Physical Chemistry A - The mechanism of N-methylformamide metathesis with dimethyl carbonate, which leads to the formation of N,O-dimethyl carbamate, is studied using the...     

Enthalpies of transfer of N-methylformamide,formamide, and N,N-dimethylformamide from methanol to methanol+dimethylsulfoxide mixtures

The enthalpies of transfer of formamide, N-methylformamide and N,N-dimethylformamide from methanol to methanol+dimethylsulfoxide solvent systems have been measured. These data are analysed in terms of a recently developed model of solvation in mixed solvents. The results of the data analyses indicate that preferential solvation of the different functional groups of the amides differs, the carbonyl oxygen being preferentially solvated by methanol and the nitrogen protons are by dimethylsulfoxide.     

The static electric permittivity of solutions of organic molecules in dipolar solvents

The permittivity of solutions of pyrazine and of 1,4-diazabicyclo-[2,2,2]-octane (TED) in various dipolar solvents has been measured at 10 MHz by means of a sensitive bridge method. The solvents used were water, methanol, formamide, N-methylformamide, N,N-dimethylformamide, and dimethylsulfoxide. The results of the measurements are compared with those of theoretical mixture formulas. It is shown that — depending on structural properties — the permittivity attributed to the solvation shells around the organic solute molecules is changed with respect to the pure solvent value.