DMF) And N,N-dimethylacetamide Research Articles

The dynamics of liquid formamide, N-methylformamide, N,N-dimethylformamide, and N,N-dimethylacetamide. A dielectric relaxation study

The results of dielectric relaxation experiments on formamide (FA), N-methylformamide (NMF), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMA), performed between 238.15 K and 338.15 K in the frequency range 0.2 <- v/GHz <- 89 are presented. Whereas the FA spectra can be formally fitted with a Davidson-Cole relaxation-time distribution, two relaxation processes can be resolved for the other liquids. For DMF and DMA the long relaxation time, τ 1( T), follows the Vogel-Fulcher-Tammann equation. For these liquids τ 1( T) probes the essentially isotropic rotational diffusion of the molecular dipole vector. For the hydrogen-bonding liquids FA and NMF a modified Eyring equation is more appropriate to describe τ 1( T). From the parameters the average number of monomers in the chains of H-bonded NMF molecules is deduced, as well as the number of hydrogen bonds which must be broken before relaxation in FA can occur. The data suggest that the observed high-frequency contribution in the spectra mainly reflects the onset of inertial contributions.

Ultrasonic and Volumetric Study of Binary Mixtures of Benzyl Alcohol with Amides

Abstract The density (ρ) and ultrasonic speed (u) in binary mixtures of benzyl alcohol (BA) with formamide (FA), N-methylacetamide (NMA), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMA), including those of pure liquids, were measured at 35 °C over the entire composition range. The isentropic compressibility (ks), deviations in isentropic compressibility (Δks) and ultrasonic speed (Δu) from linear dependence on the composition, excess volume (VE), apparent molar isentropic compressibility (Kφ,s) and apparent molar volume (Vφ) of amides in benzyl alcohol were calculated. The variation of these parameters with composition of the mixtures suggests that the strength of interaction (BA–FA) &amp;lt; (BA–BA) or (FA–FA), whereas the interaction (BA-substituted amide (NMA, DMF, and DMA)) &amp;gt; (BA–BA) or (amide–amide). Moreover, the values of Δks are found to depend on the positions of the methyl groups, while those of VE seem to depend on the number of such groups in the amide molecule.

Individual solvation numbers around the nickel(II) ion in an N,N-dimethylformamide and N,N-dimethylacetamide mixture determined by Raman spectrophotometry.

Individual solvation numbers around the nickel(II) ion have been determined by titration Raman spectroscopy in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) mixtures at 298 K. The in-plane bending vibration (delta(O=C-N)) of DMF and the stretching vibration (v(N-CH3)) of DMA were used in the present analysis. These Raman bands of solvent molecules shift to higher frequencies upon coordination of the solvent molecules to the metal ion. By analyzing the band intensities of free and bound solvent molecules with increasing concentration of the metal ion, the solvation number around the metal ion can be evaluated. Because the individual solvation numbers of DMF and DMA around the nickel(II) ion in the mixture are determined independently, the total solvation number is obtained as their sum. It was found that the total solvation number remains 6 in all mixtures of the DMA mole fraction x = 0 - 1. Although DMF and DMA have practically the same electron-pair donor capacities, the nickel(II) ion prefers DMF to DMA, and an equal solvation number is attained at x = 0.75. This is ascribed to the solvation steric effect of DMA.

Preparation and Thermal Properties of Dicyanovinyl End-Capped Reactive Oligomers Linked with Azomethine Bond

New dicyanovinyl end-capped reactive oligomers 2—5 containing flexible alkyl units were prepared from the condensation reaction of diamines with 1-(p-formylphenyl)-1-phenyl-2, 2-dicyanoethene (1) by forming an azomethine linkage. Two arylate oligomers 7 and 8 containing azomethine bond were also prepared and compared with oligomers 2—5. All the oligomers were characterized by spectroscopies and elemental analysis. The reactive oligomers showed a good solubility in polar aprotic solvent such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMAc), and they were partially soluble in common organic solvents such as tetrahydrofuran (THF) and acetone. Their thermal properties including melting temperature, curability and thermal stabilities were examined. These oligomers undergo a curing reaction around 280—340°C. Upon heating the oligomers, thermally stable and insoluble network polymers were obtained.

Thermodynamics and structure of chloro-complexes of aluminium(III) in N,N-dimethylformamide and N,N-dimethylacetamide

Formation of chloro-complexes of AlIII has been studied by spectrophotometry, calorimetry and 27Al NMR spectroscopy in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) at 298 K. Formation constants of the AlIII–Cl- system were obtained spectrophotometrically on the basis of those of the NiII–Cl- system by means of competitive complexation between AlIII and NiII ions. All data can be explained well in terms of formation of mono- and dichloro-complexes of AlIII in DMF, and mono- and trichloro-complexes in DMA, and their formation constants, formation enthalpies and entropies were determined. Formation entropies of chloro-complexes of AlIII in DMF are significantly less than the corresponding values of GaIII and InIII. It is thus suggested that the formation of inner-sphere AlCl2+ and AlCl2+ is strongly suppressed, and the chloro-complexes are present mainly as the outer-sphere [Al(DMF)6]3+Cl- and [Al(DMF)6]3+2Cl- complexes in DMF. This is indeed evidenced by the 27Al NMR. On the other hand, in DMA, the large and positive enthalpy and entropy values indicate that the mono- and trichloro-complexes are inner-sphere ones, AlCl2+ and AlCl30. The 27Al NMR signal ascribed to AlCl30 is largely shifted to a lower magnetic field indicating that the complex is tetrahedrally four-coordinated, [AlCl3(DMA)]0, and that a geometry change takes place upon complexation of the trichloro-complex in DMA.

Molecular Contact Complexes of Amides and Oxygen

Contact transfer charge (CCT) absorption spectra of N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) with molecular oxygen (O2) have been investigated. These solvents form contact complexes with O2 and have strong ultraviolet CCT absorption bands with intensities that are related to the partial pressure of the applied O2 and the mole percentages of DMF and DMA in DMF/acetonitrile (MeCN) and DMA/MeCN mixtures, respectively. Electron spin resonance spectra and luminol chemiluminescence tests confirm the absence of the formation of superoxide ions from oxygenated DMF and DMA solutions.

Synthesis and properties of aromatic polyamides based on 4,4′‐(1,5‐naphthalenedioxy)dibenzoic acid

Abstract4,4′‐(1,5‐Naphthalenedioxy)dibenzoic acid (3), a novel aromatic dicarboxylic acid monomer, was prepared by nucleophilic substitution reaction of 1,5‐dihydroxynaphthalene and p‐fluorobenzonitrile in N,N‐dimethylformamide (DMF) in the presence of potassium carbonate and subsequent alkaline hydrolysis of the intermediate dinitrile, 4,4′‐(1,5‐naphthalenendioxy)dibenzonitrile. Using triphenyl phosphite (TPP) and pyridine as condensing agents, a series of novel aromatic polyamides were synthesized by direct poly‐condensation of diacid 3 and twelve aromatic diamines in N‐methyl‐2‐pyrrolidone (NMP) solution containing dissolved calcium chloride. The resulting polyamides had inherent viscosities above 1,14 and up to 4,45 dL/g. Most of these polyamides are readily soluble in polar solvents, such as NMP, DMF, and N,N‐dimethylacetamide (DMAc). Transparent, flexible, and tough films could be cast from their DMAc or NMP solutions. Most of these polymers were amorphous in nature, as indicated by their wide‐angle X‐ray diffractograms. Thermogravimetric analysis (TG) showed that all the polyamides were stable up to 450°C in both air and nitrogen atmosphere. Most of them revealed a distinct glass transition on the differential scanning calorimetry (DSC) traces in the range of 183–259°C.

ChemInform Abstract: RAMAN INTENSITY CALCULATIONS WITH THE CNDO METHOD. PART II. N,N‐DIMETHYLFORMAMIDE AND N,N‐DIMETHYLACETAMIDE

Abstract A study is reported of polarizabilities and Raman intensities (RI) of some vibrations of formamide, N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA). The substitution of the hydrogens of formamide by methyl groups leads to considerable changes of frequencies, polarizabilities and RI of these molecules. The normal coordinate analysis and the semiempirical CNDO calculation of the RI are an effective tool in describing the vibration spectra of formamide, DMF and DMA. A relationship between the extension of the conjugated system and the RI is found for these molecules.

Thermal reactions of lead(IV) chloride complexes in the solid state. Part II. Thermolysis of molecular complexes of PbCl 4 and H 2PbCl 6 with N,N-dimethylformamide and N,N-dimethylacetamide

The following molecular complexes of PbCl 4 and H 2PbCl 6 with N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) are obtained: PbCl 4 · 2 DMF, PbCl 4 · 2 DMA, H 2PbCl 2 · n DMF and H 2PbCl 6 · n DMA. The thermal decomposition of these compounds is studied both by thermal analysis, and isothermally in a device to separate reaction products. The products of thermal reactions are PbCl 2, Cl 2, HCl, and appropriate amides or their hydrochlorides. In addition, a variety of products of secondary reaction, including those of pyrolysis of the amides (amines, CO, CO 2 and nitriles) and chlorination (e.g. COCl 2) are detected. The effect of sample weight, temperature, rate of removal of volatile products, and presence of certain substances on the course of the thermolysis is also investigated. An attempt is made to elucidate the thermal proceses taking place during the decomposition.

Cryoscopic studies on amides in benzane

Molal freezing point depression (ΔT o f of N-methylformamide (NMF), N-methylacetamide (NMA), N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) have been determined in benzene by cryoscopic measurements. From these results, molecular weight, degree of association and equilibrium constant have been evaluated. The observed deviations from linear behaviour in ΔT o f versus concentration plots appear to indicate the existence of Monomer ⇄ Dimer equilibrium almost at all concentrations for NMF and NMA as compared to the normal linear feature for DMF and DMA, a novelty explained in terms of hydrogen bonding and supports our previous conclusions [1] drawn from dielectric measurements.

Solvolysis in Carboxamides. II. Solvolytic Elimination of 7β-Methylbicyclo[3.3.1]non-3β-yl Tosylate in Carboxamides

Abstract Solvolysis of 7β-methylbicyclo[3.3.1]non-3β-yl tosylate (1) was carried out in a series of carboxamides, N-methylformamide (NMF), N-methylacetamide (NMA), N,N-dimethylformamide (DMF), and N,N-dimethyl-acetamide (DMA), as solvents. The rate (k1 first-order rate constant) of 1 decreases in the order NMF&amp;gt;NMA&amp;gt;DMF&amp;gt;DMA, a linear free-energy relationship being found between the rates of 1 and those of 1-adamantyl tosylate in acetic acid and 80% ethanol as well as the carboxamides. The products consist of olefin (≥96%) (exo-7-methylbicyclo[3.3.1]non-2-ene (4) and 3-methylbicyclo[3.3.1]non-2-ene (5)) and small amounts of esters (acetates or formates, ≤4%). The content of rearranged olefin 5 is considerably less than that of acetolysis (55%) and ethanolysis (55%), decreasing in the order NMF (34%)&amp;gt;NMA(22%)&amp;gt;DMF(13%)&amp;gt;DMA(9%). A linear reactivity-selectivity relationship holds between log k1 and log (%5/%4) for the four carboxamide solvents. The observed kinetic isotope effect (kH/kD=1.01±0.03) for 7α-deuterium-tagged derivative (1-7α-d) in NMF indicates that the σ(C(7)–H)-assisted ionization process for the solvolysis of 1 in the amides is absent. The results are in line with the stepwise mechanism which involves the formation of an intimate ion-pair intermediate followed by competitive processes such as 1,5-hydride shift, syn-El reaction, and nucleophilic substitution by the amide molecules. Substitution by the amide molecule leads to the formation of a cationic imidate, the hydrolysis of which affords the carboxylic esters. It is proposed that the syn-El process via an intimate ion-pair intermediate is affected by the tosylate anion reactivity in each amide solvent and suppressed by the hydrogen bonding of the each amide with the tosylate anion.

The infrared spectra of some simple N-substituted amides in the vapor state

The vapor absorptions of N-methylformamide (NMF), N-methylacetamide (NMA), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMA) have been recorded with a prism spectrometer between 4000 cm −1 and 415 cm −1. The contour changes resulting from methyl substitution and the consequent increase in asymmetry of the cis configuration proposed for N-methylformamide, are compared with those in the theoretical contours. As a first approximation, the rigid models for the four molecules are assumed to be valid at the temperatures used. Some of the gross structural features in the spectra are consistent with theory, but the results show the dangers inherent in the use of the theoretical contours as a basis for the detection of minor configurational differences in complex molecules.

Rate Processes and Nuclear Magnetic Resonance Spectra. II. Hindered Internal Rotation of Amides

Mathematical methods are presented for calculating rate constants of processes which narrow nuclear magnetic resonance absorption lines having discrete components. High resolution proton spectra show that the R1CO-NR2R3 skeletons of N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) are planar and suggest that N-methylformamide, N-methylacetamide, N-methylformanilide and N-methylacetanilide exist predominantly in one configuration. The presence of a significant amount of double bond character in the C–N amide bond is proved by the temperature dependent coalescence observed for the chemically shifted proton doublet of the N(CH3)2 groups in DMF and DMA, which gives values of about 22 and 19 kcal respectively for the free energy of activation required for reorientations about the bond.