Acetamide Molecules Research Articles

Computer simulation of the atomic structure of regenerated cellulose

The atomic structure of amorphous sulfate hardwood pulp obtained via regeneration in a dimethyl acetamide–LiCl solution is studied with the use of X-ray diffraction and computer simulation. When dimethyl acetamide appears within a cellulose chain, it becomes swollen. A chosen cluster has a complex structure and contains two cellulose chains II distorted by twisting and bending and two chains deformed by dimethyl acetamide molecules. A cluster with the formula unit (C6O5H8.5Li1.5) • (H2O)2.8 is obtained after relaxation with the addition of water. The uncertainty-profile factor for the model and experimental curves of X-ray scattering intensity distribution I(s) is 8%, and the distribution curve of s-weighted interference function H(s) calculated for the model best fits the experimental curve.

Structural insight into the reaction mechanism of Pd-catalyzed nitrile hydration: Trapping the [Pd(H2O)4]2+ cation through a supramolecular complex

Four new bis(oxamato)palladate(II) complexes of formula (n-Bu4N)2[Pd(2,4,6-Me3pma)2]·2CH3CN (1), (n-Bu4N)2[Pd(2,4,6-Me3pma)2]·2CH3CONH2 (2) and (n-Bu4N)4[Pd(H2O)4][Pd(4-Xpma)2]3·2CH3CONH2 with X=Br (3) and Cl (4) (2,4,6-Me3pma=N-2,4,6-trimethylphenyloxamate, 4-Brpma=N-4-bromophenyloxamate, N-4-chlorophenyloxamate and n-Bu4N+=tetra-n-butylammonium) have been obtained and characterized by single crystal X-ray diffraction. All of them contain bis(oxamato)palladate(II) anions and bulky n-Bu4N+ cations, but compounds 3 and 4 have also the out of the ordinary [Pd(H2O)4]2+ inorganic cation. Acetonitrile and appealing acetamide are present as lattice molecules in compounds (1) and (2–4), respectively. While 1 was prepared in a neutral solution, species 2–4 were obtained in a basic medium. The acetamide molecules are the natural consequence of the acetonitrile hydration reaction during the oxamate-palladate(II) complexation. Interestingly, the use of a different oxamate ligand supports (through a molecular-recognition interaction) the structural grasping of the [Pd(H2O)4]2+ species, which can be considered as a reaction intermediate for the nitrile hydration.

Orientational Jumps in (Acetamide + Electrolyte) Deep Eutectics: Anion Dependence

All-atom molecular dynamics simulations have been carried out to investigate orientation jumps of acetamide molecules in three different ionic deep eutectics made of acetamide (CH3CONH2) and lithium salts of bromide (Br(–)), nitrate (NO3(–)) and perchlorate (ClO4(–)) at approximately 80:20 mole ratio and 303 K. Orientational jumps have been dissected into acetamide–acetamide and acetamide–ion catagories. Simulated jump characteristics register a considerable dependence on the anion identity. For example, large angle jumps are relatively less frequent in the presence of NO3(–) than in the presence of the other two anions. Distribution of jump angles for rotation of acetamide molecules hydrogen bonded (H-bonded) to anions has been found to be bimodal in the presence of Br(–) and is qualitatively different from the other two cases. Estimated energy barrier for orientation jumps of these acetamide molecules (H-bonded to anions) differ by a factor of ∼2 between NO3(–) and ClO4(–), the barrier height for the latter being lower and ∼0.5kBT. Relative radial and angular displacements during jumps describe the sequence ClO(4)– > NO3(–) > Br(–) and follow a reverse viscosity trend. Jump barrier for acetamide–acetamide pairs reflects weak dependence on anion identity and remains closer to the magnitude (∼0.7kBT) found for orientation jumps in molten acetamide. Jump time distributions exhibit a power law dependence of the type, P(tjump) ∝ A(tjump/τ)(−β), with both β and τ showing substantial anion dependence. The latter suggests the presence of dynamic heterogeneity in these systems and supports earlier conclusions from time-resolved fluorescence measurements.

Thermal decomposition behavior and de-intercalation mechanism of acetamide intercalated into kaolinite by thermoanalytical techniques

De-intercalation is the inverse of the intercalation process, which can be easily and rapidly determined by thermal analysis. Research on the de-intercalation process is beneficial to exploring the intercalation mechanism that is still unclear in the case of kaolinite intercalation. The objectives of this study were (a) to investigate the thermal decomposition behavior of the intercalation compound of kaolinite and (b) to determine the kinetics of de-intercalation process by thermal analysis to study the mechanism of de-intercalation reaction in kaolinite. Here, the kaolinite–acetamide intercalation compound that was prepared by the direct intercalation method was investigated. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy results showed that acetamide molecules were inserted into the interlayer space of kaolinite and apparently formed new hydrogen bonds with the inner surface hydroxyl groups of kaolinite. The basal spacing of kaolinite increased from 0.721 to 1.102nm upon intercalation with acetamide. The thermogravimetric (TG) and differential scanning calorimetry (DSC) curves indicated that the decomposition process of the intercalation compound could be divided into two steps. The first step was attributed to the de-intercalation of the intercalated molecules at a temperature of about 181°C, and the second step corresponded to the dehydroxylation of kaolinite at a temperature of about 502°C. The completed kinetic triplet of the de-intercalation reaction was obtained through thermal analysis kinetics methods. The apparent activation energy Ea of the de-intercalation process was calculated to be about 73.6kJmol−1 by an iterative procedure. The pre-exponential factor A was estimated to be in the range of 1.06×1010s−1 to 7.92×1010s−1 by the Dollimore method. The optimized mechanism function of the de-intercalation process of acetamide was determined to be an nth-order chemical reaction through the Malek method. The mechanism function is G(α)=[1−(1−α)1−n]/(1−n), f(α)=(1−α)n and experiments showed that the value of n increased with increased heating rate.

Dielectric Relaxations of (Acetamide + Electrolyte) Deep Eutectic Solvents in the Frequency Window, 0.2 ≤ ν/GHz ≤ 50: Anion and Cation Dependence.

Dielectric relaxation (DR) measurements in the frequency range 0.2 ≤ ν/GHz ≤ 50 have been carried out for neat molten acetamide and six different (acetamide + electrolyte) deep eutectic solvents (DESs) for investigating ion effects on DR dynamics in these ionic DESs. Electrolytes used are lithium salts of bromide (LiBr), nitrate (LiNO3), and perchlorate (LiClO4); sodium salts of perchlorate (NaClO4) and thiocyante (NaSCN); and potassium thiocyanate (KSCN). With these electrolytes acetamide forms DESs approximately at an 80:20 mol ratio. Simultaneous fits to the measured permittivity (ε′) and loss (ε″) spectra of these DESs at ∼293 K require a sum of four Debye (4-D) processes with relaxation times spread over picosecond to nanosecond regime. In contrast, DR spectra for neat molten acetamide (∼354 K) depict 2-D relaxation with time constants ∼50 ps and ∼5 ps. For both the neat and ionic systems, the undetected dispersion, ε∞ – n(D)2, remains to be ∼3–4. Upon comparison, measured DR dynamics reveal pronounced anion and cation effects. Estimated static dielectric constants (ε0) from fits for these DESs cover the range 12 < ε0 < 30 and are remarkably lower than that (ε0 ∼ 64) measured for molten acetamide at ∼354 K. Hydrodynamic effective rotation volumes (Veff) estimated from the slowest DR relaxation time constants vary with ion identity and are much smaller than the molecular volume of acetamide. This decrease of ε0 and Veff is attributed respectively to the pinning of acetamide molecules by ions and orientation jumps and undetected portion to the limited frequency coverage employed in these measurements

Preparation of open and closed forms of the lvt network with Cu(ii) complexes of structurally related 1,2-diazole ligands

Reported here are the synthesis and structural characterisation of two topologically related coordination polymers: [Cu(L1)(CH3CONH2)], 1, and [Cu(L2)(NMP)]·0.5NMP·0.5H2O, 2, (NMP = N-methyl-pyrrolidinone) prepared from 1H-indazole-3-carboxylic acid, H2L1, and 1H-pyrazole-3-carboxylic acid, H2L2, respectively. Both 1 and 2 crystallise in the tetragonal space group I41/a and form 3-dimensional coordination polymers described by the lvt topology, in which [Cu2L2] dimers form four-connected nodes linked through carboxylate groups. Within 1 the presence of a Cu-bound acetamide molecule (formed in situ by the solvothermal hydration of acetonitrile) propagates hydrogen bonding between dimer units that, combined with the steric bulk of the indazole fragment, yield a closed (non-porous) framework. In 2, however, Cu-bound NMP, which does not participate in hydrogen bonding, coupled with the less bulky nature of the pyrazole-backbone, gives rise to an open framework of an otherwise isostructural network.

Bis(2,2′,2′′-nitrilotriacetamide-κ3O,N,O′)nickel(II) dinitrate tetrahydrate

In the title compound, [Ni(C6H12N4O3)2](NO3)2·4H2O, the NiII cation is located on an inversion center and is N,O,O′-chelated by two nitrilo­tris­(acetamide) mol­ecules in a distorted octa­hedral geometry. The complex cations, nitrate anions and lattice water mol­ecules are connected by O—H⋯O and N—H⋯O hydrogen bonds, forming a three-dimensional supra­molecular structure.

Specific Conductivities and Viscosities of 0.1LiNO3 + 0.9[xCH3CONH2 + (1 – x)CO(NH2)2] as Functions of Mole Fraction, x, and Temperature

Specific conductivities and viscosities of molten mixtures of lithium nitrate, acetamide, and urea with the composition, 0.1LiNO3 + 0.9[xCH3CONH2 + (1 – x)CO(NH2)2], have been measured as functions of mole fraction of acetamide (0.40 ≤ x ≤ 0.75) and temperature (283.15 ≤ T/K ≤ 353.15). The Vogel–Tammann–Fulcher (VTF) equation describes reasonably well the experimental specific conductivity and viscosity data. A minimum in the conductivity is then explained in terms of rigid complex formation between Li+ and acetamide molecules. Subsequently, the mixture composition dependence of the B parameter (obtained via fit to VTF equation) has been related to this solution structural modification.

Ionic acetamide coordination in its complexes with rare-earth iodides

A series of [Ln(CH3CONH2)4(H2O)4]I3 (Ln = rare-earth metal) complexes was completed with seven new compounds (Ln = Ce, Pr, Sm, Tb, Tm, Yb, Lu); two (Ln = Ce, Tm) were studied by X-ray diffraction. The coordination polyhedron of eight oxygen atoms is a distorted square antiprism. No tetrad effect was found for Ln–O bond lengths. The structure is stabilized by a system of intermolecular hydrogen bonds. The most striking feature of the structures is the recently predicted ionic acetamide coordination. The acetamide molecules are non-planar (the Ln–O–C–N torsion angles are 159–170°) and Ln–O–C bond angles vary in the 146.0–156.8° range.

Heterogeneity and viscosity decoupling in (acetamide + electrolyte) molten mixtures: A model simulation study

Recent time-resolved fluorescence experiments with (acetamide + electrolyte) melts have revealed pronounced decoupling of solute and solvent dynamics from medium viscosity. Here we examine the diffusion–viscosity ( D– η) relationship by performing molecular dynamics simulations approximating acetamide molecules as dipolar Lennard–Jones (L–J) spheres and ions as L–J spheres with point charges. Interestingly, eventhough simulated viscosities are found to be approximately an order of magnitude lower than those from experiments, simulated diffusion coefficients are larger by ∼500–4000 times than the hydrodynamic predictions using the experimental viscosities. Simulated particle motions exhibit strong dynamic heterogeneity via pronounced non-Gaussian character of particle displacements. A signature of an extremely fast dipole orientation is also observed.

The preparation and properties of a novel electrolyte of electrochemical double layer capacitors based on LiPF 6 and acetamide

A novel electrolyte applied in electrochemical double-layer capacitors (EDLCs) has been prepared based on lithium hexafluorophosphate (LiPF 6) and acetamide and subsequently characterized by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), electrochemical techniques and so on. The mixtures of LiPF 6 and acetamide at the molar ratios of 1:4 to 1:6 exist as liquids below 25 °C, which is attributed to the melting point depression of mixture and the coordination of the polar groups (C O and NH groups) of acetamide with Li + and PF 6 − ions. The strong interaction between LiPF 6 and acetamide results in the rupture of the electrovalent bond of LiPF 6 and the breakage of hydrogen bonds among the acetamide molecules, leading to the formation of a liquid electrolyte. The LiPF 6/acetamide electrolyte with a molar ratio of 1:5.5 exhibits a 5.2 V electrochemical window and suitable ionic conductivity at room temperature. In particular, the coin-type cells with carbon electrodes and LiPF 6/acetamide electrolyte possess high thermal stability and electrochemical properties, showing that the as-prepared LiPF 6/acetamide electrolyte is a promising candidate for EDLCs.

Bis[N-benzyl-2-(quinolin-8-yloxy)acetamide] monohydrate

In the title compound, 2C18H16N2O2·H2O, the dihedral angles between the quinoline rings and the benzene rings in the two independent acetamide mol­ecules are 80.09 (5) and 61.23 (5)°. The crystal packing is stablized by O—H⋯N and N—H⋯O hydrogen bonds between the acetamide and water mol­ecules.

A theoretical study on structural, spectroscopic and energetic properties of acetamide clusters [CH3CONH2] (n = 1–15)

Insights into the formation of hydrogen bonded clusters are of outstanding importance and quantum chemical calculations play a pivotal role in achieving this understanding. Structure and energetic comparison of linear, circular and standard forms of (acetamide)(n) clusters (n = 1-15) at the B3LYP/D95** level of theory including empirical dispersion correction reveals significant cooperativity of hydrogen bonding and size dependent structural preference. A substantial amount of impact of BSSE is observed in these calculations as the cluster size increases irrespective of the kind of arrangement. The interaction energy per monomer increases from dimer to 15mer by 90% in the case of the circular arrangement, by 76% in the case of the linear arrangement and by 34% in the case of the standard arrangement respectively. The cooperativity in hydrogen bonding is also manifested by a regular decrease in average OH and C-N bond distances, while average C=O and N-H bond lengths increase with increasing cluster size. Atoms-In-Molecules (AIM) analysis is used to characterize the nature of hydrogen bonding between the acetamide molecules in the cluster on the basis of electron density (ρ) values obtained at the bond critical point. An analysis of N-H bond stretching frequencies as a function of the cluster size shows a marked red shift as the cluster size increases from 1 to 15.

Structural features of the crystalline iodide complexes of some rare-earth elements with carbamide and acetamide

New acetamide and carbamide complexes LnI3 · 4Ur · 4H2O (Ln = La, Eu, Dy, Ho, Y; Ur is carbamide) and LnI3 · 4AA · 4H2O (Ln = Nd, Eu, Dy, Ho, Y; AA is acetamide) are synthesized. The complexes are characterized by the data of chemical analysis, IR spectroscopy, and X-ray diffraction analysis. The ligands (water, carbamide, and acetamide molecules) are coordinated by the rare-earth element atoms through the oxygen atom, and the coordination polyhedron is a distorted square antiprism. The iodide ions are not coordinated and are located in the external sphere. The structural characteristics of the complexes are compared in the series [Ln(L)4(H2O)4]I3 (Ln = La, Nd, Eu, Gd, Dy, Ho, Er; L = AA, Ur).

Complexes of lanthanum, gadolinium, and erbium iodides with acetamide: Synthesis and structure

New acetamide complexes of lanthanum, gadolinium, and erbium iodides of the composition LnI3 · 4AA · 4H2 O (Ln = La, Gd, Er; AA = CH3CONH2) are synthesized and studied. The synthesized complexes are characterized by the data of chemical analysis and IR spectroscopy and are studied by X-ray diffraction analysis. The coordination of the ligands (water and acetamide molecules) by the lanthanum, gadolinium, or erbium atom occurs through the oxygen atoms. The coordination polyhedron of the Ln atom is a distorted square antiprism. The iodide ions are not coordinated and exist in the external sphere.

An analytic potential energy function for the amide–amide and amide–water intermolecular hydrogen bonds in peptides

An analytic potential energy function is proposed and applied to evaluate the amide-amide and amide-water hydrogen-bonding interaction energies in peptides. The parameters in the analytic function are derived from fitting to the potential energy curves of 10 hydrogen-bonded training dimers. The analytic potential energy function is then employed to calculate the N-H...O=C, C-H...O=C, N-H...OH2, and C=O...HOH hydrogen-bonding interaction energies in amide-amide and amide-water dimers containing N-methylacetamide, acetamide, glycine dipeptide, alanine dipeptide, N-methylformamide, N-methylpropanamide, N-ethylacetamide and/or water molecules. The potential energy curves of these systems are therefore obtained, including the equilibrium hydrogen bond distances R(O...H) and the hydrogen-bonding energies. The function is also applied to calculate the binding energies in models of beta-sheets. The calculation results show that the potential energy curves obtained from the analytic function are in good agreement with those obtained from MP2/6-31+G** calculations by including the BSSE correction, which demonstrate that the analytic function proposed in this work can be used to predict the hydrogen-bonding interaction energies in peptides quickly and accurately.

Molecular Dynamics Simulation of LiTFSI−Acetamide Electrolytes: Structural Properties

The liquid structures of nonaqueous electrolytes composed of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and acetamide, with LiTFSI/acetamide molar ratios of 1:2, 1:4, and 1:6, were studied by molecular dynamics simulations. The simulations indicate that the Li+ cations prefer to be six-coordinate by the sulfonyl oxygen atoms of the TFSI- anions and the carbonyl oxygen atoms of the acetamide molecules, rather than by the most electronegative nitrogen atom of the TFSI- anion. Therefore, close Li+-TFSI- contact pairs exist in the system. The TFSI- anion prefers to provide only one of four possible oxygen atoms to coordinate to the same Li+ cation. Three conformations (cis, trans, and gauche) of the TFSI- anions were found to coexist in the liquid electrolyte. At high salt concentrations, the TFSI- anions mainly adopt the gauche conformation in order to provide more oxygen atoms to coordinate to different Li+ cations, while simultaneously reducing the repulsion among the Li+ cations. On the other hand, the fraction of TFSI- anions adopting the cis conformation is largest for the system with the molar ratio of 1:6, in which many clusters, mainly composed of the Li+ cations and the TFSI- anions, are immersed in the acetamide molecules. The size and charge distribution of clusters were also investigated. In the system with the molar ratio of 1:2, nearly all of the ions in the PBC (periodic boundary conditions) box aggregate into a bulky cluster that gradually disassembles into small clusters with decreasing salt concentration. The addition of acetamide molecules was found to effectively relax the liquid electrolyte structure, and the system with the molar ratio of 1:4 was found to exhibit a more homogeneous liquid structure than the other two electrolyte systems with molar ratios of 1:2 and 1:6.

Safening efficacy of halogenated acetals, ketals and amides and relationship between the structure and effect on glutathione and glutathione S-transferases in maize

Abstract Halogenated acetal, ketal and acetamide type molecules were synthesized and tested for their ability to alleviate toxicity of acetochlor to maize and differentially enhance the glutathione (GSH) content and glutathione S-transferase (GST) activity in shoots and roots of maize. Safening experiments revealed that the dichloroacetals were inactive, while dichloroketals were effective as safeners. The degree of induction of GSH levels and GST activity measured with CDNB and acetochlor substrates were not correlated with the protective effects observed. Since both the herbicide and the experimental safeners, as chemical stressors, induce specific GST activities, we can conclude that increased GST activities are not solely responsible for the safening effect. The protective efficacy of dichloroketal safeners does not seem to be associated with enhanced herbicide detoxication by glutathione conjugation.

Proton Character of the Peptide Unit in the Ca2+-Binding Sites of Calcium Pump

The effect of forming calcium pump structures in biological systems on the proton character of the peptide unit has been studied theoretically using the density-functional theory calculations with a large basis set. One acetic acid, one acetate, and three acetamide molecules as well as the modeling peptide unit (MPU) have been employed to mimic the amino acid residues forming the Ca2+-binding sites. To highlight the limiting case of the Ca2+-binding effect on the proton property and the proton countertransport possibility in the direction opposite to the ion, the MPU bounded by the bare or the hydrated Ca2+ has also been investigated. The natural bond orbital (NBO) analysis indicates that the increase of the p-character of the (N-H) sigma orbital results in weakening of the N-H bond which is lengthened when a Ca2+ ion is introduced to the MPU. Calculated NMR shielding sigma(H1) of the MPU shifts upfield upon the Ca2+ ion combination, which reveals the donating of the electron from the amide H as represented by the increase of the calculated positive natural charge for amide H of the MPU. Moreover, the proton affinities (PA) and gas-phase basicities (GB) for the amide nitrogen active site of the MPU are reduced; that is, the acidity of the amide hydrogen gets stronger because of the influence of the Ca2+ ion. To prove the transport possibility of the N-H proton in the direction opposite to the Ca2+ ion along the N-H...O=C hydrogen bond in the helical peptide linkage, NH3 and H2O are used here to assist the dissociation of the amide H of the MPU, and the calculated results show the notable decrease of the deprotonation energies compared to that of the case without this assistance. Moreover, calculated results also reveal that the variation of the quantities discussed here for amide H of the MPU gets smaller when the acidity of Ca2+ ion decreases. Ionization states of the acidic residues forming the Ca2+-binding sites may influence the activity of the amide H of the MPU and further affect the transport tendency of the peptide unit proton in the direction opposite to Ca2+.

Evaluation of N–H bond dissociation energies in some amides using ab initio and density functional methods

The performance of ab initio and DFT methods in the evaluation of N–H bond dissociation energies of formamide, N-methyl formamide, urea, and acetamide molecules has been analyzed. Both restricted and unrestricted HF and MP2 fail to provide reliable results because of unreliable spin localization of the radical. The composite methods G3, G2MP2, and CBS-Q, however, provide fairly accurate bond dissociation energies, the results for urea and acetamide agree with the experimental values. The ROB3LYP/6-311++G(d,p) method is observed to be the alternative to composite method keeping in view the relatively lower computational effort and a small loss in accuracy. The N–H bond dissociation energy of all the amides is higher than N–H bond dissociation energy for NH 3 molecules at all the levels of theory.