Mohamed Bahri

Short-range order in liquid N-methylformamide HCONHCH3, as studied by x-ray scattering and density functional theory calculations

The local order in liquid N-methylformamide has been studied by using x-ray diffraction and a density functional theory (DFT). Experimental data were analyzed to yield the total structure function SM(q) and the intermolecular pair correlation function gL(r). DFT calculations, using, namely, the standard TZV basis set, were performed to study the relative stability of the two possible isomers (cis and trans) and to examine some possible intermolecular arrangements in the liquid state. X-ray measurements can be interpreted in term of cyclic trimers of cis form molecules where each monomer can establish two N–H⋯O hydrogen bonds that are described.

X-ray scattering and density-functional theory calculations to study the presence of hydrogen-bonded clusters in liquid N-methylacetamide

A structural investigation of liquid N-methylacetamide (NMA) is performed by x-ray scattering and density functional theory (DFT). Experimental data are analyzed to yield the total structure function SM(Q) and the pair correlation function g(r). The DFT calculations, using the standard triple zeta valence basis set augmented by a diffuse function for carbon, nitrogen and oxygen atoms, are performed on the one hand to study the structure and stability of the two possible conformers cis and trans. On the other hand, they are meant to examine some possible clusters which may describe the intermolecular arrangement in liquid NMA. Among two series of dimers and trimers associations, the spectra are particularly interpreted in terms of: Trans NMA dimers and trimers which resemble the short-range crystal structure, mixed cis and trans trimers and cis cyclic trimers. The H-bonding parameters and the intermolecular energy for each model are described.

Structural investigations of N-methylformamide-water mixtures at various concentrations

Abstract.Structural investigations of N-methylformamide-water mixtures (NMF-water) are performed at room temperature and atmospheric pressure for two water molar fractions xw = 0.66 and xw = 0.75 . This paper extends our recent study on the equimolar system. H-bond networks are preferentially formed between NMF and water molecules. Among a large variety of DFT optimized models, X-ray scattering data shows that the local order of each mixture is better described by a tetramer where one NMF molecule is connected to three water molecules. No self-association is observed in the considered systems. The effect of hydration is compared to the temperature and pressure effects in some hydrogen-bonded liquids.Graphical abstract

H-bonding network in fully deuterated N-methylformamide-water mixtures as studied by neutron scattering. Complementarity to X-ray study

Abstract.In complementarity with X-ray scattering and as extension of our previous publication, neutron scattering measurements are combined to DFT calculation to investigate the structural features of N-methylformamide-water mixtures (NMF-water) for three water molar fractions xw = 0.5 , 0.66 and xw = 0.75 . The recorded data at atmospheric pressure and room temperature are analyzed to yield the structure factor, the molecular form factor and the pair correlation function. Neutron investigations corroborate the X-ray ones and clearly show that liquid order in solutions is well accounted for by a tetramer. In this cluster, an NMF molecule is connected to three water molecules by one N-D ... O and two O-D ... O hydrogen bonds.Graphical abstract

Synthese et Etude Conformationnelle Par RMN (1H, 13C, 31P) et DFT des Cycloalcoxyphosphinallenes et des Hydrazones β-Cycloalcoxyphosphonatees

Abstract The addition of hydrazine and its derivatives to cycloalkoxyphosphinallenes leads to β-(5,5-dialkyl-2-oxo-1,3,2-dioxaphosphoranyl)-hydrazones in good yields. The structure of the obtained compounds were elucidated by the NMR (1H, 13C, 31P) spectroscopy and density functional theory (DFT) calculations at B3LYP/6-311++G (2d, 2p) level of theory. GRAPHICAL ABSTRACT

A hydrogen-sensitive analysis of the structure of deuterated liquid formamide

ABSTRACT Structural investigations of deuterated liquid formamide were performed by using neutron scattering, ab-initio calculations and classical Molecular Dynamics (MD) simulations. The recorded neutron data are analysed to yield the total structure factor SM (Q), the molecular form factor F (Q), the distinct pair correlation function gL(r) and particularly the deuterium-oxygen signature of H-bond interactions. Neutron scattering data, as well as recent x-ray studies, clearly show that the local order of the liquid is largely described by one dimer, two trimers and one tetramer. Molecular Dynamics simulations show that neutron scattering data can be reproduced by three different force fields.

Synthesis and structural Studies of phosphonothioamidates

GRAPHICAL ABSTRACT Abstract The reaction of isothiocyanates with dialkylphosphites in the presence of strong base yielded the phosphonothioamides 2. Treatment of 2 with methyl iodide afforded the corresponding thioimidates 3 with high yields. All compounds were characterized on the basis of their IR, NMR Spectroscopy (1H, 13C, 19F, and 31P) and in some cases by elemental analysis, HRMS data, and calculations using Density Functional Theory (DFT)-B3LYP//6-311G** and evolution study by 31P-NMR in an external lock with D2O. The conformational molecular structure of compounds 2d and 2f were determined by single-crystal X-ray diffraction analysis.