scholarly journals Theoretical Study of The Chemical Reactivity of A Class of Trivalent Phosphorus Derivatives Towards Polyhaloalkanes: DFT Study.

2021 ◽  
Author(s):  
Ali Barhoumi ◽  
Mohammed El idrissi ◽  
Abdellah Zeroual ◽  
Abdessamad Tounsi ◽  
Salam Bakkas ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Activation Barrier ◽  
Chemical Reactivity ◽  
Nucleophilic Attack ◽  
Trivalent Phosphorus ◽  
Reactivity Indices ◽  
Theoretical Predictions ◽  
The One ◽  
Good Agreement

Abstract In the current work, the chemical reactivity of some trivalent phosphorus derivatives R2PR' towards polyhaloalkanes CCI3POR''2 was studied by the quantum method DFT/B3LYP/6-311G (d,p). The introduction of substituents for the trivalent phosphorus derivative and polyhaloalkane allowed us to have more information on these reactions. On the one hand, the calculation of reactivity indices derived from the DFT/B3LYP/6-311G(d,p) method and the gapLUMO-HOMO show that trivalent organophosphorus derivatives behave as nucleophiles, while polyhaloalkanes act as electrophiles. On the other hand, the calculation of the activation barrier and the determination of the free enthalpy variation prove that the kinetic and thermodynamic products of these reactions result from the nucleophilic attack of the phosphorus atom on the chlorine halogen. All these theoretical predictions are in very good agreement with the experimental results.

scholarly journals Determination of the Height of Hard X-Ray Sources in the Solar Atmosphere by Measurement of Photospheric Albedo Photons

1975 ◽  
Vol 68 ◽  
pp. 239-241
Author(s):  
John C. Brown ◽  
H. F. Van Beek
Keyword(s):  
Solar Atmosphere ◽  
The Other ◽  
X Ray ◽  
Theoretical Predictions ◽  
Source Models ◽  
The One

SummaryThe importance and difficulties of determining the height of hard X-ray sources in the solar atmosphere, in order to distinguish source models, have been discussed by Brown and McClymont (1974) and also in this Symposium (Brown, 1975; Datlowe, 1975). Theoretical predictions of this height, h, range between and 105 km above the photosphere for different models (Brown and McClymont, 1974; McClymont and Brown, 1974). Equally diverse values have been inferred from observations of synchronous chromospheric EUV bursts (Kane and Donnelly, 1971) on the one hand and from apparently behind-the-limb events (e.g. Datlowe, 1975) on the other.

scholarly journals Nanomechanics of few-layer materials: do individual layers slide upon folding?

2020 ◽  
Vol 11 ◽  
pp. 1801-1808
Author(s):  
Ronaldo J C Batista ◽  
Rafael F Dias ◽  
Ana P M Barboza ◽  
Alan B de Oliveira ◽  
Taise M Manhabosco ◽  
...  
Keyword(s):  
2D Materials ◽  
Adhesion Energy ◽  
Flexural Properties ◽  
2D Systems ◽  
Number Of Layers ◽  
Graphene Flakes ◽  
Theoretical Predictions ◽  
Tip Enhanced Raman Spectroscopy ◽  
Good Agreement

Folds naturally appear on nanometrically thin materials, also called “2D materials”, after exfoliation, eventually creating folded edges across the resulting flakes. We investigate the adhesion and flexural properties of single-layered and multilayered 2D materials upon folding in the present work. This is accomplished by measuring and modeling mechanical properties of folded edges, which allows for the experimental determination of the bending stiffness (κ) of multilayered 2D materials as a function of the number of layers (n). In the case of talc, we obtain κ ∝ n 3 for n ≥ 5, indicating no interlayer sliding upon folding, at least in this thickness range. In contrast, tip-enhanced Raman spectroscopy measurements on edges in folded graphene flakes, 14 layers thick, show no significant strain. This indicates that layers in graphene flakes, up to 5 nm thick, can still slip to relieve stress, showing the richness of the effect in 2D systems. The obtained interlayer adhesion energy for graphene (0.25 N/m) and talc (0.62 N/m) is in good agreement with recent experimental results and theoretical predictions. The obtained value for the adhesion energy of graphene on a silicon substrate is also in agreement with previous results.

Explicit formulation for the axial collapse of a pipe during drilling

2010 ◽  
Vol 224 (8) ◽  
pp. 1547-1549
Author(s):  
A Almasi
Keyword(s):  
Closed Form ◽  
Plastic Hinge ◽  
Variable Length ◽  
Experimental Results ◽  
Displacement Curve ◽  
Explicit Formulation ◽  
Theoretical Predictions ◽  
Hinge Zone ◽  
Good Agreement

New closed-form expressions are introduced for ax-symmetric progressive axial collapse of pipes that use a plastic folding mechanism based on variable length of an active plastic hinge zone. A procedure for determination of a load—displacement curve of axial pipe collapse is presented. Theoretical predictions give a good agreement with the experimental results owing to the influence of presented new refinements.

Paper 31: Capsule-Pipeline Flow—A Theoretical Study

1969 ◽  
Vol 184 (7) ◽  
pp. 89-100
Author(s):  
V. K. Garg ◽  
G. F. Round
Keyword(s):  
Theoretical Study ◽  
Theoretical Solution ◽  
Experimental Results ◽  
Free Flow ◽  
Average Flow ◽  
Pipe System ◽  
Liquid Carrier ◽  
Pipeline Flow ◽  
Theoretical Predictions ◽  
Good Agreement

Theoretical predictions of the behaviour of various parameters governing the free flow of a single, very long, denser-than-liquid carrier, cylindrical capsule in a horizontal pipeline are reported in this paper. The study was carried out for average flow velocities of approximately 1–10 ft/s in pipes of diameters 4, 6, 12, and 24 in with diameter ratios varying from 0·9 to 0·99. While two liquid carriers—water and an oil ( μ = 10 cP and sp. gr. = 0·85)—were used, the eccentricity of the capsule-pipe system was fixed at 0·999. The theoretical solution was found to be in good agreement with the experimental results.

scholarly journals A Theoretical Study of Chemical Reactivity of Tartrazine Through DFT Reactivity Descriptors

2017 ◽  
Vol 58 (4) ◽  
Author(s):  
Luis Humberto Mendoza Huizar
Keyword(s):  
Free Radicals ◽  
Theoretical Study ◽  
Chemical Reactivity ◽  
Nucleophilic Attack ◽  
Initial Attack ◽  
Reactivity Descriptors ◽  
Pcm Model ◽  
Total Energies ◽  
Global And Local ◽  
Global Reactivity Descriptors

<p>In this work we have calculated global and local DFT reactivity descriptors for tartrazine at B3LYP/6-311++G (2d,2p) level. Global reactivity descriptors such as ionization energy, molecular hardness, electrophilicity, and total energies were calculated to evaluate the tartrazine reactivity in aqueous and gas conditions. Local reactivity was evaluated through the Fukui function. The influence of the solvent was taken into account with the PCM model. The results indicate that the solvation process modifies the reactivity descriptors values. From our results, it was found that an electrophilic attack allows a direct cleavage of the N=N bond. If a nucleophilic attack is considered as initial attack, it is necessary a second attack by free radicals or electrophiles to cleave the N=N bond. In the case of an initial attack by free radicals, tartrazine requires a subsequent nucleophilic attack to cleave the N=N bond.</p>

A Theoretical Study of Silanol Polymerization

1986 ◽  
Vol 73 ◽  
Author(s):  
Larry W. Burggraf ◽  
Larry P. Davis
Keyword(s):  
Complex Systems ◽  
Molecular Orbital ◽  
Anionic Polymerization ◽  
Theoretical Study ◽  
State Of The Art ◽  
Activation Barrier ◽  
Polymerization Process ◽  
Nucleophilic Attack ◽  
Semi Empirical ◽  
Coordinate Structures

ABSTRACTWe have applied state-of-the-art semi-empirical molecular orbital methods to a study of the anionic polymerization of silanols to form silica. In particular, we have considered nucleophilic attack on silanols and subsequent reactions of the products. Hydroxide addition proceeds without activation to form five-coordinate silicate anions. Five-coordinate structures can also be formed by oligomerization following the attack of hydroxide on neutral silanols to abstract a proton. These five-coordinate structures are predicted to play a key role as intermediates in the polymerization process. Water can be eliminated from these anions, but with a substantial activation barrier. The activation barrier appears to be lower for the larger, more complex systems. These predictions are consistent with a rapid pre-equilibrium to form dimer anions followed by the slower reaction to form higher oligomers.

Two-dimensional viscous gravity currents flowing over a deep porous medium

2001 ◽  
Vol 440 ◽  
pp. 359-380 ◽  
Author(s):  
JAMES M. ACTON ◽  
HERBERT E. HUPPERT ◽  
M. GRAE WORSTER
Keyword(s):  
Porous Medium ◽  
Numerical Solutions ◽  
Gravity Current ◽  
Constant Volume ◽  
Two Dimensional ◽  
Theoretical Predictions ◽  
Self Similar ◽  
Coefficient Of Viscosity ◽  
Good Agreement

The spreading of a two-dimensional, viscous gravity current propagating over and draining into a deep porous substrate is considered both theoretically and experimentally. We first determine analytically the rate of drainage of a one-dimensional layer of fluid into a porous bed and find that the theoretical predictions for the downward rate of migration of the fluid front are in excellent agreement with our laboratory experiments. The experiments suggest a rapid and simple technique for the determination of the permeability of a porous medium. We then combine the relationships for the drainage of liquid from the current through the underlying medium with a formalism for its forward motion driven by the pressure gradient arising from the slope of its free surface. For the situation in which the volume of fluid V fed to the current increases at a rate proportional to t3, where t is the time since its initiation, the shape of the current takes a self-similar form for all time and its length is proportional to t2. When the volume increases less rapidly, in particular for a constant volume, the front of the gravity current comes to rest in finite time as the effects of fluid drainage into the underlying porous medium become dominant. In this case, the runout length is independent of the coefficient of viscosity of the current, which sets the time scale of the motion. We present numerical solutions of the governing partial differential equations for the constant-volume case and find good agreement with our experimental data obtained from the flow of glycerine over a deep layer of spherical beads in air.

An Experimental and Theoretical Study of Transitional Turbulent Pulsatile Flow in a Channel

1976 ◽  
Vol 43 (4) ◽  
pp. 559-563 ◽  
Author(s):  
L. C. Thomas ◽  
J. Min
Keyword(s):  
Pulsatile Flow ◽  
Time Scale ◽  
Theoretical Study ◽  
Experimental Measurements ◽  
Surface Renewal ◽  
Theoretical Predictions ◽  
Good Agreement

Experimental measurements of the time scale τ(t) of the burst phenomenon are reported for laminar-transitional turbulent, fully developed, pulsatile flow in a channel. Theoretical predictions for τ(t) which are developed on the basis of a quasi-steady surface renewal formulation are shown to be in good agreement with the data.

Laminar Free Convection From a Downward-Projecting Fin

1968 ◽  
Vol 90 (1) ◽  
pp. 63-70 ◽  
Author(s):  
G. S. H. Lock ◽  
J. C. Gunn
Keyword(s):  
Boundary Layer ◽  
Free Convection ◽  
Prandtl Number ◽  
Experimental Program ◽  
Boundary Layer Problem ◽  
Theoretical Predictions ◽  
Theoretical Results ◽  
Good Agreement ◽  
Quiescent Fluid

A theoretical analysis of conduction through and free convection from a tapered, downward-projecting fin immersed in an isothermal quiescent fluid is presented. The problem is solved by assuming quasi-one-dimensional heat conduction in the fin and matching the solution to that of the convection system, which is treated as a boundary layer problem. For an infinite Prandtl number, solutions are derived which take the form of a power law temperature distribution along the fin. The effect of this power (n) on heat transfer, drag, and the corresponding boundary layer profiles is discussed. It is shown that n is independent of the fin profile and dependent on a single nondimensional group χ. The theoretical results for infinite Prandtl number are compared with corresponding results derived from previous work using a Prandtl number of unity. The effect of Prandtl number on the determination of n and consequently the fin effectiveness is found to be extremely small. The results of an experimental program are also presented. These consist of temperature profiles and the n — χ relation for different fin geometries and surrounding fluids. Comparison with the theoretical predictions reveals good agreement.

scholarly journals Theoretical Study of Reaction Between Nitrilimine and 1,4 Oxazine 2 Carboxylate by MP2 and DFT Methods

2018 ◽  
Vol 34 (6) ◽  
pp. 2992-2997
Author(s):  
H. El-Hadki ◽  
F. Hlimi ◽  
M. Salah ◽  
K. Marakchi ◽  
N. Komiha ◽  
...  
Keyword(s):  
Energy Surface ◽  
Theoretical Study ◽  
Basis Set ◽  
Dft Methods ◽  
Reactivity Indices ◽  
B3lyp Method ◽  
Transition Structures ◽  
Potential Energy Surface Calculation ◽  
Good Agreement ◽  
Surface Calculation

The regioselectivity of the reaction between phenyldiazen-1-ium-1-ylidene p-tolyl methanide and ethyl 4-benzoyl-4H-benzo [1,4]oxazine-2-carboxylate were studied by means of the DFT/B3LYP method coupled by the 6-31g(d) basis and MP2 in connection with 6-31G(d) and 6-31G+(d,p) basis set. The mechanism of this regioselectif reaction has performed by transition state optimization, evaluation of the potential energy surface, calculation of IRC and reactivity indices. Location and verification of minima and transition structures have been realized by using the Berny's algorithm. The process of formation of the two regioisomers is achieved through concerted and asynchronous mechanism. The results are in good agreement with the experimental data.

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