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

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.

The Azide-Allene Dipolar Cycloaddition: Is DFT Able to Predict Site- and Regio-Selectivity?

The site- and regio-selectivity of thermal, uncatalysed 1,3-dipolar cycloadditions between arylazides and mono- or tetra-substituted allenes with different electronic features have been investigated by both conceptual (reactivity indices) and computational (M08-HX, ωB97X-D, and B3LYP) DFT approaches. Both approaches show that these cycloadditions follow a nonpolar one-step mechanism. The experimental site- and regio-selectivity of arylazides towards methoxycarbonyl- and sulfonyl-allenes as well as tetramethyl- and tetrafluoro-allenes was calculated by DFT transition state calculations, achieving semiquantitative agreement to both previous and novel experimental findings. From the mechanistic standpoint, 1H-NMR evidence of a methylene-1,2,3-triazoline intermediate reinforces the reliability of the computational scheme.

Global reactivity Indices and Electron Localization Function calculations in the formation of boron nitride molecule

<p>The present study focuses on topological analysis of electron density population, structural and thermodynamic properties involved in the reaction between Boric Acid (H₃BO₃) and Ammonia (NH₃) in the synthesis of boron nitride (BN) used in cancer therapy medication and biomedical applications. The compound above has similar properties to carbonaceous materials. Indeed, it exists mainly in the two cubic and hexagonal forms, which are respectively identical to diamond and graphene surfaces. DFT/ M06-2X/aug-cc-pVDZ calculations were performed to determine global reactivity indices and the reaction process that operates via three transition states. ELF function has been achieved to describe the evolution of forming bonds along the IRC path.</p>

Predictive and Discriminative Power of Pressure Reactivity Indices in Traumatic Brain Injury

BACKGROUND Dysfunctional cerebral blood flow autoregulation plays a crucial role in the secondary damage after traumatic brain injury. The pressure reactivity index (PRx) can be used to monitor dynamic cerebral blood flow autoregulation indirectly. OBJECTIVE To test different versions of the long pressure reactivity index (LPRx), which is based on minute-by-minute data and calculated over extended time windows, and to study their predictive ability and examine whether “long” and “short” pressure reactivity indices could improve predictive power. METHODS PRx and 3 versions of the LPRx calculated over 20-, 60-, and 240-min time windows were assessed in relation to outcome at 6 mo in 855 patients with traumatic brain injury. Predictive power and discriminative ability of indices were evaluated using area under the operator curves and determination of critical thresholds. PRx and LPR indices were combined to evaluate whether LPR indices could improve outcome prediction by adding information about static components of autoregulation. RESULTS Correlation of each LPRx with the PRx decreased with increased time windows. LPR indices performed successively worse in their predictive and discriminative ability from 20-min to 240-min time frames. PRx had a significantly higher predictive ability compared to each LPRx. Combining LPRx and PRx did not lead to an improvement of predictive power compared to the PRx alone. CONCLUSION The critical threshold and predictive value of the PRx for unfavorable outcome and mortality have been confirmed in one of the largest so far published patient cohorts. LPRx performed significantly worse, and its discriminative and predictive abilities decreased with an increasing calculation window.

Profiling C4N radicals of astrophysical interest

ABSTRACT Based on a theoretical study of neutral, anion, and cation $\text{C}_{4}\text{N}$ chains, we suggest that this molecular species can still be observed in space. We analyse the dependence on n of the enthalpies of formation across the $\text{C}_{{{ n}}}\text{N}$ family and present possible chemical pathways of $\text{C}_{4}\text{N}$ production, which are not only exoenergetic but also barrierless. To further assist astronomical observation, we report estimates obtained at the CCSD(T) level of theory for astrophysically and astrochemically relevant properties. These include structural and chemical data, dipole moments, vibrational frequencies, rotational and centrifugal distortion constants as well as electron affinity, ionization potential, and related chemical reactivity indices. Our results indicate that anion chains can be easily detected in space than neutral chains; $\text{C}_{4}\text{N}^{-}$ possesses a smaller enthalpy of formation and a substantially larger dipole moment than $\text{C}_{4}\text{N}^{\text{0}}$.