Ab initio quantum mechanical calculation of the reaction probability for the reaction

Abstract

PostprintThis is the accepted version of a paper published in Chemical Physics. This paper has been peerreviewed but does not include the final publisher proof-corrections or journal pagination.Citation for the original published paper (version of record):Farahani, P., Lundberg, M., Karlsson, H O. (2013) Ab initio quantum mechanical calculation of the reaction probability for the Cl-+ PH2Cl -> ClPH2 + Cl-reaction. AbstractThe S N 2 substitution reactions at phosphorus play a key role in organic and biological processes.Quantum molecular dynamics simulations have been performed to study the prototype reaction Cl − +P H 2 Cl → ClP H 2 +Cl − , using one and two-dimensional models. A potential energy surface, showing an energy well for a transition complex, was generated using ab initio electronic structure calculations. The one-dimensional model is essentially reflection free, whereas the more realistic two-dimensional model displays involved resonance structures in the reaction probability. The reaction rate is almost two orders of magnitude smaller for the two-dimensional compared to the one-dimensional model. Energetic errors in the potential energy surface is estimated to affect the rate by only a factor of two. This shows that for these types of reactions it is more important to increase the dimensionality of the modeling than to increase the accuracy of the electronic structure calculation.

Theoretical study of a derivative of chlorophosphine with aliphatic and aromatic Grignard reagents: SN2@P or the novel SN2@Cl followed by SN2@C?

“…, of the TSs of the S N 2@P-b, S N 2@P-f, S N 2@Cl and S N 2@C-f pathways Full optimisation with no symmetry constraints was performed using the B3LYP [43][44][45] hybrid functional and the 6-31++G(d,p) basis set in the gas phase. We selected this method based on previous reports involving S N 2@P. 20,33,[46][47][48] The stationary points were characterised by frequency computations to verify that the TSs have only one imaginary frequency 49 and these were checked by intrinsic reaction coordinate (IRC) computations. The same computational method was employed based on the polarisable continuum model (PCM) 50 to perform bulk solvation with THF by incorporating BH 3 in the reaction system to mimic the experiment conditions.…”

“…Full optimisation with no symmetry constraints was performed using the B3LYP 43–45 hybrid functional and the 6-31++G(d,p) basis set in the gas phase. We selected this method based on previous reports involving S N 2@P. 20,33,46–48 The stationary points were characterised by frequency computations to verify that the TSs have only one imaginary frequency 49 and these were checked by intrinsic reaction coordinate (IRC) computations.…”

“…The bent Cl-P-C bond angle of the S N 2@P-b pathways is contrary to the typical near-linear TSs which are reported for anionic S N 2-b reactions. 14,33 This reects the effect of the presence of the countercation Mg 2+ . The small relative Gibbs free energy barriers (DDG s ) between the TSs of S N 2@P-b and S N 2@P-f pathways do not explain the drs (98 : 2 and 1 : 99 for the P-inverted and P-retained organophosphorus products, respectively) obtained in the experiment.…”

Theoretical Study of a Derivative of Chlorophosphine with Aliphatic and Aromatic Grignard Reagents: SN2@P or the Novel SN2@Cl Followed by SN2@C?

“…The bent Cl-P-C bond angle of the SN2@P-b pathways is contrary to the typical near-linear TSs which are reported for anionic SN2-b reactions. 14,37 This reflects the effect of the presence of the countercation Mg 2+ . The small relative Gibbs free energy barriers (ΔΔG ≠ ) between the TSs of SN2@P-b and SN2@Pf pathways do not explain the drs (98:2 and 1:99 for the P-inverted and P-retained organophosphorus products, respectively) obtained in the experiment.…”

“…Full optimisation with no symmetry constraints was performed using the B3LYP [32][33][34] hybrid functional and the 6-31++G(d,p) basis set in the gas phase. We selected this method based on previous reports involving SN2@P. 20,[35][36][37][38] The stationary points were characterised by frequency computations to verify that the TSs have only one imaginary frequency 39 and these were checked by intrinsic reaction coordinate (IRC) computations.…”