Facilitated inversion complicates the stereodynamics of an S_N2 reaction at nitrogen center

Abstract

Multiple-inversion, the analogue of the double-inversion pathway recently revealed for SN2@C, is the key mechanism in SN2 at N center undermining stereospecificity.

Detailed quasiclassical dynamics of the F− + CH3Br reaction on an ab initio analytical potential energy surface

“…The Journal of Chemical Physics ARTICLE scitation.org/journal/jcp simulations using either the quasiclassical trajectory (QCT) or the time-dependent quantum method. [29][30][31][32][33][34][35][36][37][38][39] QCT computations on these PESs revealed a novel double-inversion mechanism, 40 front-side complex formation, 41,42 multiple-inversion pathway for N-centered S N 2 reactions, 34 and branching ratios for substitution and elimination (E2) processes, 35 as well as showed unprecedented agreement with experiments. 35,41,43 On the one hand, the analytical PES-based approach is more accurate and more efficient than direct dynamics.…”

“…[20][21][22][23][24][25][26][27][28] In 2013, we initiated an analytical potential energy surface (PES)based approach for S N 2 reactions by reporting a high-level fulldimensional ab initio analytical PES for the F − + CH 3 Cl system. 29 Later, we developed global analytical PESs for several ion-molecule reactions, such as F − + CH 3 F, 30 F − + CH 3 Br, 31 F − + CH 3 I, 32 OH − + CH 3 I, 33 F − + NH 2 Cl, 34 and F − + CH 3 CH 2 Cl. 35 These analytical PESs allow the use of higher-level electronic structure theory than direct dynamics and enable efficient dynamics…”

“…Recently, we developed a program system, called ROBOSURFER, 31 which automates the above procedure, enabling efficient PES developments. Since 2020, four of our S N 2 PESs (F − + CH 3 Br, OH − + CH 3 I, F − + NH 2 Cl, and F − + CH 3 CH 2 Cl) 31,[33][34][35] have been developed using ROBOSURFER besides the F/Cl + C 2 H 6 PESs 44,45 and several ongoing work. The F − + CH 3 Br reaction was used as a test system during the initial development of the ROBOSURFER program package.…”

A real space picture of the role of steric effects inSN2reactions

“…[10][11][12] The archetypal example involves a substitution reaction of halogen-like groups taking place over a carbon based electrophile, 6 though substitution reactions of electrophiles of different chemical nature have also been explored. [13][14][15][16] Indeed, the S N 2 reaction constitutes one of the basic kernels of classical organic chemistry and it has been widely studied both computationally [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] and experimentally. 9,[35][36][37][38] It is generally believed 4 that the feasibility of the bimolecular substitution reactions is determined by a combination of multiple factors, including the nature of the nucleophile and leaving groups, the skeleton of the electrophile and the solvent.…”

ManyHF: A pragmatic automated method of finding lower-energy Hartree–Fock solutions for potential energy surface development

“…Indeed, in many cases, the combination of an explicitly correlated coupled cluster calculation with single, double, and perturbative triple excitations [CCSD(T)-F12] 21,22 and at most a triple-zeta basis set is both computationally affordable and sufficiently accurate for PES development. [23][24][25][26] Corrections for basis set incompleteness, inner-shell correlation, and relativistic effects can be added in a straightforward manner, if needed, to yield efficient composite schemes. 24,26,27 In some cases, even deficiencies in CCSD(T) can be efficiently addressed via composite schemes that include Brueckner coupled-cluster calculations.…”