SN2 Reactions with an Ambident Nucleophile A Benchmark Ab Initio Study of the CN-+ CH3Y [Y = F, Cl, Br, and I] Systems /
We characterize the Walden-inversion, front-side attack, and double-inversion SN2 pathways leading to Y- + CH3CN/CH3NC and the product channels of proton abstraction (HCN/HNC + CH2Y-), hydride-ion substitution (H- + YH2CCN/YH2CNC), halogen abstraction (YCN-/YNC- + CH3 and YCN/YNC + CH3-), and YHCN-/...
Elmentve itt :
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| Dokumentumtípus: | Cikk |
| Megjelent: |
2022
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| Sorozat: | JOURNAL OF PHYSICAL CHEMISTRY A
126 No. 6 |
| Tárgyszavak: | |
| doi: | 10.1021/acs.jpca.1c10448 |
| mtmt: | 32699789 |
| Online Access: | http://publicatio.bibl.u-szeged.hu/24760 |
| Tartalmi kivonat: | We characterize the Walden-inversion, front-side attack, and double-inversion SN2 pathways leading to Y- + CH3CN/CH3NC and the product channels of proton abstraction (HCN/HNC + CH2Y-), hydride-ion substitution (H- + YH2CCN/YH2CNC), halogen abstraction (YCN-/YNC- + CH3 and YCN/YNC + CH3-), and YHCN-/YHNC- complex formation (YHCN-/YHNC- + 1CH2) of the CN- + CH3Y [Y = F, Cl, Br, and I] reactions. Benchmark structures and frequencies are computed at the CCSD(T)-F12b/aug-cc-pVTZ level of theory, and a composite approach is employed to obtain relative energies with sub-chemical accuracy considering (a) basis-set effects up to aug-cc-pVQZ, (b) post-CCSD(T) correlation up to CCSDT(Q), (c) core correlation, (d) relativistic effects, and (e) zero-point energy corrections. C-C bond formation is both thermodynamically and kinetically more preferred than N-C bond formation, though the kinetic preference is less significant. Walden inversion proceeds via low or submerged barriers (12.1/17.9(F), 0.0/4.3(Cl), -3.9/0.1(Br), and -5.8/-1.8(I) kcal/mol for C-C/N-C bond formation), front-side attack and double inversion have high barriers (30-64 kcal/mol), the latter is the lower-energy retention pathway, and the non-SN2 electronic ground-state product channels are endothermic (ΔH0 = 31-92 kcal/mol). © 2022 The Authors. Published by American Chemical Society. |
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| Terjedelem/Fizikai jellemzők: | 889-900 |
| ISSN: | 1089-5639 |