Insights into the kinetics and molecular mechanism of the Newman-Kwart rearrangement

The kinetic and thermodynamic parameters of Newman-Kwart rearrangement (NKR) of N , N -dimethyl O -arylthiocarbamate into N , N -dimethyl S -arylcarbamate have been evaluated using the Minnesota density functionals (M06-2X and MN15-L) conjugated with the aug-cc-pVTZ basis set and compared with bench...

Ausführliche Beschreibung

Gespeichert in:
Bibliographische Detailangaben
Veröffentlicht in:New journal of chemistry 2021-09, Vol.45 (36), p.16978-16988
Hauptverfasser: Sanie, Mitra, Zahedi, Ehsan, Ghorbani, Seyed Hosein, Seif, Ahmad
Format: Artikel
Sprache:eng
Schlagworte:
Online-Zugang:Volltext
Tags: Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
Beschreibung
Zusammenfassung:The kinetic and thermodynamic parameters of Newman-Kwart rearrangement (NKR) of N , N -dimethyl O -arylthiocarbamate into N , N -dimethyl S -arylcarbamate have been evaluated using the Minnesota density functionals (M06-2X and MN15-L) conjugated with the aug-cc-pVTZ basis set and compared with benchmark CBS-QB3 results. Environments of diphenyl ether and o -dichlorobenzene solvents were simulated implicitly by means of the SMD solvation model. The employed temperatures 505 K in diphenyl ether and 413 K in o -dichlorobenzene were more than two times larger than the cross-over temperature, implying shallow tunneling. The evaluated kinetic and energetic parameters using the CBS-QB3 method were in excellent agreement with the experimentally supplied data. The rate constant in diphenyl ether can be expressed by original and modified Arrhenius equations k CBS-QB3/Eckart 404-606K = 6.46 × 10 12  exp(−19944.6/ T ) and k CBS-QB3/Eckart 404-606K = 1.26 × 10 10 T 0.865  exp(−19516.8/ T ), respectively. Topological evolution along the reaction has been studied at the B3LYP/CBSB7 level in an o -dichlorobenzene environment using the quantum chemical topology tools. The electron density in C-O and C-S bonds was strongly polarized toward the oxygen and sulfur atoms, respectively, in such a manner that carbonyl and thiocarbonyl bonds cannot be described by Lewis's bonding model. Topological and chemical events along the reaction may be described as: (i) formation of a new monosynaptic basin V(C 1 ) associated with the pseudoradical center on the ipso-carbon atom by means of Fold (F † ) type catastrophe, and (ii) transformation of disynaptic basin V(C 1 ,O) into the monosynaptic basin V 3 (O) associated with the heterolytic rupture of the C 1 -O bond by means of elliptic umbilic (E) catastrophe, and merging of V 3 (S) and V(C 1 ) monosynaptic basins into the new disynaptic basin of V(C 1 ,S) associated with the formation of the C 1 -S bond via usual sharing of the non-bonding electron densities (C 1 -to-S coupling of pseudoradical centers) by means of a Cusp (C) type catastrophe. The detailed picture of chemical events along the NKR reveals that the electron density flow does not take place in a cyclic and one-way curve, suggesting a non-concerted mechanism. Kinetics and molecular mechanism of the Newman-Kwart rearrangement (NKR) of N , N -dimethyl O -arylthiocarbamate into N , N -dimethyl S -arylcarbamate have been investigated theoretically.
ISSN:1144-0546
1369-9261
DOI:10.1039/d1nj02966e