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...
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Veröffentlicht in: | New journal of chemistry 2021-09, Vol.45 (36), p.16978-16988 |
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Hauptverfasser: | , , , |
Format: | Artikel |
Sprache: | eng |
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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. |
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ISSN: | 1144-0546 1369-9261 |
DOI: | 10.1039/d1nj02966e |