Gas-Phase Elimination Reaction of Ethyl (5-cyanomethyl-1,3,4-thiadiazol-2-yl)carbamate: A Computational Study
The gas‐phase elimination reaction of ethyl (5‐cyanomethyl‐1,3,4‐thiadiazol‐2‐yl)carbamate has been studied computationally at the MP2/6–31++G(2d,p) level of theory. The values of the activation parameters and rate constants for the thermal decomposition were evaluated over a temperature range from...
- Autores:
- Tipo de recurso:
- Fecha de publicación:
- 2015
- Institución:
- Universidad de Medellín
- Repositorio:
- Repositorio UDEM
- Idioma:
- eng
- OAI Identifier:
- oai:repository.udem.edu.co:11407/2285
- Acceso en línea:
- http://hdl.handle.net/11407/2285
- Palabra clave:
- Carbon
Carbon dioxide
Carboxylation
Chemical reactions
Computation theory
Ethylene
Gases
Radioactivity logging
Rate constants
Reaction kinetics
Temperature distribution
1 ,3 ,4-thiadiazole
Activation parameter
Arrhenius expressions
Computational studies
Cyclic transitions
Gas-phase elimination
Intrinsic reaction coordinate calculations
Temperature dependence
Thermal logging
- Rights
- restrictedAccess
- License
- http://purl.org/coar/access_right/c_16ec
| Summary: | The gas‐phase elimination reaction of ethyl (5‐cyanomethyl‐1,3,4‐thiadiazol‐2‐yl)carbamate has been studied computationally at the MP2/6–31++G(2d,p) level of theory. The values of the activation parameters and rate constants for the thermal decomposition were evaluated over a temperature range from 405.0 to 458.0 K. The temperature dependence of the rate constants was used to deduce the modified Arrhenius expression: log k405–458 K = (9.01 ± 0.49) + (1.32 ± 0.16) log T – (6946 ± 30) 1/T, which is in good agreement with the expression obtained from experimental data. The results confirm that the mechanism is a cis‐concerted elimination that occurs in two steps: The first one corresponds to the formation of ethylene and an intermediate, 5‐(cyanomethyl)‐1,3,4‐thiadiazol‐2‐yl‐carbamic acid, via a six‐membered cyclic transition state, and the second one is the decarboxylation of this intermediate via a four‐membered cyclic transition step, leading to carbon dioxide and the corresponding 1,3,4‐thiadiazole derivative (5‐amino‐1,3,4‐thiadiazole‐2‐acetonitrile). The connectivity of transition states with their respective minima was verified through intrinsic reaction coordinate calculations, and the progress of the reaction was followed by means of Wiberg bond indices, resulting that both transition states have an “early” character, nearer to the reactants than to the products. |
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