Video Experimental Relacionado
Updated: May 29, 2026
09:48
Original Experimental Approach for Assessing Transport Fuel Stability
Published on: October 21, 2016
Predicción teórica sobre la estabilidad térmica del ozono cíclico y el túnel de oxígeno fuerte
1Department of Chemistry and Biochemistry, National Chung Cheng University, Chia-Yi, 621, Taiwan.
Journal of the American Chemical Society
|September 6, 2011
Resumen
El ozono cíclico se isomeriza rápidamente para abrir el ozono debido a efectos de túnel cuántico significativos, lo que explica su naturaleza esquiva. La identificación experimental del ozono cíclico, especialmente con el etiquetado isotópico, ahora puede ser factible.
Área de la Ciencia:
- Química teórica es la química teórica.
- La Dinámica Química es la Dinámica Química.
- La mecánica cuántica es la mecánica cuántica.
Sus antecedentes:
- El ozono cíclico es una molécula difícil de alcanzar.
- Su estabilidad está determinada por la isomerización al ozono normal (abierto).
- La identificación experimental no ha tenido éxito.
Objetivo del estudio:
- Investigar la reacción de isomerización del ozono cíclico con el ozono normal.
- Determinar la estabilidad del ozono cíclico en condiciones térmicas.
- Explicar los desafíos en la identificación experimental.
Principales métodos:
- Cálculo de la dinámica de doble nivel utilizando la teoría del estado de transición variacional.
- La inclusión de túneles multidimensionales.
- Datos de superficie de energía potencial de alto nivel de MRCISD+Q/aug-cc-pVQZ.
- Recorrido de reacción de bajo nivel de B3LYP/cc-pVTZ.
Principales resultados:
- Se observaron efectos de túnel significativos por debajo de 300 K (factor de ~200 a 300 K, >10^7 a 200 K).
- La isomerización es mucho más rápida de lo que se pensaba debido a los túneles y a la energía potencial que cruza la superficie.
- La vida media estimada del ozono cíclico es de ~10 s a 200 K y ~70 s por debajo de 100 K.
- Los efectos de isótopos cinéticos calculados (KIE) para la sustitución de (18) O son altos (hasta 10 a bajas temperaturas).
Conclusiones:
- El túnel cuántico juega un papel crucial en la rápida isomerización del ozono cíclico.
- La corta vida media calculada explica la dificultad en la detección experimental.
- Los altos KIEs sugieren que el etiquetado isotópico del ozono cíclico podría facilitar la identificación experimental.
Videos de Conceptos Relacionados
01:46Oxidative Cleavage of Alkenes: Ozonolysis
In ozonolysis, ozone is used to cleave a carbon–carbon double bond to form aldehydes and ketones, or carboxylic acids, depending on the work-up.
Ozone is a symmetrical bent molecule stabilized by a resonance structure.
Ozone is a symmetrical bent molecule stabilized by a resonance structure.
01:17Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
02:30Stability of Substituted Cyclohexanes
This lesson discusses the stability of substituted cyclohexanes with a focus on energies of various conformers and the effect of 1,3-diaxial interactions.
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
02:14Combustion Energy: A Measure of Stability in Alkanes and Cycloalkanes
The low reactivity in alkanes can be attributed to the non-polar nature of C–C and C–H σ bonds. Alkanes, therefore, were initially termed as “paraffins,” derived from the Latin words: parum, meaning “too little,” and affinis, meaning “affinity.”
Alkanes undergo combustion in the presence of excess oxygen and high-temperature conditions to give carbon dioxide and water. A combustion reaction is the energy source in natural gas, liquified petroleum gas (LPG), fuel oil, gasoline, diesel fuel, and...
Alkanes undergo combustion in the presence of excess oxygen and high-temperature conditions to give carbon dioxide and water. A combustion reaction is the energy source in natural gas, liquified petroleum gas (LPG), fuel oil, gasoline, diesel fuel, and...
02:55Temperature Dependence on Reaction Rate
The Collision Theory
Atoms, molecules, or ions must collide before they can react with each other. Atoms must be close together to form chemical bonds. This premise is the basis for a theory that explains many observations regarding chemical kinetics, including factors affecting reaction rates.
The collision theory is based on the postulates that (i) the reaction rate is proportional to the rate of reactant collisions, (ii) the reacting species collide in an orientation allowing contact between...
Atoms, molecules, or ions must collide before they can react with each other. Atoms must be close together to form chemical bonds. This premise is the basis for a theory that explains many observations regarding chemical kinetics, including factors affecting reaction rates.
The collision theory is based on the postulates that (i) the reaction rate is proportional to the rate of reactant collisions, (ii) the reacting species collide in an orientation allowing contact between...
03:40Hess's Law
There are two ways to determine the amount of heat involved in a chemical change: measure it experimentally, or calculate it from other experimentally determined enthalpy changes. Some reactions are difficult, if not impossible, to investigate and make accurate measurements for experimentally. And even when a reaction is not hard to perform or measure, it is convenient to be able to determine the heat involved in a reaction without having to perform an experiment.