Video Experimental Relacionado
Updated: Jul 11, 2026
07:36
Versatile CO2 Transformations into Complex Products: A One-pot Two-step Strategy
Published on: November 9, 2019
Síntesis, aislamiento y equilibrio de 1,9- y 7,8-C70H2
Science (New York, N.Y.)
|April 15, 1994
Resumen
La energía libre relativa de los isómeros C(70) H(2) se midió utilizando el equilibrio catalizado por platino. El isómero 1,9 es más estable, con una diferencia de energía libre de 1,4 kcal/mol, coincidiendo con los cálculos ab initio.
Área de la Ciencia:
- La química de los fullerenos es muy compleja.
- Química orgánica es la química orgánica.
- Química computacional es la química computacional.
Sus antecedentes:
- Los fullerenos, como el C70, son alótropos de carbono con propiedades electrónicas únicas.
- Los derivados de hidrocarburos de los fullerenos se sintetizan para explorar su comportamiento químico.
- Comprender la estabilidad de los isómeros es crucial para las aplicaciones de fullereno.
Objetivo del estudio:
- Para medir la energía libre relativa de 1,9- y 7,8-C(70) H(2) isómeros.
- Para comparar resultados experimentales con cálculos teóricos.
- Para validar métodos computacionales para estudios de derivados de fullereno.
Principales métodos:
- Síntesis de los isómeros C(70) H(2) a través de la hidroboración de C(70).
- Equilibrio catalizado por platino de los isómeros 1,9- y 7,8-C(70) H(2).
- Medición de la energía libre relativa a 295 K.
Principales resultados:
- Se encontró que el isómero 1,9-C(70) H(2) era más estable que el 7,8-isómero.
- Se determinó que la diferencia de energía libre relativa experimental era de 1,4 ± 0,2 kcal/mol.
- Los cálculos de Ab initio HF/6-31 G(*) predijeron con precisión esta diferencia de energía (1.3 kcal/mol).
Conclusiones:
- Las mediciones experimentales confirman la mayor estabilidad del isómero 1,9-C(70) H(2).
- Los cálculos ab initio son confiables para predecir las energéticas derivadas del fullereno.
- Los métodos semiempíricos mostraron un acuerdo pobre, lo que indica limitaciones para estos sistemas.
Videos de Conceptos Relacionados
![[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12422.jpg&w=3840&q=75)
01:21[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement
The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
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...
02:33Stereoisomerism of Cyclic Compounds
In this lesson, we delve into the role of ring conformation and its stability, which determines the spatial arrangement and, consequently, the molecular symmetry and stereoisomerism of cyclic compounds. 1,2-Dimethylcyclohexane is used as a case study to evaluate the possible number of stereoisomers. Here, given the multiple (n = 2) chiral centers, there are 2n = 4 possible configurations that lack a plane of symmetry, as the ring skeleton exists in a non-planar chair conformation. In addition,...
02:02Chair Conformation of Cyclohexane
The chair conformation is the most stable form of cyclohexane due to the absence of angle and torsional strain. The absence of angle strain is a result of cyclohexane’s bond angle being very close to the ideal tetrahedral bond angle of 109.5° in its chair conformer. Similarly, the torsional strain is also absent owing to the perfectly staggered arrangement of bonds.
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
02:37Disubstituted Cyclohexanes: cis-trans Isomerism
Depending upon the different spatial orientation of the substituents, the disubstituted cycloalkanes exhibit two types of stereoisomers. The cis isomers have the substituents on the same side of the ring, whereas the trans isomers have the substituents on the opposite sides. These stereoisomers exhibit different physical properties and cannot be interconverted without breaking the carbon-carbon bonds.
In cyclohexane, the substituents can occupy different positions generating distinct isomers.
In cyclohexane, the substituents can occupy different positions generating distinct isomers.
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...