平面与扭曲单片基的活性衰变途径
Frederick D Lewis1, Xiaobing Zuo
1Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA. lewis@chem.northwestern.edu
Journal of the American Chemical Society
|July 17, 2003
概括
甲基组改变了烯的几何结构,影响了它的光化学行为. 非平面结构导致蓝移过渡和更快的衰变路径,受C=C扭曲或系统间交叉的影响.
科学领域:
- 摄影化学的使用.
- 频谱学是一种光谱学.
- 计算化学计算化学
背景情况:
- styrene及其衍生物是具有多种应用的基本有机分子.
- 了解它们的光化学行为对于设计新材料和新工艺至关重要.
- 替代物对分子几何学和兴奋状态动态的影响是关键研究领域.
研究的目的:
- 为了研究甲基组替代对烯基本状态构造,光谱和光化学行为的影响.
- 为了将分子几何学的变化与激发状态属性和衰变途径的变化相关联.
- 阐明了替代烯中激发状态的衰变的机制.
主要方法:
- 实验光谱学 (UV-Vis,光) 探测电子转换和单子寿命.
- 取决于温度的单元生命周期的动态建模,以确定激活参数.
- 对基态形状和二面角的计算分析.
主要成果:
- 在alpha-vinyl或ortho-phenyl位置的甲基化增加了phenyl-vinyl二面角,导致平面性降低.
- 在双替代的烯中观察到高度非平面的几何形状,包括直角形状.
- 降低平面性导致pi,pi过渡的蓝色转移和更短的单元寿命.
- 动力分析显示,C=C扭曲是中度非平面烯 (<60度) 主导的衰变途径,而平面烯和高度非平面烯表现出不同的衰变机制.
结论:
- 分子几何学,特别是-乙烯二面角,显著决定了替代烯的光化学行为.
- 甲基替代提供了一种调整兴奋状态动态和衰变路径的手段.
- 这项研究阐明了烯衍生物中的构造,电子转换和兴奋状态失活机制之间的相互作用.
相关概念视频
Nonsense-mediated mRNA Decay
11.7K
The Upf proteins that carry out nonsense-mediated decay (NMD) are found in all eukaryotic organisms, including humans. Each protein has an individual role, but they need to work in collaboration. Upf1 is an ATP-dependent RNA helicase that unwinds the RNA helix. Because Upf1 can unwind any RNA, Upf2 and Upf3 are required to help Upf1 discriminate between nonsense and normal mRNAs.
Usually, Upf3 binds to an Exon Junction Complex (EJC) at mRNA splice sites. If a ribosome fully translates the mRNA,...
Usually, Upf3 binds to an Exon Junction Complex (EJC) at mRNA splice sites. If a ribosome fully translates the mRNA,...
11.7K
Nonsense-mediated mRNA Decay
3.3K
No description available
3.3K
Radioactive Decay and Radiometric Dating
37.0K
Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. The number of disintegrations per unit time is called the activity (A), which is directly proportional to the number of nuclei in the sample. The decay constant (λ) is an average probability of decay per nucleus in unit time.
37.0K
Interference and Decay
444
Forgetting is a complex cognitive phenomenon influenced by several factors, among which interference and decay are particularly prominent. These processes explain why individuals often struggle to retrieve specific information from memory, leading to lapses in recall that can be observed in everyday situations.
Interference occurs when competing memories hinder the retrieval of particular information. It can be classified into two types: proactive and retroactive interference. Proactive...
Interference occurs when competing memories hinder the retrieval of particular information. It can be classified into two types: proactive and retroactive interference. Proactive...
444
Crystal Field Theory - Tetrahedral and Square Planar Complexes
48.4K
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
48.4K
Angle of Twist: Problem Solving
764
An electric motor applies a torque of 700 N·m to an aluminum shaft, triggering a stable rotation. Two pulleys, B and C, are subjected to torques of 300 N·m and 400 N·m, respectively. The modulus of rigidity is provided as 25 GPa. With the knowledge of the length and diameter of each segment, the twist angle between the two pulleys can be computed. First, a section cut is made between pulleys B and C, and the cut cross-section is analyzed using a free-body diagram. Given that the torque...
764


