概括
臭氧通过与植物的反应产生有毒有机氧化物 (ROOH) 来损害植物. 这一发现有助于解释臭氧引起的森林减少,特别是在污染地区.
科学领域:
- 植物科学 植物科学
- 环境化学环境化学
- 生态生态学 生态生态学
背景情况:
- 臭氧 (O3) 是一种已知的植物毒素,破坏植物细胞完整性,光合作用和作物产量.
- 臭氧暴露与森林衰退有关,可能是通过与应力乙烯的相互作用.
- 由植物排放的生物源性挥发性有机化合物 (BVOCs),如异烯和单烯,与大气氧化剂发生反应.
研究的目的:
- 调查臭氧-基反应在植物损伤中的作用.
- 识别导致植物毒性的特定反应产物.
- 提出一种臭氧引起的森林衰退机制.
主要方法:
- 异二烯排放厂对臭氧的暴露.
- 对叶子组织进行有机氧化物 (ROOH) 存在的分析.
- 处理植物与在清洁空气中种植的对照植物的比较.
主要成果:
- 在暴露于臭氧的植物的叶子中检测到有机氧化物 (ROOH).
- 在保持在清洁空气中的控制工厂中没有ROOH.
- ROOH的存在表明植物叶子中的臭氧和生物基之间存在直接反应.
结论:
- 臭氧与生物基的反应产生有毒的ROOH,是臭氧植物毒性的关键机制.
- 在具有酸性沉积的环境中,这种机制可能会加剧,从而提高ROOH的稳定性.
- 该模型部分解释了红杉,挪威杉和银杉等树种中观察到的死亡回归,这些树种释放出反应性基.
相关概念视频
Oxidative 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.
Radical Autoxidation
The oxidation of an organic compound in the presence of air or oxygen is called autoxidation. For example, cumene reacts with oxygen to form hydroperoxide. Autoxidation involves initiation, propagation, and termination steps. Many organic compounds are susceptible to autoxidation—especially ethers in the presence of oxygen, which form hydroperoxides. Even though this reaction is slow, old ether bottles contain small amounts of peroxide, which leads to laboratory explosions during ether...
Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.
Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
Autoxidation of Ethers to Peroxides and Hydroperoxides
Ethers represent a class of chemical compounds that become more dangerous with prolonged storage because they tend to form explosive peroxides when standing in the air. Autoxidation is the spontaneous oxidation of a compound in air. In the presence of oxygen, ethers slowly oxidize to form hydroperoxides and dialkyl peroxides.
Radical Anti-Markovnikov Addition to Alkenes: Mechanism
The reaction of hydrogen bromide with alkenes in the presence of hydroperoxides or peroxides proceeds via anti-Markovnikov addition. The radical chain reaction comprises initiation, propagation, and termination steps.
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy radical...
The mechanism starts with chain initiation, which involves two steps. In the first chain initiation step, a weak peroxide bond is homolytically cleaved upon mild heating to form two alkoxy radicals. In the second initiation step, a hydrogen atom is abstracted by the alkoxy radical...


