Related Experiment Video
Updated: Oct 26, 2025
06:46
Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
7.6K
A structure activity relationship for ring closure reactions in unsaturated alkylperoxy radicals
1Institute for Energy and Climate Research: IEK-8: Troposphere, Forschungszentrum Jülich GmbH, Jülich, Germany. L.Vereecken@fz-juelich.de.
Physical Chemistry Chemical Physics : PCCP
|July 27, 2021
Summary
Ring closure reactions in terpenoid oxidation are fast, often exceeding 1 s-1 at room temperature. These reactions are competitive in low-NOx environments, promoting autoxidation via ring closure.
Area of Science:
- Atmospheric Chemistry
- Organic Chemistry
- Chemical Kinetics
Background:
- Terpenoids are volatile organic compounds crucial to atmospheric chemistry.
- Atmospheric oxidation of terpenoids produces unsaturated peroxy radicals.
- These radicals can undergo ring closure reactions.
Purpose of the Study:
- To investigate the rate and significance of ring closure reactions in terpenoid oxidation.
- To explore the structure-activity relationship for ring closure in unsaturated peroxy radicals.
- To assess the role of these reactions in atmospheric autoxidation.
Main Methods:
- Quantum chemical calculations.
- Theoretical kinetic studies.
- Structure-activity relationship (SAR) analysis.
Main Results:
- Ring closure reactions are comparatively fast, often exceeding 1 s-1 at room temperature.
- These reactions are significant in low-NOx atmospheric conditions.
- H-migration in resulting cycloperoxide radicals is generally slow and not competitive with decomposition.
Conclusions:
- Ring closure is an important atmospheric reaction pathway for terpenoids.
- This process can facilitate continued autoxidation.
- The impact of ring closure is highly dependent on the terpenoid's molecular structure.
Related Concept Videos
02:24Acid-Catalyzed Ring-Opening of Epoxides
7.9K
Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...
7.9K
02:26Base-Catalyzed Ring-Opening of Epoxides
9.1K
Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...
9.1K
01:17Radical Anti-Markovnikov Addition to Alkenes: Mechanism
4.1K
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...
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...
4.1K
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
6.3K
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.
6.3K
01:11ortho–para-Directing Activators: –CH3, –OH, –NH2, –OCH3
6.7K
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
6.7K
01:25Radical Anti-Markovnikov Addition to Alkenes: Overview
3.7K
The addition of hydrogen bromide to alkenes in the presence of hydroperoxides or peroxides proceeds via an anti-Markovnikov pathway and yields alkyl bromides.
3.7K