Related Concept Videos
01:14The Carbon Cycle
Carbon is the basis of all organic matter on Earth, and is recycled through the ecosystem in two primary processes: one in which carbon is exchanged among living organisms, and one in which carbon is cycled over long periods of time through fossilized organic remains, weathering of rocks, and volcanic activity. Human activities, including increased agricultural practices and the burning of fossil fuels, has greatly affected the balance of the natural carbon cycle.
02:38Structure and Nomenclature of Epoxides
Cyclic ethers are heterocyclic compounds with an oxygen atom in the ring along with carbon atoms. They are named depending on the number of carbon atoms present in their ring system. Cyclic ethers with a three-membered ring system are called “oxirane”, four-membered ring systems as “oxetane”, five-membered ring systems as “oxolane”, and six-membered ring systems as “oxane”. The cyclic structure of these rings imposes angle strain, and this strain is more in the ring having a smaller number of...
03:00Preparation of Epoxides
Overview
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
Epoxides result from alkene oxidation, which can be achieved by a) air, b) peroxy acids, c) hypochlorous acids, and d) halohydrin cyclization.
Epoxidation with Peroxy Acids
Epoxidation of alkenes via oxidation with peroxy acids involves the conversion of a carbon–carbon double bond to an epoxide using the oxidizing agent meta-chloroperoxybenzoic acid, commonly known as MCPBA. Since the O–O bond of peroxy acids is very weak, the addition of electrophilic oxygen of peroxy acids to...
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
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.
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
You might also read
Related Articles
Articles linked to this work by shared authors, journal, and citation graph.
Sort by
Same author
An Unusual Friedel-Crafts Reaction and Violation of the Markovnikov Rule in the Formation of an Adamantyl Arene.
The Journal of organic chemistry·2025
Same author
Discovering a uniform functional trade-off of the CBC-type 2,3-oxidosqualene cyclases and deciphering its chemical logic.
Science advances·2023
Same author
Computational studies on the sterol-like cyclization of a monodomain class II terpene cyclase.
Organic & biomolecular chemistry·2021
Related Experiment Video
Updated: Jul 6, 2026
09:17
Reductive Electropolymerization of a Vinyl-containing Poly-pyridyl Complex on Glassy Carbon and Fluorine-doped Tin Oxide Electrodes
Published on: January 30, 2015
Cycloheptatrienyl oxyallyl. An observable oxyallyl?
1Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37205, USA.
Journal of the American Chemical Society
|February 7, 2002
Summary
Density functional calculations reveal that substituted oxyallyls are more stable than their corresponding allene oxides. This stabilization varies, with some showing zwitterionic character and others diradical character, indicating adaptability.
More Related Videos
08:23Analyzing the Photo-oxidation of 2-propanol at Indoor Air Level Concentrations Using Field Asymmetric Ion Mobility Spectrometry
Published on: June 14, 2018
06:50O-cresol Concentration Online Measurement Based On Near Infrared Spectroscopy Via Partial Least Square Regression
Published on: November 8, 2019
Area of Science:
- Computational Chemistry
- Organic Chemistry
- Quantum Chemistry
Background:
- Allene oxides and oxyallyls are reactive intermediates in organic synthesis.
- Understanding their electronic structure is crucial for predicting reaction pathways.
- Previous studies on unsubstituted systems provide a baseline for comparison.
Purpose of the Study:
- To investigate the electronic structure of cyclopropylidene-, cyclopentylidene-, and tropyllideneallene oxides and their corresponding oxyallyls.
- To determine the reaction pathways and energy profiles for their interconversion.
- To probe the factors contributing to the stabilization of intermediate oxyallyls.
Main Methods:
- Density functional calculations were employed to model the molecular structures and reaction pathways.
- Energy calculations were performed to assess the relative stability of allene oxides, oxyallyls, and cyclopropanones.
- Analysis of electronic properties, including zwitterionic and diradical character, was conducted.
Main Results:
- All three substituted oxyallyls (10-12) were found to be stabilized relative to their parent allene oxides (7-9) and unsubstituted analogues.
- Stabilization mechanisms differed: zwitterionic character for oxyallyls 7 and 9, and diradical character for oxyallyl 8.
- Oxyallyl 12 is predicted to be a stable, observable intermediate in the absence of nucleophiles due to its lower calculated energy.
Conclusions:
- Substituted oxyallyls exhibit unique electronic properties and stabilization modes, adapting to their specific molecular environments.
- The electronic structure calculations provide valuable insights into the reactivity and stability of these important intermediates.
- Oxyallyl 12 represents a potentially isolable species, offering new avenues for synthetic exploration.