Vinylidene Carbene
Vinylidene Carbene - Related Videos
10:44
Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
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Cited by 5 •
2019
We present protocols for the isolation of stable heterocyclic carbenes. The synthesis of a cyclic (alkyl)(amino) carbene (CAAC) and an N-heterocyclic carbene (NHC) is demonstrated using filter cannulas and Schlenk technique. We furthermore present the synthesis of the related oxygen-sensitive, electron-rich mixed “Wanzlick dimer” and the reduced stable organic radical.
14:07
Preparation and Use of Carbonyl-decorated Carbenes in the Activation of White Phosphorus
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Cited by 2 •
2014
Here, we present a protocol for the synthesis of two carbonyl-decorated carbenes. The protocol makes these interesting compounds readily available to chemists of all skill levels. In addition to the synthesis of these two carbenes, their use in the activation of white phosphorus is also described.
12:19
Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
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Cited by 2 •
2018
We describe a protocol to photogenerate N-heterocyclic carbenes (NHCs) by UV irradiation of a 2-isopropylthioxanthone/imidazolium tetraphenylborate salt system. Methods to characterize the photoreleased NHC and elucidate the photochemical mechanism are proposed. The protocols for ring-opening metathesis photopolymerization in solution and miniemulsion illustrate the potential of this 2-component NHC photogenerating system.
19:58
Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions
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Cited by 1 •
2017
Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. The complexes were tested for catalytic activity in arylation and Suzuki-Miyaura reactions. For each reaction investigated, at least one of the four complexes successfully catalyzed the reaction.
11:05
Quadruply Metal-Metal Bonded Paddlewheels
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2023
Source: Corey Burns, Tamara M. Powers, Department of Chemistry, Texas A&M University Paddlewheel complexes are a class of compounds comprised of two metal ions (1st, 2nd, or 3rd row transition metals) held in proximity by four bridging ligands (most commonly formamidinates or carboxylates) (Figure 1). Varying the identity of the metal ion and the bridging ligand provides access to large families of paddlewheel complexes. The structure of paddlewheel complexes allows for metal-metal bonding,...
FAQs
The key mechanistic event is a 1,2-hydrogen shift, in which a hydrogen atom relocates within the carbon framework. This rearrangement converts the less stable vinylidene form into the more stable acetylene structure. Because the shift can occur rapidly, experiments and models must treat vinylidene carbene as a transient species whose observable lifetime depends strongly on its molecular environment and reaction conditions.
Formation and persistence depend on the surrounding molecular environment and the specific reaction conditions. These factors can determine whether vinylidene carbene remains detectable long enough for investigation or rapidly proceeds through hydrogen migration to acetylene. Consequently, changing the chemical setting can alter the balance between observing the intermediate itself and observing products or behavior associated with its rearrangement.
Potential-energy surfaces provide a framework for examining how molecular structures and reaction pathways change in energy. For vinylidene carbene, they help relate its transient existence to the lower stability of the acetylene tautomer and to the pathway for hydrogen migration. This perspective connects observed reactivity with models of chemical bonding and helps physical organic chemists analyze competing structural arrangements.
The two forms differ in both stability and reactivity. Vinylidene carbene represents a higher-energy arrangement that can undergo rapid internal hydrogen relocation, whereas acetylene is the more stable structure reached by that process. This contrast makes their relationship useful for studying tautomeric rearrangement, showing how a short-lived structure can still influence reaction mechanisms and the interpretation of chemical models.
Researchers investigate this intermediate through gas-phase reaction studies, photochemistry, spectroscopy, and computational modeling. These approaches address complementary questions: reaction experiments examine behavior under controlled conditions, photochemical methods help study processes involving light, spectroscopy probes transient chemical species, and calculations examine bonding and energy relationships. Together, they support analysis of formation, lifetime, rearrangement, and molecular structure.
Studies of vinylidene carbene provide a focused way to examine general principles of carbene reactivity, structural rearrangement, and chemical bonding. Its rapid conversion to acetylene makes it especially informative for connecting transient intermediates with reaction outcomes. In physical organic chemistry, the species also serves as a case for relating experimental observations to gas-phase behavior, photochemical investigations, and computational descriptions.