Information om | Engelska ordet CARBOCATIONS

Exempel på hur man kan använda CARBOCATIONS i en mening

• The same is true when an alkene reacts with water in an addition reaction to form an alcohol which involve formation of carbocations.
• Carbonium ions, as originally defined by Olah, are characterized by a three-center two-electron delocalized bonding scheme and are essentially synonymous with so-called 'non-classical carbocations', which are carbocations that contain bridging C–C or C–H σ-bonds.
• Brown of Purdue over the existence of so-called "nonclassical" carbocations – such as the norbornyl cation, which can be depicted as cationic character delocalized over several bonds.
• Reactive intermediates based on carbon are radicals, carbenes, carbocations, carbanions, arynes, and carbynes.
• Trimethylsilyl, tert-butyl, and isopropyl groups can form stable carbocations, hence are ipso directing groups.
• Free radical rearrangement reactions are rare compared to rearrangements involving carbocations and restricted to aryl migrations.
• This conjugate Brønsted–Lewis superacid system was developed in the 1960s by Ronald Gillespie and his team at McMaster University, and has been used by George Olah to stabilise carbocations and hypercoordinated carbonium ions in liquid media.
• Hyperconjugation can be used to rationalize a variety of chemical phenomena, including the anomeric effect, the gauche effect, the rotational barrier of ethane, the beta-silicon effect, the vibrational frequency of exocyclic carbonyl groups, and the relative stability of substituted carbocations and substituted carbon centred radicals, and the thermodynamic Zaitsev's rule for alkene stability.
• Carbenium ions are a major subset of carbocations, which is a general term for diamagnetic carbon-based cations.
• The term synartetic ion was also invoked to describe delocalized bonding in stable carbocations before the term non-classical ion was in widespread use.
• Another example of RSP can be found in the selectivity of the reaction of certain carbocations with azides and water.
• Silyl enol ethers are neutral, mild nucleophiles (milder than enamines) that react with good electrophiles such as aldehydes (with Lewis acid catalysis) and carbocations.
• Most of the intermediates involved in delignification in sulfite pulping are resonance-stabilized carbocations formed either by protonation of carbon-carbon double bonds or acidic cleavage of ether bonds which connect many of the constituents of lignin.
• An important side product in fluorinations of enolizable ketones is the corresponding vinyl fluoride, which results from deprotonation of intermediate fluoro carbocations.
• Alternatively, carbocations may be trapped intramolecularly by the carbonyl oxygen to form dihydrofurans after β-elimination.
• Cyclopropyl groups are good donors in hyperconjugation resulting in a considerable stabilization of carbocations.
• His major scientific contributions include the creation of the first silyl cation (the silicon analogue of the carbocation), elucidation of the mechanism of beta-silyl stabilization of carbocations, discovery of inductive enhancement of solvolytic participation, creation of new methods of conformational analysis by nuclear magnetic resonance spectroscopy (the R value), understanding the conformations of cyclic molecules containing heteroatoms, and development of chemical methods to examine archaeological materials.
• The classical model, (b) describes a rapid equilibration between three distinct carbocations rather than delocalization.
• Limitations of this approach are unpredictable carbocation rearrangement in more complexly branched alkanes, the incompatibility of carbocations with many nucleophilic functional groups, and the risk of cation quenching by elimination pathways.

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