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Distinguishing between both mechanisms requires consideration of inductive and mesomeric effects that could stabilize or destabilize a potential carbocation in the S N 1 pathway. Usage of hydrohalic acids takes advantage of the fact that these agents are able to protonate the ether oxygen atom and also provide a halide anion as a suitable ...
The strength of inductive effect is also dependent on the distance between the substituent group and the main group that react; the longer the distance, the weaker the effect. Inductive effects can be expressed quantitatively through the Hammett equation, which describes the relationship between reaction rates and equilibrium constants with ...
Among the simplest examples are the methenium CH + 3, methanium CH + 5, acylium ions RCO +, and vinyl C 2 H + 3 cations. [2] Until the early 1970s, carbocations were called carbonium ions. [3] In the present-day definition given by the IUPAC, a carbocation is any even-electron cation with significant partial positive charge on a carbon atom.
Adding the hydrogen ion to one carbon atom in the alkene creates a positive charge on the other carbon, forming a carbocation intermediate. The more substituted the carbocation, the more stable it is, due to induction and hyperconjugation. The major product of the addition reaction will be the one formed from the more stable intermediate.
The most widely practised example of this reaction is the ethylation of benzene. Approximately 24,700,000 tons were produced in 1999. [2] (After dehydrogenation and polymerization, the commodity plastic polystyrene is produced.) In this process, acids are used as catalyst to generate the incipient carbocation. Many other electrophilic reactions ...
A good example of a substitution reaction is halogenation. When chlorine gas (Cl 2) is irradiated, some of the molecules are split into two chlorine radicals (Cl•), whose free electrons are strongly nucleophilic. One of them breaks a C–H covalent bond in CH 4 and grabs the hydrogen atom to form the electrically neutral HCl.
It can also be seen as the -OH's lone pairs pushing an alkyl group off as seen in the asymmetrical pinacol example. The migration of alkyl groups in this reaction occurs in accordance with their usual migratory aptitude , i.e. phenyl carbocation > hydride > tertiary carbocation (if formed by migration) > secondary carbocation (if formed by ...
Electron-withdrawing groups exert an "inductive" or "electron-pulling" effect on covalent bonds. The strength of the electron-withdrawing group is inversely proportional to the pKa of the carboxylic acid. [2] The inductive effect is cumulative: trichloroacetic acid is 1000x stronger than chloroacetic acid.