Just How Twisted Can a Carbocation Rearrangement Get?Most students of Organic Chemistry are introduced to the carbocation rearrangement when learning the SN1 and E1 processes, as this is their first exposure to carbocations. It’s common to see a 1,2-alkyl shift or a 1,2-hydride shift. Sometimes, depending upon the level of challenge presented by the professor, there will be tandem 1,2-hydride and 1,2-alkyl shifts (Scheme I).
Markovnikov RuleWhen it comes to studying the reactivity of alkenes and alkynes with various reagents, nothing leads to more confusion than the Markovnikov Rule. Proposed in 1870 to explain a limited finite set of results, the rule persists in Organic Chemistry texts to this day. The source of confusion is not the logic of the rule, but rather the rule itself, as it is used in austerely limited form by most undergraduates to memorize the outcome of electrophilic addition reactions to alkenes and alkynes.
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The learning of acid-base theory in Organic Chemistry appears relatively simple at first because illustrative examples resemble those familiar from general chemistry. There are three fundamental definitions of acids and bases. An Arrhenius acid is something that increases the hydronium ion concentration in water, and a base increases the hydroxide ion concentration in water. A Lowry-Brønsted acid is a proton donor, and a base is a proton acceptor. Things become a bit different with the introduction of Lewis acids, electron pair acceptors, and Lewis bases, electron pair donors. It’s different because this is Organic Chemistry, and it’s the science of pushing electrons, not protons. Acid-base theory in Organic Chemistry can be unusual.