karbokationism

Karbokationism is a theoretical concept in organic chemistry that posits the existence of chemical species where a carbon atom carries a positive charge. These are more commonly known as carbocations. A carbocation is a molecule that contains a carbon atom bearing a positive formal charge and possessing only three bonds and no lone pairs. This results in a pyramidal or trigonal planar geometry around the positively charged carbon, which has an incomplete octet. Carbocations are typically highly reactive intermediates, meaning they are short-lived and are formed and consumed rapidly during the course of a chemical reaction.

The stability of carbocations is a crucial factor in understanding reaction mechanisms. Generally, carbocations are stabilized by electron-donating groups, which can delocalize the positive charge. Tertiary carbocations, where the positively charged carbon is bonded to three other carbon atoms, are more stable than secondary (bonded to two other carbons) and primary (bonded to one other carbon) carbocations. Allylic and benzylic carbocations are particularly stable due to resonance effects, where the positive charge can be spread over multiple atoms.

Karbokationism as a concept helps explain various organic reactions, including electrophilic addition to alkenes and alkynes, nucleophilic substitution reactions (like SN1), and rearrangements. The formation and subsequent reactions of carbocations are fundamental to predicting the products of many organic transformations. While the term "karbokationism" itself is not widely used in contemporary literature, the underlying principle of carbocation formation and behavior is a cornerstone of organic chemistry.