Spontaneous Transition of Alkyl Carbocations to Unsaturated Vinyl-Type Carbocations in Organic Solutions

Abstract

It was found that alkyl carbocations, when their salts are dissolved in common organochlorine solvents, decompose to unsaturated vinyl-type carbocations that are stabler in solutions. This is a convenient method for obtaining salts of vinyl cations and their solutions for further research.

A new type of C+⋯Hδ−(C=) bond in adducts of vinyl carbocations with alkenes

“…The next step is to add some more 1-chloropropane to obtain a viscous liquid phase in which alkane carbocations have been found to spontaneously convert to vinyl carbocations 20 . In our case, this is the transition C 3 H 7 + → C 3 H 5 + + H 2 .…”

“…Most likely, both the iso-C 4 H 7 + cation and isobutylene form from traces of chlorobutane isomers contained as impurities in the 1,4-dichlorobutane used to prepare vinyl cation salts. When the 1-chlorobutane impurity (and other isomers) reacts with acid H{Cl 11 }, a salt of the t-Bu + cation is produced 27 (a tertiary cationic center in carbocations arises from the well-known rearrangement of the initially formed primary carbocation into a stabler tertiary cation via rapid 1,2 shifts 28 ), which in the liquid phase converted into the vinyl iso-C 4 H 7 + cation within dozens of minutes 20 . The source of isobutylene may also be the admixture of t-Bu + cations because its formation is accompanied by the formation of the H 3 O + cation from traces of water molecules according to the equation.…”

“…It turned out that salts of vinyl cations with carborane counterions are stable at least up to 150 °C 15 – 18 . In solutions in common organochlorine solvents, they appear to be stabler than salts of alkyl carbocations and can be stored for a long time without decomposition under ambient conditions 20 . This state of affairs has opened up the possibility of studying the interaction of vinyl cations with nucleophile molecules in solutions in solvents common in chemical practice.…”

Interaction of Vinyl-Type Carbocations, C3H5+ and C4H7+ with Molecules of Water, Alcohols, and Acetone

“…With an increase in the concentration of the salt of cationic adduct R 2 C=C + H···H 2 O in solutions, the self-association of ion pairs increases (which is typical for salts of carbocations in solutions [ 29 ]). This enhances the contact interaction of H 2 O with the cation and promotes the transfer of a proton to a water molecule with the formation of H 3 O + and cationic adduct II:…”