Evgenii S Stoyanov
Novosibirsk Institute of Organic Chemistry, Russia
Title: Chloronium cations, R-Cl+-R, in condenced phases: Formation, thermal stability, and reactivity
Biography
Biography: Evgenii S Stoyanov
Abstract
Halonium ions (R2Hal+) are reactive intermediates in electrophilic chemistry and are effective methylating and protonating agents for a variety of compounds. Chloronium cations are most reactive and they were obtained as stable carborane salts, (R1-Cl+-R2)(CHB11Cl11ï€) with R1/R2 = CH3, CH2Cl, C2H5 and C3H7, at ambient conditions. We have studied: The thermal stability of the salts of chloronium ions at room and elevated temperature (up to 150ºC), interaction of the R1ï€Cl+ï€R2 cations (R1/R2 = CH3 or CH2Cl) of the solid salts with vapors of CH2Cl2 and CHCl3 and chloronium salts in dichloromethane solutions with accompanying reactions. The asymmetric cations are mostly unstable, for example, the ClСÐ2-Cl+-СÐ3 when kept at room temperature in one day it disproportionated into symmetric cations, (СÐ3)2Cl+ and (СÐ2Cl)2Cl+. At 100oC, disproportionation was completed within 5 minutes. The molecular fragment ClСÐ2ï€(Ð¥) of the compounds with Ð¥ = CHB11Cl11ï€, ï€Cl+ï€Ð¡Ð2Cl, or ï€Cl+ï€Ð¡Ð3, is involved in exchange reactions with CH2Cl2 and CHCl3, converting to CH3-(X) with formation of chloroform and CCl4, respectively. Chloronium cations can also decompose with the removal of the bridging Cl-atom as HCl, to form different carbocations. Hence, they can be a useful in many applications in the conventional chemical practice for special tasks.