Evgenii S Stoyanov
Novosibirsk Institute of Organic Chemistry, Russia
Evgenii S Stoyanov has received his PhD degree from Vernadsky Institute of Geochemistry and Analytical Chemistry (Academy of Sciences of USSR), Moscow, Russia, and the Doctor of Science degree in Chemistry in 1991 from Mendeleyev University of Chemical Technology, Russia. Presently, he is a Leading Researcher at the Institute of Organic Chemistry (Siberian Branch of Russian Academy of Sciences), Novosibirsk, Russia, and leading the study of carbocations by using the solid super-acids. He has published 139 papers in reputed journals.
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)(CHB11Cl11) 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 R1Cl+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 ClСН2-Cl+-СН3 when kept at room temperature in one day it disproportionated into symmetric cations, (СН3)2Cl+ and (СН2Cl)2Cl+. At 100oC, disproportionation was completed within 5 minutes. The molecular fragment ClСН2(Х) of the compounds with Х = CHB11Cl11, Cl+СН2Cl, or Cl+СН3, 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.