A comparison of methods for measuring relative radical stabilities of carbon-centred radicals

Abstract

This article discusses and compares various methods for defining and measuring radical stability, including the familiar radical stabilization energy (RSE), along with some lesser-known alternatives based on corrected carbon-carbon bond energies, and more direct measures of the extent of radical delocalisation. As part of this work, a large set of R-H, R-CH3, R-Cl and R-R BDEs (R = CH2X, CH(CH3)X, C(CH3) 2X and X = H, BH2, CH3, NH2, OH, F, SiH3, PH2, SH, Cl, Br, N(CH3)2, NHCH3, NHCHO, NHCOCH3, NO2, OCF3, OCH2CH3, OCH3, OCHO, OCOCH3, Si(CH3)3, P(CH3)2, SC(CH 3)2CN, SCH2COOCH3, SCH 2COOCH3, SCH2Ph, SCH3, SO 2CH3, S(O)CH3, Ph, C6H 4-pCN, C6H4-pNO2, C 6H4-pOCH3, C6H4-pOH, CF2CF3, CF2H, CF3, CCl2H, CCl3, CH2Cl, CH2F, CH2OH, CH 2Ph, cyclo-CH(CH2)2, CH2CHCH 2, CH2CH3, CH(CH3)2, C(CH3)3, CCH, CHCH2, CHCHCH3, CHO, CN, COCH3, CON(CH2CH3)2, CONH 2, CONHCH3, COOC(CH3)3, COOCH 2CH3, COOCH3, COOH, COPh), and associated radical stability values are calculated using the high-level ab initio molecular orbital theory method G3(MP2)-RAD. These are used to compare the alternative radical stability schemes and illustrate principal structure-reactivity trends. Show more