PROTON AND ALKALI METAL IONS ATTACHED TO ALKYLPEROXYL RADICALS:STRUCTURE AND STABILITY OF M+-CnH2n＋1O2(M＝H;Li;Na;K；n＝1-3）COMPLEXES

The structure and stability of the still experimentally unknown M+-CnH2n+1O2 (M = H, Li, Na, K; n = 1 ~ 3) complexes were theoretically investigated via density function theory at the B3LYP/6-311+G(3df,2p)//B3LYP/6-311G(d,p) level. The addition of alkali metal ions (Li, Na, and K) to CnH2n+1O2 are found to form only one stable structure, while proton transfer reactions with CnH2n+1O2 produce two isomers except for CH3CH2CH2O2. The optimized geometries and Mulliken population analysis indicate that the M+ (M = Li, Na, K)-CnH2n+1O2 complexes exist as ion-dipole molecules. Our prediction for the affinity energies of M+ to CnH2n+1O2 are 165.4, 178.0, 181.9 and 176.8 kcal/mol (H+); 34.3, 36.4, 37.5, and 38.4 kcal/mol (Li+); 24.4, 26.1, 26.9, and 27.5 kcal/mol (Na+); and 17.5, 19.2, 19.6, and 20.0 kcal/mol (K+), respectively. Thus, these values suggest that CnH2n+1O2-M+ (M = H, Li, Na, K) complexes could be detected as stable species in gas phase at room temperature by ion attachment mass spectrometry.