The alkylethynyl radicals, CCCnH2n + 1 (n = 1−4), and their anions

Alkyl derivatives of the ethynyl radical (C2H) have been studied using density functional theory (DFT) with DZP++ basis sets. Adiabatic electron affinities (EAad) and ZPVE-corrected electron affinities for the alkylethynyl series CCCnH2n + 1 (n = 1-4) have been computed using six different DFT functionals, i.e., BHLYP, BLYP, B3LYP, BP86, BPW91 and B3PW91. These methods have been carefully calibrated for the prediction of electron affinities [J.C. Rienstra-Kiracofe, G.S. Tschumper, H.F. Schaefer, S. Nandi, G.B. Ellison, Chem. Rev. 102 (2002) 231]. The electron affinity of C2H (2.969 ± 0.006 eV) has been compared with that of the alkylethynyl series with an attempt to determine the effect of the alkyl chain length on the electron affinities of the acetylenic species. The predicted electron affinities are 2.70 eV (C2CH3, experiment = 2.718 ± 0.008 eV), 2.74 eV (C2C2H5), 2.75 eV (C2n-C3H7), and 2.75 eV (C2n-C4H9).