Substituent effect on electron affinity, gas-phase basicity, and structure of monosubstituted propynyl radicals and their anions: a theoretical study.
The substituent effect of electron-withdrawing groups on electron affinity and gas-phase basicity has been investigated for substituted propynl radicals and their corresponding anions. It is shown that when a hydrogen of the alpha-CH(3) group in the propynyl system is substituted by an electron-withdrawing substituent, electron affinity increases, whereas gas-phase basicity decreases. These results can be explained in terms of the natural atomic charge of the terminal acetylene carbon of the systems. The calculated electron affinities are 3.28 eV (*C=C-CH(2)F), 3.59 eV (*C[triple bond]C-CH(2)Cl) and 3.73 eV (*C[triple bond]C-CH(2)Br), and the gas-phase basicities of their anions are 359.5 kcal/mol ((-):C[triple bond]C-CH(2)F), 354.8 kcal/mol (:C[triple bond]C-CH(2)Cl) and 351.3 kcal/mol ((-):C[triple bond]C-CH(2)Br). It is concluded that the larger the magnitude of electron-withdrawing, the greater is the electron affinity of radical and the smaller is the gas-phase basicity of its anion.
Lee
Gab-Yong
GY
Catholic University of Daegu, Life Chemistry, Gumrak-ri, 330, Gyeonsan, Gyeongbuk, South Korea 712-702. gylee@cu.ac.kr
D000480:Alkynes / Q000737:chemistry*; D000838:Anions / Q000737:chemistry; D003198:Computer Simulation; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry; D005740:Gases / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure
D000480:Alkynes; D000838:Anions; D005609:Free Radicals; D005740:Gases