D. A. Evans Donor-Acceptor Properties of Bonding and Antibonding States Chem 206 Donor Acceptor Properties of C-c&C-O Bonds Hierarchy of Donor Acceptor States Consider the energy level diagrams for both bonding& antibonding Following trends are made on the basis of comparing the bonding and orbitals for C-c and c-o bonds antibonding states for the molecule CH3-x where X=C, N,o,F,&H gc-C I o-bonding States: (C-x) c。 C-SP 上csp土 CH3-NH2 decreasing o-donor capacity C-C poorest donor gC-O a The greater electronegativity of oxygen lowers both the bonding g-anti-bonding States:(C-X) antibonding C-O states. Hence oc-c is a better donor orbital than gc-o CHH Io'C-O is a better acceptor orbital than gC-c CH3CH3 CH3-NH2 Donor Acceptor Properties of CsP3-CsP3& CsP3-CsP2 Bonds CH3-OH CH3-F Increasing o'-acceptor capacity best acceptor C-SE The following are trends for the energy levels of nonbonding states of several common molecules. Trend was established by photoelectron spectroscopy C-SP2 Nonbonding States gC-C W 中p卅 a The greater electronegativity of Csp? lowers both the bonding antibonding C-C states. Hence Io CSP3-CsP3 is a better donor orbital than g CsP3-CSP2 do'CSP3-CsP2 is a better acceptor orbital than oCSP3-CSP3 decreasing donor capacity poorest donorD. A. Evans Donor-Acceptor Properties of Bonding and Antibonding States Chem 206 ■ s *CSP3-CSP2 is a better acceptor orbital than s *CSP3-CSP3 C-SP3 C-SP3 s* C–C s C–C C-SP3 s C–C s* C–C C-SP2 Donor Acceptor Properties of CSP3-CSP3 & CSP3-CSP2 Bonds ■ The greater electronegativity of CSP2 lowers both the bonding & antibonding C–C states. Hence: ■ s CSP3-CSP3 is a better donor orbital than s CSP3-CSP2 ■ s *C–O is a better acceptor orbital than s *C–C ■ s C–C is a better donor orbital than s C–O ■ The greater electronegativity of oxygen lowers both the bonding & antibonding C-O states. Hence: Consider the energy level diagrams for both bonding & antibonding orbitals for C–C and C–O bonds. Donor Acceptor Properties of C-C & C-O Bonds O-SP3 s* C-O s C-O C-SP3 s C-C s* C-C better donor better acceptor decreasing donor capacity Nonbonding States poorest donor The following are trends for the energy levels of nonbonding states of several common molecules. Trend was established by photoelectron spectroscopy. best acceptor poorest donor Increasing -acceptor capacity s-anti-bonding States: (C–X) s-bonding States: (C–X) decreasing -donor capacity Following trends are made on the basis of comparing the bonding and antibonding states for the molecule CH3–X where X = C, N, O, F, & H. Hierarchy of Donor & Acceptor States CH3–CH3 CH3–H CH3–NH2 CH3–OH CH3–F CH3–H CH3–CH3 CH3–NH2 CH3–OH CH3–F HCl: H2O: H3N: H2S: H3P: