Understanding Trends in C-H, N-H, and O-H Bond Dissociation Enthalpies

摘要: Theory and experiment are now in good agreement for bond dissociation enthalpies (BDE's) and can be used as checks on each other to identify anomalous data. Both theory and experiment agree that XO-H, XNH-H, and XCH2-H BDE's decrease monotonically by ca. 60 kJ/mol along the series for X= H, but by only ca. 13 kJ/mol for X= CH3. More surprising is the fact that for X= C6H5 the OH bond is the weakest and the NH bond is the strongest (by 10-15 kJ/mol). By contrast, BDE's are essentially identical for X= CF3 and X= H. These interesting …