Applications of density functional theory (DFT) calculations to organic chemistry are shown, beginning with geometry optimization and the calculation of vibrational frequencies, infrared (IR) intensities, and thermodynamic properties. The isotropic chemical shielding values and anisotropies relevant to nuclear magnetic resonance (NMR) can be calculated using gauge-invariant atomic orbitals (GIAOs); the calculation of spin-spin couplings is possible but time-consuming. For free radicals, hyperfine couplings and g tensors pertaining to EPR can be obtained. Regarding UV/vis spectra, wavelengths and oscillator strengths can be calculated by using a time-dependent Hamiltonian. In addition to gas-phase acidities, approximate pKa values can be obtained, provided that solvation is taken into account. Several sets of substituent parameters have been calculated: Hammett σ and σ+ parameters and inductive and mesomeric effects. Regarding reaction mechanisms, geometries and energies of intermediates and transition structures have been calculated for pericyclic reactions, nucleophilic aliphatic substitutions, electrophilic aromatic substitutions, additions, and eliminations.
Part of the book: Density Functional Calculations