Quantum chemistry methods are used to study chemistry related problems. Topics include: 1) electronic structures of boron clusters. Density functional theory (DFT) are used to explore the potential energy surface and to find the global minimum structures. Subsequently, the adaptive natural density partitioning (AdNDP) analysis are used to understand the chemical bonding situations. 2) reaction mechanism for organic reactions. Based on transition state theory, DFT calculations are performed to uncover the reaction path and the structure-catalytic property relationships. Later, computational catalyst designs are carried out. 3) explore the reaction space via ab initio molecular dynamics (MD) simulations. An advanced MD technique are used to explore the reaction space for organics reactions and to computed free energy surfaces. 4) reactivities of molecular crystals. Multiple levels of theory, ranging from a semi-empirical tight-binding Hamiltonian to dispersion corrected hybrid density functionals are used to investigate crystal geometries, thermodynamic and catalytic properties of the molecular crystals.