Recently developed techniques and concepts of the density functional theory of the electronic structure of matter will be applied to various problems in the structure and reactivity of molecules of moderate complexity. The concepts used will include the recently validated concepts of electronegativity, hardness, and reactivity index. Computational methods employed will be routine. Problems treated will include, in so far as is possible, molecular conformation and molecular vibration, preferential reactivity of different sites, rates of electron transferes processes, chemisorption and catalysis. Attempts will be made to develop a simple coherent density functional theory of chemical binding and a density functional theory of dynamical chemical reaction. The results will be relevant for biology because increased understanding of molecules is essential for increased molecular-level understanding of biological processes.