Acids and bases in organic chemistry: quantitative aspects. Heteroaromatics: reactivity with electrophiles and nucleophiles. Side chain reactivity of heterocycles and tautomerism of hydroxy and amino groups. Determination of tautomeric constants. Heterocycles in life and society: hereditary information, enzymes, vitamins, photosynthesis, pharmaceuticals and phytopharmaceuticals, dyes. Multivariate experimental design in organic synthesis.