The textbook outlines the theoretical basic principles of organic chemistry: the chemical structure of organic compounds, their formulas, classification and nomenclature, isomerism, electronic effects in molecules of organic compounds, chemical bonds, and others. The peculiarity of the manual is that the author in an accessible form tried to reveal the essence of chemical processes, the properties of compounds represented by structural formulas. This work will allow students to fill in the missing knowledge for further deeper study of organic chemistry.