in organic chemistry, a generalization, formulated by Vladimir Vasilyevich Markovnikov (Markovnikov, Vladimir Vasilyevich) in 1869, stating that in addition reactions (addition reaction) to unsymmetrical alkenes, the electron-rich component of the reagent adds to the carbon atom with fewer hydrogen atoms bonded to it, while the electron-deficient component adds to the carbon atom with more hydrogen atoms bonded to it. Thus, hydrogen chloride (HCl) adds to propylene (CH₃CH=CH₂) to produce 2-chloropropane (CH₃CHClCH₃) rather than the isomeric 1-chloropropane (CH₃CH₂CH₂Cl). The rule is useful in predicting the molecular structures of products of addition reactions.