When two molecules react with one another their mutual approach and subsequent structural reorganization have to follow more or less along a minimum energy pathway in the multidimensional parameter space that defines the structure of the reacting system. Information about such paths can be obtained, in principle, by examining how the structural parameters of certain molecules or parts of molecules change in response to perturbations connected with different crystal or molecular environments. In some cases, striking correlations between independent structural parameters describing molecular sub-systems frozen in different environments have been detected. This makes it possible to arrange the individual structures in a sequence that corresponds, in a general sense, to the course of structural changes expected to occur in a chemical reaction. In this way, reaction paths for several prototypal chemical reactions (S N 1, S N 2, nucleophilic addition to carbonyl groups) have been derived.