Large and frequently occurring substructures in organic compounds obtainedby library search of infrared spectra

Comparing the infrared spectrum of a compound whose chemical structure is u nknown with the spectra of a library is a routinely used method to obtain i nformation about the unknown structure. The resulting hitlist contains comp ounds exhibiting the most similar spectra. if the unknown is not contained in the library, a method based on the maximum common substructure concept c an be applied to extract common structural features from the hitlist struct ures. The result is a set of substructures that are characteristic for the query structure. This approach has been applied to infrared spectra from a series of model compounds and has been compared with information obtained f rom mass spectra by the same procedure. A complementary chemometric method for evaluating spectral hitlists is principal component analysis of spectra l and structural data. (C) 1999 Elsevier Science B.V. All rights reserved.