Fuzzy Definition of Molecular Fragments in Chemical Structures

Abstract

This paper presents a methodology for seeking the relationships between chemical substructures (molecular fragments) and spectral parameters using a computer collection data of molecular spectra. To establish the spectrum-structure correlations, the program has to search the chemical structure base in order to find compounds containing a given molecular fragment in the molecule. There exists no sole definition of a substructure, as it always depends on the type of problem dealt with. In the problem of structural identification, fuzzy definitions of substructures are applied, and their forms are imposed by the spectral methods used.

Sensitivity of Infrared Spectra to Chemical Functional Groups

“…Vibrational spectroscopy is a fast and reproducible technique for obtaining information relevant to chemical structures . Many chemical functional groups regularly absorb in certain spectral regions, allowing for their identification. – Early methods for searching and processing infrared spectral libraries relied on manual sorting based on strong absorptions and on correlation charts .…”

SIRS-SS: A System for Simulating IR/Raman Spectra. 1. Substructure/Subspectrum Correlation

“…Similarly, the nature of the atoms and bonds in the environment of the focus may be completely specified, let undefined or split into equivalence classes (“ banalisation ”, means bleaching the atom chromatism). This flexibility in the treatment of FRELs somewhat relies on the concept of fuzzy logic already introduced in chemistry. − …”

“…This flexibility in the treatment of FRELs somewhat relies on the concept of fuzzy logic already introduced in chemistry. [41][42][43] In our case which solely concerns the prediction of wavenumbers for IR/Raman characteristic bands, the description may be limited to FRELs A or B because of the definition of "special fragments". This permits us to take into account more remote influences.…”

Plasma infrared fingerprinting with machine learning enables single-measurement multi-phenotype health screening

“…Infrared (IR) spectroscopy is a powerful top-down approach that enables the label-free profiling of a given sample by interrogating molecular fragments (i.e., functional groups) and measuring their resonant vibrational response to IR excitation. 12 , 13 , 14 This technique can employ various light sources, including globars, 15 few-cycle laser-based excitation, 16 , 17 and discrete wavelength sources such as quantum cascade lasers. 18 , 19 In broadband IR absorption spectroscopy, absorption occurs when the IR source emits frequencies that align with the vibrational frequency of a molecular fragment.…”