Two spectroscopic methods, ¹H NMR and FTIR, were developed for the monitoring of the photocatalytic degradation of acetamiprid, a widely used pyridine-based neonicotinoid insecticide, in UV-irradiated aqueous suspensions of O₂/TiO₂. The ¹H NMR method allowed also the identification of the intermediates such as 6-chloronicotinic and formic acids, as well as separate monitoring of the kinetics of degradation of acyclic and aromatic moieties based on the different chemical shifts of the protons belonging to the methyl group of the acyclic and selected proton of the heterocyclic aromatic moiety. The FTIR procedure enabled the monitoring of the kinetics of degradation of the cyano group of the compound. The obtained results are in good agreement with the comparative HPLC-DAD and HPLC-MS/MS measurements, which also enabled the identification of certain intermediates. To get a deeper insight into the complex photocatalytic process, the photocatalytic degradation of 6-chloronicotinic acid, a stable degradation intermediate of acetamiprid, was also investigated by ¹H NMR and HPLC-DAD methods. Based on the obtained data, a tentative reaction mechanism was proposed for the photocatalytic degradation of acetamiprid.

Infrared spectroscopy studies of N-methyl benzamide and N-tert-butyl benzamide in 12 organic solvents were undretaken to investigate solvent-solute interactions. The wavenumbers of carbonyl stretching vibration ν(C=O) in different solvents were correlated with the solvent acceptor number (AN), the linear solvation energy relationships (LSER), Catalan solvent parameters (SA, SB and SPP) and Buckingham equation. For both studied amides significant correlation of the position of the carbonyl band with empirical parameters was obtained. Based on obtained results it was assumed that the amide self-association and the steric effects are most important factors that determine position of carbonyl groups band in the IR spectra.

This study investigates the structural and energetic properties of hydrogen-bonded complexes between indole and a range of aliphatic, cyclic, and aromatic ketones using a combined vibrational spectroscopic and quantum-chemical approach. FTIR measurements in CCl₄ revealed redshifts in the N-H stretching vibration of indole upon complexation, with formation constants (K_a) ranging from 0.3 to 6.6 M⁻¹. Cyclohexanone displayed the strongest binding, while benzophenone exhibited the weakest interaction. Quantum-chemical calculations, employing CREST and MMFF94 conformational sampling, along with M06-2X/6-311++G(d,p) optimizations, confirmed the formation of hydrogen bonds and additional weak interactions that govern the stability of the complex. QTAIM analysis revealed moderate closed-shell hydrogen bonds with electron densities at the bond critical points (ρ) ranging from 0.010 to 0.019 a.u. and potential energy densities (V) from −18.4 to −36.4 kJ mol⁻¹. Multivariate regression analysis established strong correlations (R² = 0.928 and 0.957) between experimental binding constants and theoretical descriptors, including binding energy, NBO charge on oxygen atom, ionization potential, and electrophilicity index, highlighting the interplay between geometric, electronic, and global reactivity factors. This comprehensive study underlines the predictive power of spectroscopic and quantum descriptors for assessing hydrogen bonding in biologically relevant systems.

The results are reported of a study of hydrogen bonding between various N-substituted caproamides and tetrahydrofuran as an O-electron donor by means of FTIR spectroscopy. The spectroscopic characteristics for N-H...O hydrogen bonded complexes are given. The B3LYP functional with 6–31G** basis set has been used to calculate the structural parameters of the studied hydrogen bonded complexes. It can be assumed that both inductive and steric effects play an important role in the stability of these hydrogen bonded complexes.