We developed a web application structured in a machine learning and molecular fingerprint algorithm for the automatic calculation of the reaction rate constant of the oxidative processes of organic pollutants by • OH and SO 4•− radicals in the aqueous phasethe pySiRC platform. The model development followed the OECD principles: internal and external validation, applicability domain, and mechanistic interpretation. Three machine learning algorithms combined with molecular fingerprints were evaluated, and all the models resulted in high goodness-of-fit for the training set with R 2 > 0.931 for the • OH radical and R 2 > 0.916 for the SO 4•− radical and good predictive capacity for the test set with R ext 2 = Q ext 2 values in the range of 0.639−0.823 and 0.767−0.824 for the • OH and SO 4•− radicals. The model was interpreted using the SHAP (SHapley Additive exPlanations) method: the results showed that the model developed made the prediction based on a reasonable understanding of how electron-withdrawing and -donating groups interfere with the reactivity of the • OH and SO 4•− radicals. We hope that our models and web interface can stimulate and expand the application and interpretation of kinetic research on contaminants in water treatment units based on advanced oxidative technologies.

Ultrafast (UF) 2D NMR makes it possible to obtain a 2D NMR spectrum in less than a second. Here, UF-HSQC experiments are used for the real-time mechanistic study of an acetal hydrolysis at ¹³C natural abundance, and it is possible to characterize the presence of the hemiacetal, an intermediate with a well-known short lifetime. The assignments are confirmed and rationalized by quantum calculations of ¹H and ¹³C NMR chemical shifts and natural bonding orbital analysis.

This work aims at using theoretical calculations of shielding tensors (σ) through different methods [gauge-independent atomic orbital (GIAO), continuous set of gauge transformations (CSGT) and individual gauges for atoms in molecules (IGAIM)] and spin-spin coupling constants J using GIAO method to compare these methods and to corroborate the data obtained with the assignment of all of (1)H and (13)C NMR signals and the relative stereochemistry of the 1,6-epoxycarvone and the α-epoxypinene. All the (1)H and (13)C NMR signals were assigned unequivocally. The stereochemistry for the epoxides is trans and the B3LYP theory level with CSGT and IGAIM methods is the best choice to evaluate theoretical chemical shifts for compounds studied.

The study highlights the need for standardised sample preparation and instrumental setup protocols in order to achieve high reproducibility and obtain reliable data from HR-MAS NMR analyses.