# The Nitro-Chloro Substitution on Two Quinolinone-Chalcones: From Molecular Modeling to Antioxidant Potential

## TL;DR

This paper explores how modifying two chalcone derivatives with nitro and chloro groups affects their antioxidant properties for use in biodiesel.

## Contribution

The study introduces a combined theoretical and machine learning approach to evaluate the antioxidant potential of substituted chalcone derivatives.

## Key findings

- QC-Cl shows higher electronic stability and nucleophilicity compared to QC-NO2.
- QC-NO2 exhibits enhanced electrophilicity and comparable antioxidant activity to commercial antioxidants.
- Structural modifications significantly influence antioxidant performance in biodiesel applications.

## Abstract

The increasing demand for renewable energy has driven
the search
for sustainable biodiesel additives whose molecular structures exhibit
antioxidant potential. This study reports the synthesis and solid-state
X-ray diffraction studies of two quinolinone-chalcone derivatives,
C28H19N3O7S (QC-NO

2
) and C28H19ClN2O5S (QC-Cl). Density functional theory
calculations and Fukui function analysis were combined with a predictive
tool based on previously trained machine learning models to investigate
the impact of nitro and chloro substituents
on their physicochemical properties, molecular reactivity, and antioxidant
potential. Theoretical results indicated that QC-Cl exhibits
higher electronic stability, with larger energy gaps (599 kJ/mol)
and greater nucleophilicity, while QC-NO

2
shows enhanced electrophilicity and electron-accepting ability.
Molecular electrostatic potential maps and Fukui functions highlighted
reactive sites consistent with the substituent electronic effects,
particularly the strong electron-withdrawing character of the nitro
group. Predictions of the hydroxyl radical scavenging rate constant
(k
OH) obtained using a tool based machine
learning models demonstrated that QC-NO

2
(6.09 × 109 M–1·s–1) performs comparably to commercial antioxidants such
as BHT and TBHQ. These findings underscore the relevance of structural
modification in tuning antioxidant activity and suggest that chalcone-based
hybrids, especially QC-NO

2
, are
promising candidates to act as antioxidants in biodiesel.