4-Nitrotoluene: Para-Substituted Nitroaromatic Intermediate

4-Nitrotoluene has a benzene ring as its backbone, with a methyl group and a nitro group attached at the para positions, respectively. The aromatic ring structure is stable and readily undergoes characteristic aromatic reactions such as nitration, reduction, and oxidation. This compound is a typical aromatic nitro compound, with its chemical activity concentrated in the substituents. It serves as a key fine chemical intermediate, primarily used in the synthesis of dyes, pharmaceuticals, pesticides, and explosives, and can also be used to prepare toluidine derivatives.

DFT study on interaction of some pharmaceutical residues with 4-nitrotoluene

DFT is extensively used to study the interaction via functional groups of donors and acceptors in various systems, as it offers an excellent balance between computational cost and accuracy. With limited investigations on ECs, there is a need for an increase in the study on ECs using DFT to understand the effective interaction. Therefore, the DFT analysis on six different chiral/achiral ECs and their interaction with 4-nitrotoluene (4-NT) is proposed. Here, 4-Nitrotoluene is proposed to be a component of future functional material. Such a functionalized organic material model with immiscible nature can be very effective to manage ECs. Therefore, this study may create opportunities to develop material and monitor ECs in the environment. The present work aims to investigate the electronic properties of the selected pharmaceuticals using DFT calculations. Further, their interaction is studied with 4-Nitrotoluene to understand different aspects of the interactions. Quantum molecular descriptors, natural bond orbital (NBO) and molecular electrostatic potential surface (MEPS) analyses are performed to study the reactivity, charge transfer, and donor–acceptor interaction properties. Quantum theory of atoms in molecules (QTAIM) and non-covalent interaction (NCI) analysis are also carried out to assess the nature of interactions. A detailed analysis of these interaction parameters and their outcomes is expected to accelerate the development of more efficient water treatment materials for EC removal.[1]

The primary mode of interaction between each EC and 4-Nitrotoluene involves hydrogen bond type donor–acceptor interaction. Paracetamol establishes two different hydrogen bonds with 4-NT, one between the paracetamol -OH group and 4-NT O-atom (4-NT–Par(A)) with d = 1.98 Å and another one between the paracetamol -NH group and a 4-NT O-atom (4-NT–Par(B)) with d = 1.87 Å. The ∆E values for 4-NT–Par(A) and 4-NT–Par(B) complexes are found to be –7.53 and –8.16 kcalmol−1 respectively. Thus, the interaction involving the -NH group of paracetamol is slightly more favorable. Aspirin binds with ΔE value of –13.18 kcalmol−1, interacting through H-atom of its -OH group and the O-atom of -NO2 of 4-Nitrotoluene. Paracetamol exhibits the lowest chemical hardness with the highest electrophilicity and is the most reactive among the studied ECs. In contrast, ibuprofen, having the highest value of chemical hardness, is the least reactive molecule. MEPS is analyzed to predict the favorable interacting sites of the considered 4-Nitrotoluene. The range of estimated interaction energies indicates the effective interaction of ECs, with aspirin exhibiting the strongest interaction. The complexation leads to changes in the energy of molecular orbitals, which in turn result in modifications of global reactivity descriptors. Further, the study revealed that the complexation of the EC is primarily driven by physical interactions.

Evolution of a New Bacterial Pathway for 4-Nitrotoluene Degradation

Bacteria that assimilate synthetic nitroarene compounds represent unique evolutionary models, as their metabolic pathways are in the process of adaptation and optimization for the consumption of these toxic chemicals. We used Acidovorax sp. strain JS42, which is capable of growth on nitrobenzene and 2-nitrotoluene, in experiments to examine how a nitroarene degradation pathway evolves when its host strain is challenged with direct selective pressure to assimilate non-native substrates. Although the same enzyme that initiates the degradation of nitrobenzene and 2-nitrotoluene also oxidizes 4-nitrotoluene to 4-methylcatechol, which is a growth substrate for JS42, the strain is incapable of growth on 4-nitrotoluene. Using long-term laboratory evolution experiments, we obtained JS42 mutants that gained the ability grow on 4-nitrotoluene via a new degradation pathway. The underlying basis for this new activity resulted from the accumulation of specific mutations in the gene encoding the dioxygenase that catalyzes the initial oxidation of nitroarene substrates, but at positions distal to the active site and previously unknown to affect activity in this or related enzymes. We constructed additional mutant dioxygenases to identify the order of mutations that led to the improved enzymes. Biochemical analyses revealed a defined, step-wise pathway for the evolution of the improved dioxygenases.[2]

References

[1]Sarmah, P., Mondal, A., Kumar, R., & Saha, B. (2026). DFT study on interaction of some pharmaceutical residues with 4-nitrotoluene: a model system for nitro-functionalized material. Structural Chemistry.

[2]Ju KS, Parales RE. Evolution of a new bacterial pathway for 4-nitrotoluene degradation. Mol Microbiol. 2011 Oct;82(2):355-64. doi: 10.1111/j.1365-2958.2011.07817.x. Epub 2011 Sep 13. PMID: 21895789; PMCID: PMC10373102.