# Electrophilic and Radical Ability of Organic Nitrating Reagents

## TL;DR

This paper introduces two new scales to predict the performance of organic nitrating reagents based on their thermodynamic and redox properties.

## Contribution

The study introduces the NPD and NRA scales for evaluating nitronium release and redox behavior in nitrating reagents.

## Key findings

- NPD values correlate with Hammett constants and experimental reactivity across 150 reagents.
- Electron-withdrawing groups and cationic frameworks enhance nitronium character.
- The NRA scale captures redox behavior for radical nitration under photoredox conditions.

## Abstract

Aromatic nitration remains one of the most fundamental
yet continuously
evolving transformations in organic chemistry. While traditional “mixed-acid”
systems rely on in situ generation of the nitronium
ion under strongly acidic conditions, modern reagent design has shifted
toward discrete, stable, and tunable NO2-transfer reagents
that operate under milder and more selective conditions. Here, we
report a computationally derived Nitro Plus Detachment (NPD) scale
that quantifies the thermodynamic propensity of over 150 organic nitrating
reagents to release nitronium ions. Systematic density functional
theory (DFT) calculations across major structural classesincluding N-nitro carboxamides and carboximides, azoles, azines, sulfonamides
and sulfonimides, sulfoximines, and heteroatom- and carbon-based reagentsreveal
clear linear correlations between NPD values, Hammett substituent
constants, and experimentally observed reactivity. Electron-withdrawing
groups and cationic frameworks are shown to dramatically enhance nitronium
character. In addition, we introduce a complementary Nitro Radical
Activation (NRA) scale that captures redox behavior relevant to emerging
radical nitration strategies under photoredox conditions. Together,
these two scales establish a unified thermodynamic and redox framework
for predicting the performance of nitrating reagents and guiding the
rational design of next-generation nitrating reagents and transformations.