Solubility and Thermodynamic Analysis of 3(5)-Nitropyrazole in Different High Boiling Solvents

Abstract

3(5)-Nitropyrazole is obtained by rearrangement of 1-nitropyrazole in high boiling organic solvents. In this paper, the solubility of 3(5)-nitropyrazole in 12 high boiling solvents (anisole, benzonitrile, mesitylene, o-dichlorobenzene, 1-octanol, benzyl alcohol, 2-ethylhexyl acetate, dimethyl glutarate, cyclohexanone, N,N-dimethylformamide, N-methylformamide, and isophorone) was determined using the static gravimetric method over the temperature range of 283.15–323.15 K. The experimental results revealed that the solubility of 3(5)-nitropyrazole exhibited a positive correlation with temperature. Under ambient conditions at 298.15 K, the solubility decreased in the following order: N,N-dimethylformamide (37.705 × 10^–2), N-methylformamide (20.131 × 10^–2), cyclohexanone (13.469 × 10^–2), isophorone (11.957 × 10^–2), dimethyl glutarate (6.667 × 10^–2), benzyl alcohol (3.909 × 10^–2), benzonitrile (2.915 × 10^–2), 1-octanol (1.916 × 10^–2), 2-ethylhexyl acetate (1.220 × 10^–2), o-dichlorobenzene (0.666 × 10^–2), anisole (0.688 × 10^–2), and mesitylene (0.246 × 10^–2). The solubility of 3(5)-nitropyrazole was fitted using the Apelblat equation, λh equation, NRTL model, and van’t Hoff model. The fitting results were evaluated using average relative deviation and RMSD. The NRTL model exhibited the best overall performance. The use of Hansen solubility parameters for solubility prediction and analysis has certain limitations.