Solubility in supercritical carbon dioxide of two novel amine derivatives of 2,3-dichloronaphthalene-1,4-dione (dichlone)

Abstract

Dichlone (2,3-dichloronaphthalene-1,4-dione) is an important antimicrobial agent for agriculture, which effectiveness could be improved by modifying its structure, while the recovery of high-purity synthesized derivatives from a reaction mixture could be accomplished by extracting them with supercritical carbon dioxide. Two new amine derivatives, 2-chloro-3-((4-chlorobenzyl)amino)naphthalene-1,4-dione (dCl-2B-Cl) and 2-chloro-3-((4-chlorophenethyl)amino)naphthalene-1,4-dione (dCl‐3P‐Cl), were synthesized from dichlone, and their solubility in supercritical carbon dioxide was measured afterwards at (313, 323 and 333) K and a pressure range from (8−33) MPa. Experimental solubilities spanned from (10.3·10-6 to 22.1·10-6) mol·mol-1 for dCl-2B-Cl, and from (32.7·10-6 to 131·10-6) mol·mol-1 for dCl‐3P‐Cl. The solubility data of the dichlone family (dichlone, dCl-2B-Cl, dCl‐3P‐Cl, 2‐(benzylamino)‐3‐chloronaphthalene‐1,4‐dione (dCl-2B) and 2-chloro-3-(phenethylamino)naphthalene-1,4-dione (dCl‐3P)) was compared using three models, i.e., the Chrastil equation, the Molecular Connectivity Indices model, and the Statistical Associating Fluid Theory of Variable Range and Mie Potential equation of state, to identify the quantitative structure-property relationship between them. Solubility had an inverse relation with solute size and polarity, but there were some exceptions that could be explained by performing a stereochemical analysis, which showed that steric effects involved in the folding of dCl‐3P and dCl‐3P‐Cl provided them a better geometry for solvation than dCl-2B and dCl-2B-Cl, respectively, making them more soluble. This demonstrates that the solute geometry is an important factor in the solvation process, and it must be represented accurately to develop better predictive models.