Solubility of the pesticide diuron in organic nonelectrolyte solvents. Comparison of observed vs. predicted values based upon Mobile Order theory

Abstract

Experimental solubilities are reported at 25.0°C for diuron (also called 3-(3,4-dichlorophenyl)-1,1-dimethyl urea) dissolved in 49 different organic nonelectrolyte solvents containing ether-, chloro-, hydroxy-, ester-, methyl-, and tert-butyl-functional groups. Results of these measurements are used to test the applications and limitations of expressions derived from Mobile Order theory. For the 28 nonalcoholic solvents for which predictions could be made computations show that Mobile Order theory does provide fairly reasonable estimates of the saturation mole fraction solubilities. Average absolute deviation between predicted and observed values is 60.1%. Diuron solubilities in the alcohol solvents are used to calculate stability constants for presumed solute-solvent hydrogen bonds that are believed to occur in solution.Key words: pesticide, diuron solubilities, organic nonelectrolyte solvents, solubility predictions.

A General Treatment of Solubility. 2. QSPR Prediction of Free Energies of Solvation of Specified Solutes in Ranges of Solvents

“…13,27,28 A prediction based upon MOT for the solubility of diuron in 28 nonalcoholic solvents provided reasonable estimates with an average absolute deviation of 2.3%. The same authors, 13 using the LSER solvation equation, correlated the solubilities of diuron in 22 solvents with an average percentage error of 1.1%.…”

Calculation of solubilities of the pesticides diuron and monuron in organic nonelectrolyte solvents using UNIFAC and modified UNIFAC (dortmund) models

“…The mobile order theory gives accurate estimates of the solubilities for the alkane and aromatic hydrocarbon solvents, whereas the prediction of the solubilities in polar solvents is much poorer (De Fina et al, 2000, 2001. In the case of alcoholic solvents, the predictions did use a pesticide-alcohol association constant, the numerical value of which did vary from one alcohol to another.…”

“…In the case of alcoholic solvents, the predictions did use a pesticide-alcohol association constant, the numerical value of which did vary from one alcohol to another. Mobile order theory predictions, along with the computational procedure for calculating the solute-solvent equilibrium constants, are described in greater detail elsewhere (De Fina et al, 2000, 2001. For all other solvents except acetonitrile and ethylene glycol the calculated values using Modified UNIFAC are satisfactory.…”

“…Predicted volume fraction solubilities based upon Equations (9) and (12) Numerical values of KO; (stability constant) used were: KO; =2.2 1 0-3 m3/mol for methanol, Koi =4.0 1 0-3 m3/mol for ethanol and 2-propanol; Koi = 6.0 1 0-3 m3/mol for 1 -propanol, Koi =7.0 1 0-3 m3/mol for 1 -butanol; Koi = 8.0 1 0-3 m3/mol for 2-butano1, Koi =9.5 1 0-3 m3/mol for 1 -pentanol; KOi = 14.0 1 0-3 m3/mol for 2-methyl-1 -propanol, Koi =14.0 1 0-3 m3/mol for 1 -hexanol and 1 -heptanol and Koi =14.0 1 0-3 m3/mol for 1 -0ctanol and 1 -decanol. Tables 1 and 2 give the calculated solubilities of the diuron and monuron, respectively, using UNIFAC and Modified UNIFAC (Dortmund) in a series of organic solvents together with the experimental values measured by De Fina et al (2000 and2001). Looking at the estimated solubility data one must take into account that many of these particular systems are highly nonideal, and that the experimental solubility data cover over a 1 000-fold range in mole fraction.…”

“…A comparison between the computed solubilities obtained here and values calculated by the mobile order theory (De Fina et al, 2000 and2001) will be given.…”