Solubility of imidazoles

Domariska, U. and Kozlowska, M.K. Solubility of imidazoles in ketones. Fluid Phase Equilib., 206, 253,2003. 

Domariska, U., Pobudkowska, A., and Rogalski, M. Solubility of imidazoles, benzimidazoles and phenylimidazoles in different organic solvent, /. Chem. Eng. Data, 49, 1082, 2004. 

Imidazoles in which the imino hydrogen is available for intermolecular hydrogen bonding are soluble in polar and rather insoluble in nonpolar solvents. The solubilities of imidazole in benzene and dioxane and of 4-methylimidazole in benzene have been measured.172... 

The solubility of imidazole in water is a function of its hydrophilic nature (equilibrium constant for transfer from water to vapor, determined by vapor pressure measurements log K vjw) = — 7.2). Potential electronic interactions between solvation sites (33) do not seem to be present. When imidazole is A -methylated its hydrophilicity only decreases by a factor of 8, hence its hydrophilie character is not exceptional <87JA463>. The calculated (using semiempirical methods) iV-shielding of imidazole is 3.93 ppm (cf. 4.6 ppm experimental value). For l-methylimidazole the observed shielding of N-1 decreases by 3.6 ppm and that of N-3 increases by 9.2 ppm on hydration compared with the calculated values (1.87, 10.72 ppm, respectively) <83OMR(2l)50l>. Imidazole iV-oxides are only sparingly soluble in nonpolar solvents, but more soluble in polar solvents. 

The conversions of the poly(1,3-alkylene chlorophosphate)s to poly(methyl alkylene phosphate)s were more difficult. The method of Klosinski and Penczek, involving the reaction of the polymer with 2 moles of imidazole per mol of repeat unit followed by the reaction of this polymer with the alcohol [15) was first attempted. However, this procedure yields product that is contaminated with significant amounts of imidazole. The solubilities of imidazole and the polymers were very similar, and it was not possible to remove all of the imidazole by fractional precipitation. Several attempts were made to avoid the problems encountered with imidazole by using either triethylamine, N,N-dimethylaminopyridine or DBU as HCl sinks. However, these did not give complete reactions. The best method was found to be the reaction of the polymer with imidazole and methanol in a 1 1 2 mole ratio. This method uses only half as much imidazole as that of Klosinski and Penczek, and nearly all of the imidazole is converted to imidazole hydrochloride which can be removed by filtering the cold reaction mixture (-78 °C). 

Yield and composition of Imidazole-HCl soluble polysaccharides (mg/fruit)... 

The mixture is then chilled in an ice bath for at least 3 hours, and the olive-brown precipitate of the sparingly soluble copper complex of imidazole derivatives is filtered. The product is washed with about 500 ml. of cold water, suspended while moist (Note 4) in 11. of water, and rendered just acid to litmus by the addition of concentrated hydrochloric acid (about 40 ml.). Hydrogen sulfide is then passed into the suspension, with frequent shaking, until precipitation of the copper is complete (2-3 hours). The precipitate is filtered and extracted with 500 ml. of hot water in two or three portions. The clear, light brown to reddish brown filtrate and washings are boiled for 15 minutes, and then 60 g. (0.26 mole) of picric acid is added with stirring heating is continued until solution is complete. 

Evidently, there are a number of factors that determine which of the above-mentioned pathways of polymerization occurs. One of these is the enrichment of final copolymers with the more hydrophilic comonomer (in comparison with the composition of the initial feeds), due to a higher reactivity of NVIAz. The higher (than for NVC1) reactivity of NVIAz is determined by a stronger polarization of the double bond of the vinyl group by the imidazole moiety as compared with the caprolactam cycle. Furthermore, a good solubility of hydrophilic NVIAz can also contribute to its higher reactivity in aqueous media. 

In the case of manganese porphyrin catalyzed epoxidations, the axial ligands have been used alone or together with other additives like carboxylic acids (Banfi and coworkers) and soluble bases (Johnstone and coworkers). For example, Mansny and coworkers showed that in the presence of imidazole, 2-methylimidazole or 4-imidazole chloromanganese(tetra-2,6-dichlorophenylporphyrin) catalyzes the epoxidation of varions aUtenes including 1-alkenes by Under these conditions alkene conversion... 

The solubility of IL is strictly dependent on melting temperature of the solute, which is generally the result of the alkane or phenyl substituents at imidazolium ring. The conclusions can be taken from the solubilihes of benzimidazole and 2-phenylimidazole in water [94] and of every measured imidazoles in organic solvents [83-89]. 

The partition coefficient Kq of an organic compound in the 1-octanol/water system is used to assess the bioaccumulation potential and the distribution pattern of drugs and pollutants. The partition coefficient of imidazole and ILs strongly depends on the hydrogen bond formed by these molecules and is less than one due to the high solubility in water. The low value of the 1-octanol/water partition coefficient is required for new substances, solvents, insecticides to avoid bioaccumulation. Kqw is an extremely important quantity because it is the basis of correlations to calculate bioaccumulation, toxicity, and sorption to soils and sediments. Computing the activity of a chemical in human, fish, or animal lipid, which is where pollutants that are hydrophobic will appear, is a difficult task. Thus, it is simpler to measure the 1-octanol/water partition coefficient. This parameter is used as the primary parameter characterizing hydrophobisity. 

Chu et al. (1983, 1986) and Ghosh et al. (1990) describe modified carbodiimide protocols using the water-soluble reagent EDC instead of DCC. They also incorporate a second reactive intermediate, a phosphorimidazolide, created from the reaction of the phosphomonoester at the 5 -terminus of DNA with EDC in the presence of imidazole. A reactive phosphorimidazolide will rapidly couple to amine-containing molecules to form a phosphoramidate linkage (Fig. 398). The chemical reaction had been used previously to effect the formation of phosphodiester linkages between short DNA strands (Shabarova et al., 1983). 

---