Poor solubility

Surprisingly, the highest catalytic activity is observed in TFE. One mi t envisage this to be a result of the poor interaction between TFE and the copper(II) cation, so that the cation will retain most of its Lewis-acidity. In the other solvents the interaction between their electron-rich hetero atoms and the cation is likely to be stronger, thus diminishing the efficiency of the Lewis-acid catalysis. The observation that Cu(N03)2 is only poorly soluble in TFE and much better in the other solvents used, is in line with this reasoning. 

The selection of solvents for quantitative work is not easy. Nitro-alkanes are sufficiently inert, but nitronium tetrafluoroborate is poorly soluble in them c. 0-3 %). Nitronium salts react rapidly with acetic anhydride, and less rapidly with acetic acid, A, A -dimethylformamide and acetonitrile, although the latter solvent can be used for nitration at low temperatures. Sulpholan was selected as the most suitable solvent ... 

Dimethyl acetylenedicarboxylate (DMAD) (125) is a very special alkyne and undergoes interesting cyclotrimerization and co-cyclization reactions of its own using the poorly soluble polymeric palladacyclopentadiene complex (TCPC) 75 and its diazadiene stabilized complex 123 as precursors of Pd(0) catalysts, Cyclotrimerization of DMAD is catalyzed by 123[60], In addition to the hexa-substituted benzene 126, the cyclooctatetraene derivative 127 was obtained by the co-cyclization of trimethylsilylpropargyl alcohol with an excess of DMAD (125)[6l], Co-cyclization is possible with various alkenes. The naphthalene-tetracarboxylate 129 was obtained by the reaction of methoxyallene (128) with an excess of DMAD using the catalyst 123[62],... 

Due to its poor solubility in water, benzoic acid is dissolved in a small amount of ethanol before being diluted with water. 

Because of iodine s poor solubility, solutions are prepared by adding an excess of I-. The complexation reaction... 

Potassium acetate, mbidium acetate, and cesium acetate are very soluble ia anhydride ia contrast to the only slightly soluble sodium salt. Barium forms the only soluble alkaline earth acetate. Heavy metal acetates are poorly soluble. 

The physical and chemical properties are less well known for transition metals than for the alkaU metal fluoroborates (Table 4). Most transition-metal fluoroborates are strongly hydrated coordination compounds and are difficult to dry without decomposition. Decomposition frequently occurs during the concentration of solutions for crysta11i2ation. The stabiUty of the metal fluorides accentuates this problem. Loss of HF because of hydrolysis makes the reaction proceed even more rapidly. Even with low temperature vacuum drying to partially solve the decomposition, the dry salt readily absorbs water. The crystalline soflds are generally soluble in water, alcohols, and ketones but only poorly soluble in hydrocarbons and halocarbons. 

Diaminonaphthalene [2243-62-1 ] M 158.2, m 190°, pK 4.12. Rerystd from boiling H2O, but is wasteful due to poor solubility. Boil in chlorobenzene (charcoal), filter hot and cool the filtrate. This gives colourless crystals. Dry in a vac till free from chlorobenzene (odour), and store away from light. 

Cloud point. Measures the solubility/compatibility of a resin with solvents. The value reported is the temperature at which a specific mixture of a resin and a solvent or solvents blend gives a cloudy appearance, having been cooled from a temperature at which the mixture was clear. Commonly, a test tube of a given diameter is used and the temperature is noted when the lower end of the thermometer, placed at the bottom of the tube, disappears. Resins with cloud points below 0°C are commonly regarded as soluble and cloud points greater than 10°C indicate poor solubility/compatibility. White spirit with various aromatic contents is a widely used solvent in the determination of cloud point, but other solvents or solvents mixtures are also used. 

An antiozonant should have adequate solubility and diffusivity characteristics. Since ozone attack is a surface phenomenon, the antiozonant must migrate to the surface of the rubber to provide protection. Poor solubility in rubber may result in excessive bloom. 

The solubility coefficient S is used as a measure of water solubility. It is the ratio between the concentrations in water and air phases at equilibrium. Ethanol, a very soluble gas, has a solubility coefficient of 1 100 at, 37 C while the coefficient for nitrous oxide, a poorly soluble gas, is 0.1.5. 

The solubility of many steroids in ammonia-tetrahydrofuran-/-butyl alcohol is about 0.06 A/, a higher concentration than has been reported in other solvent systems. Still higher concentrations may be possible in particular cases by suitable variation in the solvent ratios Procedure 3 (section V) describes such a reduction of estradiol 3-methyl ether at a 0.12 M concentration. A few steriods such as the dimethyl and diethyl ketals of estrone methyl ether are poorly soluble in ammonia-tetrahydrofuran-/-buty] alcohol and cannot be reduced successfully at a concentration of 0.06 even with a 6 hour reduction period. The diethyl ketal of estrone methyl ether is reduced successfully at 0.12 M concentration using a two-phase solvent system of ammonia-/-amyl alcohol-methylcyclohexane (Procedure 4, section V). This mixture probably would be useful for any nonpolar steroid that is poorly soluble in polar solvents but is readily soluble in hydrocarbons. 

Lithium-ammonia reduction of l7a-ethyl-19-nortestosterone (68) using Procedure 8a (section V) affords the 4,5a-dihydro compound (69) in 85% yield after a reaction time of 12 minutes after a reaction time of 80 minutes, the yield of (69) is 76%. Lfsing sodium in the same reduction, the yields of compound (69) are 79 and 77 % after reaction times of 8 and 80 minutes respectively. Both the lithium and sodium enolates appear to be reasonably stable in liquid ammonia in the presence of alkali metal. Since the enolate salts are poorly soluble in ammonia, their resistance to protonation by it may be due in part to this factor. 

For proteins, the most useful columns are those with pores of 100-500 A, as seen in Fig. 10.2, because most proteins elute on the linear portions of the calibration curves. Figure 10.5 illustrates an analysis of a protein mixture on SynChropak GPC100. Small peptides can be analyzed on the 50-A SynChro-pak GPC Peptide column with appropriate mobile-phase modifications. Many peptides have poor solubility in mobile phases standardly used for protein analysis, as discussed later in this chapter. 

Tile ID and 2D NMR experiments for 5-aza-7-deaza-2 -deoxyguanosine concluded that the oxo-amino tautomer 59a is preferable in DMSO-dg whereas the oxo-imino form 59b dominates in D2O (87JOC5136). Evidence for the hydroxy-imino tautomer 59c was not found. Poor solubility of the parent compound, 5-aza-7-deazaguanine (60) did not allow study of its tautomerism, but the pK values of protonation and deprotonation for 60 are identical with those for 59. 

The 5(6)-aminomethylenepropanedinitrile derivative was cyclized smoothly in good yield (72%) by the action of AICI3 to the very poorly soluble 9-amino-8-cyanotriazolo[5,4-/]quinolone 180 (87CCC2918). 

Besides the shortcomings noted above, some of the early sulfa drugs were poorly soluble in water. Since the drugs are excreted largely unchanged in the urine, crystals of the compounds sometimes formed in the kidneys and urine with attendant discomfort and tissue damage. Considerable attention was therefore devoted to preparation of agents with better solubility characteristics. ... 

In about 5-10 minutes a clear solution resulted, whereupon slow crystallization occurred and the temperature rose to about 6°-7°C. The crystallization was permitted to continue overnight at 5°C, and the very fine precipitate was then isolated by centrifugation and in the centrifuge washed with water, ethanol, and ether, yielding the dihydrate of DL-seryl-(2,3,4-trihydroxy-benzylidene) hydrazide hydrochloride, which melted at 134°-136°C and was poorly soluble in cold water, but very readily dissolved in hot water. The condensation was also effected in absolute ethanol yielding the anhydrous form of the hydrazone, which melted at 225°-228°C. 

In this context, the enantiomeric pair containing the eutomer of cyclothiazide can be resolved by HPLC on cellulose-derived coated CSPs. Nevertheless, the poor solubility of this compound in solvents compatible with this type of support makes this separation difficult at preparative scale. This operation was achieved with a cellulose carbamate fixed on allylsilica gel using a mixture of toluene/acetone as a mobile phase [59]. 

Simple metal compounds are poorly soluble in non-coordinating ILs, but the solubility of metal ions in an IL can be increased by addition of lipophilic ligands. LLowever, enhancement of lipophilicity also increases the tendency for the metal complex to leach into less polar organic phases. 

The literature of polyimines is extensive [164-173]. A number of researchers have tried to synthesize high molecular weight polymers but failed due to poor solubility in organic solvents. Polyimines are of great interest because of their high thermal stability [174-176], ability to form metal chelates [174-177], and their semiconducting properties [178-181]. Due to insolubility and infusibility, which impeded characterization of the molecular structure, the application of these polymers is very limited and of little commercial importance. 

Lipinski, C. A. (2000). Drug-like properties and the causes of poor solubility and poor permeability. J. Pharmacol. Tox. Meth. 44 235-249. 

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