Complex formation in Organic Solvents

The complex formation in PAA-PVP-methanol and PMAA-PVP-DMF systems has also been investigated44. The composition of the complexes in these solvents has been determined by conductometric and potentiometric methods. The titration curves in methanol and DMF (Fig. 15) exhibit a typical inflection point termining the molar ratio of the components in the complex. The complex compositions in organic solvents and water are different (Table 2). For comparison the titration curves in Fig. 15 of PAA with PVP in DMSO are illustrated. The solvent (DMSO) strongly competes for hydrogen bonds and it has been already shown48 that the complex is broken down. No inflection point on the titration curves is observed in this case. 

The possibility of complex formation of random copolymers was investigated in some organic solvents (methanol, ethanol, DMF). The composition of the complexes formed in organic solvents (Table 5) and determined by titration proved to be the same as that in the mixed water-ethanol (70 30 wt-%) solvent. The viscosity of PVP-MAA/MMA and PVP-MAA/BMA complexes in organic solvents is anomalously low and exhibits all the features observed for polycomplexe solutions in water. 

Interactions between nonpolar compounds are generally stronger in water than in organic solvents. At concentrations where no aggregation or phase separation takes place, pairwise hydrophobic interactions can occur. Under these conditions, the lowest energy state for a solute molecule is the one in which it is completely surrounded by water molecules. However, occasionally, it will also meet other solute molecules, and form short-lived encounter complexes. In water, the lifetime of these complexes exceeds that in organic solvents, since the partial desolvation that accompanies the formation of these complexes is less unfavourable in water than in organic solvents. 

Antimony trioxide is insoluble in organic solvents and only very slightly soluble in water. The compound does form a number of hydrates of indefinite composition which are related to the hypothetical antimonic(III) acid (antimonous acid). In acidic solution antimony trioxide dissolves to form a complex series of polyantimonic(III) acids freshly precipitated antimony trioxide dissolves in strongly basic solutions with the formation of the antimonate ion [29872-00-2] Sb(OH) , as well as more complex species. Addition of suitable metal ions to these solutions permits formation of salts. Other derivatives are made by heating antimony trioxide with appropriate metal oxides or carbonates. 

An alternative to the formation of neutral metal chelates for solvent extraction is that in which the species of analytical interest associates with oppositely charged ions to form a neutral extractable species.6 Such complexes may form clusters with increasing concentration which are larger than just simple ion pairs, particularly in organic solvents of low dielectric constant. The following types of ion association complexes may be recognised. 

These procedures illustrate the use of N-ethyl-5-phenylisoxazolium-3 -sulfonate as a reagent for peptide synthesis.2-3 Procedure A is recommended for peptides that are not soluble in either organic solvents or in water. Procedure B illustrates the formation of a peptide that is soluble both in organic solvents and in water. Por peptides that are soluble in organic solvents and insoluble in water, the submitters recommend the use of Procedure B, except that the peptide product may be recovered directly from its solution in ethyl acetate after this organic solution has been washed successively with aqueous 5% sodium bicarbonate, water, aqueous 1 M hydrochloric acid, and water. Table I summarizes the preparation of various peptides by these procedures. Some more complex examples from other laboratories are listed elsewhere.2b... 

Also, from the dendrimer point of view, the introduction of mechanical bonds to dendrimers has an enormous potential to alter the properties of dendrimers in a controlled way. For example, in the synthesis of a Type II rotaxane dendrimers, the wheel components are introduced to the terminal groups of the dendrimers. This can improve the solubility of dendrimer in organic and/or aqueous media due to the formation of complexes soluble in such solvents. 

T], rj ). A molecular weight determination for the complex supports a monomeric structure in solution. Reaction of ZnMe2 with (H0)2Si(0 Bu)2 leads to the formation of polymeric species, [Zn0Si(0 Bu)20] , that are soluble in organic solvents [107]. For comparison, the zinc sUoxane polymer [Zn0SiPh20] reported by Hornbraker and Conrad is an insoluble material contaminated with ZnO [108]. 

Recently, van Leeuwen and co-workers provided support for the similarity between the active catalytic species in ionic liquids and in organic solvents by spectroscopic investigations [80]. These authors compared the complex formation of [Rh(acac)(CO)2] in the presence of 4 equivalents of sulfoxantphos ligand dissolved in [BMIM][PF6] and... 

PEO-based copolymers have received much attention. In this respect, PEO-PPO and PEO-PPO-PEO Pluronic copolymers were investigated in organic solvents such as formamides, as illustrated by the works of Lindmann and coworkers and Alexandridis et al. [92-94], However, the formation of reverse micelles in organic solvents from PEO-based block copolymers has been shown to be a complex phenomenon due to the ability of PEO to crystallize. 

Block copolymer/low-MW-molecule complexes were also examined in organic solvents, as recently exemplified by the works of Jiang and coworkers [319,320]. These authors investigated mixtures of PS-P4VP copolymers with various low-MW molecules including perfluorooctanoic acid and formic acid. Such molecules are expected to form hydrogen-bonded complexes with 4VP units in organic solvents such as chloroform. This further resulted in the formation of vesicles. 

The ligand (whose absorbance or fluorescence intensity is measured) will be denoted L and the metal ion M4). Let us consider first the formation of a 1 1 complex, assuming that the equilibrium does not involve protons, which is the case for investigations in organic solvents or in buffered aqueous solutions ... 

The interpretation of these effects as the formation of a proton addition complex was further supported by Plattner et al. (1952) by means of spectroscopic and conductimetric investigations. In these interactions the change of the absorption spectrum is characteristic, since the blue colour of the azulene in organic solvents is changed to a yellow colour in... 

Bands associated with the formation of ion pairs are observed. Excitation within these Charge Transfer to Ion (CTTI) bands causes reduction of metal centre (e.g. Eq, 9). Similarly short wavelength U.V. excitation of pentamino-Co(III) complexes in organic solvents is believed to cause solvent oxidation (Eq. 10). 

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