Hydrophobic phenyls

Even though one phenyl group is approximately equivalent to a three-carbon alkyl chain in hydrophobicity, phenyl Sepharose adsorbs a larger... 

Also based on porous silica support, the so-called Biomatrix phases contain a ligand that combines both hydrophilic and hydrophobic properties in the same molecule. Nonpolar analytes interact with the hydrophobic phenyl and alkyl moieties of the ligand, while the hydrophobic outer part of the ligand is supposed to be the result of hydroxyl groups that prevent the adsorption of proteins. 

Figure 10.1a also shows that the area response of Compound A in the silanized glass vials is lower than the area response in the nondeactivated glass vials. And the area response in the polypropylene vials is even lower, approximately 7% lower than in the borosilicate glass vials. Besides the lower area response, the use of plastic vials results in the appearance of additional, noninterfering peaks in the HPLC chromatogram. The silanized vials and polypropylene vials have hydro-phobic surfaces that appear to have an affinity for the hydrophobic phenyl and/or... 

The primary standard betaine dye (44) is only sparingly soluble in water and less polar solvents it is insoluble in nonpolar solvents such as aliphatic hydrocarbons. In order to overcome the solubility problems in nonpolar solvents, the more lipophilic penta-t-butyl-substituted betaine dye (45) has additionally been used as a secondary reference probe [174]. The excellent Hnear correlation between the Ej values of the two dyes allows the calculation of t(30) values for solvents in which the solvatochromic indicator dye (44) is not soluble. Introduction of electron-withdrawing substituents e.g. Cl [323], F, CF3, C6F13 [324]) in the betaine molecule reduces the basicity of its phenolate moiety, which allows the direct determination of x(30) values for somewhat more acidic solvents. Moreover, the Hpophilic and fluorophilic penta(trifluoromethyl)-substituted betaine dye (46) is more soluble in nonpolar solvents e.g. hexafluoro-benzene) than the standard dye (44) [324]. Conversely, the solubility in aqueous media can be improved through replacement of some of the peripheral hydrophobic phenyl groups in (44) by more hydrophilic pyridyl groups, to yield the more water-soluble betaine dye (47) [325]. The Ej values of these new secondary standard betaine dyes correlate linearly with the x(30) values of (44), which allows the calculation of x(30) values for solvents in which only betaine dyes (45)-(47) are sufficiently stable and soluble for the UV/Vis spectroscopic measurements [324, 325]. 

The study of potassium penicillin was extended [47] to the crystalline Li, Na, Rb, CS and free acid-penicillin. The X-ray diffraction data on these crystals yielded information on their structure, bonding, intermolecular contacts, librational oscillations or positional disorder. There are one, two or four molecules in the asymmetric unit. The crystals have layer structures composed of hydrophilic fragments (cation coordinated by the penV oxygen atoms) and hydrophobic (phenyl groups of the side chains). The principal change in the series of crystals is the variation in the radius of the cation with the increase in size of the cation the number of ligators at the cation increases from 2 to 7. 

Another example is TSK-Phenyl S-PW from Toyo Soda, Japan. To prepare this packing, hydrophobic phenyl groups are attached to TSKgel GSOOOPW, a hydrophilized methacrylate packing used for aqueous size xclusion chromatography (6). 

Aromatic polyesters have hydrophobic phenyl groups that allow them to take up only very small amounts of aqueous solvents, so that hydrolysis is oidy observed at raised temperatures and the materials generally show a good level of resistance to cold water. 

By means of calorimetric measurements reflecting the dependence of the stability constants of metal complexes on the composition of the solvent mixture, Gergely and Kiss have shown that the stability increase resulting from a decrease in the relative permittivity shows up primarily in an increase in the — dff values, whereas the dS values decrease or remain unchanged compared with those measured in aqueous medium. A comparison of the AH values for aliphatic and aromatic amino acid complexes of copper(II) has revealed that the change in the medium acts to a lesser extent on the AH values of the aromatic amino acid complexes. This is probably due to the presence of the hydrophobic phenyl group in the aromatic ligands, as a consequence of which the extent of hydration even in aqueous medium is lower than in the case of alanine. 

Unfortunately, Vertex s initial foray into varying the quinolinone moiety on 2 (ECso = 2.1 aM) came empty-handed. Replacing the quinolinone with quinolone, pyridine, alkylation of the NH on quinolone 2, and replacing the quinolinone moiety with pyridopyrimidine core structure all yielded analogs with inferior potentiator activities. Meanwhile, the naphthanol derivative 3 retained the potentiator activity (ECso = 3.5 jM). The lesson learnt from this SAR exercise is that the two features are essential to the potentiator activity (i). The hydrophobic phenyl ring is needed, and (ii). The quinolinol tautomer 2 (which is more stabilized via hydrogen bond) is favored. 

It is very probable that the salt has a polymer structure, in which the Cu-atoms are so situated and coordinated (chelated) that they are not subject to the action of ammonia molecules or to only a minor degree. The following structural presentation exhibits this shielding by the hydrophobic phenyl groups (R = CeHg) contained in the benzoinoxime molecule ... 

In our first example (Fig. 1.13), the first in which a coenzyme was linked to a cyclodextrin, we synthesized compound 25, with a pyridoxamine covalently linked to a C-6 of /3-cyclodextrin. We saw transaminations of pyruvic acid, of phenylpyruvic acid, and of indolepyruvic acid to form alanine, phenylalanine, and tryptophan, respectively, and with high selectivity for the hydrophobic phenyl and indole derivatives relative to simple pyruvic acid. Relative to its reaction with simple pyridoxamine in solution, without an attached or unattached cyclodextrin, the indolepyruvate reacted 50 times faster with compound 25. Also, we saw a 5 1 preference for the formation of the L-phenylalanine relative to the d enantiomer in transamination by compoimd 25. ... 

We also detected a hydrophobic effect in the benzoin condensation [14]. In this case, in contrast to the Diels-Alder reaction, it is not formally required that the two hydrophobic phenyl groups come together in the transition state, but our studies indicated that they do. Again there was a large increase in rate when water was the solvent, but in an ionic reaction of this sort such solvent effects could well be related only to the effect on the ions of the polar character of the medium. However, we saw that the reaction rate was increased with LiCl, but decreased when LiC104 was added. In this system LiC104 is a salting... 

Numerous studies have demonstrated the solvent influence on enzyme enan-tioselectivity, and sometimes the enantiopreference may even be reversed by medium engineering. For instance, the enantioselectivity of asymmetric reduction of prochiral ketones catalyzed by T. ethanolicus ADH can be controlled by changing the reaction medium containing either organic solvents or ionic liquids [93]. Reversal of the enantioselectivity was reported for S. cerevisiae-catalyzed reduction of hydrophobic phenyl w-propyl ketone by means of the... 

At the same time, the coordination capsule 581 efficiently binds air-sensitive white phosphorus by Scheme 4.73, thus giving an air-stable 1 1 cage complex with an encapsulated P4 guest molecule. This complex has been characterized in [73] using H and NMR spectra and by X-ray diffraction data. The P4 molecule within the cavity of a coordination capsule 581 is stabihzed by van der Waals interactions with the hydrophobic phenyl-ene ribbed fragments of its cage framework and is air stable for a long time, even in aqueous solu-... 

An examination of photoelectron transfer within multifunctional porphyrin and ubiquinone analogues linked by H-bonding interactions which serve to hold the donor and acceptor in a co-facial orientation, has been made, and is the first example of electron transfer between such structures which is complete within the picosecond range.Irradiation of colloidal syn-tetraresorcinolporphyrin having eight alkylphosphocholine side-chains (octopus porphyrin), and of the corresponding Zn(II) complex in the presence of hydrophobic phenyl-p-benzoquinone or hydrophilic naphtho-l,2-quinone-4-sulfonate, induces electron transfer to the quinone electron transfer to is also reported.A study has been made of... 

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