Phenols interactions

An assumption implicit in most adsorption studies is that adsorption is fully reversible. In other words, once the empirical coefficients are measured for a particular substance, Equations 20.6 to 20.10 describe both adsorption and desorption isotherms. This assumption is not always true. Collins and Crocker140 observed apparently irreversible adsorption of phenol in flowthrough adsorption experiments involving phenol interacting on a Frio sandstone core under simulated deep-well... 

One would expect that deprotonated substituted phenols interact with the positively charged choline group [172]. However, 31P-NMR studies on the... 

Scheme 22 The reacting phenolate interacts with the wheel of the rotaxane by hydrogenbonding... 

Theory Phenol interacts with bromine whereby the former undergoes bromination to yield a water-insoluble 2, 4, 6-tribromophenol. This reaction takes place quantitatively as shown below ... 

The involvement of tyrosine and histidine ligands had been expected from spectroscopy the electronic spectral band at —465 nm, which is responsible for the orange-red color, is characteristic of iron-phenolate interaction (89, 90), and both EPR (91, 92) and NMR (93) studies indicated metal-histidine coordination. The presence of the Asp ligand... 

Furthermore, the rate of hydrolysis of N-acetyl,N -methylimidazolium ion is exactly the same as that of fully protonated acetylimidazole, and the values of given in equation (30) are equal or nearly equal to the corresponding values of k, given in equation (32). The reaction paths and mechanism for these two compounds therefore are no doubt the same the substitution of N-methyl for N—H makes no difference in terms of reactivity. Product studies have not been extensively carried out on these two compounds. It is known that phenolates interact with acetylimidazolium ion exclusively by the nucleophilic path (Gerstein and Jencks, 1964) and that the acetate reaction occurs 78% via the general base-catalyzed hydrolytic path (Jencks et ah, 1966 Section... 

In order to interpret the experimentally determined IR pattern of phenol interacting with four water molecules, we now consider theoretical OH-stretching modes of the PhOH-W4-I-4 structures (Table 39). Contrary to the PhOH-wi-l and PhOH-u 2-l structures studied above, the vibrational assignments are particular for each structure of the PhOH-W4 complex. The most red-shifted OH-stretching vibration at 3772 (2970.1) cm is predicted for the PhOH-u 4-2 structure. It is predominantly assigned to the hydrogenstretching vibration of the Oi—Hi O2 bond and is significantly enhanced by a factor... 

However, we have shown that the novel bond formation between phenol and acetonitrile plays a role on increasing the concentration of the acetonitrile. By postulating its existence under conditions in which phenol interacts with two acetonitrile molecules, we were able to explain the experimental data that have seemed to be rather unclear during the last four decades. Moreover, we have predicted the existence of another structure formed from phenol and two molecules of acetonitrile, which is characterized by a significant downshift by 244 cm of the v(OH) stretching mode of phenol, never observed experimentally in phenol-acetonitrile complexes. We have suggested that it is likely to exist in the gas phase and non-polar solvents at lower temperatures and showed its fingerprints in order to facilitate its possible experimental detection. 

Indeed, when the principal component analysis (PCA) [40, 41] was applied to the structural parameters of the ring of 664 variously substituted phenols interacting with bases in H-bonded complexes [36], it was found that the first... 

Prevention of chill haze in beer resulting from protein—phenolic interactions... 

We have investigated the gas phase partial oxidation of benzene to phenol over zeolite H-MCM-22 using as the oxidant. H-MCM-22 is active (15% benzene conversion at 603 K) and nearly 100% selective for the partial oxidation of benzene to phenol. We have also investigated the reaction in an in-situ IR cell. Both benzene and phenol interact strongly with the Bronsted acid site whereas does not interact strongly with the zeolite. We find the presence of Bronsted acidity is critical for the reaction and we found no correlation of the activity with the iron content, as reported previously by others. 

Many phenols interact with aluminium halides to yield complexes in tautomeric ketoforms these complexes, as shown by the NMR spectra, are close analogues of hydroxyarenium ions (X = Cl or Br). 

Numerous articles give new insights on the role of phenolics in gene expression regulation in plants and animals. Indeed, phenolics interact with some chromatin elements or with components involved in signaling pathways (Fig. 6.11). Most of the regulation of... 

In the same manner, sterically hindered phenols interact with peroxide radicals as they are forming stable radicals. The mechanism of interaction is shown in Figure 19.4. 

The thermodynamic and analytical aspects of acid-base reactions in aprotic solvents are surveyed in reviews by Davis [1, 2]. The correlation of acid-base strength in water and aprotic solvents is of major importance. Early kinetic work by Bell and co-workers on the acid catalysis of (i) the ethyldiazoacetate-phenol interaction [3] (ii) the rearrangement of N-bromoacetanilide [4] and (iii) the inversion of /-menthone [5] established an order of acid strengths in aprotic media and the importance of intra-molecular hydrogen bonds e.g in picric acid). A thermodynamic method using reference acids and bases is more direct, and Bell and Bayles [6] employed the indicator acid Bromophenol Blue to obtain a basicity order for weak amine bases. Kinetic measurements on these systems have recently been made, and are considered in detail in Section 7. 

Fig. 5. Magnesia and tertiary butyl phenolic interaction with polymer acid. (The resin should be added before or at the same time as the MgO to prevent gelation during mixing.)...

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