4-Methyl-phenol acidity constant

The air-water volume ratio (Va / Vw) in a cloud is about 10s (Seinfeld, 1986). Consider now a given cloud volume that contains a certain total amount of (a) 2-4-dinitro-6-methyl phenol (DNOC), and (b) 4-chloroaniline (4-CA). Calculate the fraction of total DNOC and 4-CA, respectively, present in the water phase at equilibrium at 10°C for pH 2, 4, and 6. Neglect the effect of temperature on the acidity constant. 

IR spectrometry shows the existence of two equilibria for the complexation of phenols with carbonyl bases in CCI4 (equations 30 and 31) . Two different 1 1 stereoiso-meric complexes are formed the planar bent n complex a and the planar bidentate linear n complex b. The complex b has also been given the structnre c (ont-of-plane n complex). Experimentally, an overall complexation constant is determined which is the sum of the individual complexation constants and Kj, for each stereoisomeric complex. Massat and coworkers ° have proposed an IR method for evalnating the constants Kn and K of phenol-alkyIketone complexes. They have shown that the n vs. n complex competition depends on the alkyl branching, measured by the number of methyls alpha to the carbonyl, and on the phenol acidity, measured by pATa (equations 32 and 33). 

The antioxidant efficiency of phenolic acids, as determined by the accelerated autooxidation of methyl linoleate and scavenging of the free radical 2,2-diphenyl-1-picrylhydrazyl (141) ° methods, was found to be inversely proportional to the maximal detector response potential in the voltammetric determination of these compounds. No similar correlation was found for the flavonoids . A good correlation was found between the O—H bond dissociation energy of a phenolic compound and its effectiveness as antioxidant, expressed as the rate constant of free radical scavenging . The bond dissociation energy of the phenol O—H bond was estimated by a three-dimensional quantitative structme-activity relationship method incorporating electron densities computed using the Austin Method 1 (AMI) followed by correlation of the... 

Several feruloyl esterases have been purified and characterized (Table 1). However, comparison of their properties is difficult as the range of natural and synthetic substrates used to characterize these enzymes is diverse and the enzyme assays are not unifomi. The substrates range in size and complexity from small, soluble esters such as feruloylated oligosaccharides isolated from plant cell walls and phenolic acid methyl esters or synthetic feruloylated arabinosides to larger, more complex and often less soluble substrates such as feruloylated polymeric plant cell wall fractions (28). The only criterion used in all cases is the release of free ferulic acid or another hydroxycinnamic acid by hydrolysis of an ester bond. Specificity, as defined by Ae rate of catalysis (kca divided by the Michaelis constant gives the best indication of preferred substrates. However, hydrolysis of polymeric substrates is more complicated since not all of the esterified substituents are chemically equal, and effects such as decreased solubility and steric hindrance further complicates any results obtained. Therefore, these data should not be extrapolated to obtain kinetic constants. 

Srour, R. K. and McDonald, L. M. Determination of the acidity constants of methyl red and phenol red indicators in binary methanol- and ethanol-water mixtures. J. Chem. Eng. Data, 53, 116-127 (2008). 

Until relatively recently no kinetic studies on the nitrosation of alcohols had been reported, presumably since the reactions are very rapid and require special techniques. Some kinetic measurements on the reverse reaction, the hydrolysis of alkyl nitrites have been reported here conventional kinetic methods were used. Early workers examined the reactions of the series methyl, ethyl, i-propyl and t-butyl nitrites in an acetic acid-acetate buffer and found a small increase in rate constant along the series (Skrabal et a ., 1939). Later Allen measured the rate constants for the hydrolysis of a number of alkyl nitrites in aqueous dioxan solvent for both acid- and base-catalysed reactions (Allen, 1954). The rate constants for the O-nitrosation of alcohols were determined indirectly by measurement of the overall equilibrium constant for the process, by noting the change in the rate constant for the nitrosation of phenol in the presence of added alcohols. These, combined with the known data for the reverse hydrolysis reaction, enabled the rate constants for the forward reaction to be obtained (Schmid and Riedl, 1967). The reactivity sequence MeOH > EtOH > i-PrOH > t-BuOH was deduced, and attributed to a steric effect. 

Protonation becomes a rapid reaction in protic solvents and in the presence of acids, as demonstrated for, e.g., -butyl acrylate in aqueous solution [207], methyl acrylate in EtOH [208], cinnamates in the presence of phenol in DMF [209], and benzaldehyde in ethanolic buffer solution [210]. Rate constants for protonation of aromatic radical anions (anthracene [211], naphthalene, 2-methoxynaphthalene, 2,3-dimethoxynaphthalene) by a number of proton donors including phenols, acetic acid, and benzoic acids in aprotic DMF were found to vary from 5.0 X 10 M- s-> (for anthracene, in the presence of p-chlorophenol) to 6.2 x lO s (for anthracene, in the presence of pentachlorophenol) [212]. For dimedone, PhOH, or PhC02H the rate of protonation depends on the hydrogen-bond basicity of the solvent and increases in the order DMSO < DMF MeCN [213],... 

Values of molar Kerr constants and dipole moments of nitrogen azoles and their complexes with phenols have been obtained. " These complexes are formed by an intermolecular hydrogen bond between the pyridine-type nitrogen of the azole and the phenolic proton. " The use of dipole moments in conformational studies has shown that A-aryl- and C-aryl- and A-furyl- and C-furyl imidazoles (and benzimidazoles) are nonplanar, but l-(a-furyl)-4,5-diphenylimidazoles do have a planar bicyclic fragment. The dipole moments and conformations of azolides (A-acylazoles) have been studied. In the 1-arylimidazoles the dipole is toward the aryl group. In 4,5-di-t-butylimidazole the molecule is essentially planar, but the C-4—C-5 bond is slightly stretched. Among other imidazole derivatives which have been studied by X-ray are histidine hydrochloride, 4-acetyl-amino - 2 - bromo - 5 - isopropyl -1 - methylimidazole, 4- acetyl - 5 - methyl - 2 -phenylimidazole, and imidazole-4-acetic acid hydrochloride. 

Catalytic supercritical water oxidation is an important class of solid-catalyzed reaction that utilizes advantageous solution properties of supercritical water (dielectric constant, electrolytic conductance, dissociation constant, hydrogen bonding) as well as the superior transport properties of the supercritical medium (viscosity, heat capacity, diffusion coefficient, and density). The most commonly encountered oxidation reaction carried out in supercritical water is the oxidation of alcohols, acetic acid, ammonia, benzene, benzoic acid, butanol, chlorophenol, dichlorobenzene, phenol, 2-propanol (catalyzed by metal oxide catalysts such as CuO/ZnO, Ti02, MnOz, KMn04, V2O5, and Cr203), 2,4-dichlorophenol, methyl ethyl ketone, and pyridine (catalyzed by supported noble metal catalysts such as supported platinum). ... 

Deliquescent, orthorhombic, elongated, six-sided tablets from dimethyl phthalate. dj 1.282. mp 45-46. bp0J 83. Fomin of dicyandiamide begins at 122. Dipole moment in benzene at 2Cryoscopic constant (water) 26.8-28.4. Sp ht 0.547 cal/g/ C between 0° and 39. Heat of formation 14.05 kcal/mole (25 ) heat of combustion —176-4 kcal/-mole (25 ) heat of fusion 2.1 kcal/mole. Heat of vaporization 16.4 kcal/mole. Soly (g/100 g soln) in water at 15 77.5, at 43 100 in butanol at 20 28.8, in methyl ethyl ketone 50.5, in ethyl acetate 42.4. Sol in alcohols, phenols, amines, ethers, ketones. Very sparingly sol in benzene, haJogeaated hydrocarbons. Practically insol in cyclohexane. Solid cyanamide should be stored in a cool, dry place. Polymerizes at 122. Optimum pH for storage of solns is 4, Attacks various metals. Solns can be stored in grass provided they are stabilized with phosphoric, acetic, sulfuric, or boric acid. LDM in rats 125 mg /kg orally. 

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