Acidity constant table

Data for zeroth-order nitration in these various solvents are given in table 3.1. Fig. 3.1 shows how zeroth-order rate constants depend on the concentration of nitric acid, and table 3.2 shows how the kinetic forms of nitration in organic solvents depend on the reactivities of the compounds being nitrated. 

A similar circumstance is detectable for nitrations in organic solvents, and has been established for sulpholan, nitromethane, 7-5 % aqueous sulpholan, and 15 % aqueous nitromethane. Nitrations in the two organic solvents are, in some instances, zeroth order in the concentration of the aromatic compound (table 3.2). In these circumstances comparisons with benzene can only be made by the competitive method. In the aqueous organic solvents the reactions are first order in the concentration of the aromatic ( 3.2.3) and comparisons could be made either competitively or by directly measuring the second-order rate constants. Data are given in table 3.6, and compared there with data for nitration in perchloric and sulphuric acids (see table 2.6). Nitration at the encounter rate has been demonstrated in carbon tetrachloride, but less fully explored. ... 

The acidity constant for an organic weak acid was determined by measuring its absorbance as a function of pH while maintaining a constant total concentration of the acid. Using the data in the following table, determine the acidity constant for the organic weak acid. 

Anhydrous oxaUc acid is very soluble in polar solvents. The ionisation constant is comparable with those of many mineral acids and is exceeded only by those of a few organic acids is approximately the same as the ionisation constant of bensoic acid (see Table 1). 

This procedure can now be repeated with a base D that is slightly weaker than C, using C as the reference. In this stepwise manner, a series of p determinations can be made over the acidity range from dilute aqueous solution to highly concentrated mineral acids. Table 8-18 gives pS bh+ values determined in this way for nitroaniline bases in sulfuric and perchloric acid solutions. This technique of determining weak base acidity constants is called the overlap method, and the series of p kBH+ values is said to be anchored to the first member of the series, which means that all of the members of the series possess the same standard state, namely, the hypothetical ideal 1 M solution in water. 

Table 17.1 Acidity Constants of Some Alcohols and Phenols...

Table 22.1 Acidity Constants for Some Organic Compounds...

Mix 400 mL of pure concentrated hydrochloric acid with 250-400 mL of distilled water so that the specific gravity of the resultant acid is 1.10 (test with a hydrometer). Insert a thermometer in the neck of a 1 L Pyrex distillation flask so that the bulb is just opposite the side tube, and attach a condenser to the side tube use an all-glass apparatus. Place 500 mL of the diluted acid in the flask, distil the liquid at a rate of about 3-4 mL min-1 and collect the distillate in a small Pyrex flask. From time to time pour the distillate into a 500 mL measuring cylinder. When 375 mL has been collected in the measuring cylinder, collect a further 50 mL in the small Pyrex flask watch the thermometer to see that the temperature remains constant. Remove the receiver and stopper it this contains the pure constant boiling point acid. Note the barometric pressure to the nearest millimetre at intervals during the distillation and take the mean value. Interpolate the concentration of the acid from Table 10.5. 

Luchkevich et al. (1986, Table 6) demonstrated that for the three isomeric nitro-benzenediazonium ions and their (Z)-diazohxydroxides the acidity constants can be determined by ultraviolet spectrophotometry, by potentiometry, from the kinetics of reaction with hydroxide ions, from the (Z) (E) isomerization kinetics, and from the kinetics of azo coupling reactions. These independent methods gave surprisingly consistent results. ... 

The effect of the diazonio group on the reactivity of benzene derivatives was studied quantitatively by Lewis and Johnson (1959) by measuring the acidity constants of 3- and 4-diazoniobenzoic acid, of the 4-diazonio-anilinium ion, of 3- and 4-diazo-niophenol, and of 4-diazoniophenylacetic acid. The results are given in Table 7-3. 

The kinetics of decarboxylation of 4-aminosalicylic acid in some buffer solutions at 50 °C were studied. The first-order rate coefficients increased with increasing buffer concentration, though the pH and ionic strength were held constant (Table 217). This was not a salt effect since the rate change produced by substituting potassium chloride for the buffer salt was shown to be much smaller. It follows from the change in the first-order rate coefficients (kx) with... 

Interestingly, comparison of the values of pAHB and the acidity constants pKa in a series of the same family of compounds, such as carbonyl compounds, amines, pyridines and sulphoxides, shows that a good correlation exists between p/CHB and pgiving straight lines in each series of compounds with parallel slopes. This enables one to calculate the difference of the several pKa values at the same p/CHB value, and vice versa. Thus, at p= 0, p/CHB values of various functional groups were determined and are shown in Table 13. 

Complexes with the Fluoride Ion. For the compilation of stability constants (Table IV) of complexes with F , we have used, when needed, thermodynamic parameters (K, AH) pertaining to the dissociation of hydrofluoric acid as given by Smith and Martell (77) or extrapolated from their selection. 

Table 10.1 lists the acidity constants of some other weak acids in aqueous solution. 

Because a proton transfer equilibrium is established as soon as a weak acid is dissolved in water, the concentrations of acid, hydronium ion, and conjugate base of the acid must always satisfy the acidity constant of the acid. We can calculate any of these quantities by setting up an equilibrium table like that in Toolbox 9.1. 

To calculate the pH and percentage deprotonation of a solution of a weak acid, set up an equilibrium table and determine the H30 concentration by using the acidity constant. 

Protons are donated successively by polyprotic acids, with the acidity constant decreasing significantly, usually by a factor of about 10 , with each proton lost (Table 10.9) ... 

It is not only p-substituted phenols that have been connected by methylene groups an extended calixarene based on naphthalene units [57] has also been synthesized and its acidity constants have been measured (see Table 25 Poh and Lim, 1989, 1990). In contrast to the calix[4]arenes, the pKa of the expanded calixarene [57] did not differ much from the of the analogue [58]. This may have two explanations (i) the conformation of the expanded calixarene is different from phenol-based calix[4]arenes and a special stabilization of the anion does not occur, (ii) this stabilization occurs but it is also present in the analogue. A stabilization by the neighbouring... 

By methods analogous to those used for the tetrahedral intermediates related to carboxylic acid derivatives, Guthrie proceeded from the heat of formation of pentaeth-oxyphosphorane to free energies of the P(OEt) (OH)5 species. °° This allowed the calculation of the equilibrium constants for addition of water or hydroxide to simple alkyl esters of phosphoric acid see Table 1.7. 

Values of Kadd for the addition of water (hydration) of alkenes to give the corresponding alcohols. These equilibrium constants were obtained directly by determining the relative concentrations of the alcohol and alkene at chemical equilibrium. The acidity constants pATaik for deprotonation of the carbocations by solvent are not reported in Table 1. However, these may be calculated from data in Table 1 using the relationship pA ik = pATR + logA dd (Scheme 7). 

The rate of acid-induced demetalation depends only slightly on the nature of the head substituents X (Table I). In contrast, the tail-R groups dramatically affect k and, for the most part, k3, suggesting that tail amide O-atoms are sites of peripheral protonation. Thus, the acid tolerant Fem-TAML catalysts with tail electron-withdrawing groups should be more acid resistant and replacement of R = Me with R = F results in a remarkable stabilization. The rate constants (Table I) show that under weakly acidic conditions (pH 2-3), when the k pathway dominates over k3, fluorinated lk is 105-fold more H +-tolerant than la. 

Kv is the self-ionization constant for water (Table 3.2) and equation (3.18) reflects the not surprising inverse relation between Ka and Kh. It is only when Ka and Kv for a compound are of different magnitudes that it may be classified as an acid or a base. An example which is difficult to classify is hypoiodous acid (HOI) where K = 2.5 x lO11 mol dm 3 andKh = 3.2 x 10 10 mol dm3. Although Kb has been widely used in the past, it is a quantity which is largely redundant, for Ka (or pKa) may be used to express the strength of bases as well as acids, see Table 3.3. 

Table 4. Major building blocks of lipid bilayers in biological membranes and their speciation and acidity constants...

The dioxo complexes of W(IV) and Mo(IV), having high pKa values (Table II), are formed via hydrolysis as the rate-determining step (Scheme 4) and the observed rate constants for the inversion along the O-M-O axis for the W(IV) and the Mo(IV) complexes are therefore defined by Eq. (18). These were calculated as a function of pH, using the proton exchange rate constants (Table IV) and the acid dissociation constants (Table II)... 

Extractions of aqueous solutions of racemic amino-acid ester salts with solutions of / -6/s(dinaphthyl)-22-crown-6 [284] in chloroform revealed the dependence of the enantiomeric distribution constant on the structure of the amino acid ester (Table 64). In order to limit the concentrations of complex in the aqueous phase, inorganic salts were added. In the case of tyrosine, serine and alanine no extraction of salt was observed obviously these salts form very hydrophilic complexes. The highest degree of chiral recognition was found with [284] and p-hydroxyphenylglycine methyl ester hexafluorophosphate [A(AG°)... 

Table I. Rate Constants of the Adsorption/Desorption and Equilibrium Acidity Constants...

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