Acids in aqueous solutions

A) Benzylthiouronium salts. The sodium salt of an acid in aqueous solution will react with benzylthiouronium chloride ... 

The molecular weight of many carboxylic acids which arc freely soluble in cold water (i.e., chiefly the aliphatic acids) can readily be obtained by titrating a known weight of the acids in aqueous solution with standard sodium or potassium hydroxide solution, using phenolphthalein as an indicator. To avoid the use of unduly large quantities of the acid, it is advisable to use Mj2 caustic alkali solution, and in order to obtain a sharp end>point, this alkali solution... 

Furthermore, the number of diene - dienoplrile combinations that can be expected to undergo a Lewis-acid catalysed Diels-Alder reaction is limited. Studies by Wijnen leave little doubt that the rate of typical Diels-Alder reactions, where the dienophile is activated by one or more carbonyl functionalities, does not respond to the presence of Lewis acids in aqueous solution , at least not beyond the extent that is expected for non-specific interactions (salt effects). No coordination of the Lewis acid to the dienophile was observed in these cases, which is perhaps not surprising. Water is... 

We conclude that, when employirg hard Lewis-acids in aqueous solution, the term Lewis-acid catalysis should be used with caution, and only after evidence for a direct interaction between Lewis-acid and substrate has been obtained. 

Sodium Chloroacetate Sodium chloroacetate [3926-62-3] mol wt 116.5, C2H2C102Na, is produced by reaction of chloroacetic acid with sodium hydroxide or sodium carbonate. In many appHcations chloroacetic acid or the sodium salt can be used interchangeably. As an industrial intermediate, sodium chloroacetate may be purchased or formed in situ from free acid. The sodium salt is quite stable in dry soHd form, but is hydrolyzed to glycoHc acid in aqueous solutions. The hydrolysis rate is a function of pH and temperature (29). 

Monofluorophosphoric Acid. Monofluorophosphoric acid (1) is a colorless, nonvolatile, viscous Hquid having practically no odor. On cooling it does not crystallize but sets to a rigid glass at —78°C. It has a density of = 1.818 g/mL. Little decomposition occurs up to 185°C under vacuum but it caimot be distilled. An aqueous solution shows the normal behavior of a dibasic acid the first neutralization point in 0.05 N solution is at pH 3.5 and the second at pH 8.5. Conductance measurements, however, indicate H2PO2F behaves as a monobasic acid in aqueous solution (59). The... 

During certain substitution reactions, the carboxyl group is often replaced by the entering group. An example is fuming nitric acid, which results in the formation of trinitrophenol. Another is the bromination of saUcyhc acid in aqueous solution to yield 2,4,6-tribromophenol [25376-38-9] (eq. 6). 

Alkali metal sulfamates are stable in neutral or alkaline solutions even at boiling temperatures. Rates of hydrolysis for sulfamic acid in aqueous solutions have been measured at different conditions (Table 4) (8,10)-... 

As a weak acid (in aqueous solution) carbon dioxide neutralizes excess caustic in textile manufacturing operations. It does not injure fabrics and is easy to use. Carbon dioxide is also used for neutralizing alkaline wastewaters, treating skins in tanning operations, and carbonating treated water to prevent scaling. 

G. Kortiim, W. Vogel and K. Andrussow, Dissociation Constants of Organic Acids in Aqueous Solution, Butterworths, London, 1961. 

Figure 7 Free energy changes of halo-substituted carboxyl acid in aqueous solution upon deproto-nation referred to acetic acid.

Strong acids in aqueous solution convert allenes to ketones via an enol intermediate. This process also involves protonation at a terminal carbon. 

The first acid dissociation constant of sulfurous acid in aqueous solution is therefore defined as ... 

Both chloric and bromic acids are strong acids in aqueous solution (pX < 0) whereas iodic acid is slightly weaker, with pX 0.804, i.e. X 0.157. 

Simple l,2,3,4-tetrahydro-)3-carbolines have been aromatized in this manner. Palladium black at 160-170° or at higher temperature, palladium-maleic acid in aqueous solution, and platinum/oxygen have been used for the purpose. Palladium-on-charcoal in a high-boiling solvent has been used also to aromatize 5,6,7,8-tetrahydro-j3-carbohnes and 6,7,8,9-tetrahydro-3-carbo-hne. ... 

The rearrangement takes place in the presence of strong mineral acids (e.g. hydrochloric or sulfuric acid) in aqueous solution or water-alcohol mixtures at room temperature in some cases slight warming may be necessary. ... 

A) Preparation of p-Acetylphenoxyacetic Acid p-Hydroxy-acetophenone is treated with chloroacetic acid in aqueous solution in the presence of sodium hydroxide. The desired acid is then isolated from its sodium salt in a total yield of 80 to 82%, excess of p-hydroxy-acetophenone having been extracted with methylene chloride. 

Flo. 33. Extrapolation to zero ionic strength of the equilibrium constant of acetic acid in aqueous solution at 25°C. 

When the measurements have been made in dilute solutions, only a small extrapolation is required, to obtain the value of K at extreme dilution. Figure 33 shows this extrapolation for the dissociation of acetic acid in aqueous solution at 25°, the values of log K being plotted against the ionic strength. The point at which the curve meets the axis gives the value K = 1.754 X 10-6, while the last two experimental points correspond to the values 1.752 X 10-6 and 1.747 X 10-6. 

An example of the use of (140) is shown in Fig. 41. The small circles in Fig. 41 give the experimental values of log Kx for acetic acid in aqueous solution. The theoretical curve marked 219 is calculated from (140), with a — 1.35, C = 850.2, and d = 219. It will be seen that the agreement is better than might have been expected. To obtain still closer agreement, a somewhat larger value of d is required. The other curve in Fig. 41, calculated with d = 240, gives almost perfect agreement. 

We expect that the dissociation constant of a weak deutero-acid in D20 solution will be smaller than that of the corresponding proto-acid in aqueous solution and we may say at once that in all six cases that have... 

The Acetate Ion. For the B-coefficients of lithium acetate and potassium acetate, which are of course completely dissociated in aqueous solution, Cox and Wolfenden obtained at 25°C the values +0.397 and +0.238. These large values could be due entirely to the large size of the molecular ion or could be due partly to the fact that the anion produces order in its co-sphere. To test this, Laurence and Wolfenden measured the B-coefficient of acetic acid in aqueous solution at 25°C. 

Although benzene-sulfonic acid, CnITsSChH, is a strong acid in aqueous solution, it is not completely dissociated in formic acid solution. In a 0.1-molal solution the degree of dissociation was estimated at 60 per cent.2 This is comparable with the dissociation of HIOs in aqueous solution and is compatible with J = 0.14 electron-volt for the formation of (HCOOH2)+. Using this value the level has been included in Fig. 65. 

An acidity list covering more than 5000 organic compounds has been published E.I . Serjeant and B. Dempsey (eds.), "Ionization Constants ol Organic Acids in Aqueous Solution." IUPAC Chemical Data Series No. 23, Pergamon Press, Oxford, 1979. 

Table 11-1V. relative strengths of acids in aqueous solution... 

Were kinetics experiments carried out with HI as the source of I- and H+ ions, the rate would be proportional to the square of the analytical (formal) concentration, Chi-That is, the product [I ][H+] is equal to Chi2, since HI is a very strong acid in aqueous solution. Yet, were one to take this observation literally, not remembering the complete ionization of HI, the application of Rule 1 would have suggested a transition state containing the elements of two molecules of HI, not one. 

For the purpose of systematizing kinetic and equilibrium data, for literally hundreds of reactions, it is desirable to have a single reference series for all. Hammett adopted as the standard the acid ionization constants for substituted benzoic acids in aqueous solution at 25 °C. This choice was fortunate because the compounds are stable and for the most part readily available. Also, their pA"a s can easily and precisely be measured for nearly every substituent. Thus, one constructs a plot according to either of the following equations, in which Eq. (10-4) constitutes a further example ... 

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