Acetone, dissociation constants acids

Amino-2-hydroxybenZOiC acid. This derivative (18) more commonly known as 4-aminosa1icy1ic acid, forms white crystals from ethanol, melts with effervescence and darkens on exposure to light and air. A reddish-brown crystalline powder is obtained on recrystallization from ethanol —diethyl ether. The compound is soluble ia dilute solutioas of nitric acid and sodium hydroxide, ethanol, and acetone slightly soluble in water and diethyl ether and virtually insoluble in benzene, chloroform or carbon tetrachloride. It is unstable in aqueous solution and decarboxylates to form 3-amiaophenol. Because of the instabihty of the free acid, it is usually prepared as the hydrochloride salt, mp 224 °C (dec), dissociation constant p 3.25. 

Physical properties of the acid and its anhydride are summarized in Table 1. Other references for more data on specific physical properties of succinic acid are as follows solubiUty in water at 278.15—338.15 K (12) water-enhanced solubiUty in organic solvents (13) dissociation constants in water—acetone (10 vol %) at 30—60°C (14), water—methanol mixtures (10—50 vol %) at 25°C (15,16), water—dioxane mixtures (10—50 vol %) at 25°C (15), and water—dioxane—methanol mixtures at 25°C (17) nucleation and crystal growth (18—20) calculation of the enthalpy of formation using semiempitical methods (21) enthalpy of solution (22,23) and enthalpy of dilution (23). For succinic anhydride, the enthalpies of combustion and sublimation have been reported (24). 

Bis(ethylenediamine)oxohydroxorhenium(V) perchlorate consists of purple needles which dissolve in water or acids to give a purple solution. It is acidic, with a dissociation constant of 5 X 10 In water it partially reverts to the dioxo form but is stable in dilute acid. It is insoluble in absolute methanol and acetone. An absorption maximum at 487 m/x, molar absorbancy of 19.1, is observed together with a weak absorption at 650 m/t. 

The parameters cr , cTp, and (7"p are for the dissociation constants of m-, / -substituted benzoic acids and of p-substituted phenols, fr m and o p are for the solvolyses of m- and p-substituted phenyldime-thyl carbinyl chloride in 90% acetone-water. 0° is for the reaction of hydroxide ion with the ethyl esters of substituted phenylacetic acids. 

Dissociation Constants op Acids in Acetone Containing 10% Water... 

FIGURE 3.2 Br0nsted plot for the dehydration of acetone hydrate in acetone, catalyzed by acid. The logarithm of the catalytic rate constant is plotted versus the negative of the dissociation constant of the acid. Points are shown for 32 carboxylic acids and 15 phenols. The point labeled 47 represents 2,4-dinitrophenol. Acids of other types (e.g., oximes) fell much further off the line (see Section 3.6.3). Source Bell and Higginson (1949) by permission of the Royal Society of London. 

The iodation of acetone is catalysed by acids. The catalytic rate constant, has the following values according to the nature of the acid HA (K, acid dissociation constant) ... 

OH- solutions in DMSO-water mixtures. For acetone, the ionisation ratios were measured by spectrophotometry, but in other cases an indirect kinetic method was used. This latter is based on monitoring the rates of detritiation of a standard labelled carbon acid (HS1) both in the presence and absence of a second acid HS2 (ketone). The dissociation of HS2 brings about a decrease in hydroxide ion concentration, and, since the rate of detritiation of HS1 is proportional to [OH ], the consequent decrease in rate can be related to [(S2) ]/[HS2]. Data listed in Table 7 exhibit large variations with structure, far larger than those expected from ionisation rate constants if an enolate-like transition state were assumed (see p. 34). 

Crucial questions concern the identity of the species that act as electron donors in forming the ArN02 and ArN022 intermediates. The simplest possibility is that ArN02, is formed via direct SET from the alkoxide ion (Scheme I, path a). The resulting alkoxy radical should rapidly give an alkyl radical via H abstraction from the solvent. The a-hydroxy radical so produced is in acid-base equilibrium with its conjugate base, the acetone radical anion. The equilibrium constant for the dissociation of the 2-propanol... 

Kinetic parameters have been established for solvolysis of the pentacyanofer-rate(III) derivative [Fe(CN)5(N02)] . For aquation, which is acid-catalyzed at pH <5, A//= = 43kJmol-, =-80 J K" mol", and A =+2 cm" mol". Intrinsic and solvational contributions are presumably closely balanced in the case of A Rate constants for solvolysis of [Fe(CN)5(N02)] in water, methanol, dimethyl sulfoxide, and dimethylformamide correspond with the electron-donating abilities of the respective solvents. Activation volumes for the nonaqueous solvents, between +20 and +27 cm" mor reflect the dissociative nature of these solvoly-ses. " Rate constants for dissociation of the [Fe(CN)5(2,6-Me2pyrazine)]" anion in binary aqueous solvents containing methanol, acetone, or acetonitrile correlate well with acceptor numbers for the respective media, though with a very different... 

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