Strength acetic acid effect

Bifunctional catalysis in nucleophilic aromatic substitution was first observed by Bitter and Zollinger34, who studied the reaction of cyanuric chloride with aniline in benzene. This reaction was not accelerated by phenols or y-pyridone but was catalyzed by triethylamine and pyridine and by bifunctional catalysts such as a-pyridone and carboxylic acids. The carboxylic acids did not function as purely electrophilic reagents, since there was no relationship between catalytic efficiency and acid strength, acetic acid being more effective than chloracetic acid, which in turn was a more efficient catalyst than trichloroacetic acid. For catalysis by the carboxylic acids Bitter and Zollinger proposed the transition state depicted by H. 

All other things being equal, the strength of a weak acid increases if it is placed in a solvent that is more basic than water, whereas the strength of a weak base increases if it is placed in a solvent that is more acidic than water. In some cases, however, the opposite effect is observed. For example, the pKb for ammonia is 4.76 in water and 6.40 in the more acidic glacial acetic acid. In contradiction to our expectations, ammonia is a weaker base in the more acidic solvent. A full description of the solvent s effect on a weak acid s piQ or on the pKb of a weak base is beyond the scope of this text. You should be aware, however, that titrations that are not feasible in water may be feasible in a different solvent. 

Fig. 4. Effect of combined acetic acid content on (a) hardness, (b) absorption, (c) impact strength, and (d) temperature of cellulose acetate (8). To convert...

Another example is the acidities of a series of carboxylic acids. It is known that the substitution effect on these compounds also depends on the environment. The behavior of the halo-substituted acetic acids is one of the prototype problems for the solvent effect on acidity The order in strength of the haloacetic acids in the gas phase is... 

A very wide range of substituent effects have also been measured using acetic acid (4 vol.) and aqueous sulphuric acid (3 vol.), the rate coefficients for the corresponding strengths of the added sulphuric acid being given in Table 232 (refs. 537, 673, 679-685). It will be noted that the rate coefficients do not always increase with an increase in the strength of the sulphuric acid (as stated) and this arises from the same reason noted above except that the problem becomes more... 

Evidently the alteration of the F , values with introduction of chlorines cannot be attributed to its effect on the alteration of the strengths of the substituted acetic acids, for alcohols and esters exhibit similar changes. In order to examine the moment of the C—Cl union, some idea of the nature of its orientation at a water-air interfece must be obtained. 

Effect of Acid Strength. When a higher fatty acid is used instead of acetic acid, the oxidation rate is lower as the carbon number of the... 

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