Concept explainers
Interpretation:
The difference between the first and second ionization constants of dibasic acids decreases with increase in distance between the carboxyl groups, as shown in the table, is to be explained.
Concept introduction:
The carboxylate ion obtained by first ionization has one negative charge while the dicarboxylate anion obtained by second ionization has two negative charges. If the two negative charges are in close proximity in the anion, the repulsion between the charges makes the formation of the dianion difficult. In that case there will be a large difference between the first and second ionization constants. With increasing distance between the charges, the mutual repulsion decreases, the dianion becomes relatively stable. This results in small differences between first and second ionization constants.
To explain:
Why the difference between the first and second ionization constants of dibasic acids, oxalic, succinic and adipic acids, decreases with increase in distance between the carboxyl groups as shown in the table.
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Chapter 20 Solutions
Organic Chemistry
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- The pKa values of a few ortho-, meta-, and para-substituted benzoic acids are shown below: The relative pKa values depend on the substituent. For chloro-substituted benzoic acids, the ortho isomer is the most acidic and the para isomer is the least acidic; for nitro-substituted benzoic acids, the ortho isomer is the most acidic and the meta isomer is the least acidic; and for amino-substituted benzoic acids, the meta isomer is the most acidic and the ortho isomer is the least acidic. Explain these relative acidities. a. Cl: ortho > meta > para b. NO2: ortho > para > meta c. NH2: meta > para > orthoarrow_forwardLow-molecular-weight dicarboxylic acids normally exhibit two different pK, values. Ionization of the first carboxyl group is easier than the second. This effect diminishes with molecular size, and for adipic acid and longer chain dicarboxylic acids, the two acid ionization constants differ by about one pK unit. Dicarboxylic Acid Structural Formula pK,2 a1 Охalic НООССООН 1.23 4.19 Malonic НООСCH,COOH 2.83 5.69 Succinic HOOC(CH,),COOH 4.16 5.61 Glutaric HOOC(CH,),COOH 4.31 5.41 Adipic HOOC(CH,),COOH 4.43 5.41 Why do the two pK, values differ more for the shorter chain dicarboxylic acids than for the longer chain dicarboxylic acids?arrow_forwardAcetic, formic, hydrofluoric, and acetylsalicylic acids have the following values of pKa (25°C), respectively: 4.74, 3.74, 3.17, 3.49. Order these acids in order acidity (from highest to lowest acidity)arrow_forward
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- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning