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2. (a) This problem deals with the acidity of amines, not their basicity (or the acidity of their conjugate acids). While cyclohexylamine is a normal amine and is an extremely weak acid (pKa -36), aniline (Ph-NH2) is somewhat more acidic, with a pKa of ~28. Explain this observation by comparing both o- and t-effects on the acidity of these two amines. (b) Similar to phenols, substituted derivatives of aniline have explainable shifts in pKa. Explain the following pKas based on the o- and t-effects of the -OCH3 substituent. o-Methoxyaniline: 26 m-Methoxyaniline: 26 p-Methoxyaniline: 29 Here are the pKas (for the N-H bond, not O-H) for the hydroxyanilines: o-Hydroxyaniline: 33 m-Hydroxyaniline: 29 p-Hydroxyaniline: 30 (c) Briefly explain why all three of these pKas are above 28.

2. (a) This problem deals with the acidity of amines, not their basicity (or the acidity of their conjugate acids). While cyclohexylamine is a normal amine and is an extremely weak acid (pKa -36), aniline (Ph-NH2) is somewhat more acidic, with a pKa of ~28. Explain this observation by comparing both o- and t-effects on the acidity of these two amines. (b) Similar to phenols, substituted derivatives of aniline have explainable shifts in pKa. Explain the following pKas based on the o- and t-effects of the -OCH3 substituent. o-Methoxyaniline: 26 m-Methoxyaniline: 26 p-Methoxyaniline: 29 Here are the pKas (for the N-H bond, not O-H) for the hydroxyanilines: o-Hydroxyaniline: 33 m-Hydroxyaniline: 29 p-Hydroxyaniline: 30 (c) Briefly explain why all three of these pKas are above 28.

Chemistry
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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2. (a) This problem deals with the acidity of amines, not their basicity (or the acidity of their conjugate acids). While cyclohexylamine is a normal amine and is an extremely weak acid (pKa ~36), aniline (Ph-NH2) is somewhat more acidic, with a pKa of ~28. Explain this observation by comparing both ơ- and Tt-effects on the acidity of these two amines. (b) Similar to phenols, substituted derivatives of aniline have explainable shifts in pKa. Explain the following pKas based on the o- and t-effects of the -OCH3 substituent. o-Methoxyaniline: 26 m-Methoxyaniline: 26 p-Methoxyaniline: 29 Here are the pKas (for the N-H bond, not O-H) for the hydroxyanilines: o-Hydroxyaniline: 33 m-Hydroxyaniline: 29 p-Hydroxyaniline: 30 (c) Briefly explain why all three of these pKas are above 28. (d) Explain why the o- isomer is the highest. (e) Make predictions for the pKas of the three cyano-anilines, and provide explanations. Use actual numbers, but only the trend and your explanations will be graded. o-Cyanoaniline: m-Cyanoaniline: p-Cyanoaniline:
Transcribed Image Text:2. (a) This problem deals with the acidity of amines, not their basicity (or the acidity of their conjugate acids). While cyclohexylamine is a normal amine and is an extremely weak acid (pKa ~36), aniline (Ph-NH2) is somewhat more acidic, with a pKa of ~28. Explain this observation by comparing both ơ- and Tt-effects on the acidity of these two amines. (b) Similar to phenols, substituted derivatives of aniline have explainable shifts in pKa. Explain the following pKas based on the o- and t-effects of the -OCH3 substituent. o-Methoxyaniline: 26 m-Methoxyaniline: 26 p-Methoxyaniline: 29 Here are the pKas (for the N-H bond, not O-H) for the hydroxyanilines: o-Hydroxyaniline: 33 m-Hydroxyaniline: 29 p-Hydroxyaniline: 30 (c) Briefly explain why all three of these pKas are above 28. (d) Explain why the o- isomer is the highest. (e) Make predictions for the pKas of the three cyano-anilines, and provide explanations. Use actual numbers, but only the trend and your explanations will be graded. o-Cyanoaniline: m-Cyanoaniline: p-Cyanoaniline:
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