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.

Organic Chemistry

8th Edition

ISBN:9781305580350

Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Publisher:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Chapter23: Amines

Section23.9: Hofmann Elimination

Problem 23.14P

See similar textbooks

Similar questions

Complete the following acid-base reactions and predict the direction of equilibrium (to the right or to the left) for each. Justify your prediction by citing values of pKa for the stronger and weaker acid in each equilibrium. For values of acid ionization constants, consult Table 23.2 (Acid Strengths, pKa, of the Conjugate Acids of Selected Amines) and Appendix 2 (Acid Ionization Constants for the Major Classes of Organic Acids). Where no ionization constants are given, make the best estimate from the information given in the reference tables and sections.
Which is the stronger base: N-methylaniline (C6H5NHCH3) or benzylamine (C6H5CH2NH2). Explain your reasoning, supporting it with appropriate resonance contributors.
You could extract caffeine from neutral organics by treatment with aqueous HCl (acid). Write the structure of the conjugate acid of caffeine (after treatment with HCl) and explain why it would dissolve in the aqueous layer.
Aliphatic amines are more basic than ammonia, whereas aromatic amines are less basic than ammonia. Is that true or false?
p-Nitrobenzyl alcohol is more acidic than benzyl alcohol but p-Methoxybenzyl alcohol is less acidic. Illustrate your explanation.
According to the Evan's pKa table, phenol has a pKa of 9.95. p-Nitro and m-nitrophenol have pKas of 7.14 and 8.35 respectively. Using resonance structures, explain the observed trends in the acidity of these molecules.
Explain the observed difference in the pKa values of the conjugate acids of amines A and B.
Explain the differences in acidity between p-cyanobenzoic acid and m-cyanobenzoic acid. Illustrate your answer appropriately, showing the acid-base reaction that takes place with each of these and explaining in such terms as electronic (inductive or resonance) and/or steric effects.
Hypoglycin A, an amino acid derivative found in unripened lychee, is anacutely toxic compound that produces seizures, coma, and sometimesdeath in undernourished children when ingested on an empty stomach. (a) Draw the neutral, positively charged, and negatively charged forms of hypoglycin A. (b) Which form predominates at pH = 1, 6, and 11? (c) What is the structure of hypoclycin A at its isoelectric point?
Rank the following amines based on basicity Rationalize the electronic effects responsible for the basicity of amines
(a) Write the structures of main products when benzene diazonium chloride reacts with the following reagents :(i) H3PO2 + H2O (ii) CuCN/KCN (iii) H2O(b) Arrange the following in the increasing order of their basic character in an aqueous solution :C2H5NH2, (C2H5)2NH, (C3H5)3N(c) Give a simple chemical test to distinguish between the following pair of compounds :C6H5—NH2 and C6H5—NH—CH3
What is the predominant form of cyclohexylamine at pH 9.5? Approximately what fraction is in this form?