Bundle: Chemistry: Principles and Reactions, 8th, Loose-Leaf + OWLv2, 1 term (6 months) Printed Access Card
Bundle: Chemistry: Principles and Reactions, 8th, Loose-Leaf + OWLv2, 1 term (6 months) Printed Access Card
8th Edition
ISBN: 9781305717497
Author: William L. Masterton, Cecile N. Hurley
Publisher: Cengage Learning
Question
Book Icon
Chapter 23, Problem 30QAP
Interpretation Introduction

(a)

Interpretation:

The pH at which the zwitter ion [Z] and the cationic form [C+] of the amino acid alanine become equal needs to be calculated.

Concept introduction:

  1. Amino acids are organic compounds composed of C, H, N and O. The two main functional groups include the amino −NH2 and carboxyl −COOH group in addition to a side chain each with a characteristic pKa value.
  2. Isoelectric point (pI) is the pH at which the net charge on the amino acid is zero. For amino acid with one −COOH and one −NH2, the pI is given as:

pI = pKa1+pKa22 ------(1)

Expert Solution
Check Mark

Answer to Problem 30QAP

pH = 2.29

Explanation of Solution

The given amino acid is alanine which has the following structure:

Bundle: Chemistry: Principles and Reactions, 8th, Loose-Leaf + OWLv2, 1 term (6 months) Printed Access Card, Chapter 23, Problem 30QAP , additional homework tip  1

The structures of the respective cationic form (C+), zwitter ion (Z) and the anionic form (A-) are:

Bundle: Chemistry: Principles and Reactions, 8th, Loose-Leaf + OWLv2, 1 term (6 months) Printed Access Card, Chapter 23, Problem 30QAP , additional homework tip  2

The acid-base equilibria for alanine involving the cation and the zwitter ion forms is:

C+(aq) H+(aq) + Z(aq)Ka1=[H+][Z][C+] When [Z] = [C+]Ka1 = [H+]i.e.  [H+]=5.1×103 MpH = -log[H+]=log[5.1×103]=2.29

Interpretation Introduction

(b)

Interpretation:

The pH at which the zwitter ion [Z] and the anionic form [A-] of the amino acid alanine become equal needs to be calculated

Concept introduction:

  1. Amino acids are organic compounds composed of C, H, N and O. The two main functional groups include the amino −NH2 and carboxyl −COOH group in addition to a side chain each with a characteristic pKa value.
  2. Isoelectric point (pI) is the pH at which the net charge on the amino acid is zero. For amino acid with one −COOH and one −NH2, the pI is given as:

pI = pKa1+pKa22 ------(1)

Expert Solution
Check Mark

Answer to Problem 30QAP

pH = 9.74

Explanation of Solution

The given amino acid is alanine which has the following structure:

Bundle: Chemistry: Principles and Reactions, 8th, Loose-Leaf + OWLv2, 1 term (6 months) Printed Access Card, Chapter 23, Problem 30QAP , additional homework tip  3

The structures of the respective cationic form (C+), zwitter ion (Z) and the anionic form (A-) are:

Bundle: Chemistry: Principles and Reactions, 8th, Loose-Leaf + OWLv2, 1 term (6 months) Printed Access Card, Chapter 23, Problem 30QAP , additional homework tip  4

The acid-base equilibria for alanine involving the anion and the zwitter ion forms is:

Z(aq) H+(aq) + A(aq)Ka2=[H+][A][Z] When [Z] = [A]Ka2 = [H+]i.e.  [H+]=1.8×1010 MpH = -log[H+]=log[1.8×1010]=9.74

Interpretation Introduction

(c)

Interpretation:

The pH at the isoelectric point needs to be calculated

Concept introduction:

  1. Amino acids are organic compounds composed of C, H, N and O. The two main functional groups include the amino −NH2 and carboxyl −COOH group in addition to a side chain each with a characteristic pKa value.
  2. Isoelectric point (pI) is the pH at which the net charge on the amino acid is zero. For amino acid with one −COOH and one −NH2, the pI is given as:

pI = pKa1+pKa22 ------(1)

Expert Solution
Check Mark

Answer to Problem 30QAP

pH = 6.02

Explanation of Solution

For alanine at the isoelectric point:

pI =pH =  pKa1+pKa22 pKa1 = -log[Ka1] =log[5.1×103]=2.29 pKa2 = -log[Ka2] =log[1.8×1010]=9.74pH = 2.29 + 9.742=6.02

Want to see more full solutions like this?

Subscribe now to access step-by-step solutions to millions of textbook problems written by subject matter experts!
Students have asked these similar questions
Draw a structural formula for the major product of the acid-base reaction shown. H 0 N + HCI (1 mole) CH3 N' (1 mole) CH3 You do not have to consider stereochemistry. ● • Do not include counter-ions, e.g., Na+, I, in your answer. . In those cases in which there are two reactants, draw only the product from 989 CH3 344 ? [F
Question 15 What is the major neutral organic product for the following sequence? 1. POCI₂ pyridine ? 2. OsO4 OH 3. NaHSO Major Organic Product ✓ OH OH 'OH OH 'OH 'CI
URGENT! PLEASE HELP!

Chapter 23 Solutions

Bundle: Chemistry: Principles and Reactions, 8th, Loose-Leaf + OWLv2, 1 term (6 months) Printed Access Card

Knowledge Booster
Background pattern image
Similar questions
SEE MORE QUESTIONS
Recommended textbooks for you
Text book image
Chemistry: The Molecular Science
Chemistry
ISBN:9781285199047
Author:John W. Moore, Conrad L. Stanitski
Publisher:Cengage Learning
Text book image
Chemistry: Principles and Reactions
Chemistry
ISBN:9781305079373
Author:William L. Masterton, Cecile N. Hurley
Publisher:Cengage Learning