Book cover for Organic Chemistry

Organic Chemistry

John McMurry

ISBN #9781305080485

9th Edition

1,986 Questions

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Homework Questions

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Summary

Learning Objectives

Key Concepts

Example Problems

Explanations

Common Mistakes

Summary

This section covers the fundamental chemistry of amino acids, peptides, and proteins. Key points include the structure and stereochemistry of ?–amino acids, the formation of zwitterions in aqueous solutions, and the importance of isoelectric points in protein behavior. Detailed methods for peptide synthesis (both in solution and via the Merrifield solid-phase method) and sequencing via Edman degradation highlight the interplay between chemical reactions and biological functionality. Enzyme mechanisms and protein structures are explained, stressing the critical role of molecular interactions, such as hydrogen bonding, hydrophobic effects, and the contribution of cofactors in stabilizing transition states.

Learning Objectives

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Key Concepts

CONCEPT

DEFINITION

Acid–Base Chemistry

The study of acids and bases using both the Brønsted–Lowry (proton-donating/accepting) and Lewis (electron pair accepting/donating) frameworks, including quantification via pKa values, which together explain chemical reactivity in organic molecules. •

Example Problems

Example 1

How many of the $\alpha$ -amino acids shown in Table $26-1$ contain aromatic rings? How many contain sulfur? How many contain alcohols? How many contain hydrocarbon side chains?

Example 2

Of the 19 L amino acids, 18 have the $S$ configuration at the $\alpha$ carbon. Cysteine is the only L. amino acid that has an $R$ configuration. Explain.

Example 3

The amino acid threonine, $(2 S, 3 R)-2$ -amino- 3 -hydroxybutanoic acid, has two chirality centers. (a) Draw threonine, using normal, wedged, and dashed lines to show dimensionality. (b) Draw a diastereomer of threonine, and label its chirality centers as $R$ or $S$.

Example 4

Hemoglobin has $\mathrm{p} I=6.8 .$ Does hemoglobin have a net negative charge or net positive charge at $\mathrm{pH}=5.3 ?$ At $\mathrm{pH}=7.3 ?$

Example 5

Show how you could prepare the following $\alpha$ -amino acids from the appropriate carboxylic acids: (a) Phenylalanine (b) Valine

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Step-by-Step Explanations

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