Organic Chemistry

John McMurry

ISBN #9781305080485

9th Edition

1,986 Questions

21,829 Students Helped

Homework Questions

Summary

Learning Objectives

Key Concepts

Example Problems

Explanations

Common Mistakes

Summary

This chapter delineates the fundamental principles governing nucleophilic substitution and elimination reactions of alkyl halides. Students learn that SN2 reactions are characterized by a single-step backside attack leading to inversion of configuration, whereas SN1 reactions involve carbocation intermediates that result in racemization. Similarly, elimination reactions can proceed via E2 (concerted, anti-periplanar), E1 (via carbocations), or E1cB (through carbanions) mechanisms. Critical factors such as steric hindrance, leaving group quality, nucleophile/base strength, and solvent effects dictate the reaction pathway and kinetics. Mastery of these concepts is essential for predicting product regiochemistry and stereochemistry in both laboratory synthesis and biological processes.

Learning Objectives

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

What product would you expect from a nucleophilic substitution reaction of (S)-2-bromohexane with acetate ion, $\mathrm{CH}_{3} \mathrm{CO}_{2}^{-}$ ? Assume that inversion of configuration occurs, and show the stereochemistry of both the reactant and product.

Example 2

What product would you expect to obtain from $\mathrm{S}_{\mathrm{N}}^{2 \text { reaction of } \mathrm{OH}^{-}}$ with $(R)-2$ bromobutane? Show the stereochemistry of both the reactant and product.

Example 3

Assign configuration to the following substance, and draw the structure of the product that would result from nucleophilic substitution reaction with $\mathrm{HS}^{-}$ (reddish brown $=\mathrm{Br})$

Example 4

What product would you expect from $\mathrm{S}_{\mathrm{N}} 2$ reaction of 1 -bromobutane with each of the following? (a) NaI (b) $\mathrm{KOH}$ (c) $\mathrm{H}-\mathrm{C} \equiv \mathrm{C}-\mathrm{Li}$ (d) $\mathrm{NH}_{3}$

Example 5

Which substance in each of the following pairs is more reactive as a nucleophile? Explain. (a) $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{~N}^{-}$ or $\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}$ (b) $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~B}$ or $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}$ (c) $\mathrm{H}_{2} \mathrm{O}$ or $\mathrm{H}_{2} \mathrm{~S}$