The Bridge To Organic Chemistry E-Book

Claude H. Yoder

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 233

Veröffentlichungsjahr: 2010

Beschreibung

Make the leap from introductory to organic chemistry

The transition from first-year chemistry to an organic chemistry course can be a challenge for many students. Not only must they recall their first-year studies of bonding, structure, and reactivity, but they must also master a whole new set of nomenclature, along with the critical skill of "electron-pushing." Reviewing the fundamentals and carefully introducing the important new concepts, The Bridge to Organic Chemistry: Concepts and Nomenclature helps students smoothly bridge the gap to organic chemistry.

Concise and carefully structured, The Bridge to Organic Chemistry helps students strengthen their mastery of fundamental concepts from an introductory chemistry course and then introduces them to the new concepts of organic chemistry. Step by step, the reader will:

• Review important concepts such as structural isomerism, Lewis formulas, hybridization, and resonance and understand their roles in modern organic chemistry
• Learn organic nomenclature along with the critical skill of "electron-pushing"
• Explore mechanisms that utilize many of the concepts: Lewis acid-base chemistry, rate laws, enthalpy changes, bond energies and electronegativities, substituent effects, structure, stereochemistry, and the visualization of electron flow through the electron-pushing model

With a clear progressive style and substantial review at each step, The Bridge to Organic Chemistry puts organic chemistry and its nomenclature within the grasp of every student.

Leseprobe

Table of Contents

Cover

Table of Contents

Half title page

Title page

Copyright page

PREFACE

1 COMPOSITION

PERCENT COMPOSITION

MOLECULAR FORMULA

STRUCTURAL FORMULA

2 NOMENCLATURE

HYDROCARBONS AND RELATED COMPOUNDS

FUNCTIONAL GROUPS

CUMULATIVE NOMENCLATURE PROBLEMS

3 BONDING

THE LEWIS MODEL

THE VALENCE BOND MODEL

THE VALENCE SHELL ELECTRON PAIR REPULSION MODEL

4 STRUCTURE, ISOMERISM, AND STEREOCHEMISTRY

STRUCTURAL ISOMERS

STEREOISOMERISM

5 CHEMICAL REACTIVITY

RATE VERSUS EXTENT OF REACTION

MECHANISM

RATE OF REACTION

THE EXTENT OF REACTION: THERMODYNAMICS

TYPES OF REACTION

NUCLEOPHILES AND ELECTROPHILES

6 REACTION MECHANISMS

REACTION TYPES

BOND CLEAVAGE TYPES

MECHANISM OF HYDROGEN– CHLORINE REACTION

CHLORINATION OF METHANE: A RADICAL MECHANISM

REACTION OF METHYL CHLORIDE WITH HYDROXIDE

REACTION OF tert-BUTYL CHLORIDE WITH WATER: A TWO-STEP IONIC MECHANISM

Index

THE BRIDGE TO ORGANIC CHEMISTRY

Copyright © 2010 by John Wiley & Sons, Inc. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey

Published simultaneously in Canada

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Library of Congress Cataloging-in-Publication Data:

Yoder, Claude H., 1940–

 The bridge to organic chemistry : concepts and nomenclature Claude H. Yoder, Phyllis A. Leber, Marcus W. Thomsen.

p. cm.

 Includes bibliographical references and index.

 ISBN 978-0-470-52676-7 (Cloth : alk. paper) ISBN 978-1-118-01708-1 (ebk)

 1. Chemistry, Organic. 2. Chemistry, Physical and theoretical. I. Leber, Phyllis A., 1949– II. Thomsen, Marcus W., 1955– III. Title.

QD251.3.Y63 2010

547–dc22

2010001897

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

PREFACE

Organic chemistry is conceptually very organized and logical, primarily as a result of the mechanistic approach adopted by virtually all authors of modern organic textbooks. It continues, however, to present difficulties for many students. We believe that these difficulties stem from two major sources. The first is the need for constant, everyday study of lecture notes and textbook with paper and pencil in hand. The second is related to the integrated, hierarchical nature of organic chemistry. Many students become quickly lost simply because their knowledge of bonding, structure, and reactivity from their first course in chemistry is weak or simply forgotten. Concepts such as structural isomerism, Lewis formulas, hybridization, and resonance are generally a part of the first-year curriculum and play a very important role in modern organic chemistry. Organic nomenclature must be quickly mastered along with the critical skill of “electron pushing.”

The objective of this short text is to help students review important concepts from the introductory chemistry course or to learn them for the first time. Whenever possible, these concepts are cast within the context of organic chemistry. We attempt to introduce electron pushing early and use it throughout. Nomenclature is treated in some detail, but divided into sections so that instructors can easily indicate portions they deem to be most important. In the last chapter we provide an introduction to mechanisms that utilizes many of the concepts introduced earlier—Lewis acid–base chemistry, rate laws, enthalpy changes, bond energies and electronegativities, substituent effects, structure, stereochemistry, and, of course, the visualization of electron flow through the electron-pushing model. Hence, the chapter shows the value of certain types of reasoning and concepts and contains analyses not commonly found in organic texts.

The text is designed for study either early in the organic course or, preferably, prior to the beginning of the course as a bridge between the introductory course and the organic course. Because the text is designed to be interactive, it is essential that the student study each question carefully, preferably with the answer covered to thwart the ever-present tendency to “peek.” After careful consideration of each question using pen and paper, the answer can then be viewed and studied. In this bridge between introductory and organic chemistry we have made a serious effort to review topics as the reader progresses through the text and to focus on important concepts rather than simply to expose the student to different types of organic reactions.

The authors are indebted to Dr. Ronald Hess (Ursinus College), Dr. David Horn (Goucher College), Dr. Anne Reeve (Messiah College), Dr. Edward Fenlon (Franklin and Marshall College), Audrey Stokes, Brittney Graff, Victoria Weidner, Chelsea Kauffman, Mallory Gordon, Allison Griffith, and William Hancock-Cerutti for helpful suggestions.

CLAUDE H. YODER

PHYLLIS A. LEBER

MARCUS W. THOMSEN

2

NOMENCLATURE

The name of a compound must be unambiguous; that is, the name can leave no question about how to draw the structural formula of the compound. The International Union of Pure and Applied Chemists (IUPAC) has provided rules for names and periodically reviews and rewrites these rules. However, before the IUPAC committee began to provide the systematics of nomenclature, chemists named compounds using rules developed over the years, or simply through the use of some trivial name. The compound

was at one time known only as acetone, because it can be obtained by heating vinegar, which was known as acetum; acetone means “daughter of acetum.” Later, acetone was given the common name of dimethyl ketone, and then with the advent of the IUPAC rules acetone was named propanone. Most chemists, however, still use the trivial name acetone. Nevertheless, most of our discussion of nomenclature will follow the IUPAC rules, although you will also learn the common system and even some trivial names.

We start by dividing organic compounds into two major classes: hydrocarbons and compounds with functional groups. Hydrocarbons contain only carbon and hydrogen. Certain hydrogen replacements, called functional groups, give organic molecules characteristic chemical behaviors that are very different from those of hydrocarbons. For example, when a carbonyl group (C=O) is present in a structure, as is true for the ketone acetone, reagents that would not react with the parent hydrocarbon will react vigorously with the carbonyl group.

HYDROCARBONS AND RELATED COMPOUNDS

The simplest type of carbon compound, the hydrocarbons, contains carbon atoms linked to one another and also to hydrogen. There are four main kinds of hydrocarbons: (1) alkanes, in which all the carbon–carbon linkages are single bonds; (2) alkenes, in which one or more of the carbon–carbon linkages are double bonds; (3) alkynes, in which one or more of the carbon–carbon linkages are triple bonds; and (4) aromatics, in which the benzene ring is present. Alkenes and alkynes are sometimes referred to as unsaturated compounds because the linked carbon atoms are not bonded to as many hydrogen atoms as possible; that is, the carbons are not saturated with respect to hydrogen. Aromatic compounds (benzene relatives) have a special arrangement of alternating carbon–carbon double bonds, and represent a separate category of unsaturated hydrocarbons.

Convert each of the following compounds to its saturated analog:

Reason by analogy with what you did in the question above to predict the saturated analog of propanone. If you have forgotten the formula of propanone, it may be helpful to know that it contains a C=O bond.

The compound with the OH group is an alcohol and is the saturated analog of the ketone propanone (acetone).

Which of the following compounds is an alkene?

The cyclic compound in the middle is an alkene. The compound on the left is an alkyne; the compound on the right is an alkane.

How many carbons are there in the compound on the left in the previous question? Make sure that you can write out all the carbons and hydrogens for this compound.

There are four carbons in the formula for the alkyne on the left.

Alkanes

Even though methane (CH4) is considered an alkane, the simplest hydrocarbon that contains a single carbon–carbon bond is ethane (CH3–CH3), but alkanes exist that contain many carbons linked together. In fact, one of the very special features of the chemistry of carbon is the extent to which this linking of atoms can occur; it is at least partly responsible for the formation of very large molecules that form polymers and biologically active organic compounds. The formulas and names of some straight-chain alkanes (alkanes whose carbon atoms can be written on a straight line) are given in Table 2.1. All the names end in -ane, and from pentane to decane the names are derived from the Greek word for the number of carbon atoms in one molecule of the compound.

TABLE 2.1. Nomenclature for Straight–Chain Alkanes

CompoundNameCH4methaneCH3CH3ethaneCH3CH2CH3propaneCH3(CH2)2CH3butaneCH3(CH2)3CH3pentaneCH3(CH2)4CH3hexaneCH3(CH2)5CH3heptaneCH3(CH2)6CH3octaneCH3(CH2)7CH3nonaneCH3(CH2)8CH3decane

Write out the formula of a branched five-carbon alkane.

Refer to Table 2.1 and write out the formula of pentane with all the bonds shown clearly as above. Also write the formula using a condensed formula and using a line formula.

As we have seen, the structural formulas of organic molecules can be written in a number of ways. The formula a shows clearly all of the attachments, b is a more condensed formula, and c is the line formula. Note that the line formula must be written with the lines at angles, rather than in a straight line, in order to show the line vertices (intersections).

A student drew pentane like this:

Is it incorrect to have the end CH3 pointed down rather than at the end of a straight line?