Carey - Organic Chemistry - preface

Carey - Organic Chemistry - preface

(Parte 1 de 4)

fourth edition ORGANIC CHEMISTRY

Francis A. Carey University of Virginia

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The credits section for this book begins on page C-1 and is considered an extension of the copyright page.

Library of Congress Cataloging-in-Publication Data

Carey,Francis A.

Organic chemistry / Francis A. Carey. — 4th ed. p. cm.

Includes index. ISBN 0-07-290501-8 — ISBN 0-07-117499-0 (ISE) 1. Chemistry, Organic.I. Title.

QD251.2.C364 2000 547—dc21 9-045791 CIP

INTERNATIONAL EDITION ISBN 0-07-117499-0 Copyright ©2000. Exclusive rights by The McGraw-Hill Companies, Inc. for manufacture and export. This book cannot be re-exported from the country to which it is consigned by McGraw-Hill. The International Edition is not available in North America.

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Francis A. Careyis a native of Pennsylvania, educated in the public schools of Philadelphia, at Drexel University (B.S. in chemistry, 1959), and at Penn State (Ph.D. 1963). Following postdoctoral work at Harvard and military service, he joined the chemistry faculty of the University of Virginia in 1966.

With his students, Professor Carey has published over 40 research papers in synthetic and mechanistic organic chemistry. He is coauthor (with Richard J. Sundberg) of Advanced Organic Chemistry,a two-volume treatment designed for graduate students and advanced undergraduates, and (with Robert C. Atkins) of Organic Chemistry: ABrief Course,an introductory text for the one-semester organic course.

Since 1993, Professor Carey has been a member of the Committee of Examiners of the Graduate Record

Examination in Chemistry. Not only does he get to participate in writing the Chemistry GRE, but the annual working meetings provide a stimulating environment for sharing ideas about what should (and should not) be taught in college chemistry courses.

Professor Carey’s main interest shifted from research to undergraduate education in the early 1980s. He regularly teaches both general chemistry and organic chemistry to classes of over 300 students. He enthusiastically embraces applications of electronic media to chemistry teaching and sees multimedia presentations as the wave of the present.

Frank and his wife Jill, who is a teacher/director of a preschool and a church organist, are the parents of three grown sons and the grandparents of Riyad and Ava.

Preface xxv Introduction 1

APPENDIX 1PHYSICAL PROPERTIESA-1 APPENDIX 2ANSWERS TO IN-TEXT PROBLEMSA-9 APPENDIX 3LEARNING CHEMISTRY WITH MOLECULAR MODELS: Using SpartanBuildand SpartanViewA-64

GLOSSARY G-1 CREDITS C-1 INDEX I-1 xxv

From its first edition through this, its fourth, Organic Chemistryhas been designed to meet the needs of the “mainstream,” two-semester, undergraduate organic chemistry course. It has evolved as those needs have changed, but its philosophy remains the same. The overarching theme is that organic chemistry is not only an interesting subject, but also a logical one. It is logical because its topics can be connected in a steady progression from simple to complex. Our approach has been to reveal the logic of organic chemistry by being selective in the topics we cover, as well as thorough and patient in developing them.

Teaching at all levels is undergoing rapid change, especially in applying powerful tools that exploit the graphics capability of personal computers. Organic chemistry has always been the most graphical of the chemical sciences and is well positioned to benefit significantly from these tools. Consistent with our philosophy, this edition uses computer graphics to enhance the core material, to make it more visual, and more understandable, but in a way that increases neither the amount of material nor its level.

The central message of chemistry is that the properties of a substance come from its structure. What is less obvious, but very powerful, is the corollary. Someone with training in chemistry can look at the structure of a substance and tell you a lot about its properties. Organic chemistry has always been, and continues to be, the branch of chemistry that best connects structure with properties. This text has a strong bias toward structure, and this edition benefits from the availability of versatile new tools to help us understand that structure.

The text is organized to flow logically and step by step from structure to properties and back again. As the list of chapter titles reveals, the organization is according to functional groups—structural units within a molecule most responsible for a particular property— because that is the approach that permits most students to grasp the material most readily. Students retain the material best, however, if they understand how organic reactions take place. Thus, reaction mechanisms are stressed early and often, but within a functional group framework.Acloser examination of the chapter titles reveals the close link between a functional group class (Chapter 20, Carboxylic Acid Derivatives) and a reaction type (Nucleophilic Acyl Substitution), for example. It is very satisfying to see students who entered the course believing they needed to memorize everything progress to the point of thinking and reasoning mechanistically.

Some of the important stages in this approach are as follows:

•The first mechanism the students encounter (Chapter 4) describes the conversion of alcohols to alkyl halides. Not only is this a useful functional-group transformation, but its first step proceeds by the simplest mechanism of all—proton transfer. The overall mechanism provides for an early reinforcement of acid-base chemistry and an early introduction to carbocations and nucleophilic substitution.

•Chapter 5 continues the chemistry of alcohols and alkyl halides by showing how they can be used to prepare alkenes by elimination reactions. Here, the students see a second example of the formation of carbocation intermediates from alcohols, but in this case, the carbocation travels a different pathway to a different destination.

•The alkenes prepared in Chapter 5 are studied again in Chapter 6, this time with an eye toward their own chemical reactivity. What the students learned about carbocations in Chapters 4 and 5 serves them well in understanding the mechanisms of the reactions of alkenes in Chapter 6.

•Likewise, the mechanism of nucleophilic addition to the carbonyl group of aldehydes and ketones described in Chapter 17 sets the stage for aldol condensation in Chapter 18, esterification of carboxylic acids in Chapter 19, nucleophilic acyl substitution in Chapter 20, and ester condensation in Chapter 21.

xxvi PREFACE

The third edition of this text broke new ground with its emphasis on molecular modeling,including the addition of more than 100 exercises of the model-building type. This, the fourth edition, moves to the next level of modeling. Gwendolyn and Alan Shusterman’s 1997 Journal of Chemical Educationarticle “Teaching Chemistry with Electron Density Models” described how models showing the results of molecular orbital calculations, especially electrostatic potential maps, could be used effectively in introductory courses. The software used to create the Shustermans’models was Spartan, a product of Wavefunction, Inc.

In a nutshell, the beauty of electrostatic potential maps is their ability to display the charge distribution in a molecule. At the most fundamental level, the forces that govern structure and properties in organic chemistry are the attractions between opposite charges and the repulsions between like charges. We were therefore optimistic that electrostatic potential maps held great promise for helping students make the connection between structure, especially electronic structure, and properties. Even at an early stage we realized that two main considerations had to guide our efforts.

•An integrated approach was required.To be effective, Spartan models and the information they pro- vide must be woven into, not added to, the book’s core.

•The level of the coverage had to remain the same.

Spartan is versatile. We used the same software package to develop this edition that is used in research laboratories worldwide. It was essential that we limit ourselves to only those features that clarified a particular point. Organic chemistry is challenging enough. We didn’t need to make it more difficult. If we were to err, it would therefore be better to err on the side of caution.

Athird consideration surfaced soon after the work began.

•Student access to Spartan would be essential.

Nothing could help students connect with molecular modeling better than owning the same software used to produce the text or, even better, software that allowed them not only to view models from the text, but also to make their own.

All of this led to a fruitful and stimulating collaboration with Dr. Warren Hehre, a leading theoretical chemist and the founder, president, and CEO of Wavefunction, Inc. Warren was enthusiastic about the project and agreed to actively participate in it. He and Alan Shusterman produced a CD tailored specifically to

ALL-NEW ILLUSTRATIONSAll figures were redrawn to convey visual concepts clearly and forcefully. In addition, the author created a number of new images using the Spartan molecular modeling application. Now students can view electrostatic potential maps to see the charge distribution of a molecule in vivid color. These striking images afford the instructor a powerful means to lead students to a better understanding of organic molecules.

FULL SPARTAN IMAGE INTEGRATIONThe Spartangenerated images are impressive in their own right, but for teaching purposes they are most effective when they are closely aligned with the text content. Because the author personally generated the images as he wrote this edition, the molecular models are fully integrated with text, and the educational value is maximized. Additionally, icons direct students to specific applications of either the SpartanView or SpartanBuild program, found on the accompanying CD-ROM. Appendix 3 provides a complete guide to the Learning By Modeling CD-ROM.

ALL-NEW SPECTRAChapter 13, Spectroscopy, was heavily revised, with rewritten sections on NMR and with all the NMR spectra generated on a high-field instrument.

IMPROVED SUMMARIESThe end-of-chapter summaries are recast into a more open, easier-to-read format, inspired by the popularity of the accompanying summary tables.

NEW DESIGNThis edition sports a new look, with an emphasis on neatness, clarity, and color carefully used to heighten interest and to create visual cues for important information.

PREFACE xxvii accompany our text. We call it Learning By Modeling. It and Organic Chemistrytruly complement each other. Many of the problems in Organic Chemistryhave been written expressly for the model-building software SpartanBuild that forms one part of Learning By Modeling. Another tool, SpartanView, lets students inspect more than 250 already constructed models and animations, ranging in size from hydrogen to carboxypeptidase.

We were careful to incorporate Spartan so it would be a true amplifier of the textbook, not just as a standalone tool that students might or might not use, depending on the involvement of their instructor. Thus, the content of the CD provides visual, three-dimensional reinforcement of the concepts covered on the printed page. The SpartanView icon invites students to view a molecule or animation as they are reading the text.

Opportunities to use SpartanBuild are similarly correlated to the text with an icon directing students to further explore a concept or solve a modeling-based problem with the software.

In addition to its role as the electronic backbone of the CD component and the integrated learning approach, the Spartan software makes a visible impact on the printed pages of this edition. I used Spartan on my own computer to create many of the figures, providing students with numerous visual explorations of the concepts of charge distribution.

Comprehensive coverage of the important classes of biomolecules (carbohydrates, lipids, amino acids, peptides, proteins, and nucleic acids) appears in Chapters 25–27. But biological applications are such an important part of organic chemistry that they deserve more attention throughout the course. We were especially alert to opportunities to introduce more biologically oriented material to complement that which had already grown significantly since the first edition. Some specific examples:

•The new boxed essay “Methane and the Biosphere” in Chapter 2 combines elements of organic chemistry, biology, and environmental science to tell the story of where methane comes from and where it goes.

•Anew boxed essay, “An Enzyme-Catalyzed

Nucleophilic Substitution of an Alkyl Halide,” in Chapter 8 makes a direct and simple connection between SN2 reactions and biochemistry.

Chapter 25, and “Good Cholesterol? BadCholesterol? What’s the Difference?” in Chapter 26, cover topics of current interest from an organic chemist’s perspective.

•The already-numerous examples of enzymecatalyzed organic reactions were supplemented by adding biological Baeyer-Villiger oxidations and fumaric acid dehydrogenation.

Chapters 25–27 have benefited substantially from the Spartan connection. We replaced many of the artistrendered structural drawings of complex biomolecules from earlier editions with accurate models generated from imported crystallographic data. These include:

•maltose, cellobiose, and cellulose in Chapter 25 •triacylglycerols in Chapter 26

•alanylglycine, leucine enkephalin, a pleated - sheet, an -helix, carboxypeptidase, myoglobin, DNA, and phenylalanine tRNAin Chapter 27

All of these are included on Learning By Modeling,where you can view them as wire, ball-and-spoke, tube, or space-filling models while rotating them in three dimensions.

(Parte 1 de 4)

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