PrefaceA PREVIEW OF THE FIFTH EDITIONI believe, and research in chemical education shows, that students who make the effort to learnbut still have trouble in organic chemistry are in many cases trying to memorize their waythough the subject. One of the keys to students' success, then, is to provide them with help inrelating one part of the subject to the next-to help them see how various reactions that seemvery different are tied together by certain fundamentals. An overarching goal of my text is tohelp students achieve a relational understanding of organic chemistry. Here are some of theways that I have tried to help students meet this goal.use of an Acid-Base Framework ts a Key to UnderstandingMechanismsAlthough I have organized Organic Chemistry Sth Edition by functional group, I have usedmechanistic reasoning to help students understand the "why" of reactions. Mechanisms alone,however, do not provide the relational understanding that students need. Left to their own de-vices, many students view mechanisms as something else to memorize, and they are baffledby the "curyed-arrow" notation. I believe passionately that an understanding of acid-basechemistry is the key that can unlock the door to a mechanistic understanding of much organicchemistry. In Organic Chemistry 5th Edition,I use both Lewis acids and bases and Brpnstedacids and bases as the foundations for mechanistic reasoning. Although students have memo-rized the appropriate definitions in general chemistry, few have developed real insight aboutthe implications of these concepts for a broader range of chemistry. I have dedicated Chapter 3to these fundamental acid-base concepts. The terms "nucleophile," "electrophile," and "leav-ing group" then spring easily from Lewis and Br6nsted acid-base concepts, and the curved-arrow notation makes sense. I have provided a substantial number of drill problems to test howwell students have mastered these principles. I have reinforced these ideas repeatedly witheach new reaction type. Free-radical reactions are also covered, but not until the electron-pairconcepts are fully established.Tiered Topic Development Provides Reinforcement oflmportant ldeasI have introduced complex subjects in "tiers." This means that students will see many conceptsintroduced initially in a fairly simply way, then reviewed with another layer of complexityadded, and reviewed again at a greater level of sophistication.Acid-base chemistry discussed above, is an example of tiered development. After the ini-tial chapter on acid-base chemistry and the curved-arrow notation, these concepts are revis-ited in detail as they are used in the early examples of reactions and mechanisms, and againwith the introduction of each new reaction type.XXXIXXX|i PREFACEThe presentation of stereochemistry is another example. The basic idea of stereoisomers isintroduced in Chapter 4 (Alkenes). A full chapter on stereochemistry comes two chapterslater. Cyclic compounds and the stereochemistry of reactions follow subsequently. Then theideas of group equivalence and nonequivalence are introduced even later, both in the contextof enzyme catalysis and NMR spectroscopy.The approach to organic synthesis is yet another example. I start with simple reactions andthen show students how to think about them in reverse. Then, later, I introduce the idea of mul-tistep synthesis using relatively simple two- and three-step sequences. Later still, we have an-other discussion in which stereochemistry comes into play. Even later, the use of protectinggroups is introduced.This "tiered presentation" of key topics requires some repetition. Although the repetition ofkey points might be considered inefficient, I believe that it is crucial to the learning process.When a topic is considered after its first introduction, I have provided detailed cross-referenc-ing to the original material. Students are never cast adrift with terminology that has not beencompletely defined and reinforced.Everyday Analogies Help Students to Gonstruct Their OwnKnowledgeI believe in the constructivist theory of learning, which holds that students construct learningin their own minds by relating each new idea to something they already know. This is why therelational approach to learning organic chemistry is so important. For the same reason, I haveprovided common analogies from everyday experience for many of the discussions of chemi-cal principles so that students can relate a new idea to something they already know. One ofmany examples can be found in the sidebar on p. 164.Biological Examples Motivate Students Interested in the AlliedHealth SciencesMany organic chemistry classes are populated largely by premedical students, prepharmacystudents, and other students interested in the life sciences. Biological examples help to moti-vate these students. I have provided a number of examples from modern biochemistry andmedicine throughout the book. Amino acids and proteins have a dedicated chapter that hasbeen completely rewritten in light of modern developments. Carbohydrates also have a dedi-cated chapter that has been moved so that it now follows carbonyl and amine chemistry. I haveintegrated many other biological examples into discussions of the relevant chemistry. The ul-timate goal of these examples is to reinforce the chemistry being discussed with material thatstudents should find particularly relevant. Among these are discussions of cell membranes,bioorganic stereochemistry, pheromones, imaging agents, nucleic acids, coenzyme mecha-nisms, and many, many more. One of many such discussions, for example, is found in thesidebar on pp. 396-398 and the accompanying illustration on p. 399.Students in an Introductory course should see Examples ofContemporary Organic ChemistryThe "canon" ofundergraduate organic chemistry necessarily contains many classical reactions,but this text introduces some very modern chemistry as well. For example, the 4th edition in-troduced a section on transition-metal catalysis, a field that has literally exploded in the last fewyears. This section carefully explains the conventions used in the field for electron counting andcalculating oxidation states. This edition builds on that introduction, which previously includedPREFACE XXXIIIthe Heck and Stille reactions, by adding sections on the Suzuki coupling, alkene