Preface A PREVIEW OF THE FIFTH EDITION I believe and research in chemical education shows that students who make the effort to learn but still have trouble in organic chemistry are in many cases trying to memorize their way though the subject One of the keys to students success then is to provide them with help in relating one part of the subject to the next to help them see how various reactions that seem very different are tied together by certain fundamentals An overarching goal of my text is to help students achieve a relational understanding of organic chemistry Here are some of the ways that I have tried to help students meet this goal use of an Acid Base Framework ts a Key to Understanding Mechanisms Although I have organized Organic Chemistry Sth Edition by functional group I have used mechanistic 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 devices many students view mechanisms as something else to memorize and they are baffled I believe passionately that an understanding of acid base chemistry is the key that can unlock the door to a mechanistic understanding of much organic chemistry In Organic Chemistry 5th Edition I use both Lewis acids and bases and Brpnsted acids and bases as the foundations for mechanistic reasoning Although students have memorized the appropriate definitions in general chemistry few have developed real insight about the implications of these concepts for a broader range of chemistry I have dedicated Chapter 3 to these fundamental acid base concepts The terms nucleophile electrophile and leaving group then spring easily from Lewis and Br6nsted acid base concepts and the curvedarrow notation makes sense I have provided a substantial number of drill problems to test how well students have mastered these principles I have reinforced these ideas repeatedly with each new reaction type Free radical reactions are also covered but not until the electron pair by the curyed arrow notation concepts are fully established Tiered Topic Development Provides Reinforcement of lmportant ldeas I have introduced complex subjects in tiers This means that students will see many concepts introduced initially in a fairly simply way then reviewed with another layer of complexity added and reviewed again at a greater level of sophistication Acid base chemistry discussed above is an example of tiered development After the initial chapter on acid base chemistry and the curved arrow notation these concepts are revisited in detail as they are used in the early examples of reactions and mechanisms and again with the introduction of each new reaction type XXXI XXX i PREFACE The presentation of stereochemistry is another example The basic idea of stereoisomers is introduced in Chapter 4 Alkenes A full chapter on stereochemistry comes two chapters later Cyclic compounds and the stereochemistry of reactions follow subsequently Then the ideas of group equivalence and nonequivalence are introduced even later both in the context of enzyme catalysis and NMR spectroscopy The approach to organic synthesis is yet another example I start with simple reactions and then show students how to think about them in reverse Then later I introduce the idea of multistep synthesis using relatively simple two and three step sequences Later still we have another discussion in which stereochemistry comes into play Even later the use of protecting groups is introduced This tiered presentation of key topics requires some repetition Although the repetition of key 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 referencing to the original material Students are never cast adrift with terminology that has not been completely defined and reinforced Everyday Analogies Help Students to Gonstruct Their Own Knowledge I believe in the constructivist theory of learning which holds that students construct learning in their own minds by relating each new idea to something they already know This is why the relational approach to learning organic chemistry is so important For the same reason I have provided common analogies from everyday experience for many of the discussions of chemical principles so that students can relate a new idea to something they already know One of many examples can be found in the sidebar on p 164 Biological Examples Motivate Students Interested in the Allied Health Sciences Many organic chemistry classes are populated largely by premedical students prepharmacy students and other students interested in the life sciences Biological examples help to motivate these students I have provided a number of examples from modern biochemistry and medicine throughout the book Amino acids and proteins have a dedicated chapter that has been completely rewritten in light of modern developments Carbohydrates also have a dedicated chapter that has been moved so that it now follows carbonyl and amine chemistry I have integrated many other biological examples into discussions of the relevant chemistry The ultimate goal of these examples is to reinforce the chemistry being discussed with material that students should find particularly relevant Among these are discussions of cell membranes bioorganic stereochemistry pheromones imaging agents nucleic acids coenzyme mechanisms and many many more One of many such discussions for example is found in the sidebar on pp 396 398 and the accompanying illustration on p 399 Students in an Introductory course should see Examples of Contemporary Organic Chemistry The canon ofundergraduate organic chemistry necessarily contains many classical reactions but this text introduces some very modern chemistry as well For example the 4th edition introduced a section on transition metal catalysis a field that has literally exploded in the last few years This section carefully explains the conventions used in the field for electron counting and calculating oxidation states This edition builds on that introduction which previously included PREFACE XXXIII the Heck and Stille reactions by adding sections on the Suzuki coupling alkene metathesis and Buchwald Hartwig amination Asymmetric epoxidation is also introduced and a modern approach to understanding the rate accelerations observed for many intramolecular reactions has been developed