How your text will help you think differently about organic chemistry In the next few pages,you will find a brief sum mary of some of the features used to help you through this course.Several kinds of study aids Think 24/7 Help are provided to emphasize and review the most See how your text's media important points,and the text uses a color program is designed to build scheme that should help you identify each study understanding and bring aid and its purpose.A support package is also rganic chemistry to life available to enhance your understanding of the material. Think Blue Check out features in blue that help you organize and review the material Think Green Check out features in green that help you solve problems Think in Multiple Dimensions help you grasp the major concepts and learn organic chemistry
In the next few pages, you will find a brief summary of some of the features used to help you through this course. Several kinds of study aids are provided to emphasize and review the most important points, and the text uses a color scheme that should help you identify each study aid and its purpose. A support package is also available to enhance your understanding of the material
THINK Blue. Nucleophilic substintion Ne一 First-Exposure Icons appear several times.First-Exposure Icons,a blue pointing hand,indicate the introduction of an important reaction.When you study these reactions. it helps to know when you are seeing a reaction for the first time. ZAITSEV'S RULE:In elimination reactions,the most substituted alkene usually predominates. ChaoRs > R CHCHR > RHC-CHR d RC-CH>RHCCH Rules More aids to organize your study: in blue type.These are central to understanding the corresponding Reaction Summaries include cross-references to chapter material. reactions that are discussed elsewhere. Glossaries at the end of each chapter define and explain technical terms discussed,and help you ir reviewing the chapter material. Summary tables are provided to compare and co trast material whenever a large amount of informa tion lends itself to a concise summary
THINK Nucleophilic substitution I I I I .. -c-c- + Nuc: -c-c- + :x: I I I I H :x: H Nuc First-Exposure Icons Hundreds of reactions appear in this text-and many types of reactions appear several times. First-Exposure Icons, a blue pointing hand, indicate the introduction of an important reaction. When you study these reactions, it helps to know when you are seeing a reaction for the first time. ZAITSEV'S RULE: In elimination reactions, the most substituted alkene usually predominates. R2C=CR2 tetrasubstituted Rules > R2C=CHR trisubstituted Well-known rules, important insights, and key definitions are highlighted in blue type. These are central to understanding the corresponding chapter material. > RHC=CHR and R2C=CH2 disubstituted > RHC=CH2 monosubstituted More aids to organize your study: • Reaction Summaries include cross-references to reactions that are discussed elsewhere. • Glossaries at the end of each chapter define and explain technical terms discussed, and help you in reviewing the chapter material. • Summary tables are provided to compare and contrast material whenever a large amount of information lends itself to a concise summary
This book uses a color scheme to help you identify each study aid and its purpose.Features in BLUE help you organize and review the material. MECHANISM 6-5 Racemization in the SN1 Reaction Step I:lonization of a tetrahedral carbon gives a flat carbocation. Mechanism Boxes 0 Mechanism Boxes help you understand how reactions occur by focusing on the indi- vidual steps of each reaction. Step 2:A nucleophile may attack either side of the carbocation. They haveg bee so you can locate them easily as you thumb through the chapter. atom is stereogenic Key Mechanism Boxes KEY MECHANISM 6-8 The E1 Reaction TieElreactionreginesiontg Marked by a key icon,Key Mechanisms es the cation to give an alkene arethefundamentalmechanisticprinciple Srep /to give a curbocaion (rate-lmiting). that recur throughout the course.They are the pieces that compose most of the other,longer mechanisms. HX: You can find a full list of Key Mechanisms in the detailed Table of Contents. B氏 B-H +C-C
This book uses a color scheme to help you identify each study aid and its purpose. Features in BLUE help you organize and review the material. MECHANISM 6-5 Racemization in the SN 1 Reaction The SN 1 reaction involves ionization to a flat carbocation, which can be attacked from either side. Step 1: Ionization of a tetrahedral carbon gives a flat carbocation. Mechanism Boxes Step 2: A nucleophile may attack either side of the carbocation. Q ~ Nuc:- .. ,,111C ±_ from the top --0 from the bottom ~ Nuc:- retention or ~/ r Nuc inversion Mechanism Boxes help you understand how reactions occur by focusing on the individual steps of each reaction. They have large blue headings so you can locate them easily as you thumb through the chapter. These two products may be different if the carbon atom is stereogenic. Key Mechanism Boxes Marked by a key icon, Key Mechanisms are the fundamental mechanistic principles that recur throughout the course. They are the pieces that compose most of the other, longer mechanisms. You can find a full list of Key Mechanisms in the detailed Table of Contents. I #IH§i®lill!#@@i@®fi:M The E1 Reaction TheEl reaction requires ionization to a carbocation intermediate like the SN I , so it follows the same order of reactivity: 3° > 2° > > I 0 • A base (usually weak) deprotonates the carbocation to give an alkene. Step 1: Unimolecular ionization to give a carbocation (rate-limiting). I I -c-cl I +/ -c-c + I " H " : x: Step 2: Deprotonation by a weak base (often the solvent) gives the alkene (fast). I +/ B= - -c-c _) " B-H + " C=C / /
THINK Green. PROBLEM-SOLVING STRATEGY Problem-Solving PREDICTING SUBSTITUTIONS AND ELIMINATIONS Strategies RX:之R+:8:ow Approaching problem solving canbe challenging for many R+Nc RN (fast) 52 you break down problems into simpler pieces.Methods for approaching complicated (slow) HX: require proposing mechanisms and developing multistep syn- thesis-are provided.They serve B一C=B-H+ (fast) as a starting point,not a guaran teed route to the answers. E2 →H B 一>C=C<+B-H+8 ory abou lute and too y factors are in solvate ior or react as n hem ir ch as can be predicted eral guideline
THINK Problem-Solving Strategies Approaching problem solving can be challenging for many students, and these strategies help you break down problems into simpler pieces. Methods for approaching complicated problems-like those that require proposing mechanisms and developing multistep synthesis-are provided. They serve as a starting point, not a guaranteed route to the answers. ~~~(PR oBLEM-SOLVING STRATEGY PREDICTING SUBSTITUTIONS AND ELIMINATIONS SNl R '-~: ~ R+ + ~ ------3> R -Nuc .. :x: SN2 ·· / Nuc:- + -e-x: ------3> Nuc- c- + / '-·· "' El I I I +/ -c-c- ~ -c-c + :x: t I H "' I +/ "' / B:- -c-c ~ B-H + C=C "' / "' E2 ( H h i B:- -c-c- "c=c/ B-H ------3> + 1 ct / " (slow) (fast) .. :x: (slow) (fast) + :x : Given a set of reagents and solvents, how can we predict what products will result and which mechanisms will be involved? Should you memorize all this theory about substitutions and eliminations? Students sometimes feel overwhelmed at this point. Memorizing is not the best way to approach this material because the answers are not absolute and too many factors are involved. Besides, the real world with its real reagents and solvents is not as clean as our equations on paper. Most nucleophiles are also basic, and most bases are also nucleophilic. Many solvents can solvate ions or react as nucleophiles, or both. We will review the most important factors that determine the reaction pathway and organize them in a sequence that allows you to predict as much as can be predicted. The first principle you must understand is that we cannot always predict one unique product or one unique mechanism. Often, the best we can do is to eliminate some of the possibilities and make some good predictions. Remembering this limitation, here are some general guidelines:
When you need help solving problems,look for the features in GREEN- like Problem-Solving Strategies,Problem-Solving Hints,and Essential Problem-Solving Skills. problem-solving Hint Problem-Solving Hints Don't try to memorize your way through this chapter.Try to These hints appear in the margins and remind underst tand what hap ppens in the memorizing is necessary,but tips the author gives his own students to help simply memorizing everything them work problems and review for exams. won't allow you to predict new reactions. Essential Problem-Solving Skills in Chapter 6 1.Correctly name alkyl halides,and identify them 2.Predict the products of S.S2,E1,and E2 reactions.including stereochemistry. 3.Draw the mechanisms and energy profiles of S1.Sx2.El.and E2 reactions. 4.Predict and explain the rearrange ment first-order reactions. e faster.based on differences in sub 6.Predict whether a reaction will be first-order or second-order. 7.When possible,predict predominance of substitution or elimination. 8.Use Zaitsev's rule to predict major and mincr elimination products. Essential Problem-Solving Skills Found at the end of each chapter,this list reminds you of the skills needed to solve typi- cal problems associated with that chapter's material.The list can point out concepts you might need to review,or suggest types of problems and solutions you have not c ered.This review of problem-soling skills is often a good prelude to doing the end-of chapter problems
When you need help solving problems, look for the features in GREENlike Problem-Solving Strategies, Problem-Solving Hints, and Essential Problem-Solving Skills. Problem-Solving Hints These hints appear in the margins and remind you of facts or principles that may be useful for solving common types of problems. They are the tips the author gives his own students to help them work problems and review for exams. problem-solving Hint Don't try to memorize your way through this chapter. Try to understand what happens in the different reactions. Some memorizing is necessary, but simply memorizing everything won't allow you to predict new reactions. - Essential Problem-Solving Skills in Chapter 6 1. Correctly name alkyl halides, and identify them as 1°, 2°, or 3°. 2. Predict the products of SN1, SN2, E1, and E2 reactions, including stereochemistry. 3. Draw the mechanisms and energy profiles of SN 1, SN2, E1, and E2 reactions. 4. Predict and explain the rearrangement of cations in first-order reactions. 5. Predict which substitutions or eliminations will be faster, based on differences in substrate, base/ nucleophile, leaving group, or solvent. 6. Predict whether a reaction will be first-order or second-order. 7. When possible, predict predominance of substitution or elimination. 8. Use Zaitsev's rule to predict major and minor elimination products. Essential Problem-Solving Skills Found at the end of each chapter, this list reminds you of the skills needed to solve typical problems associated with that chapter's material. The list can point out concepts you might need to review, or suggest types of problems and solutions you have not considered. This review of problem-solving skills is often a good prelude to doing the end-ofchapter problems