Preview Organic chemistry mechanistic patterns by Ackroyd, Nathan, Browning, C. Scott, Deslongchamps, Ghislain, Dryden, Neil, Lee, Felix, Ogilvie, William Walter, Sauer, Effie (2017)

Preview Organic chemistry mechanistic patterns by Ackroyd, Nathan, Browning, C. Scott, Deslongchamps, Ghislain, Dryden, Neil, Lee, Felix, Ogilvie, William Walter, Sauer, Effie (2017) Preview Organic chemistry mechanistic patterns by Ackroyd, Nathan, Browning, C. Scott, Deslongchamps, Ghislain, Dryden, Neil, Lee, Felix, Ogilvie, William Walter, Sauer, Effie (2017) Preview Organic chemistry mechanistic patterns by Ackroyd, Nathan, Browning, C. Scott, Deslongchamps, Ghislain, Dryden, Neil, Lee, Felix, Ogilvie, William Walter, Sauer, Effie (2017) Preview Organic chemistry mechanistic patterns by Ackroyd, Nathan, Browning, C. Scott, Deslongchamps, Ghislain, Dryden, Neil, Lee, Felix, Ogilvie, William Walter, Sauer, Effie (2017)

Organic Chemistry MECHANISTIC PATTERNS Ogilvie Ackroyd Browning Deslongchamps Lee Sauer Organic Chemistry MECHANISTIC PATTERNS Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it ORGANIC CHEMWARE Organic ChemWare for use with Organic Chemistry: Mechanistic Patterns is a comprehensive ­collection of learning objects to aid in the teaching and learning of organic chemistry at the postsecondary level Designed for both individual study and classroom projection, Organic ChemWare empowers students while redefining the lecture experience It bridges the gap between the static imagery of textbooks and the dynamic world of organic chemistry Organic ChemWare includes more than 180 interactive, web-based multimedia simulations with an emphasis on: • • • • Lewis structures curved arrow notation reaction mechanisms orbital interactions • conformational analysis • stereochemistry • 1H- and 13C-NMR In the default “Study Mode,” all animations (and orbital depictions, if applicable) are accompanied by informative text vignettes, pausing the animations and describing key points and reaction details Toggling to “Presenter Mode” hides all text vignettes and zooms the animation to promote classroom focus while reducing cognitive load All animated mechanisms are depicted in dash/wedge bond line notation; the kinematic effect of bond motion helps students to perceive and understand the threedimensionality of organic structures inferred by the notation and to “think tetrahedral.” Organic ChemWare is included with every purchase of a new text Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it ORGANIC CHEMISTRY Mechanistic Patterns William Ogilvie University of Ottawa Nathan Ackroyd Mount Royal University C Scott Browning University of Toronto Ghislain Deslongchamps University of New Brunswick Felix Lee The University of Western Ontario Effie Sauer University of Toronto Scarborough Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it This is an electronic version of the print textbook Due to electronic rights restrictions, some third party content may be suppressed The publisher reserves the right to remove content from this title at any time if subsequent rights restrictions require it For valuable information on pricing, previous editions, changes to current editions, and alternate formats, please visit nelson.com to search by ISBN#, author, title, or keyword for materials in your areas of interest Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it Organic Chemistry by William Ogilvie, Nathan Ackroyd, C Scott Browning, Ghislain Deslongchamps, Felix Lee, Effie Sauer Senior Publisher, Digital and Print Content: Paul Fam Marketing Manager: Terry Fedorkiw Technical Reviewers: Philip Dutton, Barb Morra Content Development Manager: Katherine Goodes Photo and Permissions Researcher: Kristiina Paul Production Project Manager: Lila Campbell Copy Editor: Wendy Yano Cover Design: Courtney Hellam Proofreader: A Malik Basha Cover and Mechanistic Re-View Image: Yuliyan Velchev/Shutterstock.com Indexer: BIM Creatives LLC Design Director: Ken Phipps Managing Designer: Pamela Johnston Interior Design: Cathy Mayer Production Service: Cenveo Publisher Services COPYRIGHT © 2018 by Nelson Education Ltd Printed and bound in Canada 20 19 18 17 For more information contact Nelson Education Ltd., 1120 Birchmount Road, Toronto, Ontario, M1K 5G4 Or you can visit our Internet site at nelson.com Cognero and Full-Circle Assessment are registered trademarks of Madeira Station LLC ALL RIGHTS RESERVED No part of this work covered by the copyright herein may be reproduced, transcribed, or used in any form or by any means—graphic, electronic, or mechanical, including photocopying, recording, taping, Web distribution, or information storage and retrieval systems— without the written permission of the publisher For permission to use material from this text or product, submit all requests online at cengage.com/permissions Further questions about permissions can be emailed to permissionrequest@ cengage.com Every effort has been made to trace ownership of all copyrighted material and to secure permission from copyright holders In the event of any question arising as to the use of any material, we will be pleased to make the necessary corrections in future printings Organic ChemWare Icon: Ghislain Deslongchamps Art Coordinator: Suzanne Peden Illustrators: Crowle Art Group, Cenveo Publisher Services Compositor: Cenveo Publisher Services Library and Archives Canada Cataloguing in Publication Data Ogilvie, William Walter, author Organic chemistry: mechanistic patterns / William Ogilvie (University of Ottawa), Nathan Ackroyd (Mount Royal University), Felix Lee (The University of Western Ontario), Scott Browning (University of Toronto), Ghislain Deslongchamps (University of New Brunswick), Effie Sauer (University of Toronto) Includes bibliographical references and index ISBN 978-0-17-650026-9 (hardcover) 1. Chemistry, Organic— Textbooks.  I. Ackroyd, Nathan, author  II. Title QD251.3.O45 2017  547 C2016-907181-2 ISBN-13: 978-0-17-650026-9 ISBN-10: 0-17-650026-X Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it BRIEF CONTENTS About the Authors  ix Foreword  xi Preface  xii CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER Carbon and Its Compounds  Anatomy of an Organic Molecule  47 Molecules in Motion: Conformations by Rotations  86 Stereochemistry: Three-Dimensional Structure in Molecules  125 Organic Reaction Mechanism: Using Curved Arrows to Analyze Reaction Mechanisms  186 Acids and Bases  235 CHAPTER π Bonds as Electrophiles: Reactions of Carbonyls and Related Functional Groups  272 CHAPTER π Bonds as Nucleophiles: Reactions of Alkenes, Alkynes, Dienes, and Enols  328 CHAPTER Conjugation and Aromaticity  398 CHAPTER 10 Synthesis Using Aromatic Materials: Electrophilic Aromatic Substitution and Directed Ortho Metalation  431 CHAPTER 11 Displacement Reactions on Saturated Carbons: SN1 and SN2 Substitution Reactions  494 CHAPTER 12 Formation of π Bonds by Elimination Processes: Elimination and Oxidation Reactions  540 CHAPTER 13 Structure Determination I: Nuclear Magnetic Resonance Spectroscopy  577 CHAPTER 14 Structure Determination II: Mass Spectrometry and Infrared Spectroscopy  648 CHAPTER 15 π Bond Electrophiles Connected to Leaving Groups: Carboxylic Acid Derivatives and Their Reactions  696 CHAPTER 16 π Bonds with Hidden Leaving Groups: Reactions of Acetals and Related Compounds  764 CHAPTER 17 Carbonyl-Based Nucleophiles: Aldol, Claisen, Wittig, and Related Enolate Reactions  810 CHAPTER 18 Selectivity and Reactivity in Enolate Reactions: Control of Stereoselectivity and Regioselectivity 899 CHAPTER 19 Radicals: Halogenation, Polymerization, and Reduction Reactions  971 CHAPTER 20 Reactions Controlled by Orbital Interactions: Ring Closures, Cycloadditions, and Rearrangements 1011 Appendix A Answers to Checkpoint Problems  A-1 Appendix B Common Errors in Organic Structures and Mechanisms  A-137 Appendix C pKa Values of Selected Organic Compounds  A-141 Appendix D NMR and IR Spectroscopic Data  A-143 Appendix E Periodic Table of the Elements  A-145 Glossary  G-1 Index  I-1 NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it iii Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it CONTENTS About the Authors  ix Foreword  xi Preface  xii CHAPTER Carbon and Its Compounds  1.1 Why It Matters  1.2 Organic Molecules from the Inside Out I: The Modelling of Atoms  1.3 Organic Molecules from the Inside Out II: Bonding  1.4 Organic Molecules Represented as Lewis Structures  1.5 Covalent Bonding: Overlap of Valence Atomic Orbitals  11 1.6 The Shapes of Atoms in Organic Molecules  14 1.7 The Valence Bond Approach to Electron Sharing  19 1.8 Resonance Forms: Molecules Represented by More than One Lewis Structure  26 1.9 Molecular Orbital Approach to Electron Sharing  32 1.10 Other Representations of Organic Molecules  34 Bringing It Together  40 CHAPTER Anatomy of an Organic Molecule  47 2.1 2.2 2.3 2.4 Why It Matters  47 Structural Features of Molecules  48 Functional Groups and Intermolecular Forces  54 Relation between Intermolecular Forces, Molecular Structure, and Physical Properties  60 2.5 Naming Organic Molecules  67 Bringing It Together  80 CHAPTER CHAPTER Stereochemistry: Three-Dimensional Structure in Molecules 125 4.1 Why It Matters  125 4.2 Constitutional Isomers and Stereoisomers  127 4.3 Chirality Centres  135 4.4 Cahn-Ingold-Prelog Nomenclature  140 4.5 Drawing Enantiomers  148 4.6 Diastereomers  152 4.7 Meso Compounds  157 4.8 Double-Bond Stereoisomers  160 4.9 Physical Properties of Enantiomers and Diastereomers  163 4.10 Optical Rotation  164 4.11 Optical Purity  168 4.12 Fischer Projections  170 Bringing It Together  178 CHAPTER Organic Reaction Mechanism: Using Curved Arrows to Analyze Reaction Mechanisms  186 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 Why It Matters  186 Organic Reaction Mechanisms  189 Curved Arrows and Formal Charges  200 Intramolecular Reactions  203 The Stabilizing Effect of Delocalization  208 Constructing Resonance Forms  208 Evaluating Resonance Form Contributions  215 Resonance and Orbital Structure  220 Patterns in Mechanism  221 Patterns in Resonance  223 Bringing It Together  226 Molecules in Motion: Conformations by Rotations  86 3.1 3.2 3.3 3.4 3.5 3.6 3.7 Why It Matters  86 Rotation about Single Bonds  87 Steric Strain  94 Strains in Cyclic Molecules  98 Conformations of Six-Membered Rings  102 Six-Membered Rings Flip Their Chairs  108 Six-Membered Rings with Substituents  109 Bringing It Together  116 CHAPTER Acids and Bases  235 6.1 6.2 6.3 6.4 6.5 6.6 Why It Matters  235 Electron Movements in Brønsted Acid–Base Reactions  237 Free Energy and Acid Strength  240 Qualitative Estimates of Relative Acidities  243 Relative Acidities of Positively Charged Acids  251 Quantitative Acidity Measurements  257 NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it v vi 6.7 6.8 6.9 Contents Predicting Acid–Base Equilibria  259 Lewis Acids in Organic Reactions  265 Patterns in Acids and Bases  265 Bringing It Together  266 CHAPTER π Bonds as Electrophiles: Reactions of Carbonyls and Related Functional Groups  272 7.1 Why It Matters  272 7.2 Carbonyls and Related Functional Groups Contain Electrophilic π Bonds 273 7.3 Nucleophilic Additions to Electrophilic π Bonds in Carbonyls and Other Groups  277 7.4 Over-the-Arrow Notation  284 7.5 Addition of Organometallic Compounds to Electrophilic π Bonds  288 7.6 Using Orbitals to Analyze Reactions  298 7.7 Formation of Cyanohydrins from Carbonyls  299 7.8 Leaving Groups  303 7.9 Catalysis of Addition Reactions to Electrophilic π Bonds  306 7.10 Stereochemistry of Nucleophilic Additions to π Bonds 314 7.11 Patterns in Nucleophilic Additions to π Bonds 318 Bringing It Together  320 CHAPTER π Bonds as Nucleophiles: Reactions of Alkenes, Alkynes, Dienes, and Enols  328 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 Why It Matters  328 Properties of Carbon-Carbon π Bonds  330 Carbocation Formation and Function  335 Markovnikov Addition of Water to Alkenes  347 Carbocation Rearrangements  357 Addition of Halogens to Double Bonds  359 Other Types of Electrophilic Additions  364 Patterns in Alkene Addition Reactions  385 Bringing It Together  388 CHAPTER CHAPTER 10 Synthesis Using Aromatic Materials: Electrophilic Aromatic Substitution and Directed Ortho Metalation 431 10.1 10.2 10.3 10.4 Why It Matters  431 π Bonds Acting as Nucleophiles  433 Electrophilic Aromatic Substitution  434 Types of Electrophiles Used in Electrophilic Aromatic Substitution 435 10.5 Aromatic Nomenclature and Multiple Substituents  449 10.6 Directing Groups in Electrophilic Aromatic Substitution  449 10.7 Electrophilic Aromatic Substitution of Polycyclic and Heterocyclic Aromatic Compounds  466 10.8 Directed Ortho Metalation as an Alternative to Electrophilic Aromatic Substitution  472 10.9 Retrosynthetic Analysis in Aromatic Synthesis  476 10.10 Patterns in Electrophilic Aromatic Substitution Reactions  482 Bringing It Together  484 CHAPTER 11 Displacement Reactions on Saturated Carbons: SN1 and SN2 Substitution Reactions  494 11.1 Why It Matters  494 11.2 Displacement Reactions of Alkyl Halides  495 11.3 SN2 Displacements  497 11.4 SN1 Displacements  510 11.5 SN1 and SN2 as a Reactivity Continuum  520 11.6 Predicting SN1 and SN2 Reaction Mechanisms  523 11.7 Practical Considerations for Planning Displacement Reactions 524 11.8 Special Nucleophiles and Electrophiles Used in Displacement Reactions 525 11.9 Patterns in Nucleophilic Displacements on Saturated Carbons 532 Bringing It Together  534 CHAPTER 12 Conjugation and Aromaticity  398 Formation of π Bonds by Elimination Processes: Elimination and Oxidation Reactions  540 9.1 Why It Matters  398 9.2 Molecular Orbital Review: Conjugated Systems  400 9.3 Aromaticity  410 9.4 Molecular Orbital Analysis of Aromatic Rings  418 9.5 Aromatic Hydrocarbon Rings  422 Bringing It Together  426 12.1 12.2 12.3 12.4 12.5 12.6 12.7 12.8 Why It Matters  540 Alkene Formation by E2 Elimination Reactions  541 Alkene Formation by E1 Elimination Reactions  552 Dehydration and Dehydrohalogenation  557 Differentiation between Elimination Reactions and Nucleophilic Substitutions  559 Designing Reactions for Selectivity  561 Oxidation of Alcohols: An Elimination Reaction  563 Patterns in Eliminations and Oxidations  568 Bringing It Together  570 NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it 32 Chapter   Carbon and Its Compounds Practice Problem 1.8 Draw the second resonance form of the following molecules Where appropriate, include formal charges in your resonance form (three resonance forms are possible for part d) O a) C H3C CH3 NO2 b) H3C ϩ c) H3C OH C CH3 O d) H3C Organic ChemWare 1.33 Resonance: Carbonyl group C NH2 Integrate the Skill 1.9 The following molecule has four significant resonance forms Use the formal charge method to draw each of them ϩ Organic ChemWare 1.34 Resonance: Imine H2N NH2 C NH2 Organic ChemWare 1.35 Resonance: Nitrile A molecular orbital (MO) maps out, point by point in space, the probabilities of finding electrons in the volume of space around the nuclei of a molecule Molecular orbitals are often represented as a shape that depicts the probability of finding an electron within that volume of space 95 percent of the time A s molecular orbital (s MO) has its amplitude concentrated along the axis between the nuclei of the molecule A bonding molecular orbital is a molecular orbital with a high electron density in the volume of space between the atoms of the molecule Electrons in bonding molecular orbitals stabilize a molecule 1.9 Molecular Orbital Approach to Electron Sharing The valence bonding approach described in Section 1.7 is one method of modelling the bonding in organic molecules The molecular orbital (MO) approach is a second method, which extends the idea of bonding to the entire molecule.This approach involves mixing a set of atomic orbitals to obtain a set of molecular orbitals that describe the likelihood of finding electrons in the space around the molecule Two of the molecular orbitals of carbon monoxide, CO, are shown in Figure 1.10 The distinct shape of each orbital describes the probability of finding electrons around the carbon monoxide molecule This shape can be interpreted as an enclosure within which the electrons can be found 95 percent of the time Both orbitals describe a different probability distribution, but they both have amplitude along the line running through the two nuclei For this reason, these orbitals are known as s molecular orbitals (s MO) The s molecular orbital on the bottom of Figure 1.10 shows continuous electron density in the region between the carbon and oxygen atoms Orbitals that provide this “zone” of electrons between atoms are known as bonding molecular orbitals Electrons in these orbitals stabilize the molecule and hold the atoms together NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it 1.9 Molecular Orbital Approach to Electron Sharing C O s* MO (anti-bonding) se p f p t-o rla ou ove C 33 O sp sp in- ov ph as lap e er C O s MO (bonding) Figure 1.10  Two of the several molecular orbitals of carbon monoxide: a s molecular orbital and a s* molecular orbital In contrast, the orbital on the top of Figure 1.10 has a region between the two atoms where the probability of finding electrons is zero This region between the carbon and oxygen atoms represents a destabilizing interaction It is an anti-bonding molecular orbital, written as s*, where the asterisk “*” designates an anti-bonding orbital Electrons in a s* molecular orbital force the atoms apart Molecular orbitals describe bonding over the entire molecule However, the focus of organic chemistry is typically the orbitals involved in chemical reactions or particular structures If a reaction requires the breaking of a carbon-bromine bond, for example, only the orbitals involved between the carbon and bromine are analyzed, not those of the entire molecule Molecular orbitals can be thought of as a combination of the atomic orbitals of the molecule’s atoms For example, the two molecular orbitals of carbon monoxide associated with the s bond can be considered a combination of the sp orbital on its carbon atom and the sp orbital on its oxygen atom A s molecular orbital arises from the in-phase overlap of these orbitals, and a s* orbital results from the out-of-phase overlap of the atomic orbitals C Organic ChemWare 1.36 Molecular orbitals: C–O s orbitals An anti-bonding molecular orbital (s*) has nodes between the adjacent atoms of the molecule Electrons in antibonding orbitals destabilize the molecule and force atoms apart O s* C sp O sp C O s NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it 34 Chapter   Carbon and Its Compounds Although molecular orbitals are represented as a combination of atomic orbitals, the total number of orbitals is preserved Two atomic orbitals make two molecular orbitals In-phase overlap generates orbitals with lower energy than either of the contributing orbitals, and produces a bonding orbital between the atoms (electron density in between the nuclei) Out-of-phase overlap results in a higher-energy anti-bonding orbital Note that the energy change of the anti-bonding orbital relative to the starting atomic orbitals is slightly larger than the energy change for the bonding orbital To represent the combination of atomic orbitals accurately, the placing of electrons in new orbitals requires filling the lowest energy orbitals first.This produces a favourable energy situation for the molecule because electrons between the nuclei hold the nuclei together Only the filled molecular orbitals contribute to bonding, and so only the occupied molecular orbitals contribute to the bonding in the molecule Bonding orbitals are considered when analyzing the structure of molecules Anti-bonding orbitals become important when the reactivity of molecules is analyzed 1.10 Other Representations of Organic Molecules So far in this chapter, the molecules have been drawn as Lewis structures A Lewis structure uses atomic symbols to show all atoms, lines to display the molecule’s bonding electron pairs, and dots to represent non-bonding electrons.The dots are properly arrayed in pairs (lone pairs) around the atomic symbol of the atom they are associated with H H H H H H O H O H C C C C C C C C C H H H H H H H H This method of depicting a detailed structure has drawbacks First, it is time consuming to create them Second, Lewis structures explicitly present so much information that they become cluttered, making it difficult to identify key features that contribute to structure and reactivity Alternatively, to facilitate the writing and interpreting of chemical structures, several shorthand styles can be used to represent organic molecules The most common of these are condensed structures and line structures Sometimes the different shorthand drawing styles can be combined in one structure, depending on the feature of interest in the molecule For example, condensed formulas are used for non-reacting portions of a molecule, and Lewis structures may be helpful for studying reactivity The Lewis structure is especially valuable when new functional groups or reactions are encountered 1.10.1 Condensed structure Typically, a condensed structure (or formula) is used only for small molecules or portions of molecules because it is difficult to depict molecules of even moderate size using this style In condensed structures, the solid lines of covalent bonds are not shown It is assumed that the person interpreting the structure knows the valence of the atoms involved The valence—number of connections—that each atom has can be derived from the group of the periodic table that the atom resides in (Section 1.10.1.1) CH3(CH2)4CHOHCHCHCHO In a condensed structure, the atoms are presented in a list Carbons are followed by the hydrogens that are directly bonded to them If the hydrogens listed after a carbon represent fewer than four bonds (maximum number for carbon), it is understood that the next atom listed is bonded to that carbon NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it 1.10 Other Representations of Organic Molecules CH3CH2CH2CH2CH2CHOHCHCHCHO This carbon is connected to three hydrogens and one carbon (valence full) H H C C H If a structure cannot account for four connected atoms there must be multiple bond connections CH3CH2CH2CH2CH2CHOHCHCHCHO This carbon is connected to one hydrogen and two carbons This does not give a full valence and so there must be additional bonds to fill the valence C C C H If multi-atom groups are attached to a carbon, those groups may be listed in parentheses, including any necessary subscripts CH3(CH2)4CHOHCHCHCHO CH3CH2CH2CH2CH2CHOHCHCHCHO Some groups are very common and have condensed abbreviations that must be recognized C6H5 ϭ HC HC H C C H C CH 1.10.1.1 The HONC rule To interpret condensed structures properly, it is useful to remember the appropriate number of bonds for each atom H O N C element “normal” number of bonds Hydrogen can accommodate only one pair of bonding electrons Each of the other elements in organic molecules typically accommodates four electron pairs Based on the number of electrons “supplied” with each atom, this leads to a “normal” number of bonds for each element Oxygen forms two bonds (and carries two lone pairs) Nitrogen forms three bonds (and carries one lone pair).When oxygen or nitrogen atoms carry less than the normal number of bonds, they usually have an extra lone pair and are negative When these atoms form more than this number of bonds, they effectively over-share some electrons and become positive Carbon atoms that carry three bonds can be negative or positive, depending on whether or not they have a lone pair NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it 35 36 Chapter   Carbon and Its Compounds carbon normally forms four bonds H H H H H H O H H C C C C C C C C C H H H H H H H H O CH3(CH2)4CHOHCHCHCHO oxygen normally forms two bonds The position of elements in the periodic table can also be used as a guide to find the number of bonds an atom “normally” forms (atoms in lower periods have the ability to form more bonds than the group number indicates) number of bonds to obtain a neutral structure H B C N O F Al Si P S Cl Br I 1.10.2 Line structure Line (or bond-line) structures are used extensively to depict the shape of a molecule, effectively reducing the clutter of a Lewis structure Line structures are valuable because they can be created quickly, and also they emphasize the shapes and functional (reactive) parts of molecules.The following conventions apply when drawing and interpreting line structures All bonds between atoms (other than hydrogen) are drawn as solid lines in a zig-zag pattern The atomic symbols of the carbon atoms are not shown; rather, each vertex and line terminus represents a carbon atom, and carbons are understood to be present at each bond transition carbon at each terminus carbon at each change in bond type carbon at each vertex The elemental symbols of heteroatoms (any element other than carbon or hydrogen) are shown, but lone pairs of electrons are not shown O N Cl Hydrogens are not shown unless the hydrogen is connected to an explicitly drawn atom When hydrogens are shown, the bonds to them are not; rather the hydrogens are listed after the symbol of the atom to which they are connected NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it 1.10 Other Representations of Organic Molecules ϩ OH hydrogens are shown when attached to an explicitly drawn atom NH2 C H2 The number of hydrogens connected to each carbon is implied by the fact that the number of groups of electrons at each carbon must total four For example, if three bonds are shown to a carbon, the fourth bond must be to a hydrogen that is not shown H C Three bonds are shown to this carbon The fourth bond must be to a hydrogen While lone pairs are not usually included on line structures, it is important to remember they are there; in fact, it is a good habit to add them to line structures to aid in problem solving The connectivity of a line structure is important, not what the overall drawing looks like Most molecules can be drawn in more than one way All these structures depict the same molecule O O O O 1.10.2.1 Wedged and hashed bonds in line structures The following two structures show the same molecule represented by two different drawings When drawn correctly, the wedged bonds and hashed bonds at one of the carbons convey the tetrahedral geometry at that carbon atom O HO H In the second drawing, the carbon-hydrogen bonds can be removed without a loss of information Hydrogen atoms connected to carbons are not typically included in line structures The bonds that remain—two in the plane of the page and one projecting outward—indicate that the carbon-hydrogen bond not represented must be projecting back into the page O OH NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it 37 38 Chapter   Carbon and Its Compounds Checkpoint 1.7 Organic ChemWare 1.37 Line-angle structure: Clovene You can now draw an organic molecule as a Lewis structure, condensed structure, or a line structure Solved Problem Draw the line structure for the molecule CH3CH2NHCH2C(CH3)2(CH2)2Cl Use wedged bonds and hashed bonds at the carbon atom indicated in blue Organic ChemWare 1.38 Line-angle structure: Cholesterol Step 1: Examine the condensed structure proceeding from left to right to identify the longest chain Note the atomic sequence C–C–N–C–C–C–C–Cl has eight heavy (non-hydrogen) atoms.Two of these are carbons from the (CH2)2 grouping in the condensed structure Note that the two CH3 groups in parentheses, bonded to the blue carbon atom, are not part of the chain Organic ChemWare 1.39 Line-angle structure: Codeine CH3 groups to be added here H N Cl Step 2: Add the two CH3 groups to the line structure using a dashed bond and a wedged bond; make sure they are placed on the correct carbon atom H N Cl Practice Problem 1.10 a) Draw the line structures of the following molecules H C  i)     H H H O H H H C C C C N C H C H H H C H H H H H H H ii)  H C C C H H H H C C C H H b) Draw the condensed structures corresponding to the compounds shown in part (a) c) Draw Lewis structures, including lone pairs of electrons, of the following condensed structures   i)   CH3CH2COCH3 ii)  (CH3)2CCHCH(OH)CH3 d) Draw the line structures that correspond to the condensed structures shown in part (c) Integrate the Skill 1.11 Draw the Lewis structure of the following molecule, including lone pairs of electrons ϩ [CH3(CH2)3CHOHCH2CCC(OH)CH3] NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it 1.10 Other Representations of Organic Molecules CHEMISTRY: EVERYTHING AND EVERYWHERE Graphene: A Material of the Future? Laguna Design/Science Source 123dartist /Shutterstock.com Carbon occurs in nature in a surprising variety of structures One of these elemental forms, diamond, consists of an extended, regularly repeating arrangement of sp3-hybridized carbon atoms Their tetrahedral shape yields an extended network of strong covalent carbon-carbon single bonds that extends three-dimensionally from one end of the diamond to the other A diamond is essentially a single (giant) molecule, whose interlocking array of bonds gives it extreme hardness and mechanical strength A particularly interesting form of elemental carbon is graphene All the carbon atoms of graphene are sp2 hybridized The trigonal planar shape at each carbon atom yields a “chicken wire” network of repeating hexagons of carbon that extends in two dimensions, rather than across three dimensions as in diamond trigonal planar shape at each carbon produces a two-dimensional sheet a (very!) small sheet of graphene This sheet of carbon atoms could consist of vast numbers of carbon atoms, yet it is only one atom thick! The carbon atoms of a graphene sheet can be seen in the following image produced by a scanning tunnelling microscope only one atom thick SOURCE: A T N’Diaye, J Coraux, T N Plasa, C Busse, T Michely, “Structure of epitaxial graphene on Ir(111),” New J Phys 10, 043033 (2008) (“IOP select”-Artikel, “Best of 2008”) In addition to the s bonding between the sp2-hybridized carbon atoms, the molecular bonding model of graphene describes delocalized p bonding across the entire sheet The following figure shows one of the many bonding p molecular orbitals of a small graphene sheet Note the absence of any nodes in this particular bonding Continued NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it 39 Chapter   Carbon and Its Compounds orbital, which describes the extensive sharing of two p electrons among all the carbon atoms of the sheet This delocalized sharing arises from in-phase overlap of the 2p orbitals on each sp2-hybridized carbon atom Like diamond, a graphene sheet—such as ones already made a few centimetres long—is a single, giant molecule Two p electrons delocalized over entire sheet arising from graphene sheet .overlapping 2p orbital lobes on top one of the bonding p MOs of a graphene sheet .and overlapping 2p orbital lobes on bottom The planarity and bonding of the graphene sheet imparts some remarkable and potentially useful properties Since carbon is one of the lightest elements of the periodic table, graphene is, by weight, the strongest material currently known—more than 200 times stronger than steel on a kilogram-for-kilogram basis! One square metre of graphene sheet—only one atom thick—would weigh less than 0.001 grams, about the same as a human hair 15 centimetres long In addition to strength, graphene has remarkable bonds that allow it to conduct electricity better than most metals and make it highly impermeable to gases and liquids Its bonds also allow sheets of graphene to be twisted or stretched much more than almost any other substance Carbon nanotubes, another interesting form of the element, can be thought of as graphene sheets rolled into the shape of a tube Due to their extraordinary electrical and mechanical properties, scientists are currently investigating carbon nanotubes for potential applications Because of their strength, some are suggesting that nanotubes may serve as microscopic cables Although their diameters are only about 1029 metres, the longest nanotube produced to date (a single molecule) is over half a metre in length! Forance/Shutterstock.com 40 Bringing It Together Living things are made of giant molecules such as proteins, polysaccharides, and nucleic acids These compounds are modular, meaning they are formed by linking together long chains of small molecules Proteins consist of many molecules of amino acid, polysaccharides consist of many sugars, and nucleic acids consist of nucleotide bases The small building-block molecules are simpler than the giant complex molecules, and they are mostly made of carbon These small structures result from the ability of carbon to bond with itself and form extended chains and rings This ability was dramatically illustrated by the experiments of Stanley Miller in 1952 NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it Francis Leroy, Biocosmos/Science Source Bringing It Together Science Source To simulate the primordial atmosphere of Earth, Miller constructed a synthetic mixture of gases—water, ammonia, methane, and hydrogen He then subjected this mixture to an electric discharge to simulate lightning After several days he found a gooey pink material in the flask By analyzing this “primordial ooze,” he determined it was composed of amino acids identical to those found in modern living things More recently, researchers have simulated the primordial ocean near undersea vents The mineral-rich water, when heated (like it is beside an undersea volcano), contains substances that are also rapidly converted to the molecules of life The building blocks of life assemble themselves under the right conditions (which are surprisingly common) This self-assembly occurs because carbon readily bonds with itself, a unique property among elements NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it 41 42 Chapter   Carbon and Its Compounds You Can Now • Identify bond types in organic molecules as being s bonds or p bonds • Predict the geometry of atoms in molecules using VSEPR theory • Predict the hybridization of atoms in molecules using the valence bond model • Predict the bonding in molecules using a molecular orbital description • Draw Lewis structures for molecules using the formal charge method • Draw condensed structures of organic molecules • Draw organic molecules as line structures • Construct simple resonance forms using the formal charge method • Construct resonance hybrids from resonance forms Problems 1.12 Organic compounds containing boron (atomic num­ ber 5) are becoming increasingly important in the ­creation of new and important organic molecules in the laboratory a) Draw the atomic orbital energy diagram for a neutral boron atom Be sure to show its electrons in the diagram b) From this diagram, write its ground-state electron configuration c) Identify the valence electrons of boron in the diagram How many valence orbitals does a boron atom have? 1.13 a) Explain why the 1s orbital of a hydrogen atom is its valence orbital, but its 2s orbital is not b) Explain why the 1s orbital of a carbon atom is not one of its valence orbitals Increasing energy 1.14 Silicon, phosphorus, sulfur, and chlorine are important third-row elements in organic chemistry The orbital energy diagram of an atom that includes its 3s, 3p, and 3d valence orbitals is shown here 3d 3p 3s 2p 2s 1s a) Identify the degenerate sets of atomic orbitals in the diagram b) Which orbitals are of lower energy: the 3p or the 3d? c) Knowing the shape of a 1s and 2s atomic orbital, what shape you predict for the 3s orbital? d) Based on the shape of 2p orbitals, what shape you predict for the 3p orbitals? e) A silicon atom has a total of 14 electrons and is located directly beneath carbon in the periodic table Use the atomic energy level diagram for carbon shown in Figure 1.4 as a basis for determining the ground-state electron configuration of silicon Place the 14 electrons of silicon in the correct positions on the right-hand side of the diagram f  ) If the ground-state electron configuration of carbon can be written as 1s22s22p2, write out the groundstate electron configuration of silicon based on your work in part (e) g) Based upon your work in part (e), how many valence electrons does a silicon atom have? Use your answer to draw the Lewis dot diagram of a silicon atom How does this compare with the Lewis dot diagram of carbon? 1.15 Draw the following molecules as Lewis structures a) CH3NH2 b) CH3CHCHCH2CH3 c) C2H2 d) CH3CH2CHO e) CH3CH2OH2! f  ) (CH3CH2)3N g) CH3CN h) CH3CH(OH)CH3 i) CH3NCO j) (CH3)3C! k) CH3CH2O@ l) [CH3C(OH)CH3]! (two structures) 1.16 Methylamine, CH5N, has a C–N single bond Draw the Lewis structure of methylamine, filling the valence atomic orbitals of all atoms Identify the bonding and non-bonding (lone) electron pairs of the molecule NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it Problems 1.17 Draw the complete Lewis structure of a molecule with the following characteristics (parts a–d), showing all atoms, lone pairs of electrons, and formal charges Make sure that your assigned formal charges sum to the overall charge on the molecule a) a molecule of formula C2H5N having no formal charge on any atom b) a cation of formula C2H8N1 c) an anion of formula C2F3O− having a C5O double bond d) two neutral molecules of formula C2H3N, both having a C5N triple bond (Hint: one has no formal charges, whereas the other has two.) 1.18 Draw complete Lewis structures for the following condensed structures a) (CH3)2CHCH2NH2 b) HO(CH2)2CH5C(CH2CH3)2 c) Cl2CHCH2CONHCH3 d) NH(CH2CN)2 1.19 In the following molecules, assign (non-zero) formal charges to those atoms that have them H H H H H C C O a) H C C C OH CH2 H H H b) H C C C CH3 1.20 Add the appropriate lone pairs of electrons to each atom in the following Lewis structures H a) H C C c) H3C d) H N C H H C C C H H e) H C c) H C C C C C H H d) H H H f ) C C H N C H C H H H i)  H H H C iv)  C O Br O C C H H H C H C Li H O H H O H H H H H H H C H H H H C 1.21 Use the electronegativities provided in Figure 1.7 as a basis for answering the following questions a) Which is more polar: a N–H bond or a B–H bond? What is the important distinction between them? b) Redraw the following molecules and place dipole arrows to indicate the direction of the dipole at each of the bonds highlighted in blue iii)  C H Ϫ N C H H CH3 H H C H H H H H H O C O H H Ϫ  ii)  H H H H C ϩ O C C C b) H H H H C H H CH3 O H H H H H H C H CH3 C C H O OH N H CH3 H3C 43 C C Cl H c) For each molecule shown in part (b), identify which carbon atom you would you expect to be the most electron deficient NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it 44 Chapter   Carbon and Its Compounds 1.22 Use the VSEPR concept to predict the electron pair geometry at each non-hydrogen atom in the following molecules H H H H H 1.26 Draw the resonance forms for each of the following molecules a) [CH3CHCHCHCHCH3] (three forms) b) CH3C(NH)CH3 (two forms) ϩ OH a) H C C C C N C H H H H H b) C ϩN H H H C C C O H C d) H c) O F H2C H 2C C H2 CH2 CH2 1.25 For each of the following structures, indicate the hybridization of each non-hydrogen atom, predict the geometry of the electrons pairs around the atom, and predict the geometry of the atoms around each atom a) HOCH2CHCHC(O)CH2CH3 b) CH3CH(CH3)CCCH2CH2CN c) H3CHC H2C CH (two other forms) CH C H2 H C CH (one other form) CH2 C H2 1.27 Draw line structures for each of the following Lewis structures H a) H C C C C O C H 1.24 Draw the Lewis structure of each of the following, showing the geometry around each atom with the proper bond notation (Hint: draw the longest chain of atoms in the structure in a zig-zag style in the plane of the paper.) a) CH3CH2CH2OH2! b) CH3CH2C(O)CH2CHCH2 c) (CH3CH2)2NH d) (CH3CH2C(CH3)2 H2 C O H2C C H H H O Ϫ O 1.23 For the molecules of Question 1.22, employ the VB model of bonding and use the geometries predicted to assign a hybridization for each non-hydrogen atom e) H2C H H H d) c) H2C H2 C N H ϩ CO CH2 OH d) H3C C CH3 e) (CH3)3C! H H Ϫ H ϩ C H H O C H H b) C C H C C H C H Br H H H C H H H Ϫ H c) H C C N C C H H H H H C H H Ϫ H H O ϩ H H C C C N C H d) H H H H C H H H H H H e) H C C O C C H H H H H H H C H H O N C C C H H H C H H H H H H f  ) H C C C C C N H H H H H H H H g) H C C C C C C C O H H H H H NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it Problems 1.28 Draw the complete Lewis structure for each of the following line structures CN e) OH f ) a) 1.30 Draw all of the molecules in Question 1.29 as condensed structures O b) 1.31 Convert the following to Lewis structures Br c) O a) Ϫ N d) e) OH O ϩO b) Ϫ O Br O f  ) Ϫ NH N c) g) ϪO d) h) ϩ NH3 1.33 Draw line structures for the following condensed structures a) CH3CH2CH(CH3)CH2CO2H b) CH3(CH2)2N(CH2CH3)2 c) CH25CHOCH2CH(CH3)2 d) CH3CH2CO(CH2)2CHO i) CO2H O Ϫ 1.29 Convert the following to Lewis structures O a) 1.34 Draw line structures for the following molecules Use wedged bonds and dashed bonds at any atom with tetrahedral geometry a) NH2CH2C(CH3)2OH b) BrCH2CH2CH(CH2CH2Br)CH2CH2Br c) (CH3)2CH(CH2)3OCH3 d) CH3CH2COCH2C(OH)(CH3)CH2COCH2CH3 1.35 Consider the following molecule O b) Nϩ 1.32 Draw all of the molecules in Question 1.31 as condensed structures O j) 45 OH Br O d) O N O O ϩ O c) O H a) Predict the geometry at each non-hydrogen atom b) The localized bond labelled as “1” arises from the overlap of an sp2 hybrid orbital on one carbon atom with an sp3 hybrid orbital on the other NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it 46 Chapter   Carbon and Its Compounds Based upon the geometries you determined for part (a), assign hybridizations to each non-­ hydrogen atom and then use them to describe each of the labelled localized bonds, through 6, in terms of the atomic orbital overlap between the two participating atoms 1.36 In formamide, CH3NO, the N, O, and one H atom are bound to the carbon atom, while the other two H atoms are bonded to the N atom a) Draw a complete Lewis structure of formamide, in which all valence atomic orbitals are filled and no atom bears a formal charge b) Formamide can be drawn using two other possible Lewis structures that are resonance forms of the molecule Draw these Lewis structures 1.37 a) Boron lies one position to the left of carbon in the periodic table Based on this information, how many valence electrons does boron have? b) Borane, BH3, is an important reagent in organic chemistry Draw its Lewis structure and predict its shape c) Based on its shape, assign a hybridization to the boron atom of borane What is the total number of electrons in the valence orbitals of the boron atom due to sharing with its three neighbours? 1.38 What is the fundamental difference between a bonding p molecular orbital and an anti-bonding p molecular orbital in terms of the p bonding in a molecule? MCAT Style Problems 1.39 What is the geometry and hybridization of the atom indicated by the blue arrow? OH a) tetrahedral and sp3 hybridized b) trigonal planar and sp2 hybridized c) trigonal pyramidal and sp2 hybridized d) trigonal planar and sp3 hybridized 1.40 Which of the following structures carries an overall molecular charge? a) CH3CH2CHCHCH2COOH b) CH3CH2CHCHCH2OH c) CH3CH2CHCHCHO d) CH3CH2CHCHCHOH Challenge Problem 1.41 The following molecule represents an important group that acts as an electron pair donor in many types of chemical reactions.There are three significant resonance forms of this structure (including the one depicted) Draw these forms and use them to predict the sites on the molecule that can act as electron pair donors O Ϫ O NEL Copyright 2018 Nelson Education Ltd All Rights Reserved May not be copied, scanned, or duplicated, in whole or in part Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s) Nelson Education reserves the right to remove additional content at any time if subsequent rights restrictions require it ... subsequent rights restrictions require it Organic Chemistry by William Ogilvie, Nathan Ackroyd, C Scott Browning, Ghislain Deslongchamps, Felix Lee, Effie Sauer Senior Publisher, Digital and... it ORGANIC CHEMWARE Organic ChemWare for use with Organic Chemistry: Mechanistic Patterns is a comprehensive ­collection of learning objects to aid in the teaching and learning of organic chemistry. .. Library and Archives Canada Cataloguing in Publication Data Ogilvie, William Walter, author Organic chemistry: mechanistic patterns / William Ogilvie (University of Ottawa), Nathan Ackroyd (Mount