Chemistry 3719 Class Notes from Livescribe

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Lecture 1 + Intro: Structure Determines Properties; Chapter 1 (1.1-1.8)

Review of atomic structure and Lewis dot sructures; principles of bonding in molecules containing first row elements. Electronegativity values and consequences in polar and non-polar bonds. Formal charge as a book-keeping device in covalently bonded molecules. Introduction to resonance structures as a method to explain delocalized bonding.

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Lecture 2: Structure Determines Properties; Chapter 1 (1.8-1.14)

More detail on resonance structures and delocalization. Use of shorthand to represent molecules quickly; structural formulae and inclusion of non-H and C atoms in diagrams; inclusion of lone pairs. Shapes of molecules using VSEPR theory; comparison of methane, ammonia, and water. Molecular dipole moments in small molecules. Use of curved arrow notation in mechanism. Introduction to acids and bases.

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Lecture 3: Structure Determines Properties; Chapter 1 (1.14-1.16)

Concepts in acid-base equilibria; dissociation of HBr in water and mechanistic description. Conversion to pKa and use in determining position of equilibrium. Structural influences in acid strength across and down the periodic table. Relationship between acid and conjugate base strength (no need for pKb). Examples of typical acid-base reactions encountered in Organic Chemistry.

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Lecture 4: Alkanes and Cycloalkanes; Chapter 2 (2.1-2.20)

Families of hydrocarbons classified by level of unsaturation. Discussion of bonding in H2 and the ideas of bonding/antibonding molecular orbitals. Structural isomers of alkanes and their names. Classification of alkyl radicals as primary, secondary, and tertiary. Cycloalkane structure and nomenclature. Oxidation numbers and introduction to hybridization patterns.

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Lecture 5: Alkanes and Cycloalkanes; Chapter 2 (2.5-3.1)

More discussion of hybridization patterns for C, N, and O. Application to more complex molecules to highlight the consistency and the concept. Further detail on oxidation levels at C and how electronegative substituents influence the electronic envirnment around C. Use of oxidation numbers in classifying chemical changes. Introduction to Chapter 3: Conformational Analysis.

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Lecture 6: Alkanes and Cycloalkanes; Conformations; Chapter 3 (3.1-3.7)

Energetic changes within molecules as a consequence of rotation and flexibility. Use of Newman depeictions to trace interactions during bond rotations; definitions of important relationships. Examples of ethane, butane, and higher alkanes and discussion of individual energy profiles. Analysis of small cycloalkanes; possibilities of torsional strain. Introduction to cyclohexane analysis.

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Lecture 7: Alkanes and Cycloalkanes; Conformations; Chapter 3 (3.7-3.11)

Representations of cyclohexane on paper; introduction to chair and boat conformations. Definitions of axial and equatorial positions and "up/down" relationships as one moves around the cycle. Detailed discussion of the ring-flip process and axial/equatorial changes as a consequence. Introduction to cis/trans isomerism in cyclopropane and extension to cyclohexane.

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Lecture 8: Alkanes and Cycloalkanes; Conformations; Chapter 3 (3.8-3.14)

Detailed discussion of relative stabilities of cis/trans isomers in 1,2-, 1,3-, and 1,4-disubstituted cyclohexanes. Position of equilibrium in each case and relative population of each conformer. Effect of size of substituents in more complicated examples. Inferences in biological molecules and pharmaceuticals. Definition and nomenclature of bicyclic systems.

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Lecture 9: Alcohols and Alkyl Halides; Chapter 4 (4.1-4.8)

Introduction to functional groups; classification of alcohols and alkyl halides; use of the different nomenclature systems. Bonding patterns and hybridization models in alcohols and alkyl halides and general overall structures. Introduction to mechanism in alcohol to alkyl halide conversion.

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Lecture 10: Alcohols and Alkyl Halides; Chapter 4 (4.8)

Introduction to reaction profiles using a simple bimolecular acid-base reaction; axes, activation barrier, transition state, etc. Detailed discussion of the reaction of a tertiary alcohol with HX. Arrow-pushing mechanism and relationship to reaction profile. Intermediacy of the carbocation electrophile; definition and determination of the rate-determining step.

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Lecture 11: Alcohols and Alkyl Halides; Chapter 4 (4.8-4.17)

Details of carbocation formation and structure; hyperconjugation as a stabilizing effect. Relative stability of carbocations and their energy profiles. Effect of structure on rate of formation. Complete definition of unimolecular nucleophilic substitution at sp3 C (SN1) and alternative bimolecular process (SN2).

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Lecture 12: Alcohols and Alkyl Halides; Chapter 4 (4.17-4.19)

Halogenation of alkanes by free radicals. Discussion of overall conversion and how mechanism must be different to previous reactions. Analysis of bond strengths and likely events that will allow for H-abstraction. Details of radical chain process, intermediates, and side-reactions that detract. Selectivity at different types of C-H bond; selectivity differences when using Cl and Br radicals.

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Lecture 13: Structure and Preparation of Alkenes; Chapter 5 (5.1-5.5)

Basic structure of the pi bond and review of hybridization patterns. Nomenclature of simple examples and relation to alcohols and alkyl halides in naming hierarchy. Occurrence of cis and trans isomers in alkenes. Use of the Cahn-Ingold-Prelog rules to determine configuration. Physical properties of alkenes such as dipole moments.

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Lecture 14: Structure and Preparation of Alkenes; Chapter 5 (5.5-5.10)

Substitution patterns in alkenes and relative stabilities of isomers based on inductive stabilization of sp2 carbon. Stereoisomerism in cyclic alkenes and associated strain in smaller cycles. Preparation of alkenes by elimination reactions; definition of alpha and beta carbons and swapping of sigma bonds for pi bond. Introduction to E1 mechanism and Zaitsev rule.

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Lecture 15: Structure and Preparation of Alkenes; Chapter 5 (5.11-5.13)

Detailed mechanism of E1 process and associated reaction profile. Required conditions, reversibility of reaction, and observed regioselectivity. Catalytic behaviour of acid and laboratory procedures to ensure isolation of alkene product(s). Alternative E2 pathway when carbocation is precluded. Possibility of skeletal rearrangements of carbocations in the E1 mechanism.

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Lecture 16: Structure and Preparation of Alkenes; Chapter 5 (5.13-5.18)

Stereoisomer formation in E1 and E2 reactions. Use of base and alkyl halides to form alkenes by E2 pathway; more useful process since Zaitsev rule still applies and there are no carbocations to undergo rearrangement. Discussion of preferred orientation of groups for fast E2 elimination and kinetic isotope effects to study mechanistic pathway.

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Lecture 17: Addition Reactions of Alkenes (6.1-6.10)

Definition of addition reactions and use in synthesis of various classes of compounds. Mechanism of electrophilic addition using HX; intermediacy of carbocation and subsequent trapping by nucleophile. Addition to unsymmetrical alkenes and regiochemical outcome. Markovnikoff rule and reaction profiles to understand major/minor outcomes. Carbocation rearrangements. Hydration with aqueous acid.

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Lecture 18: Addition Reactions of Alkenes (6.10-6.13)

Hydration of alkenes through carbocations; mechanism and regiochemical outcome. Hydroboration/oxidation sequence to reverse regiochemistry in the synthesis of alcohols from alkenes. Detailed mechanism and concepts of syn addition and retention of configuration in oxidation process. Examples of both hydration protocols in alcohol synthesis.

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Lecture 19: Addition Reactions of Alkenes (6.12-6.17)

Stereochemistry of hydroboration-oxidation process; syn addition and retention. Anti addition of Br2 in aprotic solvents to produce the trans product; inference of modified carbocation (bromonium ion) in mechanism. Related outcome of addition of Br2 in water to produce bromohydrins.

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Lecture 20: Addition Reactions of Alkenes (6.18-6.20)

Addition of HBr to alkenes in the presence of peroxides; regiochemical outcome and mechanistic inferences. Use of different HBr addition to alkenes in synthesis to give desired major product. Formation of epoxides from bromohydrins and also by addition of peracids; stereochemical outcomes in each case. Ozonolysis of alkenes; mechanism and uses.

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Lecture 21: Addition Reactions of Alkenes (6.20-6.21)

Details of ozonolysis of alkenes; mechanism of addition, cycloreversion, and second cyclization. Reduction of product and uses in the synthesis of carbonyl compounds. Uniqueness of the process in which both a pi bond and a single bond are broken sequentially. Introduction to Chapter 7; chirality and stereochemistry.

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Lecture 22: Stereochemistry (7.1-7.6)

Introduction to asymmetry and definitions of terms; chiral and achiral, stereogenic center, enantiomer. etc. Examples of asymmetry at sp3 C atoms; discussion of optical rotation and how it is measured. Use of the Cahn-Ingold-Prelog system for assigning priority to substituents and application to the (R)/(S) nomenclature device.

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Lecture 23: Stereochemistry (7.6-7.11)

More examples of naming compounds using the (R)/(S) system. Basics of Fischer projections and working out configuration. Reactions that give chiral products. Molecules with two chiral centers and the definition of diastereomers. Basis on the 2n idea when n chiral centers are present.

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Lecture 24: Stereochemistry (7.11-7.14)

Use of Fischer projections to describe multiple chiral centers in acyclic molecules. Interconversion between Fischer and wedge-dash representations and interpretation of configuration. Stereocenters in cyclic molecules and relationship to earlier ideas of cis/trans isomerism. Occurrence of meso compounds. Reactions that produce diastereomers.

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Lecture 25: Nucleophilic Substitution (8.1-8.2)

Review of bimolecular substitution mechanism from earlier chapters. Expansion of the chemistry by using halide leaving groups and different nucleophiles. Synthesis of different derivatives such as ethers, esters, nitriles, and azides. Discussion of relative nucleophile ability, i.e. nucleophilicity. Halides as nucleophiles and their relative abilities as leaving groups.

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Lecture 26: Nucleophilic Substitution (8.3-8.5)

Stereochemical inversion in bimolecular substitution reactions; detailed discussion of transition state and reaction profile. Further detail on relative nucleophilicities depending upon factors such as electronegativity, ion size, and electron delocalization. Review of unimolecular substitution from earlier.

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Lecture 27: Nucleophilic Substitution (8.6-8.9)

Solvolysis of alkyl halides where the solvent is the nucleophile. Stereochemical consequences in chiral systems; formation of carbocation results in equal amounts of enantiomeric products to produce racemic mixtures. Use of optical rotation data in determining mechanism. Carbocation rearrangements in SN1 reactions.

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Lecture 28: Nucleophilic Substitution (8.10-8.12)

Effects of solvents in bimolecular and unimolecular substitution reactions; polar protic versus polar aprotic. Examples of reaction setups and typical conditions for each type of process. Bimolecular substitution versus elimination in alkyl halides; effect of steric environment around electrophilic carbon. Sulfonate esters as substrates.

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Lecture 29: Alkynes (9.1-9.6, 9.12)

Review of sp hybrid carbon and of alkyne structure. Nomenclature and lack of configurational isomerism around the triple bond. Acidity of acetylene and of terminal alkynes; deprotonation to form acetylide nucleophiles and subsequent alkylation to generate higher alkyne products. Hydration of alkynes to form ketones; introduction to tautomerism.

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Lecture 30: Alkynes (9.12-9.10.2)

More detail on hydration of alkynes and keto-enol tautomerism. Synthetic uses in sequence with alkyne alkylation. Discussion of "click" chemistry where alkynes and azides react to form the aromatic 1,2,3-triazole heterocycle, a linker that has found wide use in Chemical Biology. Introduction to conjugation in the allyl group (Chapter 10).

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Lecture 31: Conjugation (10.1-10.6)

The allyl carbocation and its inference in unimolecular substitution reactions; regioisomer as a consequence of allylic delocalization. Reversible/irreversible reactions to produce thermodynamic or kinetic products, respectively. Allylic halogenation through the allylic radical using Cl and Br radicals.

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Lecture 32: Conjugation (10.7-10.14)

Structure and relative stability of the allylic carbanion. Structures of conjugated and non-conjugated dienes; conformations in conjugated systems and hindered rotation. Synthesis of dienes by elimination reactions (E1 and E2); regiochemical outcome to produce conjugated product. Addition of HBr to 1,3-butadiene and discussion of kinetic/thermodynamic outcomes.

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Lecture 33: Conjugation (10.15-10.17)

The Diels-Alder cycloaddition between a conjugated diene and a pi bond (dienelophile) to yield a cyclohexene-type product. Requirements for the reaction in terms of diene geometry. Mechanistic interpretation in terms of frontier orbital overlap; stereochemical outcomes and evidence for a concerted process. Examples in complex molecule synthesis.

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Lecture 34: Arenes and Aromaticity (11.1-11.7)

History and structure of benzene; Kekule and Robinson structures and accepted view of pi cloud delocalization. Molecular orbital pictures to explain stability of benzene. Structures and names of common benzene derivatives; introduction to ortho, meta, and para substitution patterns.

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Lecture 35: Arenes and Aromaticity (11.9-11.15)

Overview of reactions of arene systems. Benzylic halogenation through the resonance-stabilized benzyl radical; importance of correct resonance structures and retention of aromatic system in product. Oxidation at benzylic position to form carboxylic acids. Uni- and bimolecular substitution, as well as E1 and E2 reactions at benzylic carbons.

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Lecture 36: Arenes and Aromaticity (11.16-11.23)

Addition reactions of alkenylbenzenes; inference of resonance-stabilized benzylic carbocation. Polymerization of styrene through radical chain process. Huckel's rule and its application to various conjugated cycles. Discussion of stability of benzene versus the instability of 1,3-cyclobutadiene and 1,3,5,7-cyclooctatetraene Examples of heterocyclic aromatic compounds.