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UH CHEM 3332 - Halogentation of Side Chains
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CHEM 33332 1st Edition Lecture 17Outline of Last Lecture Nucleophilic Aromatic Substitution of Aryl Halides-No Sn2 on sp2!!! )or SN1 either!)Two pathways:I. Addition/Elimination Mechanism: takes place if strong electron withdrawing (deactivating) groups are ortho and/or para to the halide; the more deactivators, the faster the reaction rateNu=Addition:Elimination:II. Elimination/ Addition- takes place when there are NO strong electron withdrawing )deactivating) groups ortho or para to the halide; requires harsh conditionsNu=Mechanism:Elimination:Addition:Birch Reduction of Substituted Benzenes:-electron withdrawing groups activate a carbon for reduction because the carbanion stabilized-electron donating groups deactivate a carbon for reduction because the carbanion is destabilizedExamples:1.2.3.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Side Chain of Reactions of Benzene DerivativesI. Oxidation- the benzene ring and the bond to the first carbon of a side chain can survive harsh oxidizing conditions1.2.3.Evidence for Benzene Existence:Add furan to reaction mixture:Addition Reactions of BenzeneI. Chlorination of BenzeneII. Catalytic HydrogenationIII. Birch Reduction dissolving metal reductionMechanism Outline of Current Lecture II. Halogentation of Side Chains-Benzylic position is similar to allylic position-abstraction of hydrogen on benzylic position gives resonance stabilized radicalChlorination vs. bromination:Caution:1.2.III. Nucleophilic Substitution of Benzylic Halides- Sn1 or Sn2 readily ovvurs-which one?-depends on the reaction conditionsSubstitution of benzylic halides, continuedReactions of Phenols-some similarities to previously studied reactions of aliphatic alcohols/some differencesI.II.III.IV. Oxidation of Phenols of QuinonesV. Electrophilic Aromatic Substitution of Phenol-readily undergoes halogenation, nitration, sulfonation and Friedel-Crafts rections-need less reactive catalyst for Friedel-Crafts reactions:VI. Electrophilic Aromatic Substitution of Phenoxide anionStrongly activated- can use weak electrophiles like CO2Chapter 18: Keytones and AldehydesCarbonyl compounds: reagents/solvents/and constituents of fabrics/flavorings/plastics/drugs/proteins/carbohydrates/nucleic acids I. StructureII. Physical PropertiesA. Boiling PointB. SolubilityIII. Reactivity:A. AcidityB. Reactivity of Aldehyde vs. KeytoneIV: Aldehyde and Keytone NomenclatureA. As parent: (priority over alcohols, amines, alkanes, alkynes, ethers)1. Aldehydes – drop “e” from alkane and add “al”For cyclic aldehydes add “carbaldehyde”2. Ketones- drop “e” from alkane name, add “one”For cyclic keytones: since carbonyl is part of ring, same as acyclic keytones; carbonylis always #1As substituents:IV. Spectroscopy of Aldehydes and Ketones (Summary)A. IR – look for carbonyl stretch Conjugation lowers frequency:Ring strain raises frequency:B. hNMRC. C13NMRD. UVCurrent


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UH CHEM 3332 - Halogentation of Side Chains

Type: Lecture Note
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