Ochem Study Guide PDF

1. Aromatic Compounds and Aromaticity ​ Aromaticity: Huckel's Rule (4n + 2 π-electrons). ​ Resonance structures and delocalization in aromatic systems. ​ Electrophilic Aromatic Substitution (EAS): Mechanism and major reactions. ○​ Common EAS Reactions: ​ Halogenation (B...

1. Aromatic Compounds and Aromaticity ​ Aromaticity: Huckel's Rule (4n + 2 π-electrons). ​ Resonance structures and delocalization in aromatic systems. ​ Electrophilic Aromatic Substitution (EAS): Mechanism and major reactions. ○​ Common EAS Reactions: ​ Halogenation (Br₂, FeBr₃/Cl₂, AlCl₃). ​ ​ Nitration (HNO₃, H₂SO₄). ​ ​ Sulfonation (SO₃, H₂SO₄). ​ ​ Friedel-Crafts Alkylation (RCl, AlCl₃). ​ ​ Friedel-Crafts Acylation (RCOCl, AlCl₃). ​  ​ Activating vs. Deactivating Substituents: Understanding how groups like -OH, -NO₂, -CH₃ influence reactivity. ○​ ​ Ortho/Para vs. Meta Directing Groups. ^ 2. Reactions of Alcohols and Phenols ​ Alcohols: ○​ Nucleophilic Substitution (Sn1, Sn2). ○​ Oxidation Reactions: ​ Primary alcohols → Aldehydes → Carboxylic acids. ​ Secondary alcohols → Ketones. ​ Tertiary alcohols → No oxidation. ○​ Jones Reagent (CrO₃): Strong oxidant. ​ ○​ ○​ ○​ ○​ ○​  ○​ PCC: Mild oxidation (alcohol to aldehyde). ​ ○​ Williamson Ether Synthesis: Alcohol + Alkoxide → Ether. ​ Phenols: ○​ Electrophilic Substitution: Nitration, sulfonation. ○​ Reactivity of phenols: Stronger acids than alcohols. ○​ Reaction with strong bases: Formation of phenoxide ions. 3. Carbonyl Chemistry ​ Aldehydes and Ketones: ○​ Nucleophilic Addition: General mechanism (addition of nucleophiles like water, alcohols, amines). ○​ Reduction: Aldehydes → Primary alcohols, Ketones → Secondary alcohols (NaBH₄, LiAlH₄). ○​ Oxidation: Aldehydes → Carboxylic acids. ○​ Aldol Condensation: Aldehydes or ketones react to form β-hydroxy ketones or aldehydes, followed by dehydration to form α,β-unsaturated carbonyl compounds. ○​ Cannizzaro Reaction (for non-enolizable aldehydes): One molecule is reduced to alcohol and the other is oxidized to a carboxylate anion. ​ Reactions of α,β-unsaturated Carbonyl Compounds: ○​ Michael Addition (1,4 addition). ○​ Conjugate addition vs. direct addition. ​ Enolate Chemistry: ○​ Formation of enolates (using strong bases like LDA or NaH). ○​ Claisen Condensation: Ester + Base → β-keto ester. ○​ Dieckmann Condensation: Intramolecular version of Claisen. 4. Carboxylic Acids and Derivatives ​ Carboxylic Acid Reactions: ○​ Reduction: Carboxylic acids → Alcohols (LiAlH₄). ○​ Decarboxylation: Carboxylic acids → Hydrocarbons (e.g., β-keto acids). ○​ Esterification: Carboxylic acids + Alcohol → Esters (Fischer esterification).  ​ Acid Chlorides, Esters, and Amides: ○​ Nucleophilic Acyl Substitution (acid chlorides and esters react with nucleophiles). ○​ Amide Hydrolysis: Amides → Carboxylic acids (acidic or basic). ​ Transesterification: Exchange of alkyl groups in esters. ​ Reduction of Esters and Amides: ○​ Esters → Aldehydes or Alcohols (LiAlH₄). ○​ Amides → Amines (LiAlH₄). 5. Synthesis and Retrosynthesis ​ Retrosynthetic Analysis: Breaking down a target molecule into simpler synthons. ​ Strategies: ○​ Functional group interconversion (FGI). ○​ Disconnection approach: Identifying key bonds to break. ​ Common Reactions in Synthesis: ○​ Grignard Reactions: Organomagnesium reagents react with carbonyl compounds. ○​ Aldol and Claisen Condensation: Building carbon-carbon bonds. ○​ Cross-coupling reactions: Suzuki, Heck, and Sonogashira reactions. 6. Organometallic Chemistry ​ Organolithium Reagents: RLi → Nucleophilic substitution. ​ Grignard Reagents: RMgX → Nucleophilic addition to carbonyls. ​ Organocuprates (Gilman reagents): R₂CuLi → Coupling reactions. ​ Reaction with Aldehydes and Ketones: Carbonyl addition. 7. Radical Reactions ​ Radical Substitution: Halogenation (Br₂, light) on alkanes. ​ Radical Addition to Alkenes: Addition of HBr to alkenes in the presence of peroxides (anti-Markovnikov). ​ Radical Polymerization: Formation of polymers from alkenes (e.g., polyethylene, polystyrene). 8. Pericyclic Reactions ​ Cycloaddition Reactions: ○​ Diels-Alder Reaction: Diene + Dienophile → Cyclohexene derivative (synthesizing 6-membered rings). ​ Sigmatropic Rearrangements: [1,5] and [1,3] shifts, such as the Cope rearrangement. ​ Electrocyclic Reactions: Ring closure or opening in conjugated systems (thermal vs. photochemical conditions). 9. Spectroscopy and Structure Determination ​ NMR Spectroscopy: ○​ Proton NMR (¹H NMR): Chemical shifts, coupling constants, integration. ○​ Carbon-13 NMR (¹³C NMR): Understanding splitting patterns and chemical shifts. ​ IR Spectroscopy: Identifying functional groups based on absorption frequencies. ​ Mass Spectrometry: Fragmentation patterns for structural identification.