Advanced Organic Chemistry

65 lessons, pages 3816–3880.

Advanced Organic Chemistry: An Overview — Pericyclic reactions, photochemistry and synthesis planning
What Are Pericyclic Reactions? — Concerted reactions through cyclic transition states
Molecular Orbitals of Conjugated π Systems — Ethene, butadiene, hexatriene and allyl orbitals
Frontier Molecular Orbital Theory — HOMO–LUMO interactions and orbital phase
Orbital Symmetry and the Woodward–Hoffmann Rules — Allowed and forbidden pericyclic processes
Classifying Pericyclic Reactions — Cycloadditions, electrocyclic, sigmatropic, cheletropic and group transfer
The Diels–Alder Reaction: Mechanism — A concerted [4+2] cycloaddition forming six-membered rings
Diels–Alder Stereochemistry: The Suprafacial Rule — Retention of alkene geometry and the s-cis diene
The Endo Rule and Secondary Orbital Interactions — Kinetic versus thermodynamic adducts
Regioselectivity in Diels–Alder Reactions — Ortho and para rules from orbital coefficients
Dienes and Dienophiles: Reactivity and Electron Demand — Normal and inverse electron-demand cycloadditions
Lewis Acid Catalysis and Asymmetric Diels–Alder Reactions — Lowering the LUMO and controlling facial selectivity
Hetero-Diels–Alder and Intramolecular Variants — Heterocycle formation and fused ring systems
[2+2] Cycloadditions: Thermal Forbiddenness and Ketenes — Why most thermal [2+2] reactions fail and ketene exceptions
1,3-Dipolar Cycloadditions — Azides, nitrile oxides and five-membered heterocycles
Electrocyclic Reactions: Ring Opening and Closing — Cyclobutenes, cyclohexadienes and their open-chain partners
Conrotatory and Disrotatory Motion — Terminal rotation dictated by HOMO symmetry
Predicting Electrocyclic Stereochemistry — The 4n and 4n+2 rules applied to substituted systems
Sigmatropic Rearrangements: Notation and Principles — The [i,j] labelling system for migrating σ bonds
[1,5]-Hydrogen Shifts and Suprafacial Migration — Hydrogen migration across cyclopentadienes and dienes
The Cope Rearrangement — [3,3] shifts of 1,5-dienes including the oxy-Cope
The Claisen Rearrangement — Allyl vinyl ethers to γ,δ-unsaturated carbonyls
Chair Transition States in [3,3] Shifts — Predicting alkene geometry and stereocentres
Cheletropic Reactions — Carbene additions and sulfur dioxide extrusion
Group Transfer Reactions: The Ene Reaction — Allylic hydrogen transfer with bond reorganisation
Aromatic Transition States: Hückel and Möbius — An alternative way to predict allowed reactions
Correlation Diagrams — Tracking orbital symmetry from reactants to products
Pericyclic Reactions in Nature and Synthesis — Biosynthetic cycloadditions and strategic ring construction
Pericyclic Reactions: Problem Solving — Identifying reaction types and predicting products
Principles of Photochemistry: Absorbing Light — Photon energy, chromophores and electronic transitions
Excited States: Singlets and Triplets — Electron spin and the multiplicity of excited states
The Jablonski Diagram — Absorption, internal conversion and intersystem crossing
Fluorescence and Phosphorescence — Radiative decay, lifetimes and Stokes shifts
Quantum Yield and Photochemical Efficiency — Counting photons against molecules reacted
Photosensitisation and Quenching — Energy transfer between excited and ground-state molecules
Photochemical Pericyclic Reactions: Reversing the Rules — Excited-state HOMOs and switched selection rules
Photochemical [2+2] Cycloadditions — Building cyclobutanes and strained rings with light
Photochemical Electrocyclisation: Vitamin D — Ring opening of 7-dehydrocholesterol in skin
Cis–Trans Photoisomerisation and Vision — Retinal, rhodopsin and photostationary states
Carbonyl Photochemistry: Norrish Type I and II — α-Cleavage and γ-hydrogen abstraction
The Paternò–Büchi Reaction — Carbonyl–alkene photocycloaddition to oxetanes
Photoredox Catalysis — Visible-light single-electron transfer in modern synthesis
Singlet Oxygen in Organic Chemistry — Photosensitised oxidation, endoperoxides and ene reactions
Photochemistry in Industry, Nature and Medicine — Photodynamic therapy, sunscreens and photodegradation
Photochemistry: Problem Solving — Excited-state pathways and product prediction
Introduction to Retrosynthetic Analysis — Working backwards from a target molecule
Disconnections and Synthons — Imaginary bond cleavages and idealised fragments
Synthetic Equivalents — Real reagents that deliver synthon behaviour
Functional Group Interconversion — Changing functional groups to enable disconnections
One-Group C–X Disconnections — Ethers, esters, amides and amines
Two-Group Disconnections: 1,3-Dioxygenated Patterns — Aldol and Claisen condensation logic
1,5-Dicarbonyls and the Michael Reaction — Conjugate addition as a strategic disconnection
Illogical Disconnections: 1,2- and 1,4-Patterns and Umpolung — Reversing polarity with acyl anion equivalents
Disconnecting Rings: Robinson Annulation and Diels–Alder — Strategies for carbocyclic targets
C–C Disconnections via Organometallic Reagents — Grignard, organolithium and cross-coupling logic
Chemoselectivity and Protecting Groups — Masking reactive groups during multistep synthesis
Stereocontrol in Synthesis Planning — Relative stereochemistry and diastereoselective steps
Chiral Pool, Auxiliaries and Asymmetric Catalysis — Three routes to single enantiomers
Linear and Convergent Synthesis — Step count, overall yield and route design
Synthetic Strategy: Choosing the Best Route — Key disconnections, simplification and practicality
Green Chemistry and Atom Economy in Synthesis Design — Reducing waste, steps and hazardous reagents
Case Study: Retrosynthesis of a Drug Molecule — Planning a route to a pharmaceutical target
Landmark Total Syntheses — Lessons from classic natural product syntheses
Retrosynthesis: Problem Solving — Designing multistep routes to unfamiliar targets
Advanced Organic Chemistry: Unit Review — Pericyclic reactions, photochemistry and retrosynthesis together