🧬 Organic Chemistry: An Introduction

What you’ll learn

1. The Molecule That Killed a TheoryExplain why organic chemistry cannot be learned by memorization, and state the principle — electrons move from rich to poor — that replaces it.Wöhler's 1828 synthesis of urea from an inorganic salt undermined the claim that life's molecules required a vital force, opening all of carbon chemistry to the laboratory. What followed was a combinatorial explosion — tens of millions of known compounds — which makes memorization hopeless and forces the subject to be organized around one repeating principle: electrons flow from electron-rich sites to electron-poor ones.
2. Why Carbon and Nothing ElseExplain how carbon's tetravalence, catenation and bond strengths produce the combinatorial explosion of organic compounds, and why silicon cannot do the same.Carbon forms four strong bonds and, uniquely, bonds to itself indefinitely in chains, branches and rings, so molecular size and shape have no ceiling. Silicon sits directly beneath carbon and shares its tetravalence, but its bonds to itself are far weaker while its bond to oxygen is far stronger — so silicon chemistry collapses into rock rather than building a biochemistry.
3. Learning to Read the DrawingsRead and interpret skeletal (line-angle) structures, and explain why this convention is used instead of showing every atom.Skeletal structures draw a carbon at every vertex and line end, leave C–H hydrogens implicit, and show only heteroatoms explicitly — compressing the drawing to exactly the information that predicts reactivity. The convention is not shorthand for its own sake: by deleting the unreactive carbon-hydrogen background, it makes the reactive sites the only things visible.
4. The Verb of a MoleculeExplain the functional group concept and why a group's reactivity is largely transferable across the molecules that carry it.A functional group is a small arrangement of atoms whose chemistry is nearly independent of the carbon skeleton it rides on, which reduces tens of millions of compounds to a manageable set of behaviours. The skeleton is not irrelevant — it tunes physical properties and can hinder access — but the group is what reacts, so recognizing groups is how chemists read an unfamiliar molecule.
5. Names as AddressesDecode a systematic IUPAC name into a structure by reading its root, suffix and prefixes.A systematic name is an assembly instruction rather than a label: the root gives the longest carbon chain, the suffix names the principal functional group, and numbered prefixes locate everything else. Because the rules are reversible, any chemist anywhere can turn a name into exactly one structure and any structure into exactly one name.
6. Shape Is Not OptionalRelate sigma and pi bonding to hybridization, and explain why single bonds rotate freely while double bonds are rigid and planar.A single bond is a sigma bond with electron density along the internuclear axis, so rotating around it costs nothing; a double bond adds a pi bond formed from sideways p-orbital overlap, and rotating would break that overlap. The resulting rigidity makes alkenes flat and locks their substituents into cis or trans arrangements — a geometric fact with consequences from vision to margarine.
7. Same Formula, Different MoleculeDistinguish constitutional isomers from stereoisomers, and explain chirality and why enantiomers can behave differently in the body.Isomers share a molecular formula but differ in connectivity (constitutional) or in spatial arrangement (stereoisomers), and a carbon with four different groups produces two non-superimposable mirror images called enantiomers. Because biological receptors are themselves chiral, they can bind one enantiomer and not its mirror — a fact whose consequences ranged from ineffective drugs to the thalidomide disaster.
8. The Electron MapUse electronegativity differences to locate electron-rich and electron-poor sites on a molecule, and classify them as nucleophiles and electrophiles.Unequal sharing of bonding electrons gives molecules a map of partial charges, and every organic reaction is an electron-rich site (nucleophile) attacking an electron-poor site (electrophile). Learning to read that map converts organic chemistry from memorization into prediction, because the map identifies where a reaction must occur before any reaction is known.
9. The Grammar of MechanismRead and draw curved-arrow notation, and use it to express a reaction mechanism as electron movement.A curved arrow denotes the movement of an electron pair from where it starts to where it ends, always drawn from the nucleophile to the electrophile. The notation is not decorative: it enforces electron bookkeeping, so a mechanism that cannot be drawn with legal arrows is a mechanism that cannot happen.
10. Two Ways to Make a SwapContrast the SN2 and SN1 mechanisms, and explain how substrate structure selects between them and determines the stereochemical outcome.SN2 is a single concerted step in which the nucleophile attacks the back of the carbon as the leaving group departs, inverting the stereocentre and requiring an uncrowded substrate. SN1 instead ionizes first to a flat carbocation that can be attacked from either face, giving a racemic mixture — so substrate crowding and carbocation stability, not preference, decide which route a molecule takes.
11. Adding Across a Double BondExplain electrophilic addition to alkenes, and derive Markovnikov's rule from carbocation stability rather than memorizing it.An alkene's exposed pi electrons attack an electrophile, generating a carbocation that is then captured — so the alkene is the attacker rather than the target. Which carbon takes the positive charge is decided by carbocation stability, and that single consideration derives Markovnikov's rule, turning a memorized 'rich get richer' slogan into a prediction.
12. Why Some Hydrogens Let GoUse resonance stabilization of the conjugate base to explain the enormous acidity difference between carboxylic acids and alcohols.Acidity is decided by the stability of the anion left behind, not by the strength of the O–H bond, and a carboxylate's charge is delocalized over two equivalent oxygens while an alkoxide's is stranded on one. That single difference is worth roughly eleven orders of magnitude in Ka — the reason vinegar is an acid and ethanol is not.
13. The Ring That Refused to ReactExplain aromaticity as delocalization over a cyclic conjugated system, and why benzene undergoes substitution rather than the addition expected of an alkene.Benzene has the formula of a highly unsaturated compound but behaves as if it has no double bonds, because its six pi electrons are delocalized in rings above and below a perfectly regular hexagon. That delocalization is worth a large stabilization, so benzene substitutes rather than adds — since adding would destroy the very delocalization that makes it stable.
14. The Carbonyl Runs EverythingExplain why the carbonyl group is organic chemistry's central electrophile, and how one mechanistic pattern generates esters, amides, polymers and metabolism.In C=O, a large electronegativity gap acting through a double bond leaves the carbon strongly electron-poor — the most important electrophile in the subject. Nucleophilic attack on that carbon, followed by the pi bond reforming and a leaving group departing, is a single pattern that produces esters, amides, proteins, polyesters and most of biochemistry.

Questions this course answers

Grounded in trusted sources

• OpenStax — Organic Chemistry (2023)
• Clayden, Greeves & Warren — Organic Chemistry, 2nd ed. (2012)
• Wöhler, F. 'Ueber künstliche Bildung des Harnstoffs', Annalen der Physik 88, 253 (1828)
• Kekulé, A. 'Sur la constitution des substances aromatiques', Bulletin de la Société Chimique de Paris 3, 98 (1865)
• Markovnikov, V., Annalen der Chemie 153, 228 (1870)
• Vargesson, N. 'Thalidomide-induced teratogenesis: history and mechanisms', Birth Defects Research C 105, 140 (2015)
• Pauling electronegativities (C 2.55, H 2.20, N 3.04, Cl 3.16, O 3.44) — OpenStax Chemistry 2e, ch. 7.2 (2019)
• Bond enthalpies (C–C 346, Si–Si 222, Si–O 452 kJ/mol) — OpenStax Chemistry 2e, Appendix

Every Wunder lesson is built from real, reputable sources — never invented.

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