OC Ch 01 — 15-Minute Revision

Last-hour revision. Each card is one of the chapter's seven slide sections, compressed to the must-knows + the past-paper trap + the medical hook. If you have time for one more pass — pick the cards with ★★★.

1.1 · Vital Force & Wöhler

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Story

Pre-1828, all organic compounds had been isolated from living things (citric acid from lemon, lactic acid from milk, urea from urine, soap from animal fat). Belief = a "vital force" was needed.

Wöhler 1828

Heated ammonium cyanate NH₄OCN (inorganic) → got urea (NH₂)₂C=O (organic). One experiment, theory dead.

⚠ T/F trap (2019 III.1)

"Wöhler's synthesis demonstrated Vital Force Theory was correct." — F. The opposite.

1.2 · Features of organic compounds

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Five-point checklist

Elements: C, H, plus O, N, S, P, halogens.
Bonds: covalent (not ionic).
m.p./b.p.: low.
Density: usually < 1.
Solubility: low in H₂O, good in organic solvents (like-dissolves-like).

Inorganic exceptions that contain C

CO, CO₂, H₂CO₃ (carbonic acid), MCO₃ (carbonates), MHCO₃ (bicarbonates), MCN (cyanides), MOCN (cyanates).

⚔ Why it matters

Drug lipophilicity = "like-dissolves-like" applied to pharmacology. Lipid-soluble drugs cross BBB; ionised water-soluble drugs do not.

1.3 · Covalent bonds, electronegativity, polarity

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Electronegativity (Pauling)

F 4.0 > O 3.5 > N, Cl 3.0 > Br 2.8 > C, S 2.5 > H 2.1.

Polar bond vs polar molecule

Polar bond needs Δχ > 0. Polar molecule needs polar bonds + asymmetric geometry so dipoles don't cancel.

Molecule	Bonds polar?	Symmetric?	Molecule polar?
CCl₄	Yes	Tetrahedral — yes	No
CHCl₃	Yes	No (3 Cl + 1 H)	Yes
CO₂	Yes	Linear — yes	No
H₂O	Yes	Bent 104.5° — no	Yes

Bond parameters

C–C 154 pm / 347 kJ · C=C 134 / 614 · C≡C 120 / 839. Shorter = stronger.

1.4 · Hybridization & VSEPR

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Why hybridise

Atomic C is 2s²2p² — only 2 unpaired electrons. Yet methane is CH₄ with 4 equivalent bonds. Hybridization recombines s + p to give 4 equivalent hybrid orbitals.

State	Mix	Shape	Angle	σ	π	Example
sp³	1s+3p	Tetrahedral	109.5°	4	0	CH₄, alkanes, R–OH
sp²	1s+2p +1p left	Trigonal planar	120°	3	1	CH₂=CH₂, C=O, benzene
sp	1s+1p +2p left	Linear	180°	2	2	HC≡CH, HCN, CO₂

✨ Mnemonic

Count domains (bonded atoms + lone pairs) at the central atom: 4 → sp³, 3 → sp², 2 → sp. Angles open as p orbitals leave the mix.

⚠ T/F trap (2019 III.4)

"C=C consists of two identical π bonds." — F. C=C = 1σ + 1π. Two π's belong to the triple bond.

Rotation rule

σ rotates freely (cylindrical overlap). π cannot rotate — this locks cis/trans isomers of alkenes (Ch 3).

1.5 · Structural representations

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Four ways to draw the same molecule

Lewis dot — every valence electron shown.
Full / dash-line — every bond drawn.
Condensed (CH₃CH₂OH) — C–H bonds omitted.
Bond-line / skeletal — zig-zag; carbons implied at vertices/ends; heteroatoms drawn.

✨ Valence shortcut

C=4, O=2, N=3, H/X=1. At any bond-line vertex: implicit H's = 4 − (bonds drawn).

1.6 · Functional groups & homologous series

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Functional group

The atom or small group of atoms that determines a molecule's main reactivity. Compounds with the same FG share reactivity = belong to the same family.

FG	Family	Suffix	FG	Family	Suffix
none	Alkane	-ane	–OH	Alcohol	-ol
C=C	Alkene	-ene	–CHO	Aldehyde	-al
C≡C	Alkyne	-yne	>C=O	Ketone	-one
ring	Aromatic	—	–COOH	Carboxylic acid	-oic acid
R–O–R′	Ether	—	–COO–R′	Ester	-oate
–NH₂	Amine	-amine	–CONH₂	Amide	-amide

Homologous series

Same FG + same general formula, adjacent members differ by CH₂. e.g. CH₃OH → C₂H₅OH → C₃H₇OH.

1.7 · Structural isomerism (this chapter)

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Type	What differs	Worked example
Chain	Carbon skeleton	C₄H₁₀ → n-butane vs isobutane
Positional	FG position on same skeleton	C₃H₈O → 1-propanol vs 2-propanol
Functional group	Different FG entirely	C₂H₆O → ethanol vs dimethyl ether

Isomer counts to memorise

C₄H₁₀ = 2 (n-butane, iso) · C₅H₁₂ = 3 (n-, iso-, neopentane) · C₂H₆O = 2 (ethanol, DME).

⚔ Clinical hook

Stereoisomers (next: thalidomide tragedy) are introduced in Ch 3 + Ch 8 (sugars, amino acids). Same molecular formula, different 3-D arrangement → one isomer cures, the other harms.

📝 Full Notes ✅ Q-Bank ⚡ 5-min 🌙 Day-Before 🏠 All OC Units

McMurry & Ballantine 8e Ch 12 · TMU Slide pp.1–55 · Past Papers 2019–2022