Connection Note — Linking OC-02 Concepts — Notes

Concept Connections Within OC-02

Connection 1: Hybridization → Acidity → Nucleophilicity

$sp^{3}$ (alkane) → 25% s → pKa ~50 → carbanion very unstable (bad nucleophile)

$sp^{2}$ (alkene) → 33.3% s → pKa ~44 → vinyl anion unstable

sp (alkyne) → 50% s → pKa ~25 → acetylide anion relatively stable → useful carbon nucleophile (acetylide alkylation)

The same hybridization that makes alkynes most acidic makes the acetylide ion the best carbon nucleophile in this series.

Connection 2: Radical Stability ↔ Carbocation Stability

3° radical > 2° radical > 1° radical (same as carbocation stability)

This is why Markovnikov (carbocation) and anti-Markovnikov (radical) both follow the "more stable intermediate" principle — just with different intermediates. The product regiochemistry differs because the FIRST species to add differs ( $H^{+}$ vs Br•).

Connection 3: syn vs anti Addition

Reaction	Addition Type	Reason
$H_{2}$ /Lindlar's	Syn	$H_{2}$ delivered from same face of catalyst surface
Na/liq. $NH_{3}$	Anti	Radical anion mechanism; trans vinyl anion preferred
$Br_{2}$ / $CCl_{4}$	Anti	Bromonium ion; $Br^{-}$ attacks opposite face
$H_{2}$ /Pd–C (catalytic)	Syn	Same as Lindlar's but goes to alkane

Connection 4: Ozonolysis ↔ Structure Elucidation

Ozonolysis is the reverse problem of synthesis. Given carbonyl fragments → reconstruct the alkene by replacing =O on each C with =C connecting the two fragments.