Practical Applications of OC-02 Chemistry

1. Selective Alkene Synthesis from Alkynes

To make cis-2-butene from 2-butyne: CC#CC --[$H_{2}$, Lindlar's catalyst]--> C/C=C\C (cis-but-2-ene)

To make trans-2-butene from 2-butyne: CC#CC --[Na, liq. $NH_{3}$]--> C/C=C/C (trans-but-2-ene)

These are the ONLY two synthetic routes to control alkene geometry in this chapter.

2. Acetylide Alkylation (C–C Bond Formation)

Terminal alkyne → sodium acetylide → react with alkyl halide → new C–C bond:

CC#C + NaN$H_{2}$ → CC#$C^{-}$$Na^{+}$ + $NH_{3}$

CC#$C^{-}$$Na^{+}$ + $CH_{3}I$ → CC#CC (but-2-yne) + NaI

This is one of the few methods in introductory organic chemistry to form a new C–C bond.

3. Double Bond Location via Ozonolysis

Unknown alkene → reductive ozonolysis → identify carbonyl fragments → deduce structure:

If ozonolysis gives $CH_{3}CHO$ + $CH_{3}CHO$ → symmetric alkene with –CH($CH_{3}$)– on each side → 2-butene.

If ozonolysis gives HCHO + $CH_{3}$CO$CH_{3}$ → 2-methylpropene (C$H_{2}$=C($CH_{3}$)_{2}).

4. Selective Bromination for Synthesis

1-Bromopropane (primary alkyl halide, useful for Williamson ether synthesis): CC=C + HBr + ROOR → CCCBr (anti-Markovnikov)

2-Bromopropane (secondary alkyl halide): CC=C + HBr (no peroxide) → CC(Br)C (Markovnikov)