SN2 Reaction of Acetylide Ions with Alkyl Halides
Notes: This works best for primary or methyl alkyl halides. Sodium (Na) is not crucial, it’s just a spectator ion.
Notes: Be prepared to see the alkyl halide either as the reactant (example 1) or above the arrow (example 2). It is also common to see the alkyne as starting material with a two-step deprotonation/SN2 process (example 4).
Since this is an SN2 reaction, everything you’ve previously learned about SN2 reactions still applies. Example 5 with one equivalent of nucleophile will react preferentially to displace the better leaving group Br(-).
Notes: Really important! There aren’t many ways of making C–C bonds in Org 1, but this is one of them. This is one of the most USEFUL ways of making C–C bonds. Furthermore, alkynes are really versatile and can be turned into all kinds of other functional groups.
(Advanced) References And Further Reading
This is a classic reaction taught to undergraduate students taking organic chemistry. Its utility lies in the fact that it allows a simple way to form C-C bonds.
Kenneth N. Campbell and Barbara K. Campbell
Org. Synth. 1950 30, 15
An extremely simple example of this reaction. The deprotonation is done with Na metal in liquid ammonia, and care has to be taken to avoid the conditions of dissolving metal reduction (the procedure states that the reaction should not turn blue).
- Synthesis of Unsymmetrical Alkynes via the Alkylation of Sodium Acetylides. An Introduction to Synthetic Design for Organic Chemistry Students
Jennifer N. Shepherd and Jason R. Stenzel
Journal of Chemical Education 2006, 83 (3), 425
A nice paper that describes the adaptation of this reaction for undergraduate teaching labs.
Org. Synth. 1950, 30, 15
DOI Link: 10.15227/orgsyn.030.0015
Org. Synth. 1977, 57, 26
DOI Link: 10.15227/orgsyn.057.0026