Alkynes

Alkyne Deprotonation

NaNH₂; forms acetylide ion.

Acetylide SN2 Reactions

Acetylide ion + 1° alkyl halide (Cl, Br, I);

Acetylide with 2° Alkyl Halides

Acetylide ion + 2° alkyl halide; E2 elimination favored; forms alkene.

Acetylide Addition to Carbonyls

Acetylide ion + aldehyde or ketone; then H₃O⁺ workup; forms propargylic alcohol.

BuLi Deprotonation + Epoxide Attack

BuLi then epoxide; then H₃O⁺ workup; solvent: THF; SN2 opening at less substituted carbon.

Alkyne Catalytic Hydrogenation

H₂ with Pd, Pt, or Ni; solvent: EtOH; full reduction to alkane.

Lindlar’s Catalyst (Partial Hydrogenation)

H₂ with Pd/BaSO₄ and quinoline; solvent: EtOH; cis alkene only.

Metal–Ammonia Reduction (Na/NH₃)

Na in NH₃(l); trans alkene formation.

Alkyne Addition to Halogens (X₂)

Cl₂ or Br₂; solvent: CCl₄; 1 eq → dihalide, 2 eq → tetrahalide.

Hydrogen Halide Addition to Alkynes (HX)

HCl, HBr, or HI; Markovnikov addition; forms geminal dihalide.

Radical HBr Addition to Alkynes

HBr + ROOR; anti-Markovnikov addition; stops at alkene stage.

Mercuric Ion–Catalyzed Hydration of Alkynes

HgSO₄, H₂SO₄, H₂O; Markovnikov hydration gives enol which tautomerizes to ketone