Organic Chemistry: Alkyne Reactions and Products

1. Preparation of alkynes (double elimination)

Reagents: 1) excess NaNH2 2) A.W. (acid wash) | Starting material: geminal or vicinal dihalide | Product: alkyne | M/AM: N/A | Syn/anti: N/A

1. 1) excess NaNH2 2) A.W. (acid wash)

Name: Preparation of alkynes (double elimination) | Product: alkyne from geminal or vicinal dihalide | M/AM: N/A | Syn/anti: N/A

2. Hydrohalogenation (2 equivalents)

Reagents: excess HX | Product: geminal dihalide (2 X on same C) | M | Syn/anti: N/A

2. Excess HX added to an alkyne

Name: Hydrohalogenation (2 equivalents) | Product: geminal dihalide | M | Syn/anti: N/A

3. Hydrohalogenation (1 equivalent)

Reagents: 1 equivalent HX | Product: vinyl halide (haloalkene) | M | Syn/anti: both

3. 1 equivalent HX added to an alkyne

Name: Hydrohalogenation (1 equivalent) | Product: vinyl halide | M | Syn/anti: both

4. Acid-catalyzed hydration

Reagents: HgSO4, H2SO4, H2O | Product: ketone (methyl ketone for terminal alkyne) | M | Syn/anti: N/A

4. HgSO4, H2SO4, H2O added to an alkyne

Name: Acid-catalyzed hydration | Product: ketone after tautomerization | M | Syn/anti: N/A

5. Hydroboration-oxidation

Reagents: 1) R2BH, THF 2) H2O2, NaOH | Product: aldehyde from terminal alkyne | AM | Syn/anti: N/A for final carbonyl

5. 1) R2BH, THF 2) H2O2, NaOH

Name: Hydroboration-oxidation | Product: aldehyde from terminal alkyne | AM | Syn/anti: N/A for final carbonyl

6. Halogenation (1 equivalent)

Reagents: 1 equivalent X2, CH2Cl2 | Product: trans dihaloalkene | M/AM: N/A | Anti

6. 1 equivalent X2, CH2Cl2 added to an alkyne

Name: Halogenation (1 equivalent) | Product: trans dihaloalkene | M/AM: N/A | Anti

7. Halogenation (2 equivalents)

Reagents: excess X2, CH2Cl2 | Product: tetrahalide (4 X added) | M/AM: N/A | Syn/anti: N/A overall

7. Excess X2 added to an alkyne

Name: Halogenation (2 equivalents) | Product: tetrahalide | M/AM: N/A | Syn/anti: N/A overall

8. Ozonolysis

Reagents: 1) O3 2) H2O | Product: carboxylic acids; terminal alkyne gives CO2 as one fragment | M/AM: N/A | Syn/anti: N/A

8. 1) O3 2) H2O added to an alkyne

Name: Ozonolysis | Product: carboxylic acids (plus CO2 for terminal alkyne) | M/AM: N/A | Syn/anti: N/A

9. Alkylation of terminal alkynes

Reagents: 1) NaNH2 2) R-X (primary alkyl halide) | Product: longer internal alkyne | M/AM: N/A | Syn/anti: N/A

9. 1) NaNH2 2) R-X added to terminal alkyne

Name: Alkylation | Product: longer carbon chain via new C-C bond | M/AM: N/A | Syn/anti: N/A

10. Dissolving metal reduction

Reagents: Na, NH3(l) | Product: trans alkene | M/AM: N/A | Anti

10. Na, NH3(l) added to an alkyne

Name: Dissolving metal reduction | Product: trans alkene | M/AM: N/A | Anti

11. Complete hydrogenation

Reagents: excess H2, Pt (or Pd/C) | Product: alkane | M/AM: N/A | Syn additions

11. Excess H2, Pt added to an alkyne

Name: Complete hydrogenation | Product: alkane | M/AM: N/A | Syn additions

12. Hydrogenation with poisoned catalyst

Reagents: H2, Lindlar catalyst | Product: cis alkene | M/AM: N/A | Syn

12. H2, Lindlar catalyst added to an alkyne

Name: Partial hydrogenation with poisoned catalyst | Product: cis alkene | M/AM: N/A | Syn

13. Keto-enol tautomerization

Conditions: acid or base catalysis | Product: carbonyl compound from enol (ketone or aldehyde) | M/AM: N/A | Syn/anti: N/A

13. Enol converts to ketone or aldehyde

Name: Keto-enol tautomerization | Conditions: acid or base catalysis | Product: keto form | M/AM: N/A | Syn/anti: N/A