Organic Chemistry - Alkynes

Saturation

Unsaturated

General formula of linear alkynes

C (n) H (2n-2)

General formula of cycloalkynes

C (n) H (2n-4)

Polarity

Non-polar

What increases its boiling point?

Increasing number of carbons

What lowers its boiling point?

More substitution along carbon chain

Hydrohalogenation reaction reagent, catalyst, product and mechanism

Reagent: HX

Catalysts: none

Product: geminal dihalide

Mechanism: electrophilic addition

Acid catalyzed hydration reagent, catalysts, product, mechanism

Reagent: H2O

Catalysts: H2SO4 and HgSO4

Product: keto form from enol form (keto-enol tautomerism)

Mechanism: electrophilic addition

Halogenation reagent, catalyst, product, mechanism

Reagent: X2

Catalysts: none

Product: geminal dihalide

Mechanism: electrophilic addition

Hydroboration-oxidation reagent, catalyst, product, reaction

Reagent: (BH3)2

Catalysts: none

Product: aldehyde from enol (keto-enol tautomerism)

Mechanism: electrophilic addition then oxidation

Metal acetylide reaction reagents, catalyst, product, mechanism

Reagent: metal acetylide + RX

Catalysts: none

Product: alkyne-R + metal-X

Mechanism: nucleophilic addition

Catalytic Hydrogenation for Pd/C catalyst

Reagent: 2H2

Catalysts: Pd/C

Product: alkane

Mechanism: reduction of alkynes

Catalytic Hydrogenation for Lindlar Catalyst

Reagent: H2

Catalysts: lindlar caralyst (poisoned Pd or Pd/CaCO3

Product: cis alkene

Mechanism: reduction of alkynes

Catalytic Hydrogenation for NaNH2 or LiNH2 catalyst

Reagent: H2

Catalysts: NaNH2 or LiNH2

Product: trans alkene

Mechanism: reduction of alkynes

Ozonolysis reagent, catalys, product, mechanism

Reagent: 1. O3

Catalysts: 2. Zn, H3O+

Product: if terminal alkyne, CO2. if internal alkyne, carboxylic acid

Mechanism: oxidation of alkynes