Alkynes Flashcards
What are Alkynes?
Alkynes are unsaturated hydrocarbons containing carbon-carbon triple bond.
What is the molecular formula for alkynes?
CnH(2n-2)
What is a main source of alkyne?
The formation of acetylene from carbide:
Acetylene is produced from the reaction of carbon (coke) and calcium oxide at temp btw 1800 - 2100°C, producing carbide.
CaO(s) + 3C →CaC2 + CO
Carbide (CaC2) reacts with water to form ethyne.
CaC2 + 2H2O → C2H2 + Ca(OH)2
Which functional group has the highest priority: Alkyl halides, Alkanes, Alkenes, Alkynes?
- Alkenes
- Alkynes
- Alkanes
- Alkyl halides
What is the first member of the alkyne group?
Acetylene or ethyne.
What acidity does Calcium carbide (CaC2) have
Calcium carbide is a strong base.
What are the physical properties of alkynes?
- Alkynes are soluble in organic solvents like propan-2-one and alcohols.
- Boiling and melting points of unbranched alkynes increases down the group due to increasing strength in intermolecular Van Der Waal forces.
- Acetylene (Ethyne) undergoes combustion in excess oxygen to produce a large amount of heat (2800°C), CO2 and water.
- Alkynes are slightly more polar than alkenes and alkanes.
- Alkynes have a slightly higher boiling and melting point than alkenes and alkanes.
What is acidity?
Acidity is the measure of the ease at which an organic molecule releases a hydrogen atom previously bonded to it.
What are the preparation of alkynes?
Alkynes can be prepared by the alkylation of acetylides in the presence of liquid ammonia
H3C–C=–CNa + CH3I →(NH3)→ H3C–C=-C–CH3 + NaI