Hydration of Alkynes Quiz

Study Notes

Hydration of Alkynes

Alkynes undergo acid-catalyzed hydration, adding water across the triple bond.
Mercuric ion acts as a catalyst, often using mercuric sulfate in aqueous sulfuric acid.
Hydration resembles that of alkenes and follows Markovnikov's rule, where the more substituted carbon gets the higher electron density.
Enol formation occurs through tautomerization, leading to the corresponding aldehyde or ketone.
For terminal alkynes like acetylene, the product is an aldehyde.
Higher alkynes yield a ketone after hydration.
Example reactions:
- $H-C\equiv C-H$ (ethyne) + $H-OH$ → Vinyl alcohol ($CH_{2}=CH-OH$).
- $H-C\equiv C-CH_{3}$ (propyne) + $H-OH$ → Propen-1-ol ($CH_{2}=C(OH)-CH_{3}$).

Halogenation (Bromination) of Alkynes

Bromine reacts with alkynes in a two-step process, first forming dibromoalkene (primarily in trans configuration), followed by formation of tetrabromides.
Reaction occurs in carbon tetrachloride ($CCl_{4}$):
- $H-C\equiv C-H$ + $Br-Br$ → 1,2-dibromoethene.
- $HC\equiv CH$ + $Br-Br$ → 1,2-dibromoethene.
Chlorination follows a similar mechanism to bromination.

Ozonolysis of Alkynes

Alkynes react with ozone, resulting in the formation of ozonides.
Ozonides can be subsequently treated with water to generate 1,2-dicarbonyl compounds.
The reaction produces hydrogen peroxide as a byproduct.

Description

Test your knowledge on the hydration of alkynes in organic chemistry. This quiz covers acid-catalyzed addition of water, the use of mercuric ions, and Markovnikov orientation. Understand the formation of enols and their conversion to aldehydes or ketones.