Convert Ethanol to But-1-yne.
Hint: First, transform the alcohol into a haloalkane. Next, take acetylene and convert it into sodium acetylide. Then, combine the haloalkane with sodium acetylide, resulting in an alkyne with an increased number of carbon atoms.
Complete step by step answer:
Ethanol is a compound of alcohol groups having a −OHfunctional group. Its formula is
CH3−CH2−OH. It is a 2 carbon compound.
But-1-yne is a compound of the alkyne group having a triple bond. Its formula is
HC≡C−CH2−CH3. It is a 4 carbon compound.
When alcohols react with hydrobromic acid in the presence of a small amount of sulfuric acid, they produce a bromoalkane. When acetylene (or ethyne) is treated with sodamide in liquid ammonia, it forms sodium acetylide. This sodium acetylide can then be converted into the desired alkyne by adding a haloalkane with the required number of carbon atoms.
To convert ethanol to but-1-yne:
We have to convert a 2 carbon compound to a 4 carbon compound.
First, convert the ethanol to bromoethane with hydrobromic acid and a little amount of H2SO4 Next, take acetylene and react with NaNH2 to form sodium acetylide. Now, add the bromoethane and acetylide to form but-1-yne. This reaction is useful for making higher alkynes have triple bonds at the first carbon atom.
The reaction and mechanism are given below:
CH3−CH2−OH→HC≡C−CH2−CH3
The mechanism of the reaction is:
Note: When 2 moles of NaNH3 are reacted with the ethyne or acetylene, both the hydrogen of the ethyne are replaced with the sodium atom. Now, this sodium acetylide can be used to make alkynes in which the triple bond is not at the first carbon atom.
