propynefrom ethyne Propene from propyne 1-bromopropene from propyn Propanone from propyne
The correct answer and explanation is :
The following transformations can be made step by step starting from ethyne (acetylene), and through various intermediate compounds leading to propanone. Let’s go through each transformation one by one.
1. From Ethyne to Propyne:
Ethyne (C₂H₂), also known as acetylene, is a simple alkyne with a triple bond between two carbon atoms. To convert ethyne to propyne (C₃H₄), we typically add a methyl group (-CH₃) to ethyne. This can be done by a methylation reaction, such as:
Ethyne (C₂H₂) + CH₃MgBr → Propyne (C₃H₄)
The Grignard reagent (CH₃MgBr) adds a methyl group to the triple-bonded carbon in ethyne, resulting in propyne (methylacetylene).
2. From Propyne to Propene:
Propyne (C₃H₄) is an alkyne with a triple bond. To reduce this triple bond to a double bond and form propene (C₃H₆), we use a hydrogenation reaction. This is done using a catalyst like palladium (Pd) or platinum (Pt), which adds hydrogen across the triple bond, converting propyne into propene.
Propyne (C₃H₄) + H₂ (with Pd or Pt catalyst) → Propene (C₃H₆)
3. From Propene to 1-Bromopropene:
The conversion of propene (C₃H₆) to 1-bromopropene (C₃H₅Br) can be achieved by an electrophilic addition of HBr. The double bond in propene undergoes addition with HBr to form the bromoalkene. Since HBr adds to the more substituted carbon in propene (Markovnikov’s rule), the product will be 1-bromopropene.
Propene (C₃H₆) + HBr → 1-Bromopropene (C₃H₅Br)
4. From Propene to Propanone:
Propene (C₃H₆) can be oxidized to propanone (C₃H₆O) using an oxidation reaction. This typically involves a reaction with ozone (O₃) followed by mild hydrolysis or using other reagents like potassium permanganate (KMnO₄) under oxidative conditions. The oxidation breaks the double bond and introduces a carbonyl group, forming propanone.
Propene (C₃H₆) + O₃ → Propanone (C₃H₆O)
Explanation:
These reactions involve common organic reactions such as addition, reduction, and oxidation. The transformation from ethyne to propyne requires a methylation step. Propyne can be hydrogenated to form propene, a simple alkene, and the addition of HBr to propene follows Markovnikov’s rule to form 1-bromopropene. Finally, propene undergoes oxidation to form propanone, which is a ketone with a carbonyl group (C=O). These steps illustrate the versatility of alkynes and alkenes in organic synthesis.