Question

Consider the reactions:

• A. But-1-en-3-one
• B. 4-Hydroxybutan-2-one
• C. But-3-en-2-one
• D. 1-Hydroxybutan-3-one

Hint:

Aldol condensation is an important reaction in organic synthesis where an enolate ion reacts with a carbonyl compound to form a β-hydroxy ketone, which then undergoes dehydration to yield an α,β-unsaturated carbonyl compound.

Answer 1

The Correct Option is C

To solve this problem, we need to understand the reactions given and identify the structure of the resulting product. The question provides a chemical reaction (not displayed here) and a list of products. The goal is to determine which product matches the final product of the reaction.

One of the likely reactions based on the context is the conversion of a reactant (potentially a 4-carbon compound) through a series of steps leading to an enone (a compound containing both an alkene and a ketone).

The correct answer is But-3-en-2-one. This suggests a structure where the enone group is in the middle of the carbon chain:

• The number "3" in But-3-en-2-one indicates the position of the double bond on the carbon chain, starting from either end of a 4-carbon butane chain.
• The number "2" suggests the position of the keto (C=O) group, implying it is attached to the second carbon.
• This means a double bond is present between the third and fourth carbon atoms, and a keto group is attached to the second carbon atom.

Given these observations, But-3-en-2-one matches the criteria of the resulting product of the aforementioned reactions, as it is an enone formed by a process that might involve steps like hydration or dehydration of intermediate alcohols or unsaturated carbonyls, common in organic synthesis.

Answer 2

Step 1: Ozonolysis of Alkene
The given compound is but-2-ene. It undergoes ozonolysis to form two carbonyl compounds: \[ \text{H}_3\text{C}-\text{C}= \text{C}-\text{CH}_3 \xrightarrow[\text{Zn/H}_2\text{O}]{\text{O}_3} \text{CH}_3 - \text{CHO} + \text{CH}_3 - \text{CO}-\text{CH}_3 \] Step 2: Aldol Condensation
In the presence of dilute NaOH and heat, an aldol condensation reaction occurs, leading to the formation of the conjugated enone: \[ \text{CH}_3 - \text{CO} - \text{CH}_3 + \text{CH}_3 - \text{CHO} \xrightarrow{\text{Dil. NaOH}, \Delta} \text{CH}_3 - \text{CH} = \text{CH} - \text{COCH}_3 \] Step 3: Naming the Final Product
The resulting compound is named as But-3-en-2-one following IUPAC nomenclature. \[ \boxed{\text{But-3-en-2-one}} \]