Question

Which of the following is structural formula of mesityl oxide?

• A. \( (CH_{3})_{2}CH - CH = CH - CO - CH_{3} \)
• B. \( (CH_{3})_{2}C = CH - CO - CH_{3} \)
• C. \( (CH_{3})_{3}C - CH = CH - CO - CH_{3} \)
• D. \( (CH_{3})_{2}CH - CH = CH - CO - CH(CH_{3})_{2} \)

Hint:

Remember Mesityl oxide = Acetone + Acetone minus Water.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
Mesityl oxide is a common name for the IUPAC compound 4-methylpent-3-en-2-one.
Step 2: Detailed Explanation:
Mesityl oxide is formed by the aldol condensation of two acetone molecules followed by dehydration.
Reaction:
\( 2 \text{CH}_{3}\text{COCH}_{3} \xrightarrow{\text{Base}} \text{CH}_{3}\text{C(OH)(CH}_{3}\text{)CH}_{2}\text{COCH}_{3} \xrightarrow{-\text{H}_{2}\text{O}} (CH_{3})_{2}C=CH-CO-CH_{3} \).
Analyzing the structure:
- It has a methyl group at carbon 4 of a pent-3-en-2-one chain.
- This corresponds to option (B).
Step 3: Final Answer:
The structural formula of mesityl oxide is \( (CH_{3})_{2}C = CH - CO - CH_{3} \).