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CH(3)CH(2)-underset(Ph)underset(|)overse...

`CH_(3)CH_(2)-underset(Ph)underset(|)overset(OH)overset(|)C-CH_(3)` cannnot be prepared by:

A

`HCHO+PhCH(CH_3)CH_2MgX`

B

`PhCOCH_2CH_3+CH_3MgX`

C

`PhCOCH_3+CH_3CH_2MgX`

D

`CH_3CH_2COCH_3+PhMgX`

Text Solution

AI Generated Solution

The correct Answer is:
To determine which method cannot be used to prepare the given compound, we need to analyze the options provided in the question. The compound in question is: \[ CH_3CH_2-Ph-CH(OH)-C-CH_3 \] This compound has a phenyl group (Ph) and a hydroxyl group (OH) attached to a carbon chain. We will evaluate each option to see if it can lead to the formation of this compound. ### Step-by-Step Solution: 1. **Identify the Structure**: The compound has a branched structure with a hydroxyl group (OH) and a phenyl group (Ph). The carbon atom with the hydroxyl group is attached to a carbon chain. 2. **Analyze the First Option**: - **Reagents**: Formaldehyde (HCHO) with phenylmagnesium bromide (PhMgBr) and ethylmagnesium bromide (CH3CH2MgBr). - **Reaction**: - PhMgBr reacts with formaldehyde to form a primary alcohol (Ph-CH2-CH(OH)-C-CH3). - This results in a 1-degree alcohol, which does not match our target compound. - **Conclusion**: This method cannot prepare the desired compound. 3. **Analyze the Second Option**: - **Reagents**: Benzaldehyde (PhC=O) with ethylmagnesium bromide (CH3CH2MgBr). - **Reaction**: - The Grignard reagent adds to the carbonyl carbon, forming a tertiary alcohol after hydrolysis. - **Conclusion**: This method can prepare the desired compound. 4. **Analyze the Third Option**: - **Reagents**: Acetone (CH3C(=O)CH3) with phenylmagnesium bromide (PhMgBr). - **Reaction**: - The Grignard reagent adds to the carbonyl carbon, leading to a tertiary alcohol after hydrolysis. - **Conclusion**: This method can prepare the desired compound. 5. **Analyze the Fourth Option**: - **Reagents**: A ketone (like 2-butanone) with phenylmagnesium bromide (PhMgBr). - **Reaction**: - Similar to the previous cases, the Grignard reagent adds to the ketone, forming a tertiary alcohol after hydrolysis. - **Conclusion**: This method can prepare the desired compound. ### Final Conclusion: The compound \( CH_3CH_2-Ph-CH(OH)-C-CH_3 \) cannot be prepared by the first option (formaldehyde with phenylmagnesium bromide and ethylmagnesium bromide), as it results in a primary alcohol instead of the desired tertiary alcohol.
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