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The reaction of C6H5CH=CHCHO with NaBH4 gives which product?

1. C6H5CH2CH2CH2OH
2. C6H5CH=CHCH2OH
3. C6H5CH2CH2CHO
4. C6H5CH2CHOHCH3

Correct answer: C6H5CH=CHCH2OH

Solution

NaBH4 reduces only the aldehyde (CHO) group to a primary alcohol (CH2OH). It does not reduce the C=C double bond, even though it is conjugated with the carbonyl. Product: C6H5-CH=CH-CH2OH (cinnamyl alcohol).

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