An organic compound X having molecular formula $C_5H_{10}O$ yields phenyl hydrazone and gives a negative respo

Question

An organic compound X having molecular formula $C_5H_{10}O$ yields phenyl hydrazone and gives a negative response to the iodoform test and Tollen's test. It produces n-pentane on reduction. X could be:

Accepted Answer

To identify compound X ($C_5H_{10}O$):
1.  **Phenylhydrazone Formation:** The reaction with phenylhydrazine indicates the presence of a carbonyl group ($>C=O$). This confirms X is an aldehyde or ketone, eliminating the alcohol (Option D).
2.  **Negative Tollen's Test:** Tollen's reagent oxidizes aldehydes to carboxylic acids (silver mirror). A negative result indicates X is **not an aldehyde**, eliminating Pentanal (Option A). X must be a ketone.
3.  **Negative Iodoform Test:** The iodoform test detects the presence of a methyl ketone group ($CH_3-C=O$).
    *   **2-Pentanone** ($CH_3-CO-CH_2CH_2CH_3$) contains this group and would give a positive test.
    *   **3-Pentanone** ($CH_3CH_2-CO-CH_2CH_3$) does not contain a methyl group attached directly to the carbonyl carbon. It gives a negative test.
4.  **Reduction:** Reduction of 3-pentanone yields n-pentane, consistent with the problem statement.

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