Question

Number of isomeric compounds with molecular formula \(C _9 H _{10} O\) which 
(i) do not dissolve in \(NaOH\)
(ii) do not dissolve in \(HCl\)
(iii) do not give orange precipitate with 2,4-DNP 
(iv) on hydrogenation give identical compound with molecular formula \(C _9 H _{12} O\) is _________

Hint:

Ethers are neutral compounds that do not react with acids, bases, or 2,4-DNP, and aromatic ethers retain their structure upon hydrogenation of the benzene ring.

Answer 1

Correct Answer: 2

Analysis of the Given Conditions:

The given conditions indicate the compound must satisfy the following:

1. Not dissolve in NaOH or HCl, which means it is a neutral compound, such as an ether.
2. Not give an orange precipitate with 2,4-DNP, meaning it is not a carbonyl compound (aldehyde or ketone).
3. On hydrogenation, give an identical compound, implying it has an unsaturated bond (e.g., an aromatic ring) that does not change the functional group upon reduction.

For the molecular formula C₉H₁₀O, possible isomeric structures satisfying the above conditions are:

1. p-Methoxy toluene (C₆H₄(OCH₃)CH₃): The methoxy group is attached to the aromatic ring in the para position.
2. o-Methoxy toluene (C₆H₄(OCH₃)CH₃): The methoxy group is attached to the aromatic ring in the ortho position.

These compounds are ethers, do not react with NaOH, HCl, or 2,4-DNP, and remain the same upon hydrogenation. 

Conclusion: The number of isomeric compounds is 2.

Answer 2

The only structure that satisfies all the given conditions is: C₆H₅-CH=CH-CH₂-CH₂-CH₂-CH₃ 
This structure is representative of a styrene molecule with a methyl group (CH3) at the end. It does not dissolve in NaOH or HCl, does not give an orange precipitate with 2,4-DNP, and upon hydrogenation, it forms ethylbenzene (C₆H₅-CH₂-CH₃), which has the molecular formula C₉H₁₂O. 
\(\therefore\) the correct answer is '2', as there are two isomeric compounds that satisfy all the given conditions.