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Question

Which among the following molecular formulae of organic compounds does NOT represent a ring structure?

This question was previously asked in
RRB Group D 2025 Question Paper (18-Aug-2026) (Shift 1)
The correct answer is

C6H14

A quick way to tell whether a hydrocarbon can be an open-chain (acyclic) compound is the general formula for saturated open-chain alkanes: \(C_nH_{2n+2}\). Any formula that matches this exactly can be drawn as a straight or branched chain with no ring. Formulae with fewer hydrogens than \(2n+2\) must contain either a double/triple bond or a ring (each ring or pi bond reduces the hydrogen count by 2).

For n = 6, the alkane formula is \(C_6H_{14}\), which corresponds to n-hexane and its branched isomers, all open-chain molecules with no ring.

The other three options have fewer hydrogens than \(C_6H_{14}\). \(C_6H_{10}\) fits cyclohexene (one ring plus one double bond), \(C_6H_6\) is benzene (a six-membered aromatic ring), and \(C_6H_8\) fits cyclohexadiene (a ring with two double bonds). Each of these must be drawn with a ring.

Hence, the molecular formula that does NOT represent a ring structure is \(C_6H_{14}\).

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Similar Questions

  1. What do methane, ethane and propane represent in the study of carbon compounds?

  2. Which property is most affected if the length of the carbon chain in an alkane increases?

  3. Why do higher homologues of alkanes produce multiple products when they react with chlorine in a substitution reaction?

  4. Select the correct option regarding the following two statements labelled Assertion (A) and Reason (R).

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  6. Which of the following statements about a homologous series are CORRECT?

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  9. Which of the following is NOT a characteristic of substitution reactions in alkanes?

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Important Questions from Hydrocarbons

  1. Which of the following base is found in soap?

  2. Which one of the following is the general formula of Alkenes?

  3. \({\rm{C}}{{\rm{H}}_3}{\rm{COOH}}\mathop \to \limits^{LiAI{H_4}} {\rm{A}}\mathop \to \limits^{PC{I_5}} {\rm{B}}\mathop \to \limits^{alc.KOH} {\rm{C}}\) Homologue of ‘C’ in the above reaction is:
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  5. Which of the following pair gives 1° carbonium ion by hydrolysis of C-Br bond?

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