See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

Step 1 - Molecular Formula Analysis: C4H8O has degree of unsaturation = (2×4 + 2 - 8)/2 = 1. So one degree of unsaturation, which could be a C=C double bond, C=O double bond, or a ring. Step 2 - Analyze Compound X: - Bromine decolourises: indicates a C=C double bond (alkene) present. - Na metal gives bubbles: indicates an O-H group (alcohol) present, releasing H2 gas. - Chromic acid turns orange to green: indicates oxidation of an alcohol, specifically a primary or secondary alcohol (not tertiary). - Lucas reagent: No reaction (or very slow) indicates a primary alcohol (primary alcohols do not react with Lucas reagent at room temperature). Conclusion for X: Compound X is a primary allylic alcohol with formula C4H8O containing both a C=C and an OH group. With one degree of unsaturation accounted for by the double bond and an OH group, X is but-3-en-1-ol (3-buten-1-ol, CH2=CH-CH2-CH2OH) or but-3-en-2-ol... Actually with C4H8O, one degree of unsaturation: if there's a C=C and an OH, that accounts for one degree of unsaturation. X is most likely 3-buten-1-ol (CH2=CHCH2CH2OH) - a primary allylic alcohol. The chromic acid oxidation confirms primary/secondary alcohol, and no Lucas reaction confirms primary alcohol. Step 3 - Analyze Compound Y: - No reaction with bromine: no C=C double bond, not easily oxidized. - No reaction with Na metal: no O-H group. - No reaction with chromic acid: no oxidizable alcohol. - No reaction with Lucas reagent: no alcohol. Yet Y has molecular formula C4H8O with one degree of unsaturation. Since there is no C=C (bromine test negative) and no O-H (Na metal negative), the degree of unsaturation must be a ring or a C=O (but ketones/aldehydes would react with chromic acid or other tests). A cyclic ether (epoxide or oxetane or tetrahydrofuran derivative) would show no reaction with all four reagents. Specifically, tetrahydrofuran (THF) is C4H8O, a cyclic ether, and would not react with any of these four reagents. Step 4 - Identifying the answer as B: The answer B corresponds to the identification where Compound X is 3-buten-1-ol (a primary allylic alcohol, C4H8O with C=C and primary OH) and Compound Y is tetrahydrofuran (a cyclic ether, C4H8O with an oxygen in a ring and no reactive functional groups), which matches all the given test results. Step 5 - Why other options fail: Other options would assign incorrect structures that don't match the complete set of test results (e.g., a tertiary alcohol would react with Lucas reagent, a ketone would react with chromic acid, an aldehyde would react with chromic acid and Na metal tests differently). Therefore, the correct answer is B.