Carbonyl reduction to alcohol followed by dehydration to a single alkene isomer

Steps:

• NaBH4 reduces the carbonyl group in each C4H8O starting compound to a secondary or primary alcohol (C4H10O).
• Heating the alcohol with excess conc. H2SO4 dehydrates it via E1 mechanism, losing H2O to form C4H8 alkenes (note: likely transcription error in formula; alkenes are C4H8).
• Analyze possible carbocation rearrangements and elimination products for each structure.
• Identify which yields only one unique alkene constitutional isomer.

Why C is correct:

• Compound C is a symmetrical ketone (e.g., 2-butanone equivalent) reducing to a secondary alcohol that dehydrates to only one alkene via a single carbocation without rearrangement options.

Why the others are wrong:

• A: Aldehyde reduces to primary alcohol yielding two alkenes (1- and 2-butene) via different eliminations.
• B: Unsymmetrical ketone gives alcohol with carbocation rearranging to two alkene isomers.
• D: Ketone reduces to alcohol allowing dehydration to three possible alkenes including branched ones.

Final answer: C