Which of the following compounds in solution will turn red litmus paper blue?

Correct answer: C. RNH₂ (amine)

Explanation: Amines have a lone pair on nitrogen and act as weak bases in water: they accept a proton to form RNH₃⁺, increasing OH⁻ and turning red litmus blue.

• A. R′OR″ (ether) — Neutral; does not appreciably affect litmus.
• B. R–C(=O)–NRR (amide) — Very weakly basic/neutral because the N lone pair is delocalized by resonance.
• C. RNH₂ (amine) — Correct. Basic in water → turns red litmus blue.
• D. R–C(=O)–R (ketone) — Neutral; does not turn red litmus blue.