NaBH4 Reactivity with Acids vs. Alcohols

Steps:

• Tartaric acid is HO2CCH(OH)CH(OH)CO2H, a dicarboxylic acid.
• Excess LiAlH4 reduces both COOH groups to CH2OH, forming J as HOCH2CH(OH)CH(OH)CH2OH, a neutral tetraol.
• NaBH4(aq) decomposes with protic acids like COOH, evolving H2 via protonation of BH4-.
• J has only alcohol groups, which are not acidic enough to react with NaBH4.

Why B is correct:

• NaBH4 reacts with carboxylic acids per its known instability toward protic acids, generating H2, but ignores neutral alcohols.

Why the others are wrong:

• A: J lacks acidic protons, so only tartaric acid reacts.
• C: Tartaric acid's COOH groups cause reaction via H2 evolution.
• D: Tartaric acid reacts due to its acidity.

Final answer: B