When an ester, such as methyl propanoate ( ), is treated with exactly one equivalent of DIBAL-H at extremely low temperatures (-78 C) followed immediately by mild acidic hydrolysis, what is the primar

Question

When an ester, such as methyl propanoate ( $CH_3CH_2COOCH_3$ ), is treated with exactly one equivalent of DIBAL-H at extremely low temperatures (-78 C) followed immediately by mild acidic hydrolysis, what is the primary organic product isolated?

Prashant Kotian · Accepted Answer

Correct answer: B. Diisobutylaluminum hydride (DIBAL-H) at -78 C is a specialized, bulky hydride donor. It reduces esters to an intermediate tetrahedral aluminate complex that is stable at low temperatures. Upon aqueous workup, this collapses to yield an aldehyde (Propanal), stopping the reaction from over-reducing to an alcohol.

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