Which one of the following reagents is used to carry out the transform

Which one of the following reagents is used to carry out the transformation given below?
CH₃(CH₂)₉COOC₂H₅ → CH₃(CH₂)₉CHO

[amp_mcq option1=”DIBAL-H/H₂O” option2=”H₂/Pd-BaSO₄” option3=”SnCl₂/HCl” option4=”LiAlH₄” correct=”option1″]

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UPSC Geoscientist – 2023

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The transformation involves reducing an ester (CH₃(CH₂)₉COOC₂H₅) to an aldehyde (CH₃(CH₂)₉CHO). Reducing an ester to an aldehyde requires a specific reducing agent that can stop the reduction at the aldehyde stage, as complete reduction of an ester yields a primary alcohol. Diisobutylaluminium hydride (DIBAL-H) is a reducing agent that, when used at low temperatures and in controlled stoichiometric amounts, can selectively reduce esters to aldehydes.

DIBAL-H is a useful reagent for the partial reduction of esters and nitriles to aldehydes.

LiAlH₄ (Lithium aluminium hydride) is a strong reducing agent that would reduce the ester completely to a primary alcohol (CH₃(CH₂)₉CH₂OH). H₂/Pd-BaSO₄ (Rosenmund catalyst) is used for the reduction of acid chlorides to aldehydes, not typically esters. SnCl₂/HCl (Stephen reduction) is a method for reducing nitriles to aldehydes via an imine intermediate. Thus, DIBAL-H is the appropriate reagent for this transformation.

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