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Ch. 18 - Ketones and Aldehydes
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
Chapter 18, Problem 10e,f

Predict the products of the following reactions:
(e) Chemical reaction diagram showing a compound with an aldehyde and methoxy group, with DIBAL-H and water as reagents.
(f) Chemical structure of a cyclic compound with two carbonyl groups, showing reaction conditions with DIBAL-H and water.

Verified step by step guidance
1
Step 1: Analyze the reagent DIBAL-H (Diisobutylaluminum hydride). DIBAL-H is a selective reducing agent that reduces esters and lactones to aldehydes under controlled conditions (low temperature, -78°C). It does not reduce the carbonyl group completely to an alcohol in this case.
Step 2: For reaction (e), identify the functional groups in the starting material. The molecule contains an ester group (O=C-OCH₃) and a double bond in the alkyl chain. DIBAL-H selectively reduces the ester group to an aldehyde without affecting the double bond.
Step 3: For reaction (f), identify the functional groups in the starting material. The molecule contains a lactone (cyclic ester). DIBAL-H selectively reduces the lactone to an aldehyde, opening the ring structure in the process.
Step 4: Consider the reaction conditions. The reaction is performed at -78°C, which ensures selective reduction to aldehydes without over-reduction to alcohols. The addition of water (H₂O) in the second step quenches the reaction and hydrolyzes the aluminum complex formed during reduction.
Step 5: Predict the products. For reaction (e), the ester group is reduced to an aldehyde, and the double bond remains intact. For reaction (f), the lactone is reduced to an aldehyde, resulting in a linear molecule with an aldehyde group at one end.

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Key Concepts

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