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Organic Chemistry 2

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Aldehyde Transformations XI

ORGO2-DCC3YS

An alternative method to transform aldehydes/ketones into the corresponding acetals involves treatment with orthoformates ($HC(OR)_3$) and an acid catalyst at room temperature. An example of this reaction is depicted below.

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This reaction process is exothermic ($ΔH$ = -3.0 kcal/mol).

What is the most likely thermodynamic driving force for this reaction?

A

The byproduct, ethyl formate, is a gas at room temperature and leaves the system as it forms. The reaction is driven to completion by Le Châtelier's principle.

B

The carbonyl group of ethyl formate is an ester and thus highly stabilized by resonance interaction with the lone pairs of the OEt group. The starting aldehyde/ketone lacks this strong resonance stabilization.

C

Acetal formation is generally a thermodynamically favorable process, and triethyl orthoformate is merely another reagent for accomplishing this thermodynamically favorable process.

D

Acetal formation transforms the group on the benzene ring from an electron-withdrawing group into an electron-donating group.