Interpretation: The mechanism should be drawn for the following transformation.
Concept Introduction:
Acetal formation: Acetal derivative of aldehyde and ketone are prepared by an acid catalyzed dehydration reaction with alcohols and
Acetals are germinal-diether derivatives of
Ketone derivatives of acetal once called ketal, but in modern usages has dropped this name.
Acid catalyzed formation reaction mechanism:
Step-1: An acid or base reaction, there is only a weak nucleophile we need to active the carbonyl group by protonating on O.
Step2: The nucleophilic O in the alcohol attacks the electrophilic C in the C=O, braking the pi-bond and giving the electrons to the positive O.
Step-3: An acid or base reaction, deprotonation of alcoholic oxonium ion neutralizes the charging giving the hemi acetal.
Step-4: In order for the –OH to leave we need to make it a better leaving group by protonation.
Step 5: Using the electrons form the other O leaving group departure is facilitated.
Step-6: The Nucleophilic O of the alcohol attacks the electrophilic C and the electrons of the pi- bonds to move to neutralize the charge on the positive O.
Step-7: Deprotonation of the alcoholic oxonium neutralizes the charge the charge on the positive O.
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Chapter 19 Solutions
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