Aldehyde + ethylene glycol under acid catalysis forms what type of protecting group?

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Multiple Choice

Aldehyde + ethylene glycol under acid catalysis forms what type of protecting group?

Under acid, an aldehyde can be protected by forming an acetal with a diol. Ethylene glycol supplies two –OH groups that attach to the protonated carbonyl, yielding a five-membered cyclic acetal (a 1,3-dioxolane) that blocks the carbonyl from further reaction. This protecting group can be removed later by acidic hydrolysis to reveal the aldehyde again. It’s not a ketal because that term applies to acetals formed from a ketone, not an aldehyde; it’s not an imine since no nitrogen is involved; and it isn’t a simple ether formation, which doesn’t protect the carbonyl.

Under acid, an aldehyde can be protected by forming an acetal with a diol. Ethylene glycol supplies two –OH groups that attach to the protonated carbonyl, yielding a five-membered cyclic acetal (a 1,3-dioxolane) that blocks the carbonyl from further reaction. This protecting group can be removed later by acidic hydrolysis to reveal the aldehyde again. It’s not a ketal because that term applies to acetals formed from a ketone, not an aldehyde; it’s not an imine since no nitrogen is involved; and it isn’t a simple ether formation, which doesn’t protect the carbonyl.

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