Illustrated Glossary of Organic Chemistry

Protection: The process of installing a protecting group.

CrO3

aq. H2SO4

Without a protecting group, both the alcohol and aldehyde are oxidized by Jones reagent. This oxidation is not chemoselective.


tBDMSCl

Imidazole
Protection

CrO3

aq. H2SO4

aq. HF

Deprotection

When the alcohol is protected with a tBDMS group, only the aldehyde is oxidized by Jones reagent. Thanks to the protecting group the oxidation is now chemoselective, but the synthesis is now two steps longer because of the protection and deprotection steps.