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What is the most commonly used protecting group for alcohols in organic synthesis and what is the mechanism of its removal under acidic conditions?

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The most commonly used protecting group for alcohols in organic synthesis is the tert-butyldimethylsilyl  TBS  group. The TBS group is introduced to the alcohol by reacting it with tert-butyldimethylsilyl chloride  TBSCl  in the presence of a base, such as imidazole.The mechanism of TBS removal under acidic conditions involves the following steps:1. Protonation of the oxygen atom in the TBS-protected alcohol by an acid  e.g., HCl or TFA . This generates a positively charged oxygen atom  oxonium ion  and makes it a better leaving group.2. Nucleophilic attack by a water molecule on the silicon atom of the TBS group. This forms a pentavalent silicon intermediate.3. The pentavalent silicon intermediate collapses, with the oxygen-silicon bond breaking and the TBS group leaving as a neutral species  tert-butyldimethylsilanol .4. Deprotonation of the oxonium ion by another water molecule, yielding the free alcohol and a hydronium ion.In summary, the TBS protecting group is commonly used for alcohols in organic synthesis, and its removal under acidic conditions involves protonation, nucleophilic attack, bond cleavage, and deprotonation steps.

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