In a variation of the Merrifield solid-phase peptide synthesis, the amino group is protected by a fluorenylmethoxycarbonyl (FMOC) group. This protecting group is removed by treatment with a weak base such as the secondary amine, piperidine. Write a balanced equation and propose a mechanism for this deprotection.

The structure of fluorenylmethoxycarbonyl (FMOC) is as follows: (latex) \text{FMOC}: \text{C}_{15}\text{H}_{11} (-\text{O}\textrm{-}\text{C(=O)}\textrm{-} \text{R})$ The amino group protected by FMOC will have the structure: (latex) \text{FMOC}\textrm{-}\text{N}\textrm{-}\text{H}\textrm{-}\text{R} And the structure of piperidine is a saturated six-membered heterocyclic ring containing a nitrogen atom: (latex) \text{Piperidine:} \text{C}_{5}\text{H}_{10}\text{N}

The balanced equation for the deprotection of FMOC protecting group by piperidine can be represented as: (latex) \text{FMOC}\textrm{-}\text{N}\textrm{-}\text{H}\textrm{-}\text{R} + \text{Piperidine} \rightarrow \text{N}\textrm{-}\text{H}\textrm{-}\text{R} + \text{FMOC}\textrm{-}\text{piperidine}

The mechanism of deprotection consists of the following steps: 1. Proton transfer: Piperidine acts as a weak base and deprotonates the amine group, forming a nitrogen anion (amide ion) and protonated piperidine. (latex)\text{N}\textrm{-}\text{H}\textrm{-}\text{FMOC} + \text{Piperidine} \rightarrow \text{N}^{-}\textrm{-}\text{FMOC} + \text{Piperidine}^{\oplus}\text{H} 2. Nucleophilic attack: The nitrogen anion (amide ion) generated in the previous step attacks the carbonyl group of FMOC, forming a tetrahedral intermediate. (latex)\text{N}^{-}\textrm{-}\text{FMOC} \rightarrow \text{Intermediate} 3. Elimination of FMOC-piperidine: The intermediate collapses with the formation of a double bond between the nitrogen and carbonyl carbon, releasing the FMOC-piperidine compound. (latex)\text{Intermediate} \rightarrow \text{N}\textrm{-}\text{H}\textrm{-}\text{R} + \text{FMOC}\textrm{-}\text{piperidine} This proposed mechanism results in the deprotection of the amino group by removing the FMOC protecting group with the help of piperidine.