Predict the product of the reaction of \((\mathrm{R})-2\) -butanol with triphenylphosphorus dibromide.

In this reaction, we have two reactants: 1. \((\mathrm{R})-2\)-butanol: It is an alcohol with the hydroxyl group (-OH) attached to the second carbon atom of a four-carbon chain. The structure is given by: ``` H H H H | | | | H-C-C-C-C-OH | H ``` 2. Triphenylphosphorus dibromide: It is a phosphorus-containing compound with three phenyl groups attached to a central phosphorus atom, as well as two bromide ions. The structure is given by: ``` Phosphorus with three phenyl groups and two bromide ions (Ph)3PBr2 ```

Given that we have an alcohol reactant and a phosphorus-containing compound, this reaction is an example of Appel reaction. The Appel reaction is used to convert alcohols into alkyl halides, in this case, the alkyl bromides. The mechanism involves the transfer of a halogen atom from the triphenylphosphorus compound to the alcohol, producing an alkyl bromide.

In the case of \((\mathrm{R})-2\)-butanol reacting with triphenylphosphorus dibromide, the reaction leads to the substitution of the hydroxyl group with a bromine atom in the chiral center of the molecule. The mechanism is as follows: 1. Nucleophilic attack of the phosphorus atom by the oxygen atom of the alcohol, resulting in the formation of an intermediate: \[ (\mathrm{R})-2\text{-butanol }+ (\text{Ph})_3\text{PBr}_2 \rightarrow [(\mathrm{R})-2\text{-butyl} \text{-O} - (\text{Ph})_3\text{P}\text{Br}]^{+}\text{Br}^{-} \] 2. Intramolecular halogen transfer from the phosphorus to the oxygen atom, resulting in the formation of the alkyl bromide and triphenylphosphine oxide: \[ [(\mathrm{R})-2\text{-butyl} \text{-O} - (\text{Ph})_3\text{P}\text{Br}]^{+}\text{Br}^{-} \rightarrow (\mathrm{R})-2\text{-bromo} \text{-butane} + (\text{Ph})_3\text{P=O} \] The stereochemistry of the product maintains the R-configuration at the chiral carbon.

The product of this reaction is the alkyl bromide \((\mathrm{R})-2\)-bromobutane, with the bromine atom replacing the hydroxyl group. The structure of \((\mathrm{R})-2\)-bromobutane is given by: ``` H H H Br | | | | H-C-C-C-C | H ```