Question

Show how to prepare polybutadiene that is terminated at both ends with primary alcohol groups.

Short answer

Question: Describe the process to prepare polybutadiene terminated at both ends with primary alcohol groups. Answer: To prepare polybutadiene terminated at both ends with primary alcohol groups, follow these steps: 1) Prepare a solution of polybutadiene in a suitable solvent like tetrahydrofuran. 2) Add diethyl chlorophosphate as an end-capping agent to the solution, with equal concentration to the polybutadiene chain ends. 3) Allow the reaction to proceed, during which diethyl chlorophosphate will react with the double bond at each end of the polybutadiene chain, forming primary alcohol groups. 4) Purify the product by removing any unreacted diethyl chlorophosphate and other byproducts using methods like solvent removal, precipitation, and filtration.

Step-by-step solution

Understanding the structure of polybutadiene

Polybutadiene is a polymer made up of butadiene monomer units which has the formula \[CH_{2}=CH-CH=CH_{2}\]. This polymer is synthesized through a polymerization process which links multiple butadiene monomers together. Typically, polybutadiene contains a carbon-carbon double bond along the polymer chain.

Identifying the reactions needed to introduce primary alcohol groups

To introduce primary alcohol groups (\[-OH\] groups) at both ends of the polybutadiene chain, a reaction is needed that can specifically target the ends of the polymer. One such reaction is called "end-capping." An appropriate end-capping reagent for this purpose is diethyl chlorophosphate \[(CH_{3}CH_{2}O)_{2}P(O)Cl\], which will convert the end chain double bonds into primary alcohol groups.

Applying the end-capping reaction

To introduce primary alcohol groups at both ends of the polybutadiene chain, the following step-by-step process should be followed: 1. Prepare a solution of polybutadiene in a suitable solvent (e.g., tetrahydrofuran). 2. Add diethyl chlorophosphate \[(CH_{3}CH_{2}O)_{2}P(O)Cl\] to the solution. The molar concentration of the end-capping agent should be equal to the concentration of the polybutadiene chain ends. This ensures that both chain ends will react with the end-capping agent. 3. Allow the reaction to proceed for a sufficient amount of time. During this process, diethyl chlorophosphate will react with the double bond at each end of the polybutadiene chain, forming primary alcohol groups. 4. Purify the product by removing any unreacted diethyl chlorophosphate and other byproducts (e.g., solvent removal, precipitation, filtration). Following this process, you will have successfully prepared polybutadiene terminated at both ends with primary alcohol groups.