Draw the displayed formula for S.
In step 1, secondary alcohol S reacts with $\text{PBr}_3$ to form T, which has molecular formula $\text{C}_4\text{H}_9\text{Br}$. State the systematic name of T.
Name the type of reaction that takes place in step 1.
State the reagent(s) and conditions needed for step 2.
Step 3 uses heating of $\text{C}_4\text{H}_9\text{CN}$ with dilute acid to make V. Complete the equation for this reaction. $\ldots \text{C}_4\text{H}_9\text{CN} + \ldots \text{H}^+ + \ldots \text{H}_2\text{O} \rightarrow \ldots$
An unlabelled sample could be S, T or U. The sample gives the infrared spectrum shown. Explain how this spectrum shows that the unknown sample contains U. In your answer, identify one relevant infrared absorption and the bond responsible for it in the region above $1500\,\text{cm}^{-1}$.