Fumaric acid may be changed into oxaloacetic acid through a two-stage route that uses the intermediate Q. $\text{HO}_2\text{CCH=CHCO}_2\text{H} \xrightarrow{\text{step 1}} Q \xrightarrow{\text{step 2}} \text{HO}_2\text{CCOCH}_2\text{CO}_2\text{H}$ In the laboratory, each stage can be carried out with just one reagent. What might Q be, and which reagent is needed for step 2?
- AQ: $\text{HO}_2\text{CCHBrCH}_2\text{CO}_2\text{H}$; reagent: warm acidified $\text{KMnO}_4$
- BQ: $\text{HO}_2\text{CCHBrCH(OH)CO}_2\text{H}$; reagent: warm $\text{NaOH(aq)}$
- CQ: $\text{HO}_2\text{CCH(OH)CH}_2\text{CO}_2\text{H}$; reagent: Fehling’s solution
- DQ: $\text{HO}_2\text{CCH(OH)CH}_2\text{CO}_2\text{H}$; reagent: warm acidified $\text{K}_2\text{Cr}_2\text{O}_7$