But-2-ene-1,4-diol is transformed in two stages, passing through an intermediate X, to form ketobutanedioic acid. $\text{HOCH}_2\text{CH}=\text{CHCH}_2\text{OH} \xrightarrow[\text{step 1}]{} X \xrightarrow[\text{step 2}]{\text{hot acidified } \text{KMnO}_4} \text{HO}_2\text{CCOCH}_2\text{CO}_2\text{H}$ What reagent might be used in step 1, and what is intermediate X?
- Acold acidified $\text{KMnO}_4$; $\text{HOCH}_2\text{CH}_2\text{CH(OH)CH}_2\text{OH}$
- Bhot acidified $\text{KMnO}_4$; $\text{HOCCCH(OH)CH}_2\text{CHO}$
- Csteam and concentrated $\text{H}_2\text{SO}_4$; $\text{HOCH}_2\text{CH(OH)CH}_2\text{CH}_2\text{OH}$
- Dwarm acidified $\text{K}_2\text{Cr}_2\text{O}_7$; $\text{HO}_2\text{CCH}=\text{CHCO}_2\text{H}$