Which of the following reagents could be used to distinguish between prop-2-en-1-ol and propan-1-ol?
ZnCl2 and conc. HCl
Both alcohols will effect a change in colour with Cr (VI) reagents. So that option is ruled out.
Lucas reagent is anhydrous ZnCl2 dissolved in conc. HCl. At room temperature, it is extremely slow to react with primary alcohols like propan-1-ol.
So no oily layer is observed. But like tertiary alcohols, allyl alcohols give a positive Lucas test very quickly so an oily layer is observed in seconds.