Chapter 9, Problem 9.54P

Although alcohol V gives a single alkene W when treated with ${\text{POCl}}_{\text{3}}\text{,}\text{and}\text{pyridine}$, three isomeric

alkenes (X–Z) are formed on dehydration with ${\text{H}}_{\text{2}}{\text{SO}}_{\text{4}}$. Draw a stepwise mechanism for each reaction

and explain why the difference occurs.